Issue: December 16, 2006
Last spring we replaced an old hedge with a row of hibiscus. They are on the west side of the west side of the house where they receive plenty of sun and were beautiful all summer. The nursery tags said nothing about winter hardiness. On November 15 they froze with our first frost. If we trim them in the spring will they grow again or have we lost them completely? We assumed, since they sold them here, that they would survive the winter.
There are tropical hibiscus plants sold and grown in New Mexico as house plants. They do especially well in sunrooms and atriums. They will freeze and die outside in the winter. There are also hardy hibiscus plants that will survive outdoors. Did your plant tags say that they were houseplants? If they didn't, I will guess (and hope) that they are the hardy types of hibiscus.
The hardy hibiscus (Hibiscus moscheutos) will freeze to the ground in the winter, but return each spring to produce an outstanding display of very large (dinner plate sized) flowers in pastel colors. The tropical hibiscus will freeze to the ground, never to grow again (depending on the microclimate of the site where they are planted). The tropical hibiscus flowers are usually not as large and in colors of bright red, yellow, or white. The leaves of the tropical types are dark, glossy green while the leaves of the hardy hibiscus are medium green and not glossy. If you remember glossy leaves, you will probably not see the plants returning in the spring.
There is another plant, sometimes called hardy hibiscus. This plant is also known as althea or rose-of-sharon (Hibiscus syriacus). It is hardy and doesn't freeze to the ground in much of New Mexico. It's flowers are smaller than the other hardy hibiscus.
It is my guess that you have the hardy hibiscus that freezes to the ground. If you cut it back now or in the spring it should resume growth and produce another summer of beautiful flowers. This hibiscus does not like dry soil so it will require some watering during the drier parts of the winter. An organic mulch of wood chips, bark, or even straw will help preserve moisture in the soil around your hibiscus. The mulch will also moderate temperature changes and protect the crown of your plants. Warming in the spring may encourage growth too early. The mulch will keep the base of the plant cool and discourage growth too early. This will help prevent freezing during one of New Mexico's famous late freezes.
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: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!