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Zucchini Growing Quick Tips

Zucchini growing
Zucchini beginning fruit development

Growing conditions. Plant zucchini in full sun in compost rich, well-drained soil. Zucchini likes to get its start in the spot where it will grow, but if you want to get a jump on the season, start seed indoors 3 to 4 weeks before the last expected frost in 4-inch biodegradable pots (that can be set directly in the ground at planting time so that the roots are not disturbed). A week before transplanting, harden off seedlings by cutting back on water and lowering the nighttime temperature to 65°F.

Sowing or setting out starts. Zucchini wants warm soil and air temperatures for growing—in the 70s°F is optimal. Zucchini seed won’t germinate in cold soil. Wait until the soil temperature has reached 60°F before direct seeding or setting out starts. Lay down a sheet of black plastic to warm the soil before sowing or planting. Plants started in chilly temperatures may become stunted.

Avoid too much zucchini. You can avoid too many zucchinis at harvest by simply not overplanting. One zucchini plant will produce 6 to 10 pounds of fruit over the course of the season. Stagger plantings so that you have a continuous harvest but are not overwhelmed.

Spacing. Space plants 2 to 4 feet apart to provide air circulation and discourage disease. A good planting strategy is to plant zucchini on low hills that easily warm in spring. Sow three seeds to a hill and when seedlings have one true leaf, thin the starts to one per hill—just snip off the weakest plants with scissors so as not to disturb the roots of the one that remains.

Pollination. Zucchini is a monoecious plant, meaning each plant has both male and female flowers. A female flower has a small swelling (the ovary) at the base of its short-stem. A male flower has a long, thin stem—and is usually larger than the female. Bees and insects must visit the male flower then the female flower for pollination.

Cross pollination. Do squash plants easily cross pollinate? Yes! But cross-pollination affects next year’s crop, not this year’s crop. If you grow zucchini from newly purchased seed each year, you won’t have to worry about plants cross pollinating. Only if you save seed, should you grow just one variety at a time.

Chilling injury. Temperatures too cold will pit the skin of zucchini. This is called chilling injury. Keep a floating row cover handy to cover seedlings and young plants if the temperature dips below 65°F at night.

Watering. Keep the soil evenly moist. Give zucchini 1 inch of water a week. The critical time for watering is during bud development and flowering. Once plants are established, mulch with straw, hay, or dried leaves to retain soil moisture and suppress weeds. Drought stressed plants are more susceptible to insect attacks.

Feeding. Zucchini are heavy feeders. Prepare the planting bed with lots of organic matter—a few inches of aged compost spread across the bed and then turned under. If leaves grow pale or plants seem weak, side-dress zucchini with well-aged compost or use a foliar spray of liquid fish or kelp fertilizer—high in phosphorus for fruit production. Don’t use a fertilizer too high in nitrogen; it will diminish your yield.

Lots of flowers, no fruit. If your plants are flowering but not producing fruit, there is may not be enough bees around for pollination. Hand pollinate flowers with a cotton swab—gather pollen from the male flower and dab it on to the golden stigma in the center of the female flower.

Harvest. Zucchini should be picked young and tender for the very best flavor. Once fruits are 4 inches long, it’s time to start the harvest. Zucchini can grow 1 to 2 inches a day so check your plants every day at harvest time. Zucchini that grows very large will be pulpy, seedy, and bitter flavored.

Cucumber beetles. Cucumber beetles emerge from dormancy in spring before the weather is warm enough for cucumbers or zucchini to begin growing. When zucchini starts growing, cucumber beetles will begin feeding on leaves and fruits. Check cucumber beetles–little yellow beetles with stripes or spots–with yellow sticky traps or cover plants with a floating row cover, but be sure to remove the cover when flowers appear and it’s pollination time.

Squash vine borers. Squash vine borers (the larvae of wasp-like moths) bore into zucchini stems and eat their way through stems. Look for sawdust-like excrement near small holes to know they are present. Plants suddenly wilt and may die. Slit the damaged vine with a sharp knife and remove the borers with a tweezers. Cover the damaged section with well-aged compost and the plant will grow on.

Blossom-end rot. Irregular watering and a soil calcium deficiency can result in poor water uptake that will result in the blossom end of the fruit (opposite the stem) becoming leathery and sunken; this is called blossom-end rot. Use ground oyster shells or a calcium-rich fertilizer to counter blossom-end rot.

Zucchini Varieties to grow:

  • Ambassador: cylindrical, dark green early variety; 50 days to harvest.
  • Costata Romanesco: great tasting, nutty flavored Italian zucchini; ribbed, gray-green with pale green flecks; 52 days to harvest.
  • Eight Ball: nutty, buttery flavor from dark green globe fruit; 40 days to harvest.
  • French White: white fruit on small bushes for small gardens; 50 days to harvest.
  • Gold Rush: uniform, cylindrical fruit, AAS winter; 45 days to harvest.
  • Spacemiser: high yield from small bush, green fruit can be harvested as baby squash; 45 days to harvest.
  • Seneca: dark green, cylindrical fruit on small bush; 42 days to harvest.

