It’s fun growing tomatoes in the garden but only when they grow well and deliver fruit. One of the worst problems is when the stem is thin and spindly. This post contains my research on how to get thick stems on tomato plants.

You can get thick stems on tomato plants by supplying sufficient NPK (nitrogen, phosphorus, and potassium) nutrients. You can add a balance organic fertilizer with these nutrients in the required amounts.

There are a lot more steps you can take to ensure your tomato plants grow healthy and thick stems. These will be able to grow lots of foliage, fruits, and be able to support the fruits without collapsing the plant.

1. Provide the tomato plant with sufficient sunlight

The most common reason for the tomato plants to develop spindly and tall stems is a lack of sunlight. The tomato plants need at least 8-10 hours of direct sunlight to grow their best.

The lack of sunlight will cause the tomato plants to stretch in the direction of the light trying to get as much as possible. This is the reason why the stems will get tall and spindly.

If you’re starting seeds indoors, make sure to give them good sunlight by placing near a windowsill.

You’ll need to rotate the seed starting trays every day so that all the sides get sufficient sunlight.

If that is not possible, you need to invest in a good set of indoor lights that will help the tomato seedlings germinate.

Once the seedlings have germinated, you need to transplant them either in containers or in the garden. Make sure to choose a spot where the tomato plant will get the required sunlight.

Avoid placing the plant in an area that gets shaded due to a portion of the house or due to other plants and trees. If you’re already growing the tomato plants, you may need to prune some tree branches or plants to allow sufficient sunlight.

Or you may need to transplant the tomato plant to another location that receives good sunlight.

The good thing is that it’s not difficult to transplant and regrow them. Make sure to remove the root ball from the soil and place it sufficiently deep in the new location.

You want to cover a good portion of the stem at least till the first set of leaves in the soil. This helps the stem develop new roots and grow thicker.

If you’re growing the tomato plants in containers, it’s easier to move them around to an area that receives the required sunlight.

2. Avoid overcrowding of the tomato plants

Another reason your tomato plants may get tall and spindly is if you’re planting them too close to each other.

When the plants grow close to each other they will compete for resources like sunlight, water, and nutrients.

When you start seeds in trays, you may plant several seeds together to get a good chance of germination. But when the seedlings germinate and grow a few inches, you need to thin them out.

Thinning is the process where you keep the heathiest seedling in the tray and cut out the remaining ones. This gives the single seedling the best resources possible to grow healthy, thick, and strong.

You need to keep a good distance between the tomato plants when growing them in the garden. The distance depends on the variety but usually, you should keep at least 1-3 feet distance between the plants.

This will help the tomato plants grow well with sufficient distance so sunlight is reaching each of them. And their roots have sufficient space to spread around in the soil without interfering with each other.

If you’re growing tomatoes in containers, I would suggest growing only one plant per container. This gives the tomato plants enough space without overcrowding with the other plants.

If you’re already facing the problem of growing the tomato plants too close whether in the garden or in the container, you need to transplant one of them to another location or container.

3. Ensure the plants are getting good nitrogen

Nitrogen is the element that will get the best growth for your tomato plant’s foliage. The tomato plant’s roots will extract and use the nitrogen from the soil.

If you want thicker tomato plant stems, make sure they are getting sufficient nitrogen. The best way to do this is to add a nitrogen-rich fertilizer to the tomato plants.

This could be a slow-release fertilizer that you put on top of the soil. Or it could be a liquid fertilizer that you spray on the soil and the foliage.

The fertilizer that you buy from the store will specific the N-P-K values. The N stands for nitrogen, P is Phosphorus, and K is potassium.

You can put some balanced fertilizer with N-P-K of 5-5-5. Or you can use a nitrogen-rich fertilizer having N-P-K of 10-5-5.

Both types are fine to give a boost of nitrogen to the soil you’re growing the tomato plants in.

Make sure to follow the instructions mentioned on the fertilizer box or container. You want to mix in the right amount with the soil.

If you add too much fertilizer to the soil, you can do more damage than harm. The excess nitrogen will burn the roots of the tomato plant and cause them the tomato plants to grow thin and spindly.

4. Make sure the tomato plant has good aeration

Along with the nutrients and sunlight, the tomato plant roots need to get sufficient oxygen from the soil.

A good supply of oxygen will help the tomato plants develop a thick and healthy stem.

The best way to ensure good aeration is to use good quality soil. This will have a good texture that ensures the required level of air circulation.

The soil has to have the right amount of clay and sand in it. Too much clay will cause the soil to lump and have poor aeration.

Too much sand in the soil will have plenty of aeration but it will cause the tomato plants to have poor root development.

If you’re growing tomato plants in-ground, you need to ensure the right soil texture. You need to test the soil with a soil test and make the necessary amendments if required.

If you’re growing the tomato plants in a raised bed, you can buy some good quality soil that has the right texture.

If you’re growing the tomato plant in a container, you can get some good quality potting soil that will help them get the right aeration.

5. Give the tomato plants adequate water

The lack of moisture is another common problem that will cause the tomato stems to get tall and spindly.

Tomato plants need a lot of water to grow well and develop healthy fruits. You need to ensure watering the tomato plants as soon as they need it.

The best way to figure this out is to stick your finger 1-2 inches inside the soil. If the tip of your finger does not feel moisture, it’s time to water the soil. This method works whether you’re growing the tomato plants in-ground or in a container.

You need to water the tomato plants thoroughly until the water has reached the entire root system. If you water just the surface, the roots will not develop deep and strong.

This is easy to figure out when using a container as you can see the water flowing out of the drainage holes.

Make sure not to overwater the tomato plants as that can cause root rot and fungal diseases in the plant.

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