Los Gatos Weekly-Times Cold weather means plants may need frost protection Tony Tomeo The recent cold weather has reminded us of one of the most important gardening concerns of this time of year. Frost protection has become necessary for many of our cold-sensitive plants. Fortunately, our winters are relatively mild, which is why we can successfully grow moderately sensitive species without protection. Some winters, however, are colder than others. December 1990, for example, was the coldest in local recorded history. Many citrus in my neighborhood--trees that had survived since they were planted in 1956--were killed. Temperatures last winter were milder than usual because of El Niño. The best way to avoid the need for frost protection is to limit the choices of species in your landscape to those that will tolerate our average winters. However, as a horticulturist, I realize there is always a desire to grow plants not recommended for our region, regardless of their cultural requirements. My old college roommate still sends tropicals from his home in Beverly Hills, where winter is only made evident by the date on the calendar. I still do whatever it takes to keep these plants alive. Cold-sensitive plants can be planted in locations where they will be sheltered by existing landscape features. Canopies of larger shade trees can be as effective as tents for frost protection. Likewise, an overhanging roof not only provides shelter, but is in direct proximity with the radiant heat of your house. Plants in containers may be out in the open during the growing seasons, but brought in under eaves or even onto the porch during cold weather. Some sensitive plants, such as citrus, require full sun and do not adapt to the shade of larger trees or overhangs. This is when tents are required. Tents may be made of just about any material in sheet form. Plastic film or burlap is common. This sheet material must be suspended above the foliage of the plants by a frame. An ideal frame may be made of four vertical stakes arranged in a square around the plant with four slats connecting the tops of each stake. The plastic film or sheet placed over this structure forms the tent. Heat is mainly lost vertically, so cover over the top is most important, and need extend only to the level of the lower foliage. If the film is transparent and up off the ground far enough to allow air to circulate freely, it does not need to be removed every day; but should come off in warmer weather, because the greenhouse-like conditions within could stimulate new growth that is more sensitive to frost. Opaque covers should only be placed over the frame the night before and removed the morning after. Always be sure that no foliage touches the cover; because it will be frozen if frost forms on the cover. Although frost only occurs on clear still nights, it is still a good idea to fasten the cover to the stakes with tacks. Most trees that require tents when young will eventually reach a mature size large enough to protect themselves from the cold. The thicker foliage retains heat energy much like a tent would. Mature avocado trees, for example, may get tip burn from frost, but should otherwise be safe. If a plant freezes, leave it alone until spring. The dead foliage is a natural insulator for the branches within, and it is actually best to wait until new growth appears on undamaged branches so you know how far back to prune the dead growth. If a plant is grafted and is frozen below the union, it should be removed or regrafted. La Niña could make this an exceptionally cold winter, so be alert. Perennial of the Week: Cyclamen Cyclamen include several species; but the most popular Cyclamen persicum, is a classic potted plant this time of year. Its colors--ranging from white, pink, rose, purple and red--and their thick deep green foliage make them well suited for seasonal planting. Some have lacy silver patterns on their leaves resembling frost. Like mums in autumn, the plants may be planted in the garden after their bloom cycle. The tubers at the base of the clumping leaves are prone to rot, so it is important to avoid overwatering. When the plants are still in their pots, they should be nearly dry before watering again. Later in the spring, the flower production will decrease, and the plants should be planted in well-drained soil so overwatering is not such a concern. Cyclamen prefer light soil, relