Guarding Your Garden Against Excessive Water

Missouri has seen a record amount of rain this year. This seems great since watering the garden became unnecessary, but too much water can have some major effects on your garden. Many people, including myself, love growing tomatoes and peppers, and these two seemed to be significantly affected (by microbial diseases) due to the overabundance of water. For minor issues, there are some useful techniques that can be utilized to try to recover your garden, like removing diseased areas and applying treatments. There are many preventative measures, such as site selection and monitoring, that should be used to ensure your garden strives despite abnormal rainfall. Let’s look at the symptoms and solutions in more depth.

General Symptoms of Excess Water

There are some easy ways to detect if your garden is getting too much water from rain or watering. If you’re getting an overabundance of rain (like this year), you definitely need to keep a close eye on your garden. The following are common symptoms if your garden is receiving too much water:

  • Yellow leaves
  • Plant looks wilted
  • Root rot
  • No new growth
  • Young leaves turn brown
  • Soil turns green (i.e. algae growth)
  • Microbial infection (varies by plant but often some form of leaf discoloration or spots)
  • Fruit cracking
  • Fruit discoloration (i.e. blossom end rot in tomatoes)

Unfortunately with all the rain this year, my tomatoes and peppers both got microbial diseases that caused leaf discoloration and spotting. My peppers got a bacterial disease called leaf spot that leads to brown/black water-soaked spots on the leaves and eventual leaf drop. The leaves also started to yellow and curl. The peppers that had already been produced didn’t have any issues, but I expect that the plant may be done producing.


My tomatoes got septoria leaf spot, a fungal disease that occurs under warm, moist conditions. I also had issues with a lot of the leaves on the plant wilting and eventually turning brown.


Last year after heavy rain in autumn, I had problems with fruit cracking open and leading to diseases in both tomatoes and watermelons. These were also quite watered down and mostly flavorless. I have not seen these issues yet this season but that’s likely because the plants were at different development stages during the excess rainfall periods. If the rainfall continues at the current rate, some of these issues will likely arise.

In the past, I have also had issues with tomato blossom end rot, which appears as a dark, moist spot on the blossom end of the fruit. This can occur from both underwatering and overwatering in combo with calcium deficiency.

There are quite a few other diseases (bacterial and fungal) that tomatoes can be infected with when exposed to too much water and are often indicated by some form of leaf discoloration or spotting. The following are two great sources that provide detailed information about symptoms, causes and treatments of other common diseases and disorders.

Clemson Tomato Diseases & Disorders

Texas A&M Ag Vegetable Problem Solver

Methods to Mitigate Issues

The best way to ensure a healthy garden is to plant and maintain it in a way that mitigates issues from arising in the case some atypical environmental factor (like excess rainfall) occurs. Obviously surplus rain cannot be avoided, but some techniques can be applied to help reduce the risk of losing your crop by reducing the amount of disease spreading microbes available and promoting rapid drying of wet leaves.

Site Selection & Drainage

My very first attempt to grow vegetables was in a pot and was a complete fail. I forgot to drill a hole in the bottom for drainage, and when we returned from vacation, the pot was flooded and overgrown with algae. Clearly, good drainage is a critical factor for preventing overaccumulation of water. Planting in an area with good drainage—such as on a hill, raised bed or in soil that does not retain too much water—is important. After my initial fail, I didn’t lose heart but created a garden plot on our hill in the backyard. This spot has been amazing for gardening because it has excellent drainage and full sun. The normal soil around this area is very dense clay, so soil amendments are needed to improve drainage. I use compost, sand and peat moss depending on the plant. In beds along my house, I’ve built up the bed height to improve drainage. Growing your plants in areas with full sun will also help with drying of the foliage after wet spells.


In limited space, cramming things in often leads to poorer quality crop and disease. Narrow down the number of plants to your family favorites and needs, rather than trying to be too ambitious. It’s best to plant in a well-ventilated space and don’t overcrowd plants. Prune lower portions to prevent infection spread from the soil and remove any diseased areas. I often use tomato cages, which are easy but can lead to foliage overcrowding. If you use this technique, make sure you prune the plant to ensure it still has good ventilation. I’ve been told that tomato trellising is a good method to provide better ventilation, but I haven’t had a chance to try this yet. Tomato Headquarters has a nice guide to help you decide how to support your tomatoes. I also cage and stake my pepper plants (depending on the plant size) and have seen improvements in yields by doing this.


