5 STEPS TO GROWING GREAT PLANTS FROM SEED

Lots more seed trays will be joining these soon.

Caring for seeds that are waiting to germinate or just starting out pretty much comes down to these three things. For light, I’m going to be honest: In almost every case, you’re going to need supplemental light. Keep it close—within inches—and on for about 18 hours a day. I don’t have nearly enough light to grow all the plants I start, so I give them a good start under the lights and then move them to the sunniest location I have to make room for more seeds needing a good start. If they start getting spindly, I’ll pop them back under the lights on a rotating basis.

As for heat, that mostly applies to germinating seeds, so once you have sprouts, it’s not as important. I feel like it’s better to leave seeds on heat until about three-quarters of them have germinated, although keep in mind that most lights will produce a fair amount of heat as well.

When it comes to moisture, you want moist growing medium for seeds. In general, I think the dampness of a rung-out sponge is a good guide for what you want. I also think that watering from below by soaking a seed tray, is preferable than watering from above. If you have to water from above, use a spray bottle on the misting function. I have been using soil blocks for a lot of things and I will just fill the bottom of a tray with about a quarter inch of water and the soil blocks just suck it up. Be aware that seed trays that aren’t covered will need water much more frequently than those that are covered.

Unless you start seeds in large pots, which only works for some things like sweet peas and beans, you’ll probably need or want to repot seedlings at least once into larger pots. Keep an eye on the root growth of seedlings; when you start seeing roots pop up around the sides it’s time to repot. Soil blocks allow roots to “air prune” to a certain extent, which is helpful, but if you plant in little modules, you want to make sure to pot on before they start going in circles. It’s not good to go up in size by a lot when you repot, so I usually go to a three- or four-inch pot. Use a regular potting mix at this point, but not one with fertilizer in it as seedlings are still susesptible to burning. And watch the watering, because it’s easy to overwater a seedling after repotting.

5. HARDEN THEM OFF

Small plants hanging out in the temporary greenhouse as they harden off. You can see the garden fabric to the left that I was using to cover some seedlings that had recently come outside and needed some additional protection.

All of the hard work and effort you’ve put into raising healthy little plants can be erased in one night if you don’t properly harden them off. Hardening off plants is the process of gradually getting them used to being outside before they are planted in the garden. Temperature is a factor, but sun is even harder for plants to get used to. You can harden off plants anywhere, just start in a shady spot for a few days and then bring them in at night. Gradually work them into more sun. Garden fabric (I’ve always called it row cover, but maybe that’s not right) is also very helpful to keep plants shaded during hardening off.

I used to load up a wagon with seed trays and pull it around the yard to adjust for the sun when I was hardening off plants. At night I’d just pull it into the garage to protect plants from low night temperatures and browsing creatures of the night. These days I use a temporary greenhouse to harden everything off.

I like to give the hardening off process an absolute minimum of a week, but usually more like two or even three weeks.