End of the Gardening Season Reminders

By C Rae Hozer, Cumberland County Master Gardener

A number of readers have asked why irises and rhododendrons in their yards were blooming during September, October and November rather than in the spring as they normally do.

Winter-2006 through autumn-2007 weather in the Upper Cumberland region of Tennessee has been far from typical. Unusual weather patterns can confuse plants. Perennials growing in temperate zones where frosts and freezes occur, take cues from their surroundings to know when it is time to go into a dormant state for the winter and when to break dormancy in the spring. Some spring-flowering plants sense environmental factors such as length of daytime and night along with soil or air temperatures to determine when they should bloom. Days and nights of equal length occur twice each year at both the vernal equinox (March 21 or 22 at our latitude) and on the autumnal equinox (September 21 or 22). Fall soil and air temperatures that stay warm later than is normal often fool rhododendrons into blooming. Autumn-flowering irises are not so common. However, newer varieties of iris have been developed whose claim to fame is producing blooms in both spring and fall. In a few years, after more re-blooming iris cultivars are planted in home gardens, autumn flowers on irises won’t be so remarkable any more.

Many species of trees and shrubs release their leaves and go into early dormancy as a survival tactic when severely drought stressed. Trees that got some rain before drought related leaf drop was too far along this year, held most of their foliage and have put on a pretty decent display of fall color. Frosty nights trigger leaf drop, also. We live on a lake which delays our frost occurrence onset, so there are still lots of leaves on the trees in my neighborhood. 

Do autumn clean-up in your landscape now. Cut seedheads from flowers and weedy plants. If you save seeds from desirable plants, put them into a container with a tight fitting lid. Keep seeds dry and cool (at 30 to 40 degrees). Don’t leave weed stalks and seeds lying on the ground. Gather and get rid of them now. Otherwise, there may be thousands of new weed seedlings next spring. Insect pests and plant diseases use the protection of garden debris to survive the winter. Slugs and other garden pests make piles of plant remains into cold-season shelters. Destroy these plant and pest hotels. Bacteria and fungal spores that cause plant diseases are all over infected plant parts. Such spores are not be killed by winter temperatures. Collect diseased leaves, stems, dried fruits, etc. Either safely burn them or bag and remove from your property.

Compost the remaining organic waste from yard and garden cleanup. The most efficient breakdown of vegetative material occurs when plant parts are chopped up before putting them on the compost heap. Cut plant stems and leaves into pieces. Use your lawn mower to shred fallen tree leaves. Those with a bagging attachment on their mowing equipment won’t have much leaf raking to do. Add the chopped mixture of grass and leaves to the compost pile. Green materials like grass clippings are nitrogen sources. Throw a handful of fertilizer on the pile every now and then for additional nitrogen. Research has shown that plant material with a higher acid content such as oak leaves and pine needles change to a neutral or mid-range pH of approximately 6.5, after broken down. Add oak leaves to the compost mix without worry about excess acidity.

This is the last 2007 column. Watch for new “Plateau Gardening” articles in February 2008.

Plateau Gardening is written by Tennessee Master Gardeners about home landscapes and gardening in our state’s Upper Cumberland Region. For answers to specific yard and garden questions or to learn how to become a Master Gardener contact UT Extension Cumberland County, P.O. Box 483, Crossville, TN 38557, (phone 931-484-6743). Email inquiries to “mgardenerrae@frontiernet.net”. Email questions may be answered either individually or through future newspaper articles.