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Zucchini and other soft-skinned summer squashes are usually pretty easy to grow. But, gardeners do sometimes face struggles with these productive crops. Perhaps your vines stopped producing in mid summer? Or the fruits were small or deformed? Or maybe your plants simply died before producing any fruits? If you found yourself asking why zucchini growing problems struck your garden, this solution guide is for you.
Top 10 zucchini growing problems
Here are ten reasons why you may have faced zucchini growing problems in the past, and tips for making sure these issues don’t happen again.
Zucchini problem 1: Improper variety selection.
Not all zucchini varieties perform the same. Some are more productive than others, and some are more disease- and pest-resistant. First and foremost, when selecting zucchini varieties for your garden, be sure to seek out disease and pest resistance whenever possible. Varieties with a high level of natural resistance often perform better and produce longer. ‘Tigress’, ‘Green Machine’, ‘Burpee Golden Glory’, and ‘Yellow Fin’ are great choices.
Zucchini problem 2: Squash vine borers.
One of the biggest zucchini growing problems is a pest known as the squash vine borer. Adult vine borers are day-flying moths that are black and red with dark wings. They’re fast flyers, so gardeners don’t often spot them. The damage caused by their larvae, however, is difficult to miss. Squash vine borer larvae feed inside the main stem of the plant, hollowing it out and eventually causing plant death. You’ll see crumbly, sawdust-like waste collected below a small hole at the base of the plant. To prevent squash vine borers, protect the lower portion of the stem with a wrap of aluminum foil (more on this technique here), or cover the plants with floating row cover until they come into bloom to keep the female moths away from egg-laying sites.
Zucchini problem 3: Poor pollination.
Zucchini and other squash are insect pollinated, meaning a bee, beetle, or other pollinator is needed to move the pollen from a separate male flower over to a female flower. If there aren’t enough pollinators present, puny or deformed fruits are the result. If your zucchini are mal-formed and stubby on the blossom end, poor pollination is the most pressing of your zucchini growing problems. To improve pollination rates, plant lots of flowering herbs and annuals in and around your zucchini patch. You can also hand-pollinate the vines by using a paintbrush or your fingertip to transfer pollen from the male flowers to the females (more on how to hand pollinate here). Another option is to plant a parthenocarpic variety that doesn’t require pollination to set fruit, such as ‘Easypick Gold’, ‘Partenon’, or ‘Cavili’.
Zucchini problem 4: Powdery mildew.
Powdery mildew is among the most pervasive fungal diseases when it comes to vine crops like zucchini. This pathogen makes the leaves appear to be covered in a talcum powder-like coating. Though it’s primarily an aesthetic issue, severe cases can lead to reduced photosynthesis and reduced production. To overcome powdery mildew, space plants properly – give each one plenty of room so air can circulate and dry off wet foliage. Plant only resistant varieties, such as ‘Anton’, ‘Dunja’, ‘Astia’, and ‘Emerald Delight’, to help combat powdery mildew which is one of the most tenacious zucchini growing problems. Organic fungicides based on potassium bicarbonate (such as GreenCure and BiCarb) are effective as preventatives, as are those based on Bacillus subtilis (such as Serenade).
Zucchini problem 5: Squash bugs.
When it comes to insects that attack squash, none are more difficult to control than squash bugs. These shield-shaped, brown insects suck out plant juices with their needle-like mouthpart, causing stippling, yellowing, and browning of the leaves.
The best way to manage squash bugs is to head to the garden every day and inspect the top and bottom of your zucchini leaves for clusters of bronze-colored, football-shaped eggs. Squash bugs are resistant to most pesticides, but very young nymphs can be controlled with applications of insecticidal soap or horticultural oil. You can read more about how to get rid of squash bugs in this article. Our Guide to Vegetable Garden Pests also has more info on this troublesome insect.
Zucchini problem 6: Poor soil.
