Bolting

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This lettuce has bolted: its leaves are now bitter and inedible.

Bolting, also called going to seed, is one of those arcane horticultural terms that throws beginning gardeners. When a plant “bolts”, that doesn’t mean it is running away, of course, but instead that has started to flower or go to seed prematurely. And by “prematurely”, I really mean before the gardener wanted it to. (It may seem the perfect moment to flower from the plant’s point of view!)

Bolting means the plant has gone beyond the vegetative stage in its life and has begun taking the next step: flowering. This is bad news for many herbs and leaf and root vegetables, like spinach, lettuce, parsley and radishes, as not only do they stop producing more of the edible part the gardener wants, but their leaves or roots become bitter or fibrous and no longer edible.

Hot or dry conditions often stimulate bolting, so you can delay it by keeping the soil cool and moist (a mulch may be helpful) or by sowing the plant in a cooler season. Many leaf vegetables, for example, grow best in spring or fall, even winter in mild climates, but bolt rapidly during the summer. Yet other plants, like onions or carrots, may bolt when they go through a cold snap.

Growing plants well is the best way to prevent bolting… and it can be helpful to grow varieties said to be slow to bolt or resistant to bolting.

The Money Tree Doesn’t Age Gracefully

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Braided money tree: Pachira glabra or P. aquatica

You’ve certainly seen the money tree around. With its scheffleralike leaves and its usually braided-stems, this houseplant really stands out from the crowd.

The money tree got its name from its five leaflets. Five is an auspicious number in Chinese tradition, associated with wealth. According to feng shui superstitions, bringing a five-leaved plant into the home will ensure financial prosperity (who knew it could be so easy!). Of course, it sometimes produces six or seven leaflets, sometimes even nine, but that’s all right too: they’re also lucky numbers.

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Money tree nursery in Taiwan.

To enhance the money tree’s luckiness, it is most often sold braided with five interlaced stems. Never four (four means death). If one stem of a five-stemmed plant dies, superstitious owners will quickly make the plant disappear.

Millions of braided money trees have been exported from Taiwan since the 1980s, where growing and producing them remains a major industry.

What Is It?

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Pachira aquatica flower in Costa Rica. P. glabra would have had white stamens. You aren’t likely to see flowers in your home.

There are actually two different species sold as money tree, both from the Malvaceae family and native to Central and South America. Pachira aquatica usually gets the credit, but it’s not nearly as widely grown as P. glabra. Both are very similar and hard to tell apart when young, but P. glabra has a more distinctly bulbous base. The feather-duster like white flowers of P. aquatica have red-tipped stamens and its large swollen fruits are a velvety mahogany brown while the otherwise similar flowers of P. glabra are entirely white while the fruits are green and smooth. Both contain edible nuts, leading to a second common name, Malabar chestnut.

Neither is likely to ever bloom indoors, but they flower readily enough when planted outdoors in tropical climates. When they do, you’ll discover the large and very attractive flowers open at night and drop off the following morning.

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My own Pachira glabra. After years of pruning, it finally has a second branch!

Both are tall forest trees in nature. This shows in their growth habit: they are very reluctant to branch when young. Even if you chop the head off a money tree, it usually produces only one replacement stem, only rarely two. As a result, potted money trees take on a distinctly ungainly look as they age. At least braided trees, each with their own set of leaves, will look fuller for a longer time.

For appearance’s sake, it’s probably best to cut them back annually in late winter. Yep, off with their heads! Don’t worry, they’ll regrow quickly. Close-up, this will lead to a lot of pruning scars and frankly, the money tree is not a plant that ages gracefully. Still, with a little luck new foliage will partly hide the scars, so they won’t be too noticeable from a distance,

Care

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If you keep chopping your tree’s head off, you can keep it this size practically for ever! Photo: DC, Wikimedia Commons

The money tree is a surprisingly tough houseplant.

Although in nature adult trees grow with their upper branches exposed to full tropical sun, young trees germinate in deep shade and retain that tolerance when grown indoors. They thrive along rivers and lakes with their roots practically soaking in water, as the name P. aquatica suggests, yet are very drought tolerant. Nor do they seem to mind if their roots are horrendously crowded in a small pot. (You’ll often see money trees grown as bonsais.)

As a result, you can put money trees in full sun or well back from the window, water them regularly or let their soil dry out completely, and either neglect them or baby them and they’ll probably survive. Normal indoors temperatures are fine. They tolerate dry air, but will look lusher under humid conditions. They don’t seem to react at all to fertilizer, but logically you’d still apply a bit in the spring and summer.

