Starting transplants for the home garden accomplishes two things: it provides a reminder that spring is on the way, and it allows your plants to get a jump on the growing season. Certain crops – tomatoes, peppers, and squashes to name a few - require a longer growing season than we see around here. If we were to plant seeds directly in the garden, we probably wouldn’t see much to show for our efforts, or at least not until the very end of the growing season. By starting these plants indoors, we stand a much better chance of good results during the growing season. The following are a few considerations for the best success.
Lots of crops benefit from an early start, but they vary in just how much time they need to grow prior to transplanting in the garden. Onions, tomatoes, peppers, and eggplant require the longest - six to eight weeks prior to transplanting; that means you will need to start them sometime around mid- to late March in order for them to be ready by late May. Crops in the Brassica family – cabbage, Brussel sprouts, broccoli, etc. – require four to six weeks. Cucumbers, squashes, and melons require only four weeks, so you can start them in early May and they’ll be ready to plant by the end of the month or in early June.
Because you are dealing with young, tender plants, you need to pay close attention to the conditions in which these plants grow. Your seedlings require 14-16 hours of light each day. While some like to keep their newly seeded flats on a sunny windowsill, this clearly does not provide enough light for good plant growth. You can purchase a small-scale grow light from many garden centers or suppliers, but you do not necessarily need an elaborate setup or special bulbs. A set of two fluorescent lights, one ‘cool’ and one ‘warm’, will give you good results. Keep the light source 3-4 inches above the tops of the growing seedlings.
Seedlings also need warm temperatures to grow, somewhere between 55-65 degrees Fahrenheit. Ambient temperatures in the living areas of most homes should be fine, but you may want to think about providing additional heat if you keep your seedlings in a cool basement or greenhouse. An electric heating pad is useful for warming things up a couple degrees, and it might be worthwhile to purchase one if you start a lot of plants indoors.
Like all growing things, seedlings need plenty of water and nutrients to grow. We recommend using potting soil for transplants, which often does not have a lot of plant nutrients in it. Water seedlings frequently enough so that the potting soil is always moist, but not excessively damp, and use a soluble fertilizer regularly.
We need to pamper seedlings in the beginning in order to get good strong growth. However, it is different in the ‘real world’ environment of the garden, where plants need to be able to endure occasional heavy rains, dry spells, and temperature fluctuations (maybe all in the same day, no less!). Subjecting tender seedlings to these conditions abruptly is too stressful; we need to provide a gradual adjustment, or what we call a hardening off period. The process starts about 10-14 days prior to when you intend to put the transplants in the garden by stopping fertilization and gradually exposing the seedlings to cooler temperatures and less moisture. You may only set the plants out for a few hours for the first couple days, but after a couple weeks you should be able to keep them outside both day and night (keep them indoors if there’s a frost in the forecast). We don’t keep the potting soil moist constantly, but we do not want it to dry out to the point where the seedlings wilt either.
There are few things to keep in mind when the time comes to transplant your seedlings to the garden. Even though you have hardened them off, these plants are still young and tender and need a little extra care. Seedlings, especially vine crops, have fragile root systems, and careful handling will prevent damage that keeps the plants from getting established. Pick a relatively cool, cloudy day for transplanting instead of a hot, sunny day that stresses the seedlings. Make sure there’s good soil-root contact by firming the soil firmly around the roots, and provide plenty of water during the first few days after transplanting. Your plants will reward your efforts with a bountiful harvest this summer.