Blossom End Rot – A Short Guide for California Gardens

Written by David S.

Blossom End Rot is a very common garden problem. It is not really a disease as the vector that causes the situation is a mineral deficiency and not a bacterial or viral infection. There is also a lot of poor information on the internet about blossom end rot and some of it is not correct. 

What is Blossom End Rot 

Generally, it is a watery soft spot near blossom portion of a developing fruit. It may look like a small blister that grows and eventually rots. It may also look like a dark bruise on the fruit. It is often confused with the shriveled end of a squash fruit or melon. Generally, when a squash fruit shrivels without the formation of a blister, the problem is not blossom end rot, but poor pollination.

TIP: To attract more pollinators to your garden plant a few flowering plants among your vegetables. Lobelia is a good choice. 

What to Do About Blossom End Rot Before You Plant 

Blossom End Rot occurs when the garden’s soil is low on plant-usable calcium. The easy way to prevent this syndrome is to amend garden soil with a calcium amendment. Green Thumb Nursery carries many products that solve the blossom end rot problem. Be sure to call us for recommendations or just stop by one of our five locations and talk with our garden experts about recommended products. 

By making sure that the garden soil is in prime condition you reduce the chances of blossom end rot from occurring. 

What to Do About Blossom End Rot in an Existing Garden

If your garden is not new, be sure to amend the soil each time you plant. Tomatoes, squash, and melons take a lot of nutrients out of the soil and before you replant in that spot, those nutrients  must re-added to the soil. A good standard organic fertilizer will help, but if you are planting tomato, pepper, eggplant, pumpkin, squash and watermelons in the same location, use a specialized product to amend the soil. A good example of this is EB Stone’s Tomato fertilizer. It is primed with all of the nutrients that tomatoes need. That level of specialization is essential for crop yields when crop rotation is not an option. 

The other option is to focus on crop rotation where you can. In short, plant the tomato, pepper, eggplant, pumpkin, squash and watermelon plants in different spots, but still amend the soil.

What to Do About Blossom End Rot Once it Starts?

Once you see Blossom End Rot on a plant’s fruit, there is no saving the fruit. The only real solution is to amend the soil immediately, pinch off the fruit that shows signs of blistering, and toss it in the compost. There is a chance that with a liquid fertilizer high in calcium that blossoms and newly developed fruit may emerge without the disorder. Again, be sure to use a fertilizer or soil amendment product that is designed for the plant. For example, if your tomato plant has blossom end rot, use a fertilizer designed for tomatoes. 

The thing to remember here is this: Plants want to produce fruit so that they can produce seeds. If you remove all of the tainted tomatoes from the plant, it is very likely that the plant will try to reproduce. That means that it will send out new shoots, produce blossoms, and then new fruit. If the soil is amended and the plant has access to all of the nutrients that it needs, the new crop will likely be free of blossom end rot. 

Soil is Good and Still there is Blossom End Rot

When the soil is good – full of nutrients – and Blossom End Rot Occurs, the problem may be related to the watering cycle for the plants. Plants must have adequate and regular water in order to uptake nutrients from the soil. Be sure to set a watering schedule and maintain it. Drip irrigation is a wonderful option and we carry many kits for drip irrigation that are easy to use and set up. If your garden is large, talk with our garden experts about how to set up a drip system. We have all the supplies to install a drip system for large gardens. 

Plants that Are Affected by Blossom End Rot:

Blossom End Rot affects a short list of plants. They are all fruiting plants and include:

  • Tomatoes – All species and varieties.
  • Pepper plants – sweet or hot 
  • Eggplant – all species and varieties 
  • Pumpkin and many gourds 
  • Squash – Both summer and winter squash are affected

Watermelon and summer melons are also plants that are susceptible to Blossom End Rot. 

Many of these plants are also plants that are popular summer garden plants throughout the Southern California area. To recap: Focus on:

  1. Maintaining good soil nutrient load by amending soil plots – even in containers – each time you remove a crop and plant something new in that space. 

  2. Learn to recognize the symptoms of Blossom End Rot so that you don’t confuse it with other plant issues, such as poor pollination. 

  3. Hedge your bets for a great yield by including flowering plants among your vegetables. This will help increase the pollination of vegetables. 

  4. Water your vegetables consistently so that the plant has the water available to uptake nutrients from the soil. Inconsistent watering can cause other plant issues and may be part of the reason why Blossom End Rot occurs. 

  5. Be sure to amend the soil with plant specific products before you plant. 

Green Thumb Nursery has five locations throughout Southern California. Our inventory changes daily so give us a call if you are looking for a specific plant or product. We are happy to check inventories for you or order products that are not in stock. We are also happy to answer your questions, both by email, on the phone or in person. Our garden experts are available in each of our nurseries and they are happy to chat with you about your garden project, products, and plant choices. 

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