Which type of seeds should be soaked before planting, and for how long? Question from Lisa of Auburn, Washington
Answer: The seeds of many different plants benefit from presoaking to encourage faster germination. With thousands of seed-grown plants on the market, I cannot speak to every single one, but I can provide some general groups that benefit from presoaking.
When it comes to soaking time, allow seeds to soak for 12-48 hours. Those with thinner seedcoats should require less time, and those with thicker coats will need more. Always use fresh water. I like to soak mine in clear glass, so I can watch them swell. Be sure to label each seed-containing glass, so you don’t forget what’s what. After soaking, I always plant my seeds in Black Gold Seedling Mix.
Seeds That Benefit from Presoaking
Most legumes, or plants in the bean family, have seeds that benefit from presoaking in fresh water. These are very satisfying to watch because they really swell as they take in water. The seeds of some commonly grown ornamental legumes, like sweetpeas (Lathyrus odoratus), have very thick, nearly watertight seed coats that need to be gently nicked or filed along the surface to open the coat and allow water in. This can be done with a nail file or cutters. Watch the video below to learn how.
Morning glories (Ipomea spp.) and cannas (Canna spp.) also have seeds that should be nicked and soaked to encourage faster germination.
Other common garden seeds that appreciate a soak are those of basil, beets, chard, corn, and squashes. Some folks also presoak tomato and pepper seeds.
Presoaking can also be educational. When larger seeds float instead of sinking, this often means that they are dead.
Happy seed starting!
Black Gold Horticulturist