“As the twig is bent, so grows the tree” is a good maxim, as relevant to raising children as it is to training a tree’s upper scaffold. But in spring, when many of the plants in our lives are seedlings, it pays to look downward. As the roots are nurtured, so grows the tomato.

For vegetables that are commonly direct-sown, such as spinach, carrots and peas, a good start is a simple matter of great soil and proper timing. Those that are started indoors and later transplanted into the garden have the advantage of an earlier start, safe from the whims of spring weather, but this carries a risk. If their roots are constrained, just at the time they should be reaching out into the soil, the plants will be stunted and never as healthy or productive as they could otherwise be.

With cucurbits such as squash, cucumbers and melons, which are rapid growers, being held back in pots for longer than two or three weeks is especially injurious. Because they aren’t planted until May, starting them now indoors would be a mistake. And with our long growing season, there’s little advantage to starting them inside.

The crops most likely to be started ahead with good results are other heat-loving ones such as tomatoes, eggplants and peppers. With fruits at stake rather than just leaves, it’s natural to want to hurry them along, but putting them in the ground before the soil has warmed will not hasten their growth, and confining them too long in small containers can be even worse. The tops will be leggy and the roots diminished.

You find this problem with seedlings that have waited too long at the garden center. You can try to tease apart their little plugs of white, matted roots, but the plants they become will win no prizes. That’s why it’s such an advantage to start your own, provided you time it right.

It pays to invest in a good collection of plastic pots that you can reuse every year. The ones I have are black, about five inches across at the top, and hold more than a quart of soil.

Many nurseries use them for potting perennial flowers and are often willing to sell you some. You or a friend might have a stash of them sitting in the garage or potting shed right now. They last for many years and stack easily for storage.

We use them for the trio of fruiting crops noted above and for artichoke plants, which we start even earlier. Because artichokes are biennials that bear the second year, we give them a few weeks of chilling once they are six weeks old, in an area safe from hard freezes, so that they think they’ve gone through their first winter and are ready to make those yummy buds. So it’s essential that they have plenty of room to grow.

When transplanting these crops, it’s important to encourage good root growth by digging a roomy hole in soil that’s loose enough for good root penetration. A shovel with a scooped shape and a pointed tip works fine, but at our farm we’ve found an unexpected ally in the post hole digger. Grab it by its two handles, plunge it into the ground, and pull the handles in opposite directions. Lift the digger, and you’ll see a hole wide and deep enough for the root ball of a plant knocked out of a pot up to six inches wide. Nestle it into the ground, and its roots are off and running.

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Barbara Damrosch is the author of “The Four Season Farm Gardener’s Cookbook”; her website is www.fourseasonfarm.com.