Issue: September 20, 2008

It is ok to compost tomatoes that had curly top virus
It is time to start inducing flowers in Christmas cacti


My tomatoes did not do well this year and I was told that the plants had a virus disease. I usually compost everything in my garden in the fall, but I began to wonder if I should compost these tomato plants. Will it cause problems if I put these plants into the compost?



If your tomato plants had curly top virus or tomato spotted wilt virus which were very common this year, it is safe to compost the plants after you remove them from your garden. These viruses do not survive long after the plant dies and cannot be spread to the plant from soil next year. Curly top viruses survive the winter in weeds, especially mustard weeds that sprout in the fall and survive the winter. They are spread from the weeds to the garden by beet leafhopper insects. Controlling weeds is the best way to manage the problem to prevent recurrence of the problem next year.

If there were fungal or bacterial diseases in the plants (plants can have more than one disease at a time), then you should not compost the plants as you clean your garden. The fungal and bacterial disease can survive in the soil and in the compost to create problems again next year. In fact, the ability of many fungi and bacteria to survive in the soil is one reason we encourage gardeners to rotate their crops so that the same plants (and related plants) are not grown in the same soil year after year.


When should I begin treating my Christmas cacti by putting them into a closet each night? I want to be sure that they bloom this winter.


The autumnal solstice occurs this year on September 22 (at 3:44 pm). That is the time that the sun crosses from the northern hemisphere to the southern hemisphere. On that date (and the dates around that date) the days and nights are each 12 hours long. Once the nights become longer than the days, some plants that bloom in the winter begin the process of forming their flower buds. The Christmas cactus, kalanchoe, and poinsettias are among those plants.

You can leave these plants outside in a place without lights at night to allow them to initiate blooming under natural conditions until there is a chance of frost. Then you should bring them indoors before a frost to a place where there will be no light from sunset to sunrise, or you can put them in a dark closet each night. If you do not want to leave them outside, you can bring them indoors and begin the process now. Remember that low temperatures (about 50 degrees) at night will help stimulate flower development.

Just remember not to leave the plants in the closet continuously. They must be brought out into the light every day and returned to the closet every night. If it is inconvenient to move the plants to and from the closet every day, you can cover the plants every evening with a black plastic bag or black cloth. You should uncover them every morning. The covering should exclude any light in the event that you must enter the room and turn on the lights during the night. Do not leave the covered plants in sunlight while they are covered or they may be injured by the heat that develops under the covering.

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:, 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, or at the Desert Blooms Facebook.

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