Seed packets are full of important information… if you can understand it.
Wouldn’t it be nice if some sort of international commission could force seed growers to all use the same symbols and terms on their seed packets? And then all that information could be published on a chart or website for all to see? Unfortunately, that isn’t about to happen, so when you pick up a seed packet in your garden center, it’s up to you to try to interpret the sometimes arcane information and symbols found there.
Here’s my attempt at straightening things out. If you see something I missed, let me know!
Front of the Packet
The front of the seed packet usually bears a colorful picture of the plant whose seeds are found inside, but not always. Some companies, notably those dealing with heirloom vegetables or organic seeds, as well as smaller companies that can’t afford color printing, stick to simple paper envelopes with only written information in black ink.
The front of the seed packet always includes the name of the plant, most often its common name if it’s a vegetable, sometimes the botanical name as well, especially if the plant is a perennial or shrub.
If it’s a cultivated variety rather than just a generic variety, the name of the variety will be shown, for example: ‘Sungold’ Cherry Tomato or ‘Autumn Colors’ Sunflower instead of just Cherry Tomato or Sunflower.
Usually if the plant is a hybrid and therefore not true to type, the name will include F1 or F2 or the word “hybrid”. Failing this, you can usually presume the plant is open pollinated (OP) and therefore that you can harvest the seed to sow in future years.
Oddly enough, many seed packets fail to mention whether the plant is a vegetable or an annual (apparently, this is something you’re just supposed to know!), although most will tell you if the plant is a perennial or a biennial.
The front of the seed packet always includes the name of the seed company and its logo and often includes the price. Any special selling point, such as “organic”, “heirloom variety”, “long blooming season” or any award the plant may have won (AAS winner for example) is also likely to be highlighted on the front of the pack.
Either Side of the Packet
The following points are found on either the front or the back of the seed packet.
Days, Days to Maturity, Days to Harvest or Harvest (vegetables), Days to Bloom (flowers): This information appears straightforward… but is not.
When applied to seeds intended to be sown directly in the garden, this is the number of days between sowing and harvesting or first bloom… and that makes perfect sense. However, if the seed needs to be started indoors, it indicates the number of days to harvest or bloom from when the seedling is transplanted outdoors.
Therefore a bean labelled 70 days will be ready to harvest 70 days (approximately) after you sow it, because beans are sown directly in the garden. However, a tomato labelled 70 days will have to be started indoors 6 to 8 weeks earlier and will produce 70 days (10 weeks) after it is transplanted, therefore it will really take 16 to 18 weeks for it to be ready to harvest. That’s a huge difference!
Seeds that are always started indoors include tomatoes, peppers, and eggplants (among vegetables) and a huge range of annual flowers, such as petunias, impatiens, begonias and pelargoniums.
Note that, under average garden conditions, plants are usually ready to harvest a few days later (if not a week or more later) than the days to maturity given.
Quantity or weight plus packed for dates are usually indicated on the packet.
Sell by, Exp., Expiry, Packed for: Seed packets should indicate somewhere what year the seed was produced for and/or when it should be removed from display. This is often overprinted on the packet in letters unlike the others, often in a margin or at the bottom of the pack. How it is expressed varies greatly from one seed company to another.You can store leftover seed for future years (see Storing Leftover Seeds), but its germination rate will likely drop over time, so it’s always best to buy fresh seed put on the market for the current year.
Contents: The weight of the contents, the number of seeds in the packet or the length of row it will cover usually appears somewhere on the packet. Since few companies express this information in the same way, it’s unfortunately very hard for gardeners to do any comparison shopping.
QR Code: Quick Response codes are bar codes that can be read by smartphones and other mobile devices and can direct you to further information about the product. Not many seed packets carry them at the moment, but that may change in the future.
Disease Resistance Codes
Not all seed packets mention this important detail, but it can be vital to gardening success, especially in the case of vegetables. Usually disease resistance is simply expressed as a series of letters, often following the plant’s name. In the example above, Tomato Roma VFN, the letters indicate plant offers resistance to verticillium wilt (V), fusarium wilt (F) and nematodes (N).
