How to Prevent Tomato Blossom Drop

Growing Vegetables
Tomato Blossom

Blossom drop is a common problem with tomatoes. Many gardeners face this issue in their garden. Since tomatoes are among the most popular gardening plants, there are many people affected by this issue.

The main problem with blossom drop is that it happens seemingly out of nowhere. It's not unusual for a healthy-looking tomato plant to set beautiful flowers, only to have them dry up and fall of long before the fruit is formed.

In order to combat this problem and to ensure that your tomatoes will not be affected by blossom drop, it's important to understand how this problem originates and how to solve it.

Common Causes of Blossom Drop

There are several common causes of blossom drop in tomatoes. You need to understand them all to know how to treat this problem. Most of them are related to sudden temperature changes and stress.

Usual causes of blossom drop in tomatoes are:

  • Too high temperature.
  • Too low temperature.
  • Too much of nitrogen.
  • Too little of nitrogen.
  • Lack of proper pollination.
  • Too high humidity.
  • Too low humidity.
  • Lack of water.
  • Stress from insect damage.
  • Stress from disease.
  • Too heavy fruit set.

How to Control Blossom Drop

Now that you know about the most common causes of blossom drop in tomatoes, you should know how to address this issue and how to prevent it. You need to observe your tomatoes carefully and to provide the best conditions they need to thrive.

Prevent Temperature Problems

To prevent temperature problems: While you can't control your climate, you can control which type of plants you have in your garden. Always grow only tomato varieties that are suited to your climate. Since inadequate temperature is the most common cause of blossom drop, you need to know which varieties to grow in your garden.

Most tomatoes thrive when the daytime temperatures are in the range between 70 degrees F (21 C) and 85 F (29 C). Many tomato varieties can tolerate higher and lower temperatures (even extreme ones) for a short period of time, if these temperatures persist for several days or nights, it will affect your plants. It may cause blossom drop in your tomatoes. With these extreme temperatures, the plant aborts setting the fruit and focuses on survival only. If the temperatures are truly extreme (over 104 F / 40 C) it may cause the blossom drop even after a few hours of such temperatures. In order to prevent this problem it's important to know your climate and to always plant only heat-resistant varieties.

Same goes for extremely cold temperatures. In the case of cooler climate, you have more options on how to prevent blossom drop in your tomatoes. First of all, never plant your tomatoes until well into spring. They need warm ground and warm weather, so it's best to wait until the climate improves to plant them. Do not plant until the nighttime temperatures don't get constantly above 55F (13 C). Tomatoes should never be started too early in the season because it won't bring any advantages and it can lead to many problems.

Another thing you can do to help your tomatoes in cooler climates is to protect your plant with covers during night. This should help them and it will prevent the blossom drop.

For cooler climates, it's important to choose early maturing tomato varieties if you wish to grow your tomatoes in spring. Some good varieties to try ate Legend, Matina, Early Girl, Oregon Spring, Silvery Fir Tree and Polar Baby.

It's best to always choose heat-tolerant (heat set) tomato varieties for places with long periods of humid and hot weather. Remember that high nighttime temperatures can affect your tomatoes more than high daytime temperatures because they don't allow tomatoes to rest. Some good varieties for this type of climate include Solar Set, Sunchaser, Sunmaster, Heat Wave, Sunpride, Surfire and Sunpride.

Pollination Problems

To avoid problems with inadequate pollination, make sure to always help your tomatoes to pollinate. Certain conditions are needed for proper pollination, such as wind, insects or hand shaking. These are needed to carry the pollen from anthers to the stigma.

Keep in mind that there are usually no insect pollinators in the garden during the weather extremes. To help pollination, it's always useful to attract more bees to you garden by planting nectar rich flowers near the tomato plants.

Humidity Problems

Ideal humidity levels for tomatoes are in the range between 40% and 70%. In case the humidity is outside of this range (be it too low or too high), it will affect your tomatoes and it may lead to blossom drop.

Inadequate humidity is problematic because it interferes with the release of pollen and with pollen's ability to stick to the stigma. In these conditions, the pollination won't occur.

To address this problem, you first need to know if the humidity levels are too high or too low. If too low, you can help your plants by hosing the foliage during the day. Another advantage to it is that it will cool the plant down. It will also raise the humidity to more acceptable levels.

However, this solution is not recommended in areas where fungus diseases are present, so you need to be careful. It is also not a recommended thing to do if you live in area with high humidity.

If your garden has a very high humidity level, you should only grow specific tomato varieties that are not affected by high humidity. Recommended varieties include Flora-Dade, Eva Purple Ball, Grosse Lisse, Moneymaker, Taxi, Jubilee, Sun Gold and Yellow Pear.

Watering Problems

Tomatoes need a lot of water. It's important to water them regularly so they can thrive. Regular watering will prevent many problems, including the blossom drop. Tomatoes need to be watered at least once per week during the dry weather. Make sure to always water your tomatoes deeply.

Keep in mind that tomatoes have very deep roots. Sometimes the roots go down as deep as 5 feet. It means that you always need to deep water your tomatoes. Shallow watering is simply not enough. In fact, it can stress and weaken your plants.

Additional Tips

Here are some additional tips you need to follow to keep your tomatoes healthy and to prevent blossom drop:

  • When planting, make sure to supply your tomatoes with plenty of organic matter. This will keep them healthy and make them thrive.
  • Don't overdo the fertilizer. Tomatoes should not be fed every week. You may add some balanced fertilized when the fruit forms. However, keep in mind that fertilizers high in nitrogen will only encourage the plant to grow more foliage and not more fruit.
  • Make sure that your tomato plants are healthy. You should always apply good culture practices and treat your plants in case a disease appears.
  • Don't overdo it. Too much of a good thing is bad. In case your tomato plant has too many blossoms, it means too many fruits and they will all compete for the limited food supply. It means that only the strongest ones will survive, which means less fruit for you. Also, with too many flowers, the plant will automatically abort some of them. Once you have harvested the initial crop, however, this problem should subside.
  • Keep in mind that there is no way to fully guarantee that the fruit will set. Many factors that can affect the fruit growth are out of your control, particularly when it comes to temperature and humidity. Sometimes, the only thing you can do is to wait for the conditions to improve on their own.
  • In case you are the only gardener in your area affected by blossom drop, chances are that it's not a temperature nor humidity problem. In this case, consider possible cultural causes of the blossom drop. It's always advisable to choose a suitable variety and to keep your plants healthy to minimize the risk of blossom drop.

Photo credit: Jutta M. Jenning

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