Until I complete my greenhouse (still in the fantasy stage) I won’t have a lot of space for plant propagation. But I do have a small but effective system for germinating seeds and rotating them into the garden. The system consists of a flat, a 50-cell tray, a ventilated dome, a heat mat, and small LED grow lights. This is a much smaller system than the ones you often see for sale, but it’s enough to keep me busy potting up seedlings.
I’m using Rapid Rooter plugs, a soilless sponge-like planting medium from General Hydroponics. The plugs have a small hole on the top. According to the manufacturer, they are a “unique matrix of composted materials bonded together with plant-derived polymers. Rapid Rooter provides the optimal air-to-water ratio within the plug matrix resulting in explosive early root growth.” The plugs are said to be organic, and I hope that is so. A main reason that I like these is that they are clean and neat. My tray is in the kitchen, and I like that these do not create any kind of mess. In addition, they seem to germinate seeds more successfully and faster than other media. (They can also be used for cuttings.) The picture below shows the tray just a few days after planting. This tray mainly has Asian vegetables from the Kitizawa Seed Co.; I will have more to say about that later.
The main downsides of the plugs are that they are a bit expensive and can’t really be reused. Instead, once the plant is rooted the entire plug is put into the soil. Also, the plugs sometimes seem to sort of float up in the garden rather than remaining level with the surround soil. I’m thinking about a way to improve that. (BTW, most of the information on the web about these is about growing cannabis. But that is one thing I do not grow.)
The plugs should be watered when they start to dry out. At first I was overwatering, and I started to get mold. Of course, as this is essentially a hydroponic rooting system, you never want the plugs to dry out.
Until the sprouts come up, I run a small heat mat to warm the plugs. It’s supposed to warm the rooting material by about 5 degrees over the ambient temperature. This is helpful for the majority of seeds. After the seedlings come up I turn off the mat.
I had a problem with the seedlings being leggy. This makes them floppy and weak at the base. It’s a sign of insufficient light. To solve this I purchased a small LED grow light. I knew I wanted LED for low heat and low energy usage. Even then the really strong systems are quite bright, large, and expensive (I supposed that’s what you’d want if you had a big operation growing cannabis or something.) For my purposes this little dual-head 10-watt desk clip grow lamp seems to be working fine. It costs less than thirty dollars. It emphasizes the red and blue ranges of the light spectrum because that is what the plants utilize best. As I understand, full-spectrum daylight grow lights, by contrast, are wasteful of energy.
I’m currently using little bamboo plant labels at this stage. For long-lasting labels in the garden I use zinc labels that react chemically with carbon pencils. Everything else eventually fades.
I find a book from the American Horticultural Society a good resource on plant propagation (I also have their excellent garden encyclopedia).