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Germinating Hard-shelled Seeds Such as Mimosa, Acacia and Bundleflower: The Hot Water Technique

A lot of species have hard-shelled seed coats that need special treatment in order to allow moisture to penetrate and reach the embryo so that germination can begin. For many species, including Hawaiian Baby Woodrose (Argyreia nervosa) and Lotus (Nelumbo Nucifera), the process of scarification, which essentially involves wearing down the seed coat by abrasion, is sufficient. But for other plants such as Acacia Maidenii, Mimosa Hostilis, Mimosa PudicaDesmanthus Illinoensis, Desmodium Gyrans, Lespedeza Bicolor and a lot of related species, the seeds are best off being softened by hot water. The simple process of subjecting them to hot water is known among growers as “The Hot Water Tek”.

Some growers will actually choose to use a combination of scarification and The Hot Water Tek in order to maximize results. If that is what you choose to do, you’ll want to start out by sanding, filing or nicking the seed coat. We generally prefer sanding or filing over nicking because it creates a larger surface are where water can penetrate. The key with scarification is not to go too deeply so that you damage the embryo. You just want to rub through the very outer shell of the seed in one spot. Since you’ll be using hot water instead of room temperature water, you do not have to be as thorough.

Next, you want to bring enough water to cover the seeds to a boil. If you’re set on saving time, you could actually begin heating the water before scarifying the seeds so that it will be ready by the time you’re done. As soon as the water begins boiling you want to let it cool just slightly before putting the seeds in. You might think that this type of heat would surely kill the embryo, but that it not the case. The seeds should remain in the water until they sprout, so it is best to pour them into a container that you can set aside for a week or so. From this treatment, most of your seeds should sprout. If there are any that do not, you can repeat the process of heating and soaking. Often you will find that seeds that didn’t sprout the first time around will do so in subsequent efforts. Not every seed will germinate, but this will give you the opportunity to maximize success.

As mentioned before, you want to leave the seeds soaking until they sprout. Some growers plant them right away, but this will give them a better chance of absorbing all the water they need to germinate. It will also allow you to monitor them individually and avoid wasting soil space on seeds that do not end up germinating. It is also a good idea to change the water daily to prevent any bacteria or mold from growing in your water.

As you start seeing sprouts, you can begin plucking them out and planting them in soil with the taproot facing down. The top of the seed should be roughly at the soil line with the root going deeper. By planting the seeds like this instead of letting them sprout in the soil, it will ensure that they get a perfect start. From here, you should simply follow the growing procedures according to the species you are growing. And there you have it: The Hot Water Tek!