Put them outside for the summer in full sun if possible (that will be the only way you could ever expect them to bloom, for example), but do acclimatize them gradually, as the leaves will burn if suddenly exposed to intense sun. Bring them in when night temperatures start to drop below 50˚ F (10˚ C).

Don’t panic when some of the old leaves turn yellow and start to drop off, usually in late winter or early spring. This is part of their growth cycle and new leaves will appear shortly, if not at the same time. Don’t expect much growth at other seasons, at least, not unless you cut it back: whatever this plant does, it will normally do it in spring.

Carry out any repotting in early spring as well. If you want their stems to swell to the bulbous shape they are capable of, they’ll need much more space than in the crowded pot in which they are usually sold.

If you want to continue to braid the stems, do so while they are young and pliable, using twist ties to hold the braids together until they solidify. The Taiwanese use yellow-, gold- or red-colored twist ties, apparently luckier than green ones.

Your plant grew from seed, but seeds are rarely available from mail order sources simply because they are so short-lived, but you can multiply your money tree from cuttings if you want.

Ugly But Alive

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The bulbous base of my P. glabra.

I have a 7-foot (2-meter) P. glabra with a single trunk, swollen at the base like a cantaloupe, that I’ve grown indoors for nearly 20 years. It’s not very pretty (all those pruning scars!), but I have managed to get it to branch, a bit, by cutting off every stem that tries to grow taller. It would certainly never win a beauty contest and I think I only keep because it clings so stubbornly to life. That is something, in my book, that ought to be rewarded.20170327E

No, Today’s Vermiculite Doesn’t Contain Asbestos

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You’ll find bits of golden vermiculite in most potting soils.

A reader recently asked me whether it was true that vermiculite contains asbestos and therefore should be avoided. It just goes to show that horticultural myths have an extended life, as this one was debunked ages ago and I thought it was long dead.

First, an explanation.

Vermiculite is a naturally occurring mineral composed of shiny flakes resembling mica. When heated to outrageously hot temperatures, about 1000°C, it puffs up like popcorn, giving a light-weight expanded rock useful not only in horticulture and also in insulation and fireproofing.

Vermiculite itself is not a health hazard. It’s an inert mineral widely employed in gardening circles, practically omnipresent in packaged growing mixes, and accepted in organic gardening.

So far, so good.

But vermiculite wasn’t always quite so innocuous. Back in the mid-twentieth century, much of the vermiculite produced in North America was taken from the Libby Mine in Montana. Sold under the trade name Zonolite, this vermiculite was contaminated with asbestos fibers, as the two are naturally copresent in the same rock formation, although this went unrecognized for some 60 years. From about 1920 to 1990, Zonolite was widely used in the construction industry throughout North America, notably as attic insulation. It was also employed, to a lesser extent, in horticulture.

By the way, Zonolite never was sold in Europe or other continents: it was strictly a North American commodity.

Following the discovery of the presence of asbestos fibers in the vermiculite it produced, the Libby Mine closed in 1990 (in fact, little Zonolite was distributed after 1980). To date, no other vermiculite mines have been found to contain asbestos and periodic tests are done to make sure it stays that way.

As a result, you can safely use any growing mix presently sold that contains vermiculite and be sure it is asbestos-free. That is, unless you have bags of potting soil dating back to before 1990 and which come from Libby, Montana… and that strikes me as being unlikely.

What About Perlite?

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White puffy perlite also inhabits your potting mixes. Photo: Ragesoss, Wikimedia Commons

Concerns about vermiculite contaminated with asbestos fibers prompted people to wonder whether if that wasn’t also the case with perlite, another expanded rock used to lighten gardening soils. But perlite, essentially a form of volcanic glass, is not formed in the same way as vermiculite and is never found in the company of asbestos. So there was never any risk of it becoming contaminated.

Avoid Inhaling Dust of Any Kind

20170326CAny text presenting the safe use of vermiculite and perlite has to include one caveat: don’t breathe in their dust.

When working with any product that gives off dust, be it vermiculite, perlite, potting soil or even flour, it is always important to protect your eyes and lungs from the dust they can release by wearing safety goggles and a dust mask, as dust can be an irritant. This is especially true if you have lung problems.

Contaminated Houses

DSC00029There are millions of homes insulated with vermiculite containing asbestos fibers in North America. Currently, the usual recommendation is not to touch this insulation, quite simply. To quote the Canadian Center for Occupational Health and Safety (CCOHS): “As long as this kind of vermiculite-based insulation remains undisturbed behind intact walls or in attic spaces and does not become airborne, it should not be a concern.”

On the other hand, if for any reason you have to disturb old vermiculite insulation, you should hire a professional who is trained and certified in handling asbestos to do the job.

