September 6, 2014

1 - Later summer is a time for several garden activities in preparation for winter.

Yard and Garden September 6, 2014


What should we be doing with our iris bulbs now? Should we dig them up? What can we do to force another bloom or 2 on roses now? What should we be doing to our lilies and dahlias in preparation for fall? When can we plant cool season vegetables? is it too late to start seed for fall planting?



Irises are best transplanted in northern New Mexico in late August to about the middle of September. So, based on your telephone number, now is probably the best time. People in southern New Mexico may be able to delay a little longer because cold weather will come later to them. Your goal is to give the iris time to establish their roots before it becomes too cold. You should not need to dig and store them over the winter because most irises are hardy enough for our winters.

Roses will probably rebloom if they have sufficient moisture. Depending on the type of rose plants you are growing, they should bloom again before frost. You may need to harvest some buds to enjoy indoors if they have not opened and a freeze is forecast, but that should be at least a month away for all but high elevation gardeners in northern New Mexico. To insure flowering next summer, you can work some phosphate fertilizer into the soil in the root zone of the roses, but not too close to the base of the plants. You do not want to injure the roots. Phosphate fertilizer does not move into the soil with irrigation so it needs to be incorporated into the soil. Do not use a fertilizer containing nitrogen because that may stimulate vegetative growth that would be injured when the temperatures drop.

Lilies are hardy and need only receive adequate moisture through the winter. Organic mulch applied after the weather cools will help keep soil temperatures from fluctuating too much during the winter and will help maintain the moisture that developing lily roots need during the winter. Dahlias, on the other hand, are not as hardy. In some locations where the soil freezes, the tuberous roots of dahlias should be dug up and stored in a non-freezing location through the winter. It is important that they be kept cool, but above freezing. They should be checked periodically to make sure that they are not drying out or rotting. Some gardeners store them in slightly damp vermiculite after treating them with fungicides to protect them over the winter.

It is too late to start seed for fall planting in much of northern New Mexico. Southern New Mexico may still be able to harvest a fall crop. However, in both locations, consider how long it is until the first frost, and then after checking the "time to harvest" information on the seed packet, you can determine if there is time to plant and harvest a crop. It would be best if you had a week or two beyond the recommended time so that you will have some time for extended harvest. Some plants, such as radishes, may mature in time to plant now. Some plants (radishes, turnips, some carrots, kale, and other cole crops) can tolerate light frost without harm. In fact, cool weather improves the quality of the vegetables. A covering on nights with hard frost forecast may help extend your harvest time. So, for some vegetables it is still possible to plant them now. If you plant in containers that may be moved to sheltered locations on cold nights, you can extend your season even more.

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.

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