Skinny Tomato Plants & Too Tall Amaryllis

Southwest Yard and Garden

Written by Dr. Curtis Smith

(Photos by Dr. Marisa Thompson)

2 reprints

Skinny Tomato Plants Started Indoors - February 23, 1997

Amaryllis Flowers Too Tall - February 11, 2000

Starts of artichokes (left) and tomatoes (right) grown from seed by Ph.D. student Chuck Havlik at the NMSU Agricultural Science Center at Los Lunas in winter 2019 became subjects for summer experiments on tomato rooting and artichoke viability. Photo credit M. Thompson.

Skinny Tomato Plants Started Indoors

By Dr. Curtis Smith

Reprint from February 23, 1997

Question: 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?

Answer: 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 that are leggy and easily fall over. Keep the plants as close to the window as possible to maximize the light they receive. Sheer curtains can help prevent leaf burn. Don't suddenly move the plants into direct sunlight because 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. Nighttime temperatures below 50°F 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 nighttime temperatures drop to about 55°F and trying to keep the daytime temperatures to about 80°F. 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.

Taller amaryllis scape (left) might cause the whole pot to fall over, especially if the second scape (right) also grows toward the light and I forget to rotate the container. Placing the original pot inside a larger pot with heavy gravel at the bottom may save the day without disturbing the forming buds or roots during bloom time. Photo credit M. Thompson.

Amaryllis Flowers Too Tall

By Dr. Curtis Smith

Reprint from February 11, 2000

Question: Why do our amaryllis stems always get extremely tall before the blossoms open? If we don't provide extra support, they will topple over. We generally keep the temperature of the house below 60°F.

Answer: It is natural for amaryllis flower scapes (long, leafless stalks) to become rather tall, but they should be capable of supporting the flowers without falling over. However, in a pot with a small bottom it becomes unstable and is prone to toppling over. Don't transplant it now, but you can place it into a larger-diameter pot or decorative container. Place some gravel or rocks in the bottom of the pot to increase the container’s weight. Be careful that no water collects around the base of the pot containing the bulb as you water the plant.

Under indoor conditions, light may be limiting. Low light levels will increase the height of the flower scapes. You are doing the right thing to keep the temperatures cool in the room where the plant is growing since this helps reduce the excess height of the flower scape. While it is flowering and the leaves are absent or dormant, fertilizing is not important. Too much nitrogen fertilizer may also cause excessive flower scape growth. If you fertilize before and during flowering, use a flowering houseplant fertilizer that is low in nitrogen and higher in phosphorus. Nevertheless, the amaryllis is genetically programmed to produce tall flower scapes.

For more gardening information, including decades of archived Southwest Yard & Garden columns, visit the NMSU Extension Horticulture page (http://desertblooms.nmsu.edu/), follow us on social media (@NMDesertBlooms), or contact your County Extension office (https://aces.nmsu.edu/county).

Curtis Smith, PhD, is the former Extension Horticulture Specialist for New Mexico State University and continues to teach and inspire. https://www.southwestgardensmith.com/.

Marisa Thompson, PhD, is the Extension Horticulture Specialist for New Mexico State University and is based at the Agricultural Science Center at Los Lunas.