Obviously, the latter aspect completely exceeds my field of knowledge: I know horticulture, not construction. If you are concerned that your home is possibly insulated with contaminated vermiculite, I suggest you contact the EPA in the United States, the CCOHS in Canada or the government body currently manages health issues in construction in your country.20170326A

A Simple Basement Cold Room

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20170325A.jpgHave you ever considered building your own cold room (root cellar) where you could store fruits and vegetables in the fall and winter and preserves throughout the year? It’s a fairly simple project when you have the space for it, ideally a basement with bare concrete walls.

In traditional the cold room of our ancestors, dug into the earth out back somewhere, cooling was carried out passively by surrounding and over it with earth. In this version most of the cooling is done by vents pierced into the wall. One brings cold air in, the other lets warm air out. And the concrete floor and walls also have a distinct cooling effect, plus being porous, they also increase the room’s humidity.

The ideal spot for a cold room is a corner in an unfinished basement. Why a corner? Because that will give you two naturally cold outside walls… and if one of those walls is a north wall, that’s even better (at least for readers in the Northern Hemisphere).

A cold room can be nearly any size. For easy circulation, just make sure it’s at least 6′ deep. Typically it will be about 8′ to 10′ long. Build custom walls to insulate the room from the rest of the basement… and obviously you’ll need to include a door in your plan as well. Since a cold room will be quite humid, use moisture-resistant building materials wherever possible, not just to eventually prevent rot, but to control any musty odors.

How to Do It

Start with the ventilation, as easy as installing two dryer vents at least 10” apart.

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Illustration: DIY Projects for the Self-Sufficient Homeowner by Betsy Matheson. Used with permission from Cold Springs Press.

In the illustration above, a window in the cold room was replaced with a plywood panel, making installing the two vents extra-easy, as you can simply cut a hole in the panel with a jigsaw, but in most cases, you’ll need to rent a core drill with 4 ½” concrete drill bit (make sure the supplier explains how to use it!) to punch two round holes through the basement’s concrete wall. This will allow you to install 4″ dryer vents (i.e. the same vents used for clothes dryers). Look for vents with internal screening to prevent insects or animals from entering. Caulk well, both indoors and out. Add an adjustable manually operated damper to each so you control airflow and therefore temperature, keeping notably the cold intake nearly closed during the coldest days of winter.

Leave the outflow vent as is (see the illustration above), but run ductwork (dryer pipe, PVC pipe) from the intake vent down to the floor to direct cold air downwards. This will give you a system where cold air flows in and down to the floor, while warm air rises and exits via the outflow vent.

The next major step is to install the wall frame and door to measure.

20170325D.jpgInsulate the walls with rigid foam panels (more moisture-resistant than fiberglass), then staple plastic vapor barrier to the outside (vapor barrier should always be placed on the warm side of the structure). Now cover the outside with paneling or drywall. You don’t need to cover the inside wall… unless you want to.

Next insulate the ceiling, this time starting with thevapor barrier, then rigid foam insulation.

Hang an exterior door with insulation in the frame, sealing the base with weather stripping.

A LED stick-up light can provide lighting or you could install electric lighting before you put in the walls. It’s easy to find a battery-operated combined thermometer/hygrometer to fix to the wall so you can check storage conditions.

Finally, add shelving to your taste, remembering the air circulation is vital, so ventilated shelving may be best.

Using Your Cold Room

20170325E.jpgYour cold room will be functional for storing fruits and vegetables from mid-fall right through to early spring. Not many vegetables can be stored longer than that. If you can maintain temperatures around 35 to 45˚F (2 to 7˚C) and high humidity, around 90 to 95% (you may need to spray the floor with water every now and then), you can store rutabagas, turnips and winter cabbages for up to 6 months, even longer for potatoes, a bit less for carrots, and 3 months or so for beets and parsnip. A cold room can also be used to blanch strong-tasting vegetables like endives and cardoon to make them less bitter. Or try planting a few stumps of celery plants in a pail of damp sand. You can then harvest pale yellow but still edible celery stalks for several months.

Apples and pears store well in a cold room… but apples give off so much ethylene gas they may cause nearby vegetables to spoil. Placing them near the exhaust vent may help.

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Store root vegetables in layers, covering each layer with slightly moist sand or dry leaves.

Fruits and most vegetables can be stored loose, in bins or baskets for example. Wrap winter cabbage loosely in newspaper. Carrots, beets, parsnip and other root vegetables are best layered and covered in slightly moist sand or dry leaves.