 

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52 Comments

  1. Hi there, I’ve planted some “Yellow Globe” zucchini. The label says they are best picked young and small but I don’t know if that means the size of a grape, walnut, or orange? What size do you think is best? Cheers.

    • Globe zucchinis reach maturity at about 45 days; young and tender can be picked at about 30 days–smaller than an orange, larger than a golf ball.

  2. I grew zucchini for the 1st time last year and have 2 questions.
    What caused the leaves to get powdery white?
    Also is there a way to successfully cage them so they don’t take up so much space or do they have to be left to go wild all over the ground?

    • The powdery white you see on your zucchini may be powdery or downy mildew. These are fungal diseases. What you see are the fungal spores which can quickly multiply and can if left unchecked damage or kill the plant. When you see an outbreak, spray with horticultural or neem oil; oil will suffocate the spores. You can also spray the leaves with compost tea which will not only inhibit the fungal growth but feed the plants as well. As far as vine sprawl is concerned, try this: as the vines begin to run away from the plant, use garden stakes to train the vines in a circle around the stem. If you plant zucchini or other vining crops on a mound, you can train the vines to circle the mound. Once plants begin to produce you can cut away the growing tips and slow the plants’ growth.

    • Zucchini and summer squash will grow well with corn and beans (this combination is known as The Three Sisters). Also, plant marigolds and nasturtiums with zucchini; these plants will help defend zucchini against pest insects. Generally, don’t plant summer squashes with root crops, which eat up a lot of nutrients in the soil or with potatoes and pumpkins which like a lot of room,

    • Yellowing zucchini leaves can indicate several possible stresses: (1) too much moisture in the soil, (2) too little moisture in the soil, (3) too much or too little nitrogen in the soil, (4) too chilly temperatures (below 60F) or too hot (above 95F). If you suspect watering is the problem, let the soil just dry out at the surface or about an inch below before you water again. You can also use a moisture meter with a probe to see how wet the soil is at 4 to 6 inches below the surface.

  3. My zucchini plants have all rotted at bottom of the stems next to the soil, I did have fruit and the leaves turned turned almost white as the fruit matured

    • Zucchini fruits that rot at the flower end of the fruit–the end opposite the stem–are commonly suffering from blossom-end rot. This is caused by a lack of calcium in the soil; calcium is important for plant cell wall development. Side dressing the plants with a fertilizer that contains calcium will alleviate this problem for hew fruits that develop on the vine. It the fruits are rotting at the stem end, this may be a sign of a bacterial disease associated with excess water or a bacterial organism in the soil that has infected the fruit because it is sitting in soil too wet. Bacterial diseases and other diseases in the garden often take hold and spread when plants are planted too close together and there is insufficient air circulation or the soil is poorly drained and stays wet. Leaves and fruits turning white may be a sign of fungal diseases such as powdery mildew or downy mildew. The white you see is fungal spores that grow rapidly and spread. Overwatering and too much nitrogen in the soil can cause mildews to grow and spread; spacing plants further apart can slow fungal diseases. All of the above said, an alternative cause of the fruit rot and fruit and leaves turning white is too little water. If that is the case, the leaves will be papery and brittle as a result of sunburn.

    • I agree. Large or small are good. Large zucchini pizza is great. Slice in half. Scoop out seeds of large. Slice a thin strip on skin side of both halves to lie flat on cookie sheet. Add pizza sauce with veggies and/or meat. Bake until zucchini is tender. Add grated mozzarella on top and bake till cheese is melted.

  4. Thanks for the article it was a good read. I’m planting green zucchini from seeds this year in Southern Ontario. My seedlings are all getting their first true leaves but they’re also all reaching. How deep up the stem can I replant my seedlings while the temps are still too cold for outdoor transplanting?

    *side not: My green bush beans are also at the same stage of growth and reaching.

    Thanks!

    • If your zucchini and beans are still indoors and you are waiting for the weather to warm, transplant them into the next largest pot and put them in full sun during the day or under grow lights. Keep the light just a few inches from the top of the plant and if the plants are in a window be sure to turn them each day. They are reaching for the light, so bring the light closer. An alternative is to transplant them into the garden under a plastic tunnel where they will remain warm until the outdoor weather warms and the protection can be removed. Zucchini stems can be buried but it is best that you wait until the stem is the thickness of a pencil; younger seedlings may rot if stems are buried.

  5. I plant squash in the Florida panhandle and when the rainy season comes they die begire I get any squash. I plant them on top of a mound.

    • In wet spring regions and wet summer regions in addition to planting on mounds, cover the mounds with plastic sheeting so that most of the rain runs off the mound and into drainage rills next to the mounds. If that is not enough, place hoops over the mounds and cover the hoops with clear plastic to create a drier growing environment. If you use plastic tunnels be sure to lift the sides when the temperatures are warm; the temperature inside a tunnel will be 10 to 20 degrees warmer than the outside temperature.

