Skinny tomato plants started indoors

I started some tomato plants inside this winter so I could move them into the garden as soon as the weather allowed. I started them on top of the refrigerator like the books said, but they are skinny and keep falling over. They don't look as good as the plants I bought last year. What is wrong?

The books recommend starting the seedlings on top of a refrigerator because in days when we didn't keep our homes too warm, the top of the refrigerator was warm. Many plants germinate from seed more quickly if the room in which they are kept is cool but the soil is warm. The refrigerator kept the soil warmer. Once the seeds have germinated and the new plants can be seen, they should be moved into a room with plenty of light for several hours each day.

Our windows usually don't allow enough hours of bright light and produce plants which are leggy and easily fall over. Keep the plants as close to the window as possible to maximize the light they receive. To prevent burning of the leaves, sheer curtains will be helpful. Don't suddenly move the plants into direct sunlight; this will burn them. Gradually increase the light to which they are exposed. If it is possible to place them outside on a brightly lighted porch during the day, this will also help, but again don't suddenly expose them to too much light. Be sure to bring them in at night. Night temperatures below 50 degrees are not good for the seedlings; freezing temperatures are especially dangerous.

It is also wise to keep the room as cool as possible, letting the night temperatures drop to about 55 degrees, and trying to keep the day temperatures to about 80 degrees. Lower temperatures will help keep the plants stocky but cannot completely overcome insufficient light.

Another measure to take is to be sure that you do not over-fertilize the plants. When plants do not receive enough light, too much nitrogen fertilizer will cause excessive and weak growth. Once the plants are outside receiving over five hours of direct sunlight, fertilization can be increased.

Fortunately, tomato plants can be planted deeply if they become too leggy. Tomatoes will form roots along the stem if it is covered by moist soil. So, try to increase the light the plants receive, reduce the temperatures somewhat, and be sure not to provide too much nitrogen fertilizer.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!