Onions, garlic, keeper tomatoes, pumpkins and squash, on the other, are not good choices for most cold rooms: they tend to spoil under cold humid conditions and are best kept in a cool, dry room somewhere else in the house

Finally, store only clean, intact, unblemished fruits and vegetables: they’re less likely to rot. And do examine your stock occasionally, removing anything that does start to spoil.

Beyond Fruit and Veggies

Of course, cold rooms can also be used to store preserves, jams, wine, beer, etc. all year long. And even in summer, they’ll be much cooler than the air outdoors and so can be used much like a refrigerator, that is, for the short-term storage of summer crops.

Good luck with your cold room!20170325B

Seedlings: To Pinch or Not to Pinch?

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Pinching is just what it sounds like: you “pinch off” the terminal bud between thumb and forefinger.

When my father taught me how to start plants from seed some 50 years ago, pinching was a very common practice. You used to pinch seedlings when they had 4 to 6 true leaves and it was almost universally applied to annuals and herbs, although rarely to vegetables.

Pinching means removing the terminal bud, the plant’s growing point. When the terminal bud is nixed, this stimulates dormant buds lower down on the plant to spring into action. Usually, each pinch at least doubles the number of stems, giving a much denser and more attractive plant with more leaves (herbs) and more flowers (annuals). It does slow the plant down a bit, but usually within 5 to 7 days, the seedling will be sprouting new growth.

Traditionally, pinching really is done exactly like the term suggests: by pinching the growing point between the thumb and forefinger. Since the bud is still soft, it comes right off. Of course, you can also cut off the bud with scissors or pruning shears… and that is still considered “pinching”.

Pinching Today

Pinching is still used on more mature plants (shrubs and houseplants notably) to keep them in check, but pinching seedlings is a bit of a dying art. Most modern varieties of annuals and herbs have been selected to be self-branching. Old-fashioned basils and coleus, for example, used to shoot straight for the sky, but many modern varieties begin producing branches almost as soon as they have true leaves. If your seedlings are producing secondary branches, they won’t need pinching. Likewise if the plant’s label suggest it branches well, is self-branching or “needs no pruning”.

That said, there are still older varieties around… and I’ve never seen a cosmos seedling that couldn’t use a pinch or two.

Here is a list of plants that it may be useful to pinch… but even with these plants, do look before you pinch.

  1. Basil
  2. Coleus
  3. Cosmos
  4. Dahlia
  5. Fuchsia
  6. Impatiens
  7. Marigold
  8. Petunia
  9. Snapdragon
  10. Sweet Pea
  11. Zinnia

10 Strange Facts About Vegetables

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Photo: clipartfest.com

“Eat your vegetables”, my mother used to say, “they’re good for you!” But I’d feed them to the dog if I got a chance.

She was right, of course, that vegetables are good for us. They’re richer in vitamins and minerals than just about anything else we can eat. But there are also a lot of fascinating facts about them that most people don’t know. Here are a few:

1. Tearless Onions

20170323A.jpgWhat gives onions their pungency and irritates our eyes to the point they tear up is the presence of various volatile sulfur compounds in their cells. Cut into an onion and the air is instantly full of tiny irritating particles. They evolved in onions as protection, to discourage animals from munching on them. However, in the rare occurrence of sulfur-free growing conditions, onions completely lose their pungency… even “onion breath” becomes a thing of the past. Even so-called “sweet onions”, genetically less pungent than most of their kin, have to be grown in soil that is poor in sulfur in order to have the mild taste we expect. Certain soils in the US West and South and in the heart of Europe, for example, are poor in sulfur… and that’s where sweet onions are grown. Try growing a sweet onion in normal garden soil, rich in sulfur, and it will leave  you crying.

2. Baby Carrots Aren’t Babies

20170323b.jpgThe so-called baby-cut carrots aren’t miniature carrots, they’re full-sized carrots trimmed down to size by industrial machines.

This technique was first used to convert substandard carrots, with blemishes or marks, ones that had no market value, into saleable items. Now, though, there is an entire industry based on producing the pre-peeled, ready-to-eat babies. Surprisingly little goes to waste: shavings account for only 0,84% of the production, largely because special carrot cultivars and tight spacing during sowing lead to long, narrow carrots easily cut into 3 to 4 pieces. Shavings are either used for animal feed or in the food processing industry (think “carrot cake”).

Of course, there are also true baby carrots: naturally miniature strains that you can grow… but you rarely find those in supermarkets!

3. Tomatoes are Legally Vegetables

20179323C.jpgBotanically speaking, tomatoes are  fruits. In fact, they are technically berries, since they are a simple fleshy fruit with many seeds and no stone (stone fruits are called drupes). However, in the United States, they are legally vegetables. Following a controversy about the tomato’s status, the U.S. Supreme Court officially decided that the tomato is a vegetable. That was way back in 1893 and the decision still holds today.