If significant rainfall has occurred, you need to keep a close eye on your crop. I have adopted a daily walk-about to check up on my garden, which is great for making sure you frequently harvest ripe crops and spot issues. If you notice potential onset of disease, employ treatment methods (removal of diseased parts and application of pest control substances). Here’s a useful guide that provides some other great pointers: 9 Vegetable Gardening Tips Following a Heavy Rain.


Mulch has many benefits. Preventing weeds, retaining more constant moisture and reducing the spread of disease from the soil onto lower leaves are some critical ones that reduce detrimental effects of excess rainfall. I like to use leaves and straw to mulch around my tomatoes and other plants as this also provides some nutritional benefits. A lot of places also recommend black plastic mulch. Here’s a guide for mulching tomato plants.


Overhead watering in my experience has been one of the biggest culprits for microbial diseases on leaves. Unfortunately it’s impossible to control rainfall in an outdoor garden, so this is one of the main reasons plants are more prone to fungal and bacterial diseases when there is excess rain. Be sure to learn the amount of irrigation required for plants and adjust your supplemental watering accordingly. The last thing you want to do is water your garden if you just received a heavy rain. Make sure to use drip hoses or water at the base of the plants if you have to water the plants.


A properly fertilized garden is necessary to grow a healthy crop. An unhealthy crop will be more susceptible to disease. Ensuring proper supplementation of calcium to tomatoes is critical to prevent blossom end rot. I like to use compost in addition to slow-release, granular fertilizers and supplemental nutrients from leaves/straw.

Weed Control

Weeds are my least favorite thing about gardening. In the past, I didn’t mulch very well and had a lot of issues. I’ve taken steps in subsequent seasons to properly mulch and have been able to reduce the weeds a lot. Common weeds harbor many garden diseases and can take valuable nutrients from your plants. Thus, it’s important to keep them under control by mulching and taking the time to weed.


Once a disease has set in, it is often difficult to get rid of it because it may overwinter. Thus, it’s important to try to rotate your crops to prevent infection in the subsequent growing season.


Cleaning up diseased parts is important to reduce the potential of further transfer of the disease to other parts or plants. When you cut off diseased sections or uproot the plant at the end of the season, be sure to throw them away and avoid adding them to your compost pile where they may harbor the microbe and later infect your entire garden.


For the preventative benefits of fungicides, apply them before symptoms occur or as soon as you first notice them. This is also the same technique used for preventing other fungicide diseases like powdery mildew on squash and black spot on roses. If you know a plant is suseptible to a certain disease, be sure to give yourself a reminder to apply fungicide. If there’s a lot of rain, you’ll also want to apply it after a heavy rainfall and reapply if there is additional rain. I like this neem oil-based organic fungicide available at Amazon or Lowe’s.


In general, the best way to try to recover a diseased plant is to remove the affected areas (leaves/branches). In the case of tomatoes and peppers, this has worked so far for me this season. If a fungal infection has occurred, also apply a fungicide to prevent further migration of the disease. I fortunately was able to recover most of my tomatoes from the leaf spot by removing the diseased areas and keeping it at bay with fungicide. Unfortunately this method did not work with two of my pepper plants, and I ended up pulling them up to prevent the disease from spreading to my other peppers. In past years, I had to deal with poor crop quality and sacrificed yield by removing affected parts (in the case of the blossom end rot). In subsequent years, I have applied preventative techniques to mitigate some issues.

With gardening there always seems to be some new disease or disorder that may arise from some environmental or unforeseen factor. Thus, it’s always important to keep learning techniques to better protect your garden. The best method of treatment is always going to be preventative care and maintenance. Once symptoms have set in, it is often too late (like my potted plants), so take the necessary steps to ensure your garden has the best chance of achieving its full potential!


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