No Need for a Drainage Layer

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Old myths die hard and one myth that refuses to die is that houseplants need a “drainage layer”. It used to be believed that you had to put a layer of gravel or pot shards at the bottom of a pot to improve drainage. But in fact, it’s the other way around! Too big a difference between the size of the soil particles and that of the drainage layer materials actually helps prevent excess water from escaping.

Besides, when you unpot a greenhouse-grown houseplant, one therefore produced by professional horticulturists, where is the drainage layer? There isn’t one, is there? Growers abandoned this old technique ages ago. Studies showing that drainage layers were a waste of time go back to the 1970s! Yet some 40 years later, people still add one.

Not sure? Here’s another way of looking at it. Almost every flower pot has at least one drainage hole, if not more, right? Do you really think that surplus water would stay in a pot with a hole in the bottom?

Next time you repot a houseplant, therefore, just fill its pot with growing mix from bottom to top. Sometimes gardening really is incredibly simple!

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10 thoughts on “No Need for a Drainage Layer

  1. The practice is still widespread in the uk. But it is promoted so that the roots of the pot plant won’t grow into the gravel/pot shard area and therefore won’t have a chance to stand in water and rot. For a plant that is to spend its entire life in a pot on a terrace or as a feature in the garden it is worthwhile (especially in wet winter areas) but for just potting plants on, I agree, it is a waste of time and it is better to simply use a free-draining mix. The other way of course to avoid pots standing in water is to raise them on pot feet.

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