Trees are one of the biggest garden investments homeowners can make. A quality tree can set off a landscape, not to mention cut down on utility bills.

Trees provide an array of wonderful benefits from flowers, to fruit, to fall colors, not to mention habitat for birds and other creatures. A yard without trees might as well be located in Phoenix.

Can you have too many trees? I'm trying to figure that out. More trees mean less grass and less sun-loving plants. Fortunately, there is no law that says grass is needed, or that peonies and iris have to be planted.

But like any investment, you have to provide some input. Most homeowners, I kid you not, believe that if you spend all your efforts on the tree the first year, you can sit back and do nothing for the next 50. You wouldn't do that to a child, so why a tree? (And trees are actually cheaper in the long run and don't talk back.)

Fall is the ideal time to plant many trees. Besides finding great deals at nurseries and garden centers, trees planted in the fall seem to establish faster than those planted between May 1 and September 1. Part of the reasoning has to do with soil temperatures and heat stress on the tree.

Planting in the fall doesn't stress the canopy or leaves of the tree. Leaves are turning and falling anyway. Essentially, though not totally accurate, the branches are going dormant. That puts less stress on a root system that has to get established.

Soil temperatures are ideal for root growth, and with less need to support all the water-sucking leaves, the roots establish quickly, growing and developing for next spring's push.

If the soil is loose, and kept from freezing for as long as possible with a six-inch layer of mulch over the planting hole, the roots will continue to grow, even when it looks like nothing is happening.

That's the first investment-a properly planted fall tree.

The next big investment is water throughout the growing season, especially in the autumn. A dry autumn and winter can do more damage to the tree than extreme cold. Without water, the roots may not grow and store nutrients for next year. It's not uncommon for me to saturate the root system of the plants weekly during October and November.

Which leads to the third investment-fertilizer.

One of the best times to fertilize a tree is in October when leaves are turning color. You're probably thinking, "But the tree isn't growing, and in fact, it's losing leaves." You'd be right with those thoughts.

Trees, though, don't think like humans. Fertilizers applied in the fall benefit next spring's flush of growth. Roots store the nutrients, especially if the soil remains on the cool side.

In most cases, if you fertilize the lawn, you'll be fertilizing the trees. However, if the turf doesn't get fed, it wouldn't hurt to fertilize the tree.

The simplest method is to punch a three-quarter-inch hole in the ground at the dripline of the tree. Go down 18 inches. (I use a 3-foot piece of rebar from an old construction site.) After punching the rod into the ground, pull it out (that's why you need 18 extra inches), and move about three feet around the tree. Once you've ringed the tree with holes every three feet, move out three feet and do the same.

If your shade tree is more than 40 years old, you could probably go three feet in toward the trunk and make another series of holes.

Put about six to eight ounces of a general fertilizer such as 10-10-10 in each hole. If you have some extra soil, you can scatter it on top. If you don't, just water and watch the soil collapse and fill in the hole.

You probably don't need to fertilize more than once every five years.

Remember that fertilizer won't cure a sick tree. It might help it along, but you need to first identify why the tree is sick.

An important thing to do this month: If you still have a poinsettia from last year and want it to bloom by Christmas, make sure you put it in absolute darkness from 5 p.m. until 8 a.m each day.

David Robson is an Extension Educator, Horticulture, at the Springfield Extension Center, University of Illinois Extension, P.O. Box 8199, Springfield, IL 62791. Telephone: (217) 782-6515. E-mail: drobson@uiuc.edu

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