Are you curious about why tomato plants are fuzzy and hairy? If so, you are probably wondering what all those hairs on tomato plants do.
So, why are tomato plants fuzzy and hairy? Tomato plants are fuzzy due to the thin hairs on the stem, leaves, and fruit. These hairs are called trichomes, and they help a tomato plant to resist cold, drought, ultraviolet light, and insect or animals pests. Trichomes also release oils that give tomato plants their distinctive scent.
Of course, the length and thickness of trichomes will depend on the variety of tomato and also on the plant’s environment.
Trichomes are an incredible and versatile tool used by tomato plants to help them survive. In this article, we’ll take a closer look at trichomes and all of the things they can do for tomato plants.
Let’s get started.
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Why Are Tomato Plants Fuzzy & Hairy?
Tomato plants are fuzzy and hairy due to the thin hairs on the stem and leaves. These thin hairs are called trichomes, and many plants have them, including tomatoes.
“Trichome” comes from the Greek “trichos”, meaning “hair”. However, trichomes are not really “hair” in the same sense that animals have hair.
Trichomes can be very short (almost invisible) or a few centimeters long. Trichomes can serve different purposes, depending on whether they are above or below ground.
With extra roots, tomato plants can absorb more water and nutrients from the soil. This increases their chance of survival and helps them to produce more fruit.
This is why you sometimes hear the advice to bury tomato transplants deep. In fact, the advice is to bury them so that only 1/3 of the plant is above ground.
The trichomes on the underground part of the vine then become extra roots to help the plant grow. You can learn more about why and how to bury tomato plants deep in my article here.
“Most plant species have hair‐like epidermal structures below and/or above ground. When present on the aerial parts, they are usually referred to as trichomes, which is derived from the Greek word trichos, meaning hair.”https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.16283
Trichomes are single or multiple cells that serve many different purposes for a tomato plant.
Each type of trichome has its own specialized purpose, ranging from defense to temperature control. Let’s take a closer look at some of the purposes of trichomes.
What is the Purpose of Trichomes?
Trichomes are not just for appearance. These tiny hair-like structures serve many important purposes for tomato plants.
“Plant trichomes not only increase the thickness of the epidermis but also act as a physical barrier against external invasion . They are not necessary for the growth and development of the plant itself; however, they have many important biological functions, including reducing the loss of plant heat, increasing the resistance of plants to cold damage and drought, and protecting plant tissues from ultraviolet light and insects”https://www.mdpi.com/2073-4395/10/3/411/htm
“High trichome density can have direct and indirect effects on photosynthesis, transpiration and leaf energy balance.”https://www.biorxiv.org/content/10.1101/2020.02.11.943761v1.full
This means that having more or less trichomes will affect:
- Temperature (protection from cold and heat)
- Photosynthesis (energy production)
- Transpiration (loss of water through leaves)
There is also some evidence that trichome density (the number of trichomes per square inch of leaf or vine) depends on both genetics and on the environment.
The same article also mentions that there are two types of trichomes:
- glandular trichomes (these produce metabolites that help to protect the plant)
- non-glandular trichomes (these tend to be longer)
“Glandular trichomes produce a rich repertoire of secondary metabolites, whereas non-glandular trichomes create a physical barrier against biotic and abiotic stressors.”https://www.biorxiv.org/content/10.1101/2020.02.11.943761v1.full
These metabolites help to protect the plant against natural enemies, including insect or animal pests.
Let’s take a closer look at what all of these trichomes can do for plants.
1. Skin Thickener
Trichomes add an extra layer of physical protection for plants. In a sense, they make a plant’s skin thicker.
This prevents damage to the plant from animals that pass by and brush against the plant (or prevents them from taking a bite!) Trichomes also make it more difficult for pests to penetrate the stem and leaves to feed on the plant’s juices.
Think about it: would you want to eat something that is hairy? Well, neither do most insects and animals!
2. Pest Repellent
Trichomes also help to repel pests, including both insects and animals. If you’ve ever tied up lots of tomato plants to keep them from falling over, you might be able to guess why.
Have you ever washed your hands after touching tomato plants and found that a yellow substance comes off? This has happened to me countless times, and I only recently found out the reason.
Remember how we talked about glandular trichomes earlier? As it turns out, those glandular trichomes on tomato plants give off essential oils.
These essential oils give tomato plants their own unique scent. This is similar to how other essential oils in mint or basil plants have their own unique scents.
Just as some pests dislike the scent of mint or basil, other pests dislike the scent of tomatoes. There is even some evidence that tomato plants can alter the compounds in these essential oils to deter pests.
For example, the trichomes on the stem and leaves deter pests from eating the “green” parts of the plant. Eating the hairs is an irritant to some animals, and the scent or flavor will repel some insects.
At the same time, this encourages animals to eat the fruit once it is ripe, thus spreading the seeds of the plant.
