Why Do Tomato Plants Have Hairy Stems

If you’ve ever seen a tomato plant up close, you’ve probably noticed that they have many small hair-looking structures growing on the sides of the stem. While plenty of people don’t think anything of those little hairs, many people also wonder why they’re there. 

After all, tomato plants aren’t exactly trying to compete for best-looking plant with those little hairs, are they? 

Nope! Like most plant structures, those hairs developed because they offer a lot of advantages to the plant, not because they look good to other tomato plants. 

Tomato plants have hairy stems that function to discourage herbivores from eating the plant and act as a natural sunscreen to protect the plant from UV light from the sun.

Let’s talk about what those little tomato hairs are called, what they do, and the difference between natural tomato hairs and diseases that look like them. 

What Are The Tiny Hairs On Tomato Plants? 

The tiny hairs on tomato plants are technically called trichomes; they aren’t hairs the way we think of them. They’re a specialized protective structure that helps tomato plants survive and protects the plant from a lot of different kinds of damage. 

One of the clearest reasons tomato plants grow trichomes is that the trichomes are irritating to herbivores and are a good delivery system for the irritating chemicals in tomato plants that keep herbivores away. 

The trichomes are also good for scattering light, which helps protect your plants from UV damage. That way, they can grow at higher elevations and in more direct light than other plants and don’t have to invest as much UV protection into the main plant cells in the stem. 

The last big reason that tomato plants grow trichomes is that they help protect the plant from both extreme heat and extreme cold. The trichomes form a small net around the plant that holds heat, which gives the plant a little longer before the surrounding temperatures become a problem. 

It’s a good strategy to survive the temporary cold shocks that sometimes precede a summer storm or light frosts early in the growing season. However, trichomes aren’t so effective that they can protect your tomato plants from hard freezes or temperatures exceeding 100 degrees Fahrenheit. 

Why Are My Plants Growing Little Hairs? 

There are a lot of plants that grow trichomes similar to tomato plants, and those little hairs often do the same kinds of things for those plants as they do for tomatoes. 

Different varieties of a plant may have more or less of those little trichomes, and individual plants also vary a bit in the density and length of their trichomes, even in the same variety. 

For the most part, though, think of those little hairs as an extra layer of protection and the plant’s way of telling animals (including you!) not to mess with that part of the plant. 

Do Tomato Hairs Turn Into Roots? 

There is a common rumor or urban myth among gardeners that the trichomes on tomato plant stems will turn into roots when they touch the ground or are buried underground. 

There is a little truth to this myth: wide varieties of tomatoes grow roots when you plant a healthy stem underground or let part of the stem touch the ground while it’s growing. 

It’s just not usually the trichomes that are forming roots. 

Instead, when the tomato can tell that it’s partially underground or next to the ground, it changes what kind of growth is happening in that area to create specialized growth structures. 

Those structures can look a bit like trichomes at first, which may be where the myth started. However, they aren’t trichomes; they’re small roots starting to grow in while the stem changes configuration to make use of the new roots. 

Are Tomato Plants Supposed To Be Fuzzy? 

Yes! A layer of trichomes or small hairy structures on the outside of your tomato plant’s stem and a little bit on the leaves is perfectly normal. These hairs are a protective structure and do a lot of work, making tomato plants hardier and more resistant to the outside elements. 

Some tomatoes are hairier than others, and some varieties have many trichomes, while some varieties have almost none. 

However, there is a difference between trichome growth and mold, powdery mildew, or stringy strands stretching between your tomato plant’s trichomes. 

What Is The White Fuzz On Tomato Plants? 

White fuzz on a tomato plant usually isn’t a good sign. You might have a white fuzzy bug nest in some cases, but the most common causes are usually fungal diseases infecting your tomato plants. 

Powdery mildew can look fuzzy, especially on your tomato plant’s leaves. 

Powdery mildew is contagious and can spread throughout your garden if you don’t treat it quickly. Applying a little baking soda to your plant’s affected leaves is usually all you need to do to cure powdery mildew. 

Another cause of white fuzz that shouldn’t be there are spider mites, which can leave a sticky stringy residue behind that looks like mini spider webs when the infestation is mild and can look like white stringy nets when infestations are more severe. 

Treat spider mites by hosing down the plant with a strong stream of water, applying insecticidal soap, or using other pesticides or neem oil to eliminate the mites. 

Things To Consider

New gardeners are often worried when a plant looks a little different from what they expect, including growing hairy trichomes when they don’t expect them. 

Remember, tomatoes come in wide different varieties, and some tomato plants grow more trichomes than others. 

Especially once you start growing heirloom tomatoes or have several tomato varieties in your garden, you might notice some big differences in the number of trichomes per plant. That’s normal. 

Depending on where you live, you may want to choose varieties that grow extra trichomes if you can. The additional trichomes offer better protection from grazing deer, high UV sunlight (important for anyone growing tomatoes at elevation), and better protection from the cold (important anywhere weather changes can be sudden and severe). 

If you seed-save, you may also want to pay attention to whether plants with more trichomes do better in your garden and grow the seeds from those plants preferentially. The more you hone in on the traits and combinations of traits that work in your garden, the bigger your harvests are likely to become!