Autumn Tree Planting
and other Fall Gardening Tips

Late summer and fall is a great time to take advantage of end of season sales at nurseries and plant some trees and shrubs. With the heat of summer over, plant water needs are less and roots make good growth in the warm soil. Just be sure to plant early enough that plants get a head start before the ground freezes.

It takes less than a minute in bright sunlight for small feeder roots to die, so protect the roots before planting. Without these, the plant must struggle to absorb moisture; transplant shock will be greater and survival lower. Make the planting hole at least a foot greater in diameter and six inches deeper than the plant's rootball. If your soil is heavy, loosen it on the inside of the hole.

In general, plant at the same depth as the plant grew in the nursery. Set the graft union on fruit trees about two inches above the soil line and the union on grafted roses about two inches below the soil line. Use plenty of water in the planting hole, but no fertilizer. And finally, put a thick organic mulch around the plant to protect it from winter damage. Be sure to allow space between the trunk and the mulch to avoid rodents' nesting next to the trunk.

If you form a basin around the base of the tree to hold irrigation water during establishment, be sure to break a hole in one side of the mound before winter. This allows puddle water to drain away from the trunk, preventing it from freezing and damaging the trunk and root system.

Renewing Perennial Beds

Fall is also the best time of year to renew your perennial beds and divide spring-flowering perennials. Most perennial plants need to be divided every couple of years in order to remain productive, but at the very least, clean up your beds to reduce overwintering pests.

To renew your beds, dig up and remove the perennials and all weeds that have encroached upon the garden. Work liberal amounts of compost into the beds. That means applying a layer of organic matter at least two inches deep and digging it into the soil. Remove the dead tops of healthy plants, leaving two-inch stubs, and discard any that have dead or damaged crowns and roots. If your plants are too big, divide them and reset the divisions at the same depth they grew previously.

Some perennials are comparatively short-lived. Columbine, lupine, delphinium, and some flax die out after a few years. If your plants are old and unhealthy, discard them for new ones. On the other hand, iris, phlox, and the hardy asters can live for many years. Lift and divide these every year or two to keep their blooms large and healthy.

Peonies often do poorly if disturbed, so leave them in place during bed renovation. However, if it's time to divide them, lift the plant from the ground with a spading fork, remove old dead stems and cut the crown into sections that each have several buds. Be careful not to damage the roots. Peonies that are planted too deeply won't flower, so be sure to replant the sections so the buds are no deeper than two inches below the soil surface. Mulch, after the ground has frozen to help avoid fluctuating temperatures. If you have a peony that you suspect might have been planted too deeply, take a spading fork and gently lift the crown. Do not remove it from the ground, just lift it so it is not planted as deeply.

Vegetable Garden

In the vegetable garden, rhubarb benefits from division. Lift the dormant crown using a spading fork and cut through it dividing the crown into sections. Be sure there is at least one main bud on each section you replant. Before replanting, prepare the soil by digging in manure or other organic matter. Replant the parent and move or give away the other sections. On light soils, plant the set so that one inch of soil covers the buds. On heavy or wet soils, plant so the buds are just above ground level. If you have several plants in your garden, space them 2 1/2 to 3 feet apart. It's also a good idea to place perennials to one end of your vegetable garden for ease of cultivation.

Fall, after the first hard frost, is a great time to work outside. The days are no longer beastly hot, and it's a pleasure to get out in the garden.

Source: Montana State University Cooperative Extension.

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