7 Causes of Tall, Spindly Tomato Plants
Tomatoes should grow short, stocky, and thick when they’re young. They need sufficient light, water, and warmth to form healthy stems and leaves. Join seasoned grower Jerad Bryant to discover the seven reasons for tall, spindly tomato plants.
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Whether you’re germinating tomatoes indoors or planting seedlings outdoors, legginess is undesirable! It can lead to broken stems, poor growth, and a late harvesting window. Leggy seedlings need more time to mature than healthy, stocky ones.
Though legginess can cause growing issues, it’s an easy problem to fix. Each reason for spindliness has a range of solutions, from providing more light to regulating moisture levels. Give your tomatoes what they prefer and they’ll reward you with bushels of fruit.
Sometimes, a spindly plant isn’t a bad sign! Climbing varieties reach up rather than out, making them suitable for trellises, arbors, stakes, or cages. Carefully inspecting your crop can help you determine what’s going wrong and how to fix it.
Red & Yellow Pear Blend Pole Cherry Tomato
Red & Yellow Pear Blend Pole Cherry Tomato Seeds
Not Enough Light
Low light is the leading cause of spindliness in tomato plants. It’s common in indoor seedlings that sit near a dim window or too far from grow lights. Young plants require strong, consistent lighting to grow their best. Place plant grow lights four to six inches away from the tops of the seedlings and move the lights up and down as needed to maintain the distance.
You may also use bright windows with direct sunlight to start seeds, though the seedlings that sprout will require more care than those sitting under grow lights. You’ll have to rotate them every few days to compensate for one-sided growth as they reach for the window. Windows with indirect light or a few hours of direct sunlight aren’t suitable for starting tomatoes.
If your seedlings are overly leggy, consider transplanting them into new containers! Pot them up right under their seed leaves, the first two leaves that emerge. New roots will form on the buried stem. Provide bright light after transplanting to prevent more spindliness from occurring.
Too Much Water
Overwatering inadvertently leads to legginess. Your plants struggle to take in nutrients and mature properly when they sit in swampy conditions. The excess moisture pushes air pockets out of the soil, effectively drowning the tomato seedlings’ roots.
Overwatering is commonly coupled with low light. Without enough light, the plants grow slowly and require less moisture and nutrients than healthy specimens. Their roots drink little water, and excessive watering can cause swamp-like conditions.
Checking the soil before you water is the best defense against overwatering. Use the simple finger test—stick your finger into the soil, pull it out, and see if wet dirt sticks to it. If it does, wait to water. If you pull out your finger and the dirt is dry and dusty, apply plenty of water to thoroughly wet the roots.
Cramped Conditions
A cramped growing site can cause issues for both mature plants and young ones. It’s common for growing seedlings to sit in cramped conditions, as they’re often spaced closely together in trays or pots. Outdoors, planting seedlings too close together can lead to spindly, mature plants with few flowers or fruits.
Cramped conditions are easy to avoid with a little care and planning. As seedlings mature, pot them up to provide them with space for their roots and shoots to sprout. Uppot tomatoes from two-inch pots to four-inch containers, and from four-inch containers to one-gallon pots.
Outdoors, prevent cramping by following spacing guidelines for your tomato varieties. Each seed packet should have the proper spacing guidelines on it. If you’re growing seeds you saved yourself, follow these general guidelines:
- Space bushy varieties three to four feet apart.
- Space climbing varieties one to two feet apart and provide support.
High Temperatures
Though tomatoes love heat and sunshine, too much warmth can promote tall, spindly plants. This issue commonly affects tomatoes sitting on germination heat mats. Though heat mats are beneficial for seed starting, they’re too hot for growing plants. Remove pots from heat mats shortly after the seeds germinate to avoid growing issues.
Tomatoes tolerate a wide range of temperatures. They’ll grow well when temperatures hover between 65-85°F (18-29°C). Temperatures lower than 50°F (10°C) and higher than 85°F (29°C) are too extreme for these fruiting crops to deal with.
If temperatures are extremely high outside, ensure tomato roots sit in moist soil. They’ll struggle when heat and arid conditions combine into a deadly combination. Moist soil is crucial to their survival during heat waves and droughts.
Bound Roots
This commonly affects seedlings that sit too long in their containers. The roots grow downward and fill the pot. Once they reach the bottom of the pot, they begin circling the edges. Cramped roots can lead to spindliness, as the tomatoes struggle to take up moisture, nutrients, and energy; they grow leggy in response.
Prevent rootbound roots by uppotting your tomatoes regularly. Check for bound roots by inspecting the bottom of each container; if you see roots poking out of the bottoms, the plant likely requires repotting. Remove them from their containers, place them in larger ones, and add soil to cover the roots.
Cramped roots also occur on outdoor specimens that grow in dense clay or silt. The roots struggle to penetrate the ground, and they sit in the planting hole. Ensure your tomatoes have well-drained, fertile, and moist soil during the growing season. If the soil is poor, consider amending it with compost.
Excess Nitrogen
Excessive amounts of nitrogen are undesirable for a few reasons. Firstly, too much nitrogen causes poor flowering and fruiting. It leads to lots of leafy growth at the expense of tomato fruits and flowers.
Secondly, excess nitrogen promotes tall, spindly tomato plants rather than stocky, strong ones. If you’re unsure of how much nitrogen is in the soil, consider using a soil testing kit to determine how much there is. Nitrogen moves readily through the soil, but it can sometimes build up after excessive fertilizing.
If there is too much nitrogen in the ground, you can run a hose on low to let water filter it out. Nitrogen moves with water, and flowing streams push it deeper into the ground.
Tomato Type
Sometimes, a spindly tomato plant has more to do with its variety than anything else! Four main types of tomatoes exist:
- Pole
- Bush
- Determinate
- Indeterminate
These four words can help you decipher what kind of tomato plant will grow. Pole varieties are often indeterminate, and bush types are often determinate, though they don’t have to be. Pole types climb, while bushy varieties grow many stems low to the ground.
Indeterminate is a term that describes tomatoes that endlessly grow. They continue flowering and growing fruits so long as the weather is warm and conducive to healthy growing. Determinate types, however, produce flowers and fruits all at once in a short harvesting window.
Semi-determinate types are also available; they may grow tall and spindly if they’re a climbing type. Semi-determinate tomatoes produce a large crop in the summer, and they continue to produce fruits until frost returns.