4. Eat Those Peels!

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Photo: Alice Wiegand, Wikimedia Commons

Peeling your vegetables before you eat them is a nutritional faux pas. In most vegetables, such as carrots, potatoes, and cucumbers, a good percentage of the nutrition is actually stored in the skin or just below the skin. That means when you peel them, you’re actually removing many of the nutrients they contain. Vegetable skins also contain a lot of fiber and fibers too are good for you.

5. If You Hate the Taste of Brussels Sprouts, It May Be In Your Genes

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Photo: Rainer Zens, Wikimedia Commons

Studies all over the world suggest that Brussel sprouts are world’s most hated vegetable. American President George H.W. Bush famously hated Brussel sprouts so much he banned them from the White House. Recent studies have shown that your like or dislike of Brussel sprouts (and other cabbages) is encoded in your DNA. There is actually a gene shared by about half the world’s population that allows them t0 enjoy the taste of Brussel sprouts, as they are genetically incapable of tasting highly bitter compounds called glucosinolates found in all cabbages, but more abundantly in Brussels sprouts. To glucosinolate tasters, that is, the other half of the population, Brussels sprouts are incredibly bitter. The researchers doing the DNA study found that for these people, Brussels sprouts taste about as appealing as (and I am quoting) “eating a rubber shoe.”

6. Carrots Are Not Really Good for Night Vision

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Part of a WWII poster encouraging people to eat carrots for improved night vision.

Unless your diet is seriously lacking in Vitamin A, carrots don’t help you see better at night. The belief that eating them does improve night vision actually stems from a WWII propaganda campaign. At the time, Great Britain was developing new radar technologies to help their aircraft better find their targets in the dark, but didn’t want the Nazis to know. So they started running stories in British newspapers claiming Royal Air Force pilots were being fed carrots to improve their night vision, thus creating a plausible explanation for their improved nocturnal aerial success. This propaganda piece was so successful that the information spread around the world and even to this day, many people still believe that eating carrots helps you see better at night.

7. The Downside of Beans

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Photo: cookbookman17, Flickr

“Beans, beans, they’re good for the heart…” So goes the first part of a popular child’s rhyme. As to being good for the heart… well, they’re as good for the heart as just about any vegetable, but what is far truer is that they assuredly do contribute to flatulence. That’s because our stomach and small intestines lack the enzymes necessary to completely break down two sugars found in beans, raffinose and stachyose. Instead, bacteria found in our large intestines tackle the job and break them down into hydrogen, nitrogen, carbon dioxide… but especially the malodorous gas methane, with often explosive results. Yes, you can take an enzyme called alpha-galactosidase (sold as Beano) before eating beans and it will break the sugars down without any unfortunate consequences. Soaking beans for several hours before cooking will also help, as this allows yeasts to start digesting the sugars.

8. Popeye Was Wrong About Spinach

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Image: jean pierre Gallot, Flickr

When I was a kid, the popular Popeye comics and cartoons showed Popeye ingesting a can of spinach and suddenly becoming incredibly strong. This wasn’t enough to encourage me to eat any more spinach than I was forced to, but it did lead to spinach gaining massively in popularity. Unfortunately, the entire idea that spinach made you stronger was based on a simple notational mistake. In 1870, German chemist Erich von Wolf reported that a 100 g serving of spinach contained 35 mg of iron, far more than any other vegetable. And iron is associated with strength, as it helps carry oxygen to your muscles. The problem is that von Wolf had mistakenly misplaced a decimal point. 100 g of spinach contained the more modest and normal quantity of 3,5 mg of iron, not 35 mg. Spinach is good for you, but not as good as many people today still believe.

9. Many Vegetables Contain Toxins

20170223I.pngThis is not something we like to think about, but many if not most vegetables (kale, carrots, Swiss chard, tomatoes, etc.) contain products (alkaloids, goitrogens, oxalic acid and others) that are toxic to humans. Fortunately, they are present in such small quantities they cause no harm. The poison, goes the saying, is in the dose and that is very true. Still, people subject to kidney stones or gout should avoid eating too much spinach  or asparagus (they contain fairly important quantities of oxalic acid, a toxin that can exacerbate both conditions) and any green parts should be removed from potatoes, as they contain solanine and other toxic alkaloids. Eating green potatoes could theoretically kill you! Also never eat the foliage or stems of any Solanaceae (tomato, potato, pepper, eggplant, etc.) as they really do contain enough solanine to make you seriously ill.

