By: Heather Rhoades
For the most part, zucchini plants are one of the most prolific performers in the garden, but even the beloved and prolific zucchini is prone to problems. One of these problems can be when the zucchini fruit on your zucchini plant grows just a little bit and then seemingly inexplicably falls off.
The most common cause of zucchini fruit falling off the plant is no or poor pollination. This means that for some reason, the flowers on your zucchini plant were not properly pollinated and the fruit was unable to produce seeds. Remember, a plant’s sole purpose is to produce seeds. When a fruit has shown it will not produce seeds, the plant will “abort” the fruit rather than invest precious time and energy in growing it.
A less common reason for zucchini fruit falling off a plant is blossom end rot. The tell tale signs of this are blacked ends on the stunted fruit.
In situations where you have poor pollination, the first place to look is at your own gardening practices. Are you using pesticides in your garden? Pesticides frequently kill off the good pollinator bugs as well as the bad bugs. If you are using pesticides, stop this practice and look into other pest control methods that will not be as harmful to the pollinators.
If you are not using pesticides, your garden may simply be a victim of a national epidemic that is affecting farmers and gardeners across the United States. The honeybee population has declined rapidly in the past decade. Honeybees are the most common kind of pollinator found in the garden and, unfortunately, they are getting harder and harder to find. Try attracting some of the less common pollinators like mason bees, bumble bees, and butterflies to your garden. In a worst case scenario you can hand pollinate the flowers on your zucchini plants.
If the problem is a blossom end rot problem, the situation will most likely remedy itself, but you can speed the process along by adding calcium additives to your soil. Blossom end rot is caused by a calcium deficiency in the soil.
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Summer squash (Cucurbita pepo), including zucchini, crookneck, straightneck, patty pan and other similar types, is common in Minnesota vegetable gardens. You can eat squash fruits cooked, raw and shredded or grated in baked goods. Squash flowers are edible, as well.
Like other “vine crops,” summer squash plants grow best and produce the most fruit in warm weather. Some varieties form long vines. Others are bush types that fit more easily into a small garden.
Squash plants have separate male and female flowers. A slender stem attaches male flowers to the plant. Female flowers grow close to the main vine. Between the flower and the vine is a small round ovary, the unfertilized fruit.
An insect must move the pollen from the male flowers to the female flowers. Bees are common squash pollinators.
Soil testing and fertilizer
Direct seeding is preferred for starting squash.
Squash seeds will not germinate in cold soil. Plants started indoors and set out into cold soil will also not grow very well. Squash plants started indoors also fail to grow in the garden because of damage during transplanting.
Use a soil thermometer and sow seeds after the last frost date, once soil temperatures are at least 70° F at the two-inch depth. In most of Minnesota, this will be sometime in late May, or early June in the north.
Some varieties of summer squash grow fruit over a longer season. Some grow many fruit within a shorter period. For a longer, more even harvest, seed only part of your squash garden at first, and then finish the planting three weeks later.
Sow seeds about a half-inch deep. For vining types that will spread out in the garden, sow their seeds two inches apart. Allow about two or three feet of space on either side of the row for the vines to spread.
After emergence, thin seedlings to stand eight to 12 inches apart. A “hill” of three or four seeds sown close together is another way to plant squash in the garden. Allow five to six feet between hills.
You can plant bush types, with very short vines, in closely spaced hills, or in closely spaced rows, with only two to three feet between rows or hills.
Black plastic mulch and row covers
Earlier planting is possible with black plastic mulch, which raises soil temperature. If uncovered, the black color of the mulch will absorb heat from the sun and warm the soil faster.
Apply black mulch after you prepare the soil in spring. Cut holes or slits in the mulch, and plant the seeds as above. After the seedlings have emerged, position the row covers over the plants, securing the edges with soil or staples.
Spun row covers raise air temperature around the plants and protect them from cold nights. Row covers keep away both pests and beneficial insects required to pollinate the flowers, so you must remove them from the plants once flowering begins.
Zucchini grow on bushy plants that produce male and female flowers. The male blossoms, which grow on long, slender stems, need to pollinate the female flowers, which have short, swollen stems that develop into the tender zucchini fruit. When male and female blossoms don't open at the same time or little bee activity occurs, you get poor pollination. Wet or windy weather early in the season can affect bee activity, while temperatures that are extremely hot or cold make pollen less viable.
Regardless of the uncertainty surrounding the potential efficacy of marigolds in nematode control, there are still plenty of very good reasons to use them as a companion crop in your vegetable garden.
Marigolds can bloom over quite a long period of time. Their blooms are therefore an excellent resource for bees and pollinators throughout the growing season.
Some marigolds are better than others for certain pollinating insect species – but many can help to draw them into your garden.
For a number of pollinators, single flower types are better than doubles, as it will be easier for them to reach the heart of the flowers. But always try to choose as many different flowers for your garden as possible, to encourage all the different pollinators that live in your area.
Although there's no cure for rot, zucchini plants suffering from blossom-end rot can usually recover if you provide consistent irrigation so the soil doesn't dry out. Remove all infected fruits so they don't become targets for other diseases, so new fruits can develop normally. Pull up and destroy any plants affected by crown rot to prevent the spread of the disease. Wash your hands after handling affected fruits and plants, and disinfect any gardening tools with a 1 part bleach to 9 parts water solution so rot isn't spread to healthy zucchini plants.
Jenny Harrington has been a freelance writer since 2006. Her published articles have appeared in various print and online publications. Previously, she owned her own business, selling handmade items online, wholesale and at crafts fairs. Harrington's specialties include small business information, crafting, decorating and gardening.