Why Flowers Fall Off of Zucchini Plants

Zucchini flowers are amazingly beautiful. The large, vibrant flowers are a nice contrast to the dense green leaves. It's as practical as it is beautiful, with delicious zucchini after the flower fades. But why do flowers sometimes fall from the plant without producing zucchini?

The most common causes of a zucchini plant losing its blooms are poor pollination, increased stress conditions such as high temperatures or poor watering, nutrient imbalances in the soil, or insects. And because zucchini are large plants with large leaves, all of these problems are made worse if the plants are crowded together.

Sometimes called flower drop or "miscarriage," this can cause the loss of your entire crop. Keep reading to find out why this happens and practical tips for preventing it from happening.

All about zucchini flowers

Like the majority of cucurbits, zucchini plants produce both male and female blooms. Both flowers are a deep yellow/orange color and each have five petals. In addition, the flowers are very different:

       The male flowers grow on thin, upright stalks called peduncles, usually growing along the main stem or near the center of the plant. A solitary stamen with five fused anthers is found inside the bloom. In many cases, the zucchini plant will produce male flowers first, and then, after a week or so, both male and female flowers. Male flowers produce the best pollen in the first few hours of flowering.

       The female flowers can be easily identified by the small clump at the base of the flower. It is the ovary that will become a zucchini once pollinated. The pistil (reproductive organ) of a flower also contains three stigmas for receiving pollen. Female flowers are usually receptive for only 24 to 36 hours, and they should be successfully pollinated within that time.

Pollination is usually by insects, when bees and other pollinators carry male flowers to female flowers. Once this happens, the zucchini will begin to sprout.

The male flowers are supposed to fall off the plant. Once they shed their pollen, their job is over, and the flower dies again. Also, the female flower will fall off once it has been fertilized and the zucchini begins to develop.

However, if the flowers are stopped for some other reason, then something is wrong. The most common reasons for zucchini blossoms to fall off the plant are:

1. Poor pollination

Bad pollination is the number one cause of zucchini plant death. This occurs when the flower is not sufficiently pollinated (which leads to fruit damage) or when it is not pollinated at all.

Insects have difficulty pollinating flowers for the following reasons:

In most cases, insects have trouble pollinating zucchini plants for the following reasons:

       Bad Weather: Most insects don't fly in bad weather. If it is cold, windy, or rainy when the plants are in flower, insects cannot pollinate the flowers.

       Bushy Plants: Zucchini are bushy plants with large leaves, and pollinators may have trouble finding the flowers if they are hidden under the foliage.

       Use of Pesticides: While some pesticides are made to target specific types of pests, most of these chemicals indiscriminately kill any pest they come into contact with. This applies to natural, organic or even homemade solutions. Some pesticides contain substances that are particularly destructive to already threatened bee populations.

Protection

Here are some tips to ensure good pollination:

Attract Pollinators: The best thing you can do is make sure your garden is full of natural pollinators. This includes bees, butterflies, ants, hoverflies, wasps, and hummingbirds, just to name a few. Making sure your garden is full of flowers is a great way to attract pollinators, and we notice a huge improvement in our zucchini crop when we plant sunflowers nearby. Insects also need to drink, so placing shallow watering cans between your plants will attract more insects. Here is a good article that discusses which plants attract pollinators.

       Growing New Varieties: Some types of zucchini, such as dunja, are less dependent on pollinators.

       Hand pollination: If bees can do their job, we can do it for them. Using a paintbrush, press on the inside of the male flower and then gently brush the inside of the female flower to transfer the pollen. Alternatively, you can pluck a male flower, peel off the petals, and rub the male stamens inside the female flower. For best results, use fresh flowers that have recently opened.

2. Environmental Stress

The second most common reason why zucchini blossoms die prematurely is a stressful environment. When environmental conditions are harsh on a plant, it sheds its flowers so it can use its energy to keep the rest of the plant healthy until conditions are more favorable.

The most common stresses that cause flowering drop with zucchini are improper temperature, insufficient sunlight, improper amount of water, transplant shock, or root damage. Here's how to protect zucchini from every problem:

Temperature

The ideal temperature for growing zucchini plants is around 20°C (70°F), although they can tolerate moderate amounts of cold weather (but not freezing), but if the temperature drops too low they will die, and you may even hurt yourself. As the temperature continues to rise, you may experience the same problem.

Many gardeners try to grow zucchini in the summer, but high temperatures can be a problem. Daytime temperatures over 32 °C (90 °F) and nighttime temperatures over 21 °C (70 °F) will damage the plant, forcing the plant to drop its flowers.

