The Vegetable Garden In October
I often associate the months of the year with the seasonal tasks to be performed in the vegetable garden. I usually think of the months of April–May as the planting season, while June–July is the growing season with its maintenance tasks of weeding and watering; August–September is the harvesting season, and October, well, that is my “paranoia” season.
October is paranoia season because in our area, it is the first frost month — usually around the 15th of the month. It can arrive earlier or later, but we know it is going to happen; we just don’t know exactly when. I always have peppers needing just a little more time to turn to that brilliant red or perfect golden yellow, or tomatoes on one plant or the other that are slow in ripening, or that one lettuce bed that is just starting to rock, so I am glued to the weather report, trying to catch that first freeze warning. I can’t count the times we’ve had a frost, and then right afterwards, Indian summer shows up smiling and bringing temperatures in the 70s and 80s for a couple of weeks after all the frost damage is done. I have finally come to the conclusion that waiting for that freeze warning is too late because there are precautions that can be taken to extend the growing season before that dreaded frost forecast.
There are two types of frost, advective and radiation. Advective frost occurs when a cold front sweeps into an area. A radiation frost occurs under calm winds and clear sky, allowing radiant heat from the earth to rise to the upper layers of the atmosphere. With radiation frost, the lack of wind prevents mixing of the air and an inversion develops. An inversion is just a fancy way of saying “things get turned around from the normal.” Normally the air closest to the ground is the warmest, but when an inversion happens, cold air collects near the ground while the warmer air lies above the trapped cold air. During an inversion, cold air is just like water running down a hill — it seeks the lowest point because it is heavier than warm air, and frost pockets may form. The first frost typically is a radiation frost that occurs on a calm, clear night.
There are several things we can do when a frost warning is issued:
Harvest early: Flowering plants such as beans, tomatoes, peppers, eggplant, squash and okra need to be harvested if there is no way to protect them. Fruit harvested in the mature green stage will still ripen, but sadly will not have the same flavor as a vine-ripened fruit.
Water before a frost: Moist soil can hold approximately four times more heat than dry soil. Moist soil can also conduct heat to the soil surface faster than dry soil, providing some frost protection. A Cornell University study suggests that the air temperature above a wet soil is 5° F higher than that above a dry soil, and in the study, that difference was maintained until 6 a.m. The conclusion of this study was that plants could benefit from watering the evening before a frost.
Cover your plants: A cover can provide anywhere from 2º to 6º F of protection, depending on the type of material used. The covers can be laid right on top of the plants or can be supported by stakes or a frame, the main difference being that there is less frost protection when the cover touches the plant. Any material can be used as cover; however, woven fabrics are better insulators than plastics or paper. The best time to apply covers is in the late afternoon after the wind dies down. Remove the covers the next morning.
Additional Tips and Tasks for October:
- Plant garlic and shallots to harvest next year.
- Harvest tender herbs (basil) before the first frost. They can be hung to dry in a cool dark place or the leaves can be frozen for use at a later time.
- Thinking about planting a fruit tree? Fall is usually cool and moist and a great time to plant. In addition, you may be able to save a little money, as local gardening centers usually have a fall sale. Water the newly-planted tree to provide sufficient moisture and prevent winter damage. Add a 3-inch layer of organic mulch, such as shredded bark around the base of the plant to retain soil moisture and regulate soil temperature. Research has shown that roots will continue to grow until the soil freezes, which is around late November in Virginia. Stake and wire newly-planted trees only if necessary. Use a piece of rubber hose around the guy wires to protect the trunk. The guy wires should be tied loosely enough so that the tree is able to move a little in the wind. The supports and stakes should be removed once the tree becomes established, usually in a couple of months. (Relf)
- Fall is an excellent time for taking soil samples in your garden. Soil test measures the pH (acidity or alkalinity) of the soil and the levels of some of the major elements required for plant growth, such as phosphorus and magnesium and potassium. If lime is required to adjust the pH, now is a good time to apply it. A free soil test kit is available from your local extension office.
- Pick up dropped fruit from under fruit trees so that deer and rodents will not be attracted to the fruit — AND to your growing tree. Raking and disposing of diseased leaves will help keep insects and diseases under control next season.
- High grass and mulch are a haven for rodents whose gnawing can severely damage trunks. Keep the grass mowed around new trees. Be sure that mulch is raked back 3-4 inches away from the tree trunk.
- Tomatoes need an average daily temperature of 65º F or higher in order to ripen. If daytime temperatures are consistently below this temperature, pick the fruits that have begun to change color and bring them inside to ripen.
- Harvest sweet potatoes before frost because cold soil temperatures can reduce the quality and storage capacity of sweet potatoes. I find that removing the vine first makes the digging a lot easier. Also, care should be taken when digging sweet potatoes because they skin and bruise very easily.
- When removing disease-infested plants or debris, do not place this refuse on the compost pile. The disease pathogen may continue to live in the compost pile and may be transmitted when the compost is applied to the garden.
- After frost, cut back all the foliage of asparagus to within 2 inches of the ground.
- There is still time to plant a winter rye cover crop. A cover crop protects the soil over the winter, traps any unused nutrients to prevent them from leeching, and adds organic matter in the spring when tilled under.
- It’s not too early to start thinking about next year’s garden. An excellent tool for planning is a garden sketch of this year’s crop locations. This will help when you’re deciding which crops you need rotate to minimize disease problems. Vegetables crops in the same botanical family are often susceptible to the same diseases and insects. For crop rotation to be effective, gardeners should not plant vegetables belonging to the same family in the same location for at least two or three years. Obviously, crop rotation in a small garden may be difficult. However, we should rotate our vegetable crops as best we can.
Phillips, Ben, “Freeze Damage in Fall Vegetables: Identifying and Preventing,” http://msue.anr.msu.edu/news/freeze_damage_in_fall_vegetables_identifying_and_preventing
“Understanding Frost,” Cornell Cooperative Extension, http://www.gardening.cornell.edu/weather/frost.pdf
Relf, Diane, Virginia Cooperative Extension, “The Virginia Gardener Newsletter,”Volume 23, Number 9/10, 2004, page 7.
Clemson Cooperative Extension, Publication HGIC 1322, “Sweet Potato,”http://www.clemson.edu/extension/hgic/plants/vegetables/crops/hgic1322.html
Virginia Cooperative Extension, Publication 426-401, “Asparagus”, http://pubs.ext.vt.edu/426/426-401/426-401.html
Colorado State University, Publication GMG #722, “Frost Protection and Extending the Growing Season,”http://www.ext.colostate.edu/mg/gardennotes/722.html