Almost everywhere you turn, flats of seedlings are crying out to be bought — from drugstores, from supermarkets, from department stores, and, of course, from nurseries.
Especially tempting are those flower seedlings already decked out with open blossoms, and tomato and pepper seedlings from whose stems dangle promising little fruits. Restraint is needed: Those seedlings that are most tempting aren’t necessarily the best ones to buy.
The ideal seedling makes the transition from seed to open ground without any hesitation in its growth, hardly knowing it has been moved. Such a plant has been well-fed, but not overfed, has been bathed in bright light, and has had no cramping from its neighbors.
Seedlings’ leaves should be lush green, not blue-green or turning yellow or brown. Plant size should be in proportion to the volume of soil, no more than three to four times the depth of the container. Those stems also should be stocky.
If the plants aren’t gangly in their containers, their roots probably have adequate room. You might want to inspect the roots anyway, just to make sure, by gingerly sliding a plant out of its cell. Do not buy a plant that is potbound, with dense masses of roots circling around the bottom of the root ball. A few roots at the edge of a rootball are OK, and means that a plant is just about ready for transplanting.
One more thing to look for is something you might already have noticed, something that might have initially have drawn you to a particular flat of plants. Flowers or fruits, of course. They are bad signs — those flowers or fruits.
Stress, such as cramped roots, often makes plants flower or fruit prematurely. Tomato fruits already on a young seedling will ripen, and ripen early, but the plant ultimately will produce fruits that are small and few. Broccolis already beginning to head up will produce only “buttons.” Flower plants already flowering will be stunted although they might recover if you pinch the flowers off.
Any seedling that you finally buy — seek those stocky, verdant, and not flowering, fruiting, or overgrown — spent most of its life in a greenhouse, so it needs to get accustomed to the bright sun, wind, and cooler temperatures of the real world. After you buy them, keep seedlings outdoors in a spot sheltered somewhat from the elements for about a week before transplanting them into the garden.