Fall is planting season for many plants, including trees. Careful planting of trees to allow for good root flare, as pictured, ensures they get the air they need to grow and thrive.

Fall is the best time of year to plant most trees, shrubs and perennials here in southern Delaware. The weather is cool, and it is generally beautiful out. Fall isn’t quite over yet, either — you still have time.

In late summer and early to mid-fall, plants (trees, shrubs and perennials are all plants) start moving the sugars and nutrients that have accumulated in the leaves down to the roots to develop a strong root system. This root system helps the plant get through the winter. This process makes fall the best time to plant most plants. Also, in fall, the tree can make new roots without having to feed its leaves, since they will fall off soon. Water requirements are much lower without the leaves on the tree.

Additionally, the ground is warm in fall, encouraging those roots to spread. Our summers here are hot enough that it can be a little more stressful on a plant, particularly a slower-growing one, to get established during the summer. Our winters are generally mild, though, making it easy.

A final reason to prefer fall planting is all the great plant sales! Many nurseries and garden centers don’t want to overwinter their plants so will sell them at a discount — a great time to get what you need.

So, when you get home with your new plant, what do you do? How do you plant it?

  • Pick the right spot — make sure the plant’s eventual, full-grown size will fit; it has the right amount of sun or shade and moisture; it’s in the correct soil; it fits its intended purpose. Get your soil tested a few weeks beforehand if you have any concerns;
  • Take the plant out of its container, or if it’s been balled and burlapped, remove the wire cage and all the burlap;
  • For shrubs and trees, shake off as much of the soil it came in as possible. This is not as necessary with perennials;
  • Don’t worry too much about disturbing the roots in this process, they will grow back;
  • Inspect the roots — you want them to spread out radially, like the spokes of a wheel. You do not want them to circle around and around. If they are circling, and you can tease them out with your fingers, do so. If they are too woody, which might be the case for some trees, cut them where they bend, where they start to circle, they will branch out. The root going around in a circle is called a girdling root, and it might kill the tree eventually. For perennials, just make a few slashes along the rootball, and cut off the bottom if it was severely rootbound.
  • Look for the root flare, particularly in trees — this is where the roots of the tree start to flare out from the trunk to become the root system. Many trees will be too deep in their nursery pots, you might need to scrape away up to several inches of soil from around the trunk, but make sure you do this. Recent research has uncovered the fact that most trees’ roots are relatively shallow, and air exchange happens in this shallow area. Burying those roots makes it very difficult for the tree to get the air it needs and will contribute to its failure.
  • For trees and shrubs, when you have inspected the roots, and gotten them ready to grow outwards, then you can dig the hole. It’s better to wait to dig, since you won’t know how big to make the hole beforehand. Dig the hole large enough to accommodate the root system or root ball. When possible, dig a hole 2 to 3 times the width of the root system, and the same depth as the root ball, to the root flare. The sides of the hole should slope toward the bottom of the root ball.
  • Place the plant on a slight mound in the hole. Spread the roots out. Back fill the hole with native soil, not amended soil. If you amend the soil you put back, you’ve just created a larger pot for the plant to grow in; you want to encourage the plant to grow well in the native soil, which amending the soil won’t do. If you have picked the right plant for the spot, it will adjust and grow in the native soil just fine. Create a small berm around the edge of the roots to keep water in when you water.
  • Mulch it with a good layer of compost (more if you’re planting in a new development with no topsoil), then mulch on top.
  • Water it in well, and remember to keep the plant moist for the next 6 months to a year.
  • Enjoy your beautiful, healthy new plants!