Extreme temperature fluctuations will also have a similar negative impact.

Protection

       Provide shade: Even something as simple as sticking an umbrella in the ground over the zucchini on hot days can help keep the ambient temperature in the right range.

       Seasonal Planting: If you anticipate hot summers, time your zucchini planting so that the majority of its blooms aren't in midsummer. Try to plant them early so they are really bearable, or plant them late so they will bear late summer or early fall depending on your climate.

Lack Of Sunlight

While shading zucchini on a hot summer day can protect them from overheating, you still need to make sure they get enough sunlight to photosynthesize properly. Without proper photosynthesis, plants will not have enough food to support themselves and their flowers, and the flowers will be the first to bloom.

Protection

       Provide Full Sun Exposure: Zucchini need full sun, which means they need 6-8 hours of sunlight each day. If possible, plant them in a location where they get full sun in the morning, partial shade in the afternoon, and full sun again in the evening.

Under water and more water

Both under-watering and over-watering are harmful to zucchini plants, and both can lead to flower drop.

Plants contain about 95% water, and will wilt and die without enough moisture. Adequate water is also necessary for transpiration, nutrient uptake, and photosynthesis. When the soil does not have enough moisture, the squash plant drops its flowers so it can focus on sustaining itself until the dry period has passed. Conditions such as drought often result in an incorrect ratio between male and female flowers, and the plant does not produce well.

In many cases, excess water leads to problems such as waterlogging. This is because when the soil becomes saturated, the roots "drown" from the lack of oxygen, and the weakened root structure cannot absorb enough moisture or nutrients to support the plant.

Protection

       Consistent watering: The ideal amount of water for courgette plants is 2 to 3 cm (about 1 inch) every week. Here is a great guide on how to properly water the garden from The Led Back Gardener.

       Good drainage: Make sure your soil is loose and well drained. Adding compost or leaf mold are great ways to improve soil water retention and drainage capacity.

Transplant Shock

Hopefully, you can transplant zucchini before they flower because it can be very difficult to plant them fresh in the garden. Transplanting zucchini when they are in bloom can force the plant to drop its flowers.

Since we always directly grow zucchini, we are spared having to deal with this particular problem. However, we encounter a similar problem when growing other cucurbits.

Protection

       Plant early: Be sure to plant zucchini before they bloom. Start the seedlings indoors about 4 to 6 weeks before you plan to transplant to ensure they are not too mature.

       Hardening off plants: Hardening off plants occurs when you gradually adapt an indoor plant to the outdoor environment. The best way to avoid implant shock is proper hardening. Here's an excellent guide on how to harden plants from the Royal Horticultural Society.

Root damage

The zucchini plant's root mass is sufficient to maintain above-ground vegetation. If the roots are damaged or removed, the remaining roots will not be able to meet the plant's needs and will suffer. Once a flowering plant is damaged, the flower drops off.

When working with zucchini, be careful not to damage the roots. Plant roots are very delicate and can be easily damaged by transplanting, deep weeding, cultivation, or heavy foot traffic on soft ground.

Protection

       Handle zucchini plants (and all) with care: When working your zucchini patch, watch out for roots hidden beneath the soil. This is especially important when weeding near your plants, so be sure not to plant too deeply.

3. Nutritional imbalance

As with all plants, there are 17 nutrients that zucchini needs to grow. When these nutrients are out of balance, they can cause problems. If your zucchini plant is dropping flowers prematurely, it is possible that the soil is too high in nitrogen or that the soil is lacking in essential nutrients.

Lots of Nitrogen

Nitrogen is one of the three most important elements that plants need to grow. It is mainly responsible for the healthy growth of lush green plants. Thus, most fertilizers (whether organic or synthetic) contain large amounts of this nutrient. Too much nitrogen can promote vegetative development at the price of blooming in fruiting plants like zucchini. Alternatively, using too much nitrogen can lead to delayed fruiting, which can be just as bad for your crop as losing all the flowers in the first place.

Because nitrogen-based fertilizers are so common, this is a very common cause of bloom drop with zucchini. Fortunately, it is easy to avoid!

Protection

       Timing of Fertilizer Use: Do not apply a nitrogen fertilizer as soon as the plant begins flowering. We do not use manure in our garden, but this does not mean that organic fertilizers are inherently problematic, on the other hand, they should be avoided at all costs. If you are using a nitrogen-rich fertilizer on zucchini, be sure to use it early in the season. Added nitrogen can be very beneficial when plants are young, but you may run into problems when the plant is starting to do well.