Here are the most common codes:
ALS Angular leaf spot
ALT Alternaria blight
BV Bean virus
CBMV Common Bean Mosaic Virus
CMV Cucumber mosaic virus
DM Downy mildew
F Fusarium wilt race 1
FF Fusarium wilt races 1 and 2
FFF Fusarium wilt races 1, 2 and 3
NY New York mosaic
Ph, PHR or LB Late blight
PM Powdery mildew
T, TMV or ToMV Tobacco mosaic virus
V Verticillium wilt
Back of the Packet
The following information is mostly likely to be found on the back of the packet.
The plant description contains all sorts of useful information.
There is usually a short description of the plant, including its taste or size if it’s a vegetable, or, in the case of flowers, its color or color range, whether the flowers are single or double, large or small, etc. Any special qualities, like whether it stores well or freezes well (vegetables) or makes a good cut flower or attracts butterflies (flowers) may also be mentioned here. The description is often flowery and overblown, but usually the essential information is there if you read it carefully.
The description can contain all sorts of truly helpful information shortened into just a few words… which you are expected to understand even though they are not always that obvious. Here are some of the terms to look out for… as well as what they mean.
Bush or Pole (beans): refers to the plant’s habit. Some beans form a short, compact plant (bush) and produce all at once while others are climbers (pole) and produce over a long season.
Cool-season: Plant that will germinate and grow best in cool weather, usually in spring or fall.
Determinate or Indeterminate (tomatoes): Determinate tomatoes form smaller plants that may not need staking. They tend to be early and produce all their fruit at once. Indeterminate tomatoes grow all season long and need staking. They tend to be slower to mature, but produce fruit over a long season.
Harden off: Gradually acclimate seedlings started indoors to outdoor conditions.
Hardiness zone: Information given for hardy plants, notably biennials and perennials. The number shown indicates the coldest zone in which the plant will be hardy (able to survive the winter). For example, zone 5 means it will be hardy in zones 5, 6, 7, 8 and 9, but not in zones 1, 2, 3 and 4. You’ll find more information on hardiness zones here.
Height and Spread (Diameter): This information is included for ornamental plants, but rarely for vegetables (although you have to wonder why not: after all, knowing how tall a vegetable will become can be very handy when planning a vegetable garden). The measurements may be included in the plant description, listed separately or be shown through icons.
Pelleted seed: seeds covered in a product (usually clay) that facilitates their handling. Multi-pellets are pellets that include several seeds and are used for plants that look best when grown in a clump, such as bedding lobelias.
Running, Bush or Non-Running (squash): Running refers to squashes (marrow, pumpkin, zucchini, etc.) with long creeping stems while bush or non-running indicate more compact or rosette-forming varieties, the latter a better choice for smaller gardens.
Treated seed is often artificially colored (left and below) to distinguish it from untreated seed (above).
Treated or Untreated Seed: Treated seed has been coated with fungicides to prevent damping-off and other diseases that can reduce germination and will not be acceptable to organic gardeners. Untreated seed has not been treated.
On many seed packets, icons above reveal most of the information.
The packet will indicate the sowing depth (if this is not indicated, sow the seed at a depth equivalent to four times its diameter), seed spacing, row spacing (vegetables), plant spacing after thinning, etc.
If the seed should be sown indoors, this will be mentioned and the sowing temperature may also be included. If no temperature is mentioned for indoor sowing, assume 70 to 75°F (21 to 24°C) is required.
Days to Germination/to Emerge: This explains how long you can expect to wait until the seeds start to sprout under normal growing conditions. Cold conditions, however, could slow germination considerably.
Many companies use icons to express the above information.
When to Sow
Sowing at just the right time is imperative in getting plants to produce and bloom early and over a long season, so this bit of information is very important. That doesn’t however mean that it is always clearly explained. Here are some terms and examples you might see.
Zone maps: These are supposed to help show you when to sow, but I find them too vague to be of much use… and they never seem to cover Canada!
Start/sow indoors: Seed needs to be started indoors in early spring.
Sow as soon as the ground can be worked: This means to sow outdoors early in the spring, after the ground has not only thawed out, but is no longer soaking wet. Temperatures are usually still quite cool.
Sow when the soil warms up: Unless other details are given, assume this means when the soil reaches 65˚F/18˚C.
