The fall sweet corn planting window opens on Aug. 15 and that day also marks the beginning of the fall gardening season. If you are thinking about a fall garden, now is the time to begin preparations.

Sweet corn, in its many varieties, makes an excellent fall garden crop, provided it is planted early enough to avoid the freezing weather that usually arrives sometime around Thanksgiving give or take a few days. It also has to be planted late enough in the summer to ensure that the temperatures have moderated in the fall by the time that tasseling and kernel formation begins. High temperatures can affect the viability of the pollen and low pollination can result in ‘skips’ or empty seed sockets. August 15 is usually the best time to plant 90 day varieties to ensure a good harvest.

Sweet corn varieties will all have different lengths of growing seasons. Some varieties take 90 days to mature while others can finish up in 60 days or less. The days to harvest are listed on the seed packet. You can plan your harvest by counting back on the calendar the number of days to harvest for each variety.

Sweet corn is a great garden crop because it is easy to grow, because it is a tall plant that easily outgrows weeds, and because it is a tasty harvest that most people love to eat. Plant the seeds into loose soil about one inch deep and keep the soil moist until the young plants emerge from the ground. Then water frequently enough to ensure that the plants do not stress for water the rest of the growing season. Fertilize two or three times during the growing season with a nitrogen fertilizer for best results. If you are a first time gardener, or new to the desert, sweet corn is a great crop to begin your gardening journey.

If you are an experienced desert gardener, you will know that there are actually multiple key dates for fall vegetable gardens. Mid-August is the time to plant cole crops, like broccoli and cauliflower. If you are brave, and fortunate that the whitefly season is light, a fall planting of squash and melons can go in about the first of September. September 15th is the magic date to begin planting leafy vegetables, root crops, and most flowers.

Temperature and the length of day are the two guiding forces that determine when the seed of a particular variety should be put into the ground. Temperature is important because most plants have a maximum and a minimum limit above or below which they simply die. They also have a range of temperature where they do their best. Tomatoes, for example, do not set fruit well when the daytime temperatures go up above 90 degrees F.

Day length is important because there must be enough hours of sunshine for the plant to effectively produce enough food through photosynthesis to support it clear through its growing cycle. In addition, many plants are sensitive to whether the days are lengthening or whether they are becoming shorter with each passing day. For these and other reasons, there is a preferred time to plant most garden plants. If we do not follow the guidelines, we often see dramatic failures in the garden.

Among the hazards of fall gardening, in addition to temperature and day length, are the various types of insect pests. The whitefly in particular is a difficult fall garden pest and favorite plants include squash, melon, pumpkin, and tomato. Their feeding can cause great stress on these plants. As temperatures cool off in the fall, whitefly populations begin to decline. Because of this some gardeners choose to delay planting until later in the fall.

For the other well-known vegetables like leaf and head lettuce, spinach, collards, radishes and turnips, plan to seed those on the September 15th date. Hold off on planting potatoes until November and early December. They need the moderate temperatures of spring to mature.

Good soil preparation is critical in the garden. Before planting, the soil should first be well tilled by spading or with a mechanical tiller. Make sure that all of the clods are broken up and that the soil is leveled so water will not flow away from the plants.

A heavy application of compost or decomposed steer manure during soil preparation will improve water penetration, soften the soil, and reduce the number of clods that have to dealt with later on. It is also a good idea to add one half pound of ammonium phosphate (16-20-0) fertilizer per 100 square feet before tilling the soil to ensure plenty of nutrients for the tender young plants once they begin to grow. If you prefer an organic nitrogen source consider chicken manure, fish emulsion, or blood meal.

Do not stress the germinating seeds and young seedlings for water during their early stages of growth. Regular light irrigations with a misting hose attachment, a sprinkler, or drip system will apply water uniformly to the garden without washing out the seeds.

All plants should be placed into the soil according to the instructions on the seed packets. The many different vegetable and flower plants each have specific planting depth requirements. Placing seed at the correct depth is critical to the success of all garden and flower plants.

When preparing your soil for planting, do not forget to plan when and how you will continue to add compost to your garden. The small one-celled micro organisms that live in the soil do their best work breaking down the organic matter when the temperatures are warm. The hotter it is, the faster they work. Because of this, the compost added at the beginning of the season may be gone long before the longer growing plants are harvested, especially if the thermometer readings stay up above the century mark well into October.

To maintain good soil organic matter levels in my vegetable and flower gardens I like to top dress my seed beds with compost after the plants have germinated, emerged from the soil, and have gained at least two or three inches in height, depending upon the type of plant. If I have time, I may also add another layer mid season. Then, when I terminate the crop or flower bed in transition to the next planting, I till in the remaining compost plus the crop residues into the soil. This practice helps me to help maintain top quality soil conditions.

There are other gardening tasks that are important. One critical assignment is to make sure that irrigations occur as necessary throughout the season. Infrequent irrigations can lead to a slowing of plant growth and a loss of vigor. This can be a problem when the plant is at a critical stage of development, such as flowering or maturing fruit. In addition, do not forget to feed your garden plants occasionally with nitrogen fertilizers to keep them green and healthy.

With proper care and good timing, vegetable and flower gardens can provide both food and color for the coming outdoor season.

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Rick Gibson is an agricultural extension agent and the director of the University of Arizona Cooperative Extension in Pinal County. He can be reached at gibsonrd@ag.arizona.edu

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