Malnutrition

Zucchini are heavy feeders, which means they absorb a lot of nutrients from the soil as they grow, and they grow best when the soil has balanced nutrients. We've already discussed the problem with excess nitrogen, but an excess of many other nutrients can lead to poor growth and consequent flower and fruit problems.

On the other hand, a nutrient deficiency can be just as bad as too much. Without adequate nutrients, plants will struggle to bloom and perform poorly throughout the year, and the plant will not have enough energy to produce flowers.

Sometimes, your soil contains an abundance of nutrients, but they can't be accessed by zucchini plants (a great example is flower end rot).

Prevention

    Adding Compost: Compost is the best source of nutrients your garden needs. It can be made entirely from decomposing plant matter, or it can also include animal dung. Either way, adding compost will ensure that your zucchini is well supplied with all the nutrients it needs. In most cases, adding a layer of 2cm to 3cm (about 1 inch) to the garden in the spring is enough to replace the nutrients lost in the previous season, but if you're worried about this, you can always add more if the soil is nutrient deficient.

       Adjust soil pH: Zucchini grows best in soil with a pH between 6.0 and 7.5. Outside of this range, some nutrients become soil-bound or unavailable to your plant. There are many easy DIY ways to test soil acidity.

       Have your soil tested: If you suspect your soil is too high or too low in certain nutrients that may cause flower drop, send the soil sample for analysis at a lab to determine what to believe.

4. Insects

There are many "bad" insects in your garden that will feed on zucchini plants. Most sap-suckers weaken the plant causing the flowers to fall off, or cutworms can cut off flower stems entirely.

But there are some insects that attack the flowers themselves, killing the flowers and causing them to die and fall from the vine.

Trips

Thrips are sap-sucking insects that feed on all parts of the plant, but are particularly attracted to flower buds. Infected flowers will be discolored with small white lines and spots where pigment has been removed from the petals. If he eats too many thrips, the flowers won't bloom at all or will soon fall off.

Here is a great site to help you identify and deal with a thrips infestation.

Tobacco worms

As the name suggests, the tobacco worm (Heliothis virescens) feeds on young flowers before they open. In their adult form, they are a widespread insect in North America, South America, England, and elsewhere. While they usually feed on tobacco plants and other crops, they cause problems with many garden vegetables and ornamental flowers, including zucchini.

The tobacco moth lays its eggs on flowers and fruits, and the emerging larvae feed on tender buds. Flowers that do bloom will have holes in their petals and may wilt and die.

Here is a very detailed guide to identifying and dealing with tobacco worms.

Protection

       Keep the Garden Healthy: In general, the agricultural and horticultural sectors need to stop thinking of certain insects as "pests." After all, it's not the insects' fault that we've created such an ideal environment for them to eat and thrive. First, we have to create an environment that doesn't like a particular bug so that it becomes a problem. The second thing is to keep our plants and gardens healthy, because healthy plants are less likely to be infected by insects than diseased ones.

       Attracting Predators: The best and most natural way to deal with pest "pests" when they occur is to attract predators to eat them. Here's a simple article to get you started in attracting predatory insects. You can also buy nematodes or other beneficial creatures that help control insect infestations.

       Monitor Plants from Infestation: No matter what pests you're dealing with in your climate, it's important to recognize their symptoms so you can get rid of them before they become a problem. Monitor your plants closely and act quickly as soon as you see pests becoming a problem.

       Homemade insect repellents: Here are some great (and natural) insect repellents you can make using common household ingredients.

5. Stuffed plants

Although this will not directly cause the zucchini flowers to drop, overcrowding will exacerbate all of the above problems and will cost you your entire crop.

Zucchini swarms affect flowers by:

  Prevent pollinators from accessing flowers

       Competition for water and nutrients

       Prevent sunlight from reaching all leaves, inhibiting photosynthesis and changing the ambient temperature.

       Create a safe environment where insects can thrive.

Fortunately, it is very easy to prevent overcrowding your plants.

Protection

       Space zucchini plants properly: Space zucchini 45 cm (18 in) apart in rows at least 60 cm (2 ft) wide. If you've had trouble crowding plants in the past, give them more space.

An abundance of flowers

Zucchini is a staple in our kitchen. Not only are they healthy, but they can be used to add flavor and crunch to a variety of dishes. We depend on a large crop of zucchini to sustain for the winter, so seeing the flowers fall off the plant prematurely is devastating.

We watched in ignorant desperation as the flowers fell with no idea why or what we should do about it. We hope these tips help you avoid that frustration and give you some ideas on how to keep your zucchini growing and thriving.