Causes of Leggy Tomatoes

Season

• Tomatoes are warm-season plants and require long frost-free seasons for growth. They lose their foliage and die down when temperatures fall under 60 degrees F in fall. The plants also grow leggy and weak in hot temperatures, with wilting and weak growth. The University of Missouri Extension notes that temperatures over 92 degrees F damage both plants and their fruit.

Sun and Space

• Tomatoes require full, bright sunshine, space for growth and air, and support during growth. They grow long, leafless stems when they have to reach for sun or air, or when they grow in crowded situations. Put tomato plants in sites that receive six to eight hours of sun every day and give them up to 36 inches in the row. Put a trellis or stake behind each plant and tie the vines up as they grow to give them better access to sun and air.

Soil and Nutrition

• Tomatoes are hungry, thirsty plants that need adequate nutrition for healthy foliage growth. Start them with rich organic compost amendments and 8-32-16 or 6-24-24 starter fertilizer. The Montana State University Extension notes that high nitrogen content in the soil leads to leggy growth. The University of Missouri Extension agrees, noting that nitrogen-heavy fertilizer also damages fruit set. Switch from balanced 10-10-10, 12-12-12 or 20-20-20 fertilizer to 5-10-10 to amend nitrogen balances and encourage fuller growth.

Water and Mulch

• Tomatoes need moist, supportive soil and adequate water to produce both fruit and foliage. Give them 2 inches of water every week to maintain these conditions, and use 2 inches of organic mulch over the soil to keep them warm and moist.