Zucchini doesn’t require excessively nutrient-rich soil, but it does perform best in soils that are high in organic matter with a soil pH around 6.5. If your pH is too far off that target mark, the plants may fail to produce quality fruit because the soil pH affects the availability of many different nutrients (more on soil pH here). You can also prevent many zucchini growing problems related to the soil by limiting the amount of nitrogen you add to your garden. Excessive nitrogen produces a lot of green leaves, often at the expense of good fruit production. Use only balanced, organic fertilizers on your zucchini patch and test your soil every few years to ensure it’s healthy and well-balanced.
Zucchini problem 7: Lack of water.
Zucchini growing problems can also stem from irregular soil moisture levels. If plants are allowed to dry out between waterings, fruit production can be negatively impacted. Drought stress is never good for vegetable crops, and zucchinis require consistent, even soil moisture throughout the growing season. If Mother Nature doesn’t supply your garden with at least one inch of water per week, it’s your job to add supplemental irrigation to prevent any possible issues. A 2-3 inch thick layer of mulch helps stabilize soil moisture levels and can reduce the need to irrigate during the hot summer months. You’ll find more information on proper mulching techniques here.
Zucchini problem 8: Blossom end rot.
Zucchini can also be affected by blossom end rot, just like tomatoes and peppers. This physiological disorder causes the blossom end of the fruit to rot into a dark, sunken canker. It’s caused by a calcium deficiency, but it’s the result of inconsistent watering. Calcium can only come into a plant as it absorbs water in through its roots. When there’s no water in the soil to absorb, the plant can’t access calcium either and blossom end rot is the result. To prevent blossom end rot from striking your zucchini, make sure the plants receive ample, consistent applications of water throughout the growing season. Adding more calcium will not solve the problem.
Zucchini problem 9: Bacterial wilt.
Though this pathogen tends to be more problematic on cucumbers, it sometimes strikes zucchini as well. Sadly, this is one of those zucchini growing problems that’s the kiss-of-death when it strikes. Spread by the cucumber beetle, bacterial wilt causes otherwise healthy plants to wilt and die without prior warning. To combat potential problems, keep cucumber beetles in check by trapping them on yellow sticky cards fastened to stakes just above the tops of the plants.
Zucchini problem 10: Not enough sun.
Though it isn’t the worst of the zucchini growing problems you might face, lack of sun can definitely affect plant health and production. Zucchini plants need a minimum of six to eight hours of full sun per day. Lower light levels can result in long, lanky plants with pale green foliage and reduced yields. Poor pollination can also be a side effect of light levels that are too low because pollinators tend to prefer foraging in sunnier areas, particularly on cooler days. Select a full-sun site when planting your zucchinis.
Here’s a quick video sharing more about these common zucchini issues:
Zucchini growing problems don’t have to decimate your crop
Though zucchini growing problems may strike your garden from time to time, with these management tips, you can manage the issues organically and enjoy bushels of delicious zucchini all season long.
For more on growing healthy zucchini, check out these related posts:
Cucumber plant problems
Guide to Vegetable Garden Pests
A Handy Guide to Harvesting Vegetables
Types of Landscape Mulch
A Compost Guide
What challenges have you faced with your zucchini crops and how did you overcome them?
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The tip of my zucchini leaf is yellow and mushy looking. What’s happening? Are there organic cures for any of the problems? I heard something about baking soda, another something about epsom salt.
Sounds like a possible fungal issue. I recommend removing the infected leaf and tossing it in the garbage. Keep a close eye on the plant and if it starts to affect the other leaves, use an organic fungicide. Avoid homemade pesticides and fungicides as they often cause more harm than good. Commercial products are always best since they are tested and properly labeled.
I have planted zucchini for the last couple of years and this is the first time I am seeing clusters of black spots under the leaves and several ants. Are these aphids and eggs? If so what is the best organic treatment if there is one?
