Planning the Fall Vegetable Garden
WOW, what a gardening season! April was dry. May was wet and cool, with near record amounts of rainfall. June arrived with 90º+ temperatures. With summer just getting underway and the dog days of summer just around the corner, it hardly seems logical to discuss planting a fall garden. But July is indeed the month to start filling garden space vacated by spring crops with succession plantings of summer vegetables, and it’s the time to plant fall vegetables that will keep your garden productive well into the late fall and early winter.
When I first began vegetable gardening, I asked an experienced gardening neighbor when he usually started a fall vegetable garden. His advice: “The first week or two in August.” Well, the result of heeding his advice was disappointing; several of my fall growing seasons were cut short. After a number of years, I have come to the conclusion that it is very difficult to define an exact “starting time for a fall garden.” Typically a fall garden is associated with cold weather crops such as spinach, kale, broccoli, cauliflower, turnips and brussel sprouts. I once heard a fall garden defined as a “mirrored” spring garden. I took that to mean that many of the “early” vegetables we plant in spring are what we plant in the fall: lettuce, peas, beets, cabbage, cauliflower and broccoli. Being a bit of a slow learner, it took me a while to realize that a fall garden is not just for cold season crops, but also an extension of summer crops. If the gardener takes a little time to do the proper planning, the vegetable garden will be productive into the late fall and early winter.
One of the most important things to know when planting late summer crops and planning your fall garden is the date the average killing frost pays a visit to your vegetable garden. In our area of central Virginia it is October 10th-October 15th.
The next important bit of information is how tolerant the various vegetables are to frost. Vegetables can be classified into three categories of by their tolerance of cold temperatures: tender vegetables (damaged by a light frost), semi-hardy vegetables (tolerate light frost) and hardy vegetables (tolerate hard frost). The following chart depicts examples of vegetables with different frost tolerances.
Chart adapted from “The Fall Vegetable Garden,” Purdue University Consumer Horticulture.
And the final piece of the puzzle is the number of days to maturity or harvest of the particular vegetables that you select to plant. Start by looking at the “days to maturity” on the seed packet. The general definition for “days to maturity” is the average number of days from the time the seed is sown (or a seedling is transplanted) to the first harvest. Remember, this is an average, depending on location, temperature, soil and all those environmental factors that affect plant growth. The days to maturity is only an average; your plants could be longer or shorter depending on the specific location where they are planted. However, the days to harvest usually paints a pretty accurate picture when you’re comparing cultivars. For example, two cucumber cultivars recommended for Virginia are ‘County Fair’ with an average of 83 days to maturity and ‘Bush Whopper’ (96 days). The 80 days or 96 days can vary several days one way or the other, but the difference between the two — 13 days — will be about right. So the cultivars selected and the planting date in the fall can mean the difference between a successful crop and unsuccessful crop.
So considering all the variables together — frost date, frost tolerance of various vegetable varieties and days to maturity — how do we decide when to plant? Unfortunately, this is going to take some good old-fashioned arithmetic! It’s simply a matter of determining the first frost date and counting backwards. Here’s how the model works: days to maturity plus fall factor (14 days) plus frost tender factor (14 days)=number of days to count back from first frost date. If the vegetable is not frost sensitive, the 14 days for the frost factor is omitted.
We know the first average frost date in our area is around October 10th-October 15th, so to be on the safe side, let’s choose October 10th.
Just for fun, let’s apply the formula to the two cucumber examples — ‘County Fair’ (55) and ‘Bush Whopper’ (68 days) — we talked about above. Cucumbers are frost-sensitive, so we need to plant and harvest before the first frost. For frost-sensitive crops, it is recommended that we add 14 days, as the crop must mature at least 2 weeks before frost in order to produce a reasonable harvest. It is also recommended that we add 14 days as the “fall factor” because the days to maturity or harvest number is based on optimum conditions. The fall factor takes into consideration that conditions are less than optimum in fall, resulting in slower growth rates due to cooler weather and shorter days. So putting the model to use, here are the planting dates:
For the cucumber cultivar called ‘County Fair‘ we add 55 days (55 day to maturity) plus 14 days (Frost Factor) plus 14 days (Fall Factor) for a total of 83 days. Next, we count back 83 days from our first frost day of October 10th and that gives us a drop-dead planting date of July 17. Thus, we would be safe to plant ‘County Fair’ cucumbers in central Virginia up until July 17th.
Looking at the cucumber cultivar ‘Bush Whopper‘(68 days to maturity) plus 14 days Frost Factor, plus 14 days Fall Factor equals 96 days. Counting back from October 10th gives us a drop dead planting date of July 4th, meaning according to the formula, we would be safe to plant ‘Bush Whopper’ up until July 4th.