      • First time grower. My zucchini plant is very lealthy, flowers and veggie growing well. However, a couple of baby zucchini grew about an inch then died. Other veggies appear to be growing well so far. What’s happening to the little ones literally dying on the vine. I also have ants hustling insid the flowers.

  6. You mentioned self pollinating when you have more flowers than fruit. 2 questions. How do i differentiate the male and female flowers? I assume some flowers are expecting and ok, correct?

    It’s my first time planting so sorry for the silly questions

    • Female flowers will have a little bulge at the stem end of the flower, this is a baby fruit. Male flowers will have no bulge.

  7. I planted my zucchini in a non biodegradable pot and I need to figure out how to transfer it to my garden bed. Can you tell me how I should transfer the seedlings?

    • Biodegradable pots are designed to be planted in the garden; you do not have to lift the plant and football out of the bio-pot. Moisten the pot and make slits in the sides and bottom so that the plant’s roots can easily escape to the garden soil. Trim the top of the bio-pot to soil level within the pot, so that the soil in the pot is flush with the soil in the garden after transplanting. If you leave a portion of the bio-pot exposed it may wick moisture away from the root ball.

  8. I live in a dry mountain climate in Northern Arizona, it was 90° yesterday and 45° last night, so will that stunt the growth of my potted zucchini. I thought that if it was above freezing, they would be okay?

    • The temperature extremes may stunt the growth of you warm-season vegetables; it is too chilly at night and on the border of two hot during the day. Since your plants are in pots, make sure they get morning and late afternoon sun but try to shield them from the midday sun. If possible drape a piece of floating row cover over the plants at night–at least until night temperatures average 60F.

  9. First time growing Zucchini and I think I have. Cut worm, the flower look like someone cut them off with a razor blade, what can I use to kill the cut worm! Thanks

    • Cutworms are soil-dwelling insects; if the flowers were on the ground, a cutworm might attack. If the flowers were cut off and disappeared it is more likely a rodent or bird made a meal of them. Place a floating row cover over the plants at night to protect them from marauders. Remove the cover during the day so that pollinators can work.

  10. Hi! Thank you for this very informative post. Is it a must to sow 2+ plants together? I have one healthy seedling grown from seed, that’s ready to be transplanted to a container now. We aren’t big zucchini eaters so I’m not keen on planting too many seedlings. However, if you say that the chances of pollination and production and significantly enhanced, I can try and buy a seedling from the store.
    Thanks in advance for your advice and time

    • You can grow a single plant and pollinators will likely find it and assist in pollination. Multiple plants simply increase the number of flowers and the attraction of bees and other pollinators.

  11. My zucchini plants are growing well with many flowers and zucchinis are emerging, but some of the leaves are drying out and turning brown. Should I cut off those leaves

    • Be sure to keep the soil evenly moist; the surface can dry out, but the soil at 3 inches below the surface and below should be moist. You can remove dry brown leaves; they won’t come back. But head off more drying of leaves by keeping the soil moist.

  12. A friend gave us a zucchini plant that he started from seed. It was in a pot when he gave it to us. We removed it and planted it in a large garden pot , gave it some B12 and set it in a sunny spot. The plant is growing, we get big beautiful flowers every day, but they only last one day. We do have some leaves that are dry and brown but I believe they are the first leaves that grew from the plant. Long story short…no fruit. We live in the high desert region of Southern California where the temperature is running in triple digits. 107° yesterday with a low in the 70’s. We water twice a day. Too hot?
    Too much water? Too much sun? Thanks

    • The temperatures are too hot; the pollen is likely drying up and dying before it can be transferred from male to female flowers. Keep the plant alive; when temperatures fall into the 80sF, the pollination will occur. If you don’t want to nurture the plant until temperatures moderate; sow new seed toward in early to mid-August–if temperatures usually moderate by late August and early September.

  13. I tried to grow zucchini Iant last year for the first time. I planeted a store blught plant It grew slme in couple days and it was eaten by either squirrel or rabbit, I mean the whole plant. How do I protect my plant next time time?

    • Here are two ways to protect crops from squirrels and rabbits: (1) exclusion: build a fence tall enough to keep the critters our to place chicken wire cages over the crops; they can’t eat what they can’t get to; (2) use a dust or spray deterrent; you can find products at the garden center that contain pepper and other irritants; these will bother the critters noses and eyes and they will go elsewhere; deterrents must be reapplied after watering.

  14. My zucchini plant has a lot of 2 inch zucchini but they don’t seem to be growing. They have been that size for probably a week or more. Will they grow? What am I doing wrong? Thanks

  15. If your weather is hot, plus 90F, the plants will simply not grow until temperatures moderate. If temperatures are less than 90F consistently, feed the plants with a dilute solution of fish emulsion or kelp meal.

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