10. There is No Such Thing as a Negative-Calorie Vegetable

20170323J.JPGThose of us who need to lose a bit of weight (or a lot of it) may have been encouraged by claims that some vegetables (celery, kale and lettuce are often cited) are negative-calorie foods, that digesting them requires more energy than the energy they release when we digest them. That means you’d lose weight just by eating them. But unfortunately, that isn’t true. Even celery, usually touted as the best negative-calorie vegetable, and which is indeed mostly composed of water and fiber, still contains about 6 to 10 calories per stalk, yet digesting it requires only about ½ calorie. Still, if you stuffed yourself with celery, you wouldn’t have much room for calorie-rich foods and you’d certainly lose weight.


Vegetables: we eat them on a daily basis, yet we know so little about them.20170323K

Succeeding With Succulents

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Succulents on display at a plant show. Photo: Stephen Boisvert, Wikimedia Commons

Succulent plants or simply succulents are fleshy plants adapted to survive in arid environments. Their main feature is their ability to store water in their leaves, stems or roots in the form of sap. In fact, that’s how they got their name: the term succulent comes from the Latin “succus”, meaning “sap”.

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The thick sap in this aloe leaf is a water reservoir typical of most succulents. Photo: Raul654, Wikimedia Commons

Cactus or succulent?

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This Rebutia is a true cactus, belonging to the Cactacaeae. Note the tufts of white fuzz from which circles of spines arise: they are areoles, only produced by true cacti.

Although you commonly hear the term “cactus and succulents”, it’s actually pretty redundant. Cacti are succulents, belonging to one of the few plant families whose members are all succulents, the Cactaceae. So all the cacti are succulents… but not all succulents are cacti, as there are plenty of plants in other families.

If you didn’t quite get that, it’s like poodles and dogs: all poodles are dogs, but not all dogs are poodles.

Adaptive Evolution in Response to Drought

Succulence has evolved independently many times in nature in many different plant families. In fact, some 65 families of plants have at least a few succulent members, including such unlikely ones as the begonia family and the orchid family.

In response to a climate that is becoming increasingly dry, those plants that are best able to tolerate drought survive and multiply while less drought-tolerant plants are gradually eliminated. When this process is repeated generation after generation, the survival of the fittest starts to operate in a big way, leading to plants that are less and less like their ancestors and more and more able to deal with drought.

Obviously, there are many ways to survive drought. Some plants learn to go dormant when water is scarce, others reduce the size of their leaves (most of the water that plants absorb is lost by evapotranspiration through the open stomata of their leaves), others adopt an annual lifestyle and learn to grow, bloom and go do seed rapidly after a rain before dying, others retreat entirely underground during the dry season, etc. Storing water reserves above ground in stems or leaves is however the most visible way plants face an arid climate.

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Euphorbia obesa has abandoned the use of leaves and carries out all its photosynthesis through its very plump green stem.

Many succulent plants, including cacti, abandoned their leaves along the way. These plants learned to carry out photosynthesis using only the chlorophyll-rich green cells in their stems. Thus leaves, which generally lose more water than stems because they’re thinner and ave greater number of stomata, were eliminated. In the case of cacti, those leaves were converted into spines.

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This succulent (Echeveria ‘Perle Von Nürnberg’) is so covered in waxy bloom that it seems more violet blue than green. Photo: Leonora Enking, Flickr

Other plants, such as the numerous plants in the Crassulaceae (crassulas, kalanchoes, sedums, etc.) and in the Asphodelaceae (aloes, haworthias, gasterias, etc.) families kept their leaves, but modified them, covering them with a thick cuticle, reducing the number of stomata and turning them into water storage facilities. Their leaves are often covered with white waxy bloom or dense hairs, both of which help reduce water loss by reflecting the sun’s excessively intense rays and thus reduce evapotranspiration.

Relearning to Breath

The evolution of succulents has also led to a rather surprising type of photosynthesis, called Crassulacean acid metabolism or CAM. (In spite of the name, this technique is not limited to the Crassulaceae, but developed independently in drought-resistant plants from many different families.)

Most plants open their stomata during the day so as to absorb carbon dioxide (CO2) and use it directly in photosynthesis which only occurs in the presence of light. In order not to lose too much water to evapotranspiration, they close their stomata at night, when there is no photosynthesis going on.

CAM plants, on the other hand, delay their respiration, opening their stomata only at night when the air is cooler and more humid and thus evapotranspiration is greatly reduced. Therefore they carry out respiration at night, but not photosynthesis, since there is no light. To be able to both breathe and photosynthesize, they store the C02 they absorb at night as malic acid. When daylight comes, they release the CO2 again, inside the leaf, and are thus able to carry out photosynthesis in the presence of sunlight, even though their stomata are firmly closed.

