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Why Does My Tomato Plant Have Bumps – Is It Normal?

Along with the many joys of growing tomatoes, we get to see so many new things as we garden. Some things may be strange, others exciting, like your first tomato or a new flower. Tomatoes can come with many strange occurrences, from wonky tomatoes to weird bumps growing along the stems, which is where we land today. So let’s answer your question as to why does my tomato plant have bumps?

The bumps on tomato plants, particularly on the stem are the beginnings of roots. The bumps can be white or sometimes referred to as tomato acne. They start as these tiny bumps and will eventually become roots if they are buried in the dirt. Those that are not covered in soil eventually harden, leading to the rough texture and bumpy look.

If you are still curious about why your tomato stem has started growing these roots and what you should do about them, you’ve come to the right place! Continue reading to find out more.

What Causes These Bumps on Tomato Stems?

It comes down that these bumps were formed because the plant was stressed. This stress causes a blockage in the tomatoes’ vascular system or the system that transports the nutrients around the plant. Having a blockage in this system means that nutrients can’t properly get around, and the plant then sends a hormone called auxin to the roots, which results in the making of new roots. But why was the plant stressed? Let’s look at the details.

  1. Root Damage
  • If the roots of the tomato plant are damaged in any way, the plant will panic and think, “I need to make new roots,” thus forming adventitious roots. 
    • Root damage can result from some soil born illness or any disturbance to the roots, like an animal trying to dig them up. It is essential to get your tomato started from a reliable source or plant the seeds yourself with soil you trust to prevent soil born illnesses. Make sure all your yard equipment is cleaned, especially if you take it to use in different gardens; this is how these illnesses spread. 
  1. High Humidity
  • Tomatoes typically enjoy a drier climate, and high humidity can stress the plant out. 
    • If you live in an area where the humidity is always high in the summer, it’s hard to control that for your tomato plants. What you can do is try throwing up shade cloth to cover your plant from the sun rays. Also, look for varieties that are humidity resistant, like cherry tomatoes. 
  1. Over Watering
  • Overwatering is the most common answer to why tomatoes form new roots. Especially when there is a poor drainage system. The roots get flooded and can form diseases and end up looking for a drier place to make new roots.
    • When you plant your tomatoes, put them in a spot where the water drains properly and get good well-draining soil. Having peat moss, perlite, and earthworms in your soil helps your soil to drain properly. On top of that, keep your tomatoes on a steady watering schedule, and don’t water them if it’s going to rain. Tomatoes need 1-2 inches of water per week. 
  1. Herbicide Exposure
  • Even if you aren’t using an herbicide, someone around you may be. Herbicides can confuse plants in any way, shape, or form. Herbicide damage can also look like curled, yellowing leaves, and the stems will swell and form small bumps. 
    • Unfortunately, you can do little to protect your tomato plants from herbicide if your neighbors are using it. Try asking them kindly to cease use to protect your garden. Luckily, tomato plants can recover from herbicide damage if the damage isn’t severe, though your yield may be affected. 

What Should I Do About Bumpy Stems?

Since bumpy stems don’t cause the plant any harm, you don’t need to do anything about them! But there are two things you can do if you would like to “fix” the problem. 

Cover with dirt

For the bumps that are closer to the ground, you can easily mound more dirt over the bumps, and once they are covered, they will sprout underground. This will help strengthen your plant since there are even more roots to feed it!

Fix your soil

Since sometimes the bumps mean you are overwatering or lacking nutrients, maybe it’s time to take a lot of your soil. Properly draining soil can help prevent water from pooling up and causing issues. Add some perlite or peat moss to your soil. It can also mean you are lacking some nutrients. Usually, nitrogen is always a good thing to add. If you lack other things like calcium or magnesium, the leaves will look depleted. 

Do Bumps Mean Anything Else?

Although these little bumps are most likely the beginning of roots forming, they can indicate a bigger problem. Take a closer look at your leaves if you notice the white bumps on the stem. If the leaves look curled, yellowing, browning, or have black spots, you may be experiencing a bacterial or fungal disease. You show put fungicide on your plants immediately before they die. 

You may also notice stunted growth along with white bumps. This is a good indicator that you may have a calcium deficiency, or it got extremely cold, or you experienced a light problem. Adding some crushed eggshells to your soil will help your calcium problem right away, and it’s great for your soil.

If cold weather is coming, protect your plants with a layer of plastic or shade cloth and harvest any tomatoes that you can before the bad weather. As for a light problem, you need to keep it in mind before you plant. Tomatoes need full sunlight (8 hours) to do what they are supposed to. So plant somewhere that isn’t shaded. 

Final Thoughts

After reviewing everything, I hope you have learned as much as there is to know. White bumps on your tomato stems. It is a fairly common problem that most tomato gardeners will face at least once in their lifetimes, maybe even every year.

These little tomato acne spots mean no harm, and your plant will continue to grow happy and healthy and produce delicious tomatoes. Cover them up with dirt, though, and you could be helping your plant out immensely!