Now let’s look at a couple of examples for bush beans: ‘Roma II‘ (59 days to maturity) and ‘Slenderette‘ (55 days to maturity).
‘Roma II’ needs 59 days to maturity plus 14 days Frost Factor plus 14 days Fall Factor, for a total of 87 days. Counting back from the October 10 frost date gives us a last date to plant of July 14th.
‘Slenderette’ needs 55 days to maturity, plus 14 days Frost Factor, plus 14 days Fall Factor for a total of 83 days, so the last date to plant ‘Slenderette’ is July 17th.
Bush beans and cucumbers are just two vegetables we can plant in July for a late fall harvest; others include beets, carrots, lettuce, mustard, and spinach. If you plan on growing your own broccoli and cauliflower seedlings, July is also the time to start them from seed so they are ready for transplanting in August.
As we move though the month of July and into the late summer months, timely planting is the key to success. Crops need sufficient time to grow and mature before the weather becomes too cold for continued growth. As the calendar moves closer to the first frost date, the selection of short-days-to-maturity cultivars becomes more and more important if you wish to have a successful fall harvest. Seed companies will sometimes helpfully label short-days-to-maturity varieties as “early season,”so always read the days to maturity on the seed packets, as shorter-days-to-maturity cultivars often have a greater chance of success for those frost sensitive crops.
Preparing the ground for planting
Before preparing the soil for the fall garden, first salvage any usable vegetables from existing crops. Since weeds often take over a garden as summer progresses, starting fresh with a fall garden is one way to get ahead of the weed problem. Remove any remaining spent crops and weeds, along with any insect-infested and diseased plants. Weeds that have seed heads should not be tilled into the garden or composted; this will prevent the spreading of pathogens and repopulating the garden with fresh weed seed.
Prepare the soil by restoring nutrients removed by spring and summer crops. A light layer of compost over the planting area will boost the soil nutrients and improve the soil texture. If compost is not added, a small application of a complete chemical or organic fertilizer may be added. Avoid deep tilling as this will break down the soil texture and increase surface soil crusting, which creates a barrier to young seedlings. Deep tilling may also cause moisture to be lost from the subsoil.
Soil in the late summer is often hot and dry, and this heat may inhibit seed germination. Germination rates may be improved by planting the seeds when the soil is moist — either after a rain or after watering the area thoroughly the day before planting. A light layer of organic mulch such as straw on top of the planted seeds will help keep the soil moist and cool. The mulch layer should not be thick enough to interfere with the germination of the seeds. Once the young seedlings emerge, that light mulch layer will help keep the soil moist and cool. It is important that the young seedlings get as much sunlight as possible, so the mulch should only be covering the soil and not engulfing the young plants. Once the plants are established, a heavier mulch may be used to hold moisture and control weeds. Keep the plants well-watered. Most vegetables need an inch of water per week to grow well. Less frequent, deep watering is preferable to light watering.
In central Virginia the first autumn frost is often followed by couple of weeks of warmer weather or Indian summer. With a little help, frost tender plants can grow throughout those weeks. Sheets, newspapers, floating row covers and buckets all can be used to protect tender plants when that first freeze is predicted. Usually the frost hits on a cloudless night (clouds tend to reflect heat back to the earth’s surface). Covering plants helps hold warmth near the ground. Following a freeze, uncover the plants after the temperature rises above 32º F.
Everything in the garden — including weeds — are growing like mad right now, but don’t let that fool you; this too shall come to an end unless you plant a fall or succession garden. With a little planning, the vegetable gardening season can be extended well into the late fall and even early winter. And in a few short months when you are sitting around the Thanksgiving table, be sure to let your family and friends know that those beets — well, they didn’t come out of a can; they were pulled just last night, and the broccoli and carrots are also fresh from the garden! Bet you never tasted sweeter carrots!
Thanks for stopping by The Garden Shed; we hope to see you again next month. In the meantime, happy gardening!
Sources:
“Vegetable Planting Guide and Recommended Planting Dates,” Virginia Cooperative Extension Publication No. 426-331, http://pubs.ext.vt.edu/426/426-331/426-331.html
“Fall Vegetable Gardening,” Virginia Cooperative Extension Publication No.426-334, http://pubs.ext.vt.edu/426/426-334/426-334.html
“Vegetables Recommended For Virginia,” Virginia Cooperative Extension Publication No. 426-480, https://pubs.ext.vt.edu/426/426-480/426-480.html
“The Fall Vegetable Garden,”Purdue University Consumer Horticulture, hort.purdue.edu/ext/fallgarden