Why Do Tomatoes Rot on the Vine? [4 Preventable Reasons]

Overwatered tomatoes are the most common cause of fruit that rots on the vine. Fertilizing your tomato plants with a high-nitrogen fertilizer also causes tomatoes to rot. If you use aggressive weeding tactics in your garden, you can damage tomato roots. This root damage prevents your tomatoes from pulling in soil nutrients, which in turn causes tomato rot. Finally, using forced-growth tactics can cause tomatoes to deplete the soil of nutrients too quickly, leading to tomatoes that rot as they grow.

Why do tomatoes rot on the vine?

What is the Most Common Type of Tomato Rot?

Blossom end rot is a common type of rot that afflicts tomatoes. Rotted spots usually appear on the bottom end of the tomato, but rotting can also occur on other parts of the plant. Once the tomatoes begin to rot on the vine, it can be very difficult to save them. So, it’s best to create garden conditions that discourage rot.

4 Reasons Why Tomatoes Rot on the Vine

There are several reasons why tomatoes rot on the vine. Fortunately, these are all things you can prevent with proper care for your plants. Below are the most common reasons for rotting tomatoes, as well as how to prevent them.

Too Much Moisture in the Soil

In the majority of cases, tomato rot is caused by too much moisture in the soil around your tomato plants. This may come from overwatering, a year of heavy rainfall, or the location of your vines. For example, if your tomatoes are planted in an area where they do not get enough sun, the soil will stay moist, which can trigger the fruit to rot on the vine.

  • Soggy soil is the number one cause of tomatoes that rot on the plant.
  • Overwatering—from artificial watering or rainfall—can cause this rot.
  • Lack of sunlight can cause the soil to stay moist longer, which triggers rot.
  • Plant tomatoes in full sun to discourage rot.
  • Follow our guide to avoid overwatering your tomatoes.

In order to discourage rot, plant your tomatoes where they will receive full sunlight. It’s also essential to choose a planting location where the soil does not stay consistently moist. Follow this up by providing 2 inches (5 cm) of water per week, and remember to reduce your watering volume when it rains.

Poor Soil Quality

Improper soil chemistry is a common cause of rotting tomatoes. Tomato plants are a bit picky with regard to the balance of nutrients in their soil. Tomatoes need a healthy dose of calcium to grow and thrive. Adding the wrong fertilizer only makes blossom end rot worse. An overdose of nitrogen fertilizer renders tomato plants unable to absorb calcium from the soil. The resulting calcium deficiency causes tomatoes to rot as they grow.

  • Tomatoes often begin rotting on the vine due to poor soil quality.
  • Adding high-nitrogen fertilizer makes soil conditions worse and causes more tomato rot.
  • High phosphorus, low nitrogen soil is the best choice for rot-free tomatoes.
  • Use this fertilizer—which contains 2 parts phosphorus to 1 part nitrogen—to boost healthy tomato growth.

In order to properly feed your tomato plants, use a fertilizer that is high in phosphorus and low in nitrogen. When looking at fertilizer labels, you will often see 3 numbers separated by dashes. The first number is nitrogen content, the second is phosphorus, and the third is potassium. For tomatoes, select a fertilizer where the second number is greater than the first number. For instance, 2-4-2 fertilizer has 2% nitrogen, 4% phosphorus, and 2% potassium. Since there is more phosphorus than nitrogen, this fertilizer will help grow healthy, edible tomatoes.

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Aggressive Weeding

Sometimes, tomato fruits and plants rot if you are too aggressive with your weeding in the garden. This is because tomatoes have very delicate root systems. These roots can be significantly damaged by pulling up weeds in the tomato root zone. When you weaken the roots of your tomato plant, they can struggle to gather soil nutrients. This leads to tomato fruits that are afflicted with blossom end rot.

  • Weeding aggressively can damage the roots of your tomato plants.
  • Root damage to tomato plants prevent proper soil nutrient uptake, which causes your tomatoes to rot on the plant.
  • Spread a layer of mulch 3–4 inches (7.5–10 cm) deep around your tomatoes to prevent weed growth without pulling weeds.

To keep your tomato plants safe and reduce your weeding work, mulch around your tomato plants. A 3–4-inch deep (7.5–10 cm) layer of organic mulch, such as wood chips, suppresses weed growth. Plus, mulch helps keep your garden soil at the right moisture level for healthy, rot-free tomatoes.

Rapid Growth

If you use forced growth techniques to grow tomatoes quickly, you can cause your tomatoes to rot on the vine. This is because rapid growth will deplete the soil’s calcium supply quickly. Once the calcium in the soil is gone, tomato plants will not be able to form proper fruit. This leads to mushy, rotten tomatoes on your plants.

  • Early fertilization, plastic mulch, and pinching back suckers can force tomato growth but cause rot later.
  • Rapid growth depletes the soil’s calcium supply, which leads to a lack of soil nutrients when the plants begin to grow fruit.
  • Prevent rot by waiting until fruit begins to form before you fertilize your tomatoes for the first time.

Although there are several tactics for forcing quick tomato growth, including using black plastic mulch as sheeting, fertilizing frequently, and pinching off suckers, these tips ultimately backfire. It’s best to provide plenty of sun, natural mulch, and wait until fruit begins to form before you start to fertilize your tomatoes.

How Do You Keep Tomatoes from Rotting on the Vine?

To keep your ripe tomatoes from rotting on the vine, make sure the soil’s moisture levels are consistent throughout the growing season. Never allow the soil to become soggy or muddy. Next, use mulch as a weed-suppressant in your garden to reduce the amount of weeding you have to do. This will protect your tomato’s roots and lead to a healthy harvest.

  • Don’t allow your tomato plants’ soil to become soggy or overly wet.
  • Use mulch to suppress weeds instead of aggressively weeding tomato beds.
  • Wait until the first green tomatoes appear on your fruit before you start fertilizing.
  • Use a fertilizer that is low in nitrogen and high in phosphorus.

Wait until green tomatoes have begun to appear on your tomato plants before you begin fertilizing. Then, fertilize once every 1–2 weeks with a low-nitrogen, high-phosphorus fertilizer. You can safely continue this fertilizer schedule until fall. With these tips, you’ll grow incredible tomatoes without rot problems.

Why are Your Tomatoes Rotting on the Vine?

If they are grown in improper conditions, tomatoes may rot on the vine. The reasons why this rot occurs are:

  • Overwatered tomatoes are extremely prone to developing blossom end rot.
  • Poor-quality soil—or using a high-nitrogen fertilizer—causes calcium deficiency that triggers tomatoes to rot as they grow.
  • Uprooting weeds near your tomatoes can destroy tomato roots—this causes nutrient deficiency for the plant that results in rotten fruit.
  • Forcing tomatoes to grow rapidly by fertilizing early and pinching off suckers can lead to rotten tomatoes down the line.

Although it is almost impossible to save tomatoes that have already begun to rot, you can change your watering, fertilizing, and weeding practices today. This way, your plants can recover and produce a healthy crop of tomatoes when they flower again.

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