Sounds like it could be aphids. They are sometimes “farmed” by ants who harvest their sweet excrement. I would look closely at them with a hand lens or magnifying glass (or take a photo with your cell phone and zoom in) to confirm the identification. If you let them go for a week or two, ladybugs and other predatory insects will likely show up and eat them. I don’t worry about small infestations. If they begin to reproduce so fast that you have more than 30 or 40 per leaf, squirt them off with a sharp stream of water from the hose. It dislodges them and easily takes care of the problem.
I made the mistake of container planting delicata squash plant starts into garden soil instead of potting soil. So far they’re growing, but will they be okay in the long-run?
They might do okay, depending on how dense your soil is. Not much you can do about it now unless you transplant them into a larger pot of potting soil.
My zucchini is dwarfed. Plat looks healthy and have many yellow flowers, but the fruit is only 3” long. What can I do
Sounds like it may be poor pollination, especially if the zucchini is stunted on the end. Here’s an article we wrote on how to hand-pollinate: https://savvygardening.com/pollinating-squash-cucumbers-pumpkins/
Help, my daughter planted a whole pack of zucchini in one pot, they are starting what seems to blossom everywhere but the zucchini is growing from the roots and becoming entangled due to too many being planted, can I separate?
Separating the plants when they’re much older than the seedling stage would destroy too much of the root system and probably kill them. I suggest choosing the sturdiest 1 or 2 plants in the pot, and cutting the rest of the plants off at their base, flush with the soil level. This allows just the 1 or 2 plants to thrive without disturbing their roots.
My two container zucchini plants are producing zuchini although two have rotted on the plant. But almost overnight the leaves are turning yellow and dying. Help! I see no bugs or pests
For zucchini to perform well in containers, they need a lot of soil. Ideally, the pot should hold at least 5 gallons of soil per plant. If the containers are smaller than that, I suggest repotting them into larger containers so they have plenty of room to grow. Be sure to fertilize every week with an organic liquid fertilizer as they are heavy feeders.
Hi,
My newly planted zucchini plants are turning brown around the edges of the leaves. They were planted a few weeks ago as small plants. Why are the edges brown?
Hi Elaine – Sounds like the plants could have a little transplant stress, which they will grow out of as they settle into their new home. This also happens sometimes when the plants were not properly hardened off prior to planting them.
Hello! Thank you for this article! I am new to growing veggies and I have crispy edges and powdery mildew on my zucchini plant leaves. They are about a month old (from seed) and seem to be struggling to grow. I live in Montreal and we have a cool climate so they have been inside with a grow light and I have been slowly hardening them off on nicer days. Is there anyway to save my plants? Should I start over?
Thank you so much!
Liz
Hi Liz –
You sowed your seeds a little too early. It sounds like they are stressed. I would suggest sowing new plants by directly seeding them out into the garden soil after the danger of frost has passed. Zucchini almost always do better when planted by seed outdoors, rather than from seeds started indoors under grow lights. They resent being transplanted.
Hi! Loved this article! I am a first year gardener and made the misstep of planting all 3 of the seedlings from the tiny pot into the same space. I didn’t realize I should have thinned or separated them. Now they all look pretty healthy with lots of new growth but my reading tells me I’m going to run out of room soon.
My questions: should I dig up the plants and try to separate the roots and transplant or cut back one or two of the three plants that are on top of each other? Or better yet, leave them alone!
I know better now for my next planting. Btw, I’m in zone 10a in San Diego and they are planted in a raised bed in full sun.
I would use a scissors to trim off one or two of the plants at their base, leaving only one. Unless you just planted them a few days ago – in which case I would say to dig them up and try to separate them. If they are too close, they’ll compete for nutrients, water, and sunlight and they won’t perform their best.
I am glad I found this article. My zuzzchini leaves have small yellow or white dots. Small like pin pricks. NOt all over. Is some discoloration normal? They do not wipe away.
Yes. Some zucchini varieties do naturally have white or creamy white markings and patterns on the leaves. If this is a varietal trait, it’s nothing to worry about.