When glandular trichomes release oil, they use metabolites produced by the plant. According to this article on NCBI:
“Some of these secondary metabolites were shown to have antifeedant, oviposition deterrent, and in some cases toxic properties toward insects.”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466034/
This means that the essential oils (containing metabolites) would:
- prevent insects from feeding on the plant
- discourage insects from laying eggs on the plant
- poison insects that ate the plant
“Both glandular and non-glandular trichomes impeded caterpillars from searching for food.”https://www.jstor.org/stable/4221246?seq=1
So, if the fuzzy appearance of tomato plant trichomes repels you, just remember that it repels insects as well!
Also, keep in mind that the stem and leaves of tomato plants are toxic not only to many pests, but to humans as well.
3. Temperature Control
Trichomes also help to protect tomato plants from extreme temperatures. For example, in the summer heat, trichomes protect the plant from sunlight and help it to cool down.
When frost threatens in the spring or fall, trichomes can protect tomato plants from cold weather. Of course, trichomes may not be enough to completely protect your tomato plants from cold.
4. Drought Resistance
Trichomes also help tomato plants to resist drought. They do this in two ways.
First, any trichomes that are buried underground become roots. With a more extensive root system, a tomato plant can store more water to help survive a drought.
Second, trichomes also reduce evaporation of water from the tomato plants. Normally, plants lose water due to transpiration from their leaves.
This is especially true in hot and sunny weather. In that case, the sun speeds up the evaporation process and dries out the plant even faster.
This makes it that much more important to be able to survive dry conditions. Trichomes come to the rescue once again!
5. Light Management
We don’t think about it much, but plants have a lot to worry about. For example, they need to manage their intake of water, nutrients, air, and light, all while trying to avoid becoming lunch for an animal.
Tomato plants do need light for photosynthesis, and there is some evidence that trichomes assist with this process.
However, too much light can damage the plant or its fruit. For example, sunscald causes tan patches on tomato fruit when the plant is exposed to too much strong, direct sunlight.
Trichomes help to protect the leaves, stems, and fruit of tomato plants from ultraviolet light. Basically, they prevent strong sunlight from becoming too much of a good thing.
Why Do Tomato Plants Smell?
As mentioned earlier, tomato plants have trichomes (fuzzy hairs). Some of these trichomes are glandular trichomes.
These glandular trichomes release essential oils, some of which defend the plant against insect and animal pests.
The essential oils released by trichomes give tomato plants their distinctive smell. This scent warns pests not to eat the plant.
It is interesting to note that the trichomes of wild and cultivated tomato plants produce different secondary metabolites. That is, the environment and genetics of tomato plants can affect what they release in their essential oils.
I Don’t Think These Are Trichomes. What Should I Do?
Seeing trichomes on your tomato plant is perfectly normal. In fact, some tomato plants have lots of trichomes that grow very thick and dense.
However, if you suspect that the fuzzy appearance of your plant is a problem, it is worth examining.
Take a closer look: is the tomato plant fuzzy in only one area? If so, there could be some type of disease affecting your plant.
For example, the following problems that affect tomato plants can give a fuzzy appearance on part of the plant:
- gray mold
- powdery mildew
- late blight
Let’s take a quick look at each of these problems and how you might identify them.
According to Penn State University, gray mold appears on seedlings at the soil line. It looks like a fuzzy gray or brown lesion. You can see pictures of gray mold on the Penn State University website.
Gray mold often happens after a plant is wounded (cut, scraped, or bent), and it can develop in cool temperatures.
One way to prevent gray mold is to use lime to provide extra calcium to your tomato plants.
Powdery mildew is a white fungus that develops on tomatoes and other plants. It has a white, powdery appearance on plants, which may look fuzzy in some cases.
Powdery mildew can occur in the garden or in greenhouses. It can spread from weeds onto your tomato plants, so be sure to prevent weeds in your garden and pull up any that do grow.
The spores that cause powdery mildew do not need wet leaves or high humidity to take hold and multiply. You can see pictures of powdery mildew on the Cornell University website.
Late blight is caused by a fungus (Phytophthora infestans) that spreads by spores on the wind or when it survives the winter inside infected potato tubers in the soil.
You will see fuzzy spots on the leaves or stems of your tomato plants if they get infected with late blight. You can learn more about how tomato plants get blight (plus prevention tips) in my article here.
Late blight can affect both tomatoes and potatoes. It thrives in cool, wet conditions.
Once plants are infected, there is no treatment. Your only option is to pull out the infected plants and try to prevent the disease from spreading to others.
Your best bet is prevention, so choose plants that will resist the disease. I wrote an article here where you can learn more about blight resistant tomato varieties.
Now you know why your tomato plants are fuzzy and hairy. You also know the purpose of these hairs (trichomes) and what they do for the plant.
I hope you found this article helpful. If so, please share it with someone who can use the information.
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