Think of it this way: it’s as if CAM plants hold their breath all day long, even though they’re running marathon, only breathing at night when they stop for a rest! (Ain’t nature amazing!)

Caring for Succulents

20170322E Opuntia polyacantha, Ken Eckert, WC

Opuntia phaeacantha, here growing in the wild in zone 3 (Alberta), is among the hardiest of cacti. Photo: Ken Eckert, Wikimedia Commons

There are succulents adapted to cold climates, especially sedums (Sedum spp.) and houseleeks (Sempervivum spp.), that can be grown outdoors year round in even the coldest climates. There are even hardy cacti (especially certain Opuntia species)! But most succulents are tropical or subtropical plants and when we grow them in colder climates, it’s as houseplants.

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These very unfortunate succulents are growing in terrariums, where high humidity and lack of drainage (so-called “drainage layers” are of no help at all) means their lives will almost certainly be very brief.

Succulents are now very popular with the general public and are used all kinds of ways, even in environments where they don’t thrive, such as in shady interiors and in terrariums. Stylists* have discovered something very interesting about succulents: they grow slowly… and die even more slowly. Even when they are mistreated, they can often survive for months, even more than a year. Therefore stylists can use them in situations that will be lethal for the plants and still get away with it. After all, when a plant dies 8 months after you bought it, you’re not likely to realize the fault lies with the person who designed the planting!

*I like to make a distinction between the people I call stylists, who tastefully arrange plants (slow-dying plants like succulents and air plants are their bread and butter) in containers without any real knowledge of or interest in the needs of the plants they use, and real horticulturists, who do know how to grow plants and would never treat them inappropriately.

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Succulents spray painted unnatural colors. This is, of course, extremely deterimental to the plant.

Some con artists go so far as to spray paint succulents in bright colors (blue, red, pink, orange, even silver or gold!) before selling them to make them more eye-catching. You may hear them claim that this in no way harms the plant, but that is obviously nonsense. A covering of paint reduces the succulent’s ability to carry out photosynthesis, yet photosynthesis is the basis of any plant’s survival. Vendors of painted plants rely on the ability of succulents to survive long-term abuse without dying, that’s all. Such a treatment is more horriculture than horticulture!

Some painted succulents manage to put out new (therefore unpainted) leaves and thus recuperate. If so, bravo for them! But it still doesn’t mean painting them wasn’t mistreating them.

I hope that your goal in growing succulents is not just to see them as temporary decorations to be tossed when they’re no longer attractive, but living plants that you can encourage to grow and thrive. Along that line, here are some tips on really making them happy:

Light

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A corner window with light coming from both sides out to be excellent for succulents, but if you want them to grow well, don’t just open the blinds, lift them!

For the vast majority of succulents, full sun, that is, a spot directly in front of a window with a southern exposure, is ideal. Still, most will adapt fairly readily to the more modest light found near an east or west window, as long as they receive a few hours of direct sunlight each day. Most suffer, however, when they are more than 3 or 4 feet (1 m) away from any window. In winter, especially, when weak sun and short days mean sunlight is extremely limited (at least in homes outside the tropics), they really will do best placed close to a south-facing window.

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Extremely etiolated cactus, showing many months of insufficient light.

When a succulent lacks light, it can show its distress in various ways: stems that stretch for the light (etiolation), abnormally pale new growth, branches or leaves that droop instead of remaining upright or leaves that are smaller than they were at purchase. This is the plant trying to tell you that it’s suffering.

However, some succulents are not so communicative: they simply stop growing when light is insufficient, looking apparently healthy for months, then die all of a sudden, without warning. If yours puts on no growth at all, especially in summer, that’s not a good sign!

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The red edges on the leaves of this jade plant (Crassula ovata) appear only in summer and only when it is receiving the really intense light it prefers.

One sign that the plant is receiving adequate lighting is when the foliage becomes edged in red during the summer months. This shows that they really get the lighting they prefer. This phenomenon is particularly evident in crassulas and echeverias.

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Haworthia fasciata is one of the few succulents that does quite well in moderate light.

There are, however, a few succulents that tolerate some shade (but must still get some daily sunlight). Some haworthias (Haworthia spp.) and gasterias (Gasteria spp.), especially those with dark green leaves, are quite shade-resistant, as are most snake plants (Sansevieria spp.). If you have to place a succulent well back from a window or in front of a north-facing window, they make good choices. Note however that although these succulents “tolerate” low light, they are not true shade plants and actually prefer at least moderate light (the snake plant, for example, will survive in shade, but will only flower if placed in the sun).