Sow after all danger of frost is past, after final spring frost, after average last frost, after the danger of spring frost, after last frost, etc.: This does not refer to the average last frost date that your local weather station might give you… or at least, should not. Remember that “average” means there’ll be a frost after that date about every second year. (That’s what average means!) What you need is the “frost-free date”, one at which there is little to no risk of frost, probably at least 3 weeks after the average last frost date. Ask your local garden club when they consider all risk of frost to be over for the season… but always be ready to adapt to any special weather conditions. An extra cold spring would mean delayed sowing for many seeds, for example.
Sow/start (indoors) xx to xx weeks before last frost: First find the frost-free date for your locality (see previous paragraph), then count backwards the number of weeks mentioned to determine when to sow indoors.
If you sow your seeds inside your home where warm temperatures are the norm, the lesser of the two dates will give the best results (i.e. if the packet indicates 6 to 8 weeks, choose 6). If you sow in a greenhouse, where lower night temperatures are likely and therefore where seedlings will grow more slowly, choose the greater of the two dates.
Hardy annual: One that can be sown outdoors early in the season and will quickly comme into bloom where it is sown. It can take light frosts. Among flowers, calendula, sweet pea and sunflower are hardy annuals. Most root vegetables and many leaf vegetables are hardy annuals, including spinach, beets, carrots and kale.
Half-hardy annual: One that needs to be started indoors in temperate climates and can be planted out after all risk of frost has passed, but while temperatures are still cool. It can be sown outdoors in mild climates with a long growing season (zones 7 and above). Examples of half-hardy annuals includes nicotiana, petunia and zinnia while cauliflower, celery and lettuce are half-hardy vegetables.
Tender annual: One that needs to be started indoors in short-season areas and shouldn’t be planted out until both the soil and the air have warmed up (minimum temperature: 55˚F/13˚C). Examples among flowers are begonias, coleus, celosias and impatiens while tomatoes, eggplants and okra are tender vegetables.
Special Sowing Needs
Many seeds have special needs in order to germinate (sprout). Here are some of the terms used and their explanation.
Cold treatment required, stratification required, stratify seeds, pre-chill: These terms means the seed must go through a cold period before germinating. Usually they should be sown in pots and placed in a refrigerator for several weeks before exposing them to heat. Many perennials require a cold treatment. For more information on cold treatment, read Time to Give Hardy Seeds Their Cold Treatment.
Direct-sow: Sow seed outdoors in the place where the plant will grow.
Don’t cover: Sow these very fine seeds on the soil surface, without covering them in soil afterwards.
Needs light to germinate: These seeds only germinate in the presence of light. Most often, they shouldn’t be covered. Place your indoor seed trays in a brightly lit spot aster sowing.
Needs darkness to germinate: Sow these seeds as per other instructions, then put their containers inside a dark plastic bag until the seeds sprout.
Sow in hills/mounds: Sow outdoors in small mounds, 5 to 6 seeds per mound. This technique is used for squashes, cucumbers, melons and, sometimes, corn (maize).
Sow in peat pots: Some seedlings won’t tolerate root disturbance and it’s best to sow them in biodegradable pots, peat pots being the best-known kind. You can then simply plant these seedlings pot and all in the garden and roots will grow right through the peat pot into the surrounding soil.
Full sun, moderate watering: sometimes icons tell it all!
The seed packet will certainly indicate basic growing conditions for the adult plant, notably whether it needs Full Sun, Partial Shade or Shade.
Soil quality may or may not be mentioned, as it is often simply assumed you’ll be sowing in rich, well-drained, slightly acid soil unless the plant has special needs (some plants do better in poor or moderately acid soil, for example).
Watering needs may be mentioned, but again, the assumption is often made that your plant will need “moderate” watering, that is, thorough watering once the soil has nearly dried out, so this need may not be included.
If the plants needs to be deadheaded (that is, have its faded flowers removed) in order for it to rebloom, or staking or trellising, that may be mentioned.
Icons are often used to express some of the above growing conditions.
Those little seed packets pack a lot of information in very little space, not all of it readily comprehensible. I hope this article will help you better interpret the valuable cultural details they offer.