Watering

Most succulents have a distinctly seasonal growth pattern. They grow in spring and summer and slip into dormancy (or near dormancy) in late autumn and winter. Therefore, you’ll need to water more often between March and October and less during the winter. Excess watering when they are nearly dormant can easily lead to rot.

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Water succulents thoroughly and let drain.

When succulents grow in a pot with drainage holes, watering is easy. During the spring and summer, water them like any indoor plant, completely humidifying the root ball each time: just pour out excess water that drips into the saucer. Then, before watering again, feel the potting soil, sticking a finger right into it, to make sure it is dry. For most of these plants, watering once a week should be quite appropriate during the growing season.

During late fall and winter, it’s better to let the soil dry out even more thoroughly, to the point it nears bone dryness. It’s more difficult to judge the watering needs of succulents at that season, but at room temperatures, watering every two weeks is usually enough. And if you keep the temperature very cold in the winter (40 to 50˚F/5 to 10 ° C), many will only need watering every 2 months!

When succulents grow in containers with no drainage hole, not only pots, but terrariums or decorative displays with nothing at all you could call a pot, watering becomes much more complicated. Just a little too much water and rot sets in. Usually you have to rely on the ability of succulents to tolerate abuse and water them less than they would prefer. This may leave them in a perpetual state of water stress, but they’re tough plants and can live that way for months, even years, without their suffering becoming too apparent. Try to water such plants a few spoonfuls at a time, but only when their soil is very dry.

Temperature

Most of the time, home temperatures are adequate for succulents: they tolerate both summer heat and the relative freshness of winter without complaint. Nor are they much bothered by air conditioning.

Most desert cacti and agaves, though, prefer a cold winter with widely-spaced waterings, at temperatures between 40 and 50˚F (5 to 10 ° C). In the case of desert cacti, especially, a cold winter helps to stimulate spring or summer bloom.

Air Humidity

Air humidity is not a factor of great importance to most succulents. The air in the type of arid climate to which they are native often goes from extremely dry during the day to very humid at night when temperatures drop, much more than it varies in the average home, where the ambiant humidity rarely tops 50%, so adapting to your home’s range of humidity levels is easy for them.

What succulents tolerate poorly is when the air is constantly moist, as in a terrarium (see Cactus Terrariums: Easy On the Eye But Sooo Hard to Manage). If you do grow them under constantly high humidity, be very, very care not to overwater.

Soil

Succulents are slow-growing plants that need little room for their roots and so can grow for years in the same pot. When you repot them, ideally in the spring, you can use a cactus potting soil or even an ordinary potting soil to which you can add some sand for extra weight if you want. No drainage layer is required.

Many people like to cover the soil in succulent pots with a layer of decorative stones. That can be quite attractive, but remember that you have to push the stones to one side and sink your finger into the real potting soil to judge whether the plant needs watering.

Fertilizer

Fertilize sparingly, at no more than 1/8th of the recommended rate, and only from March to October. Any fertilizer will do: succulents aren’t picky. Actually, even if you never apply fertilizer, they’ll still grow very well!

Propagation

There are many ways of multiplying succulents: stem cuttings, leaf cuttings, division, seeds, grafting, etc. Which method works on which plants is however variable: it’s best to check out the plant’s particulars on-line or in a book about succulents before proceeding.

Insects and Diseases

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Stem mealybugs on an Opuntia. Photo: Ann Verga, Flickr

The three most common insect pests succulents are stem mealybugs, root mealybugs and scale insects. All come in on infested plants, so isolate any new plants for 40 days and inspect them carefully before introducing them to your collection. They can be hard to eliminate and it may be necessary to cull the infested plant.

Root rot and stem rot, caused by a whole range of fungus species, are the most common diseases and are best prevented by not overwatering and by avoiding excessively humid air. Once they set in, about the only thing to do is to try and take cuttings of any uninfected plant part.

A Summer Outdoors

Cactus Plants Nature

Succulents love to spend their summer outdoors.

Most succulents appreciate spending the summer outdoors. Just don’t put them outdoors if they grow in a pot with no drainage hole. Since there is no possibility of evacuating excess water in such pots, even moderate rainfall can lead to fatal rot.

Even if your succulent was growing indoors in full sun on a south-facing window ledge, that doesn’t mean it’s ready for that same full sun outdoors. After all, glass filters out UV rays and it’s UV that burns plants, so its needs to acclimate to the change. Place it outdoors in shade for a few days, then in partial shade for a few days, then in a sunny spot protected from midday sun for a few days. Only after that will it be ready for full, unprotected sunlight.

There you go! A quick overview of succulents and how to grow them. Enjoy discovering the beauty and ease-of-care of these simple plants.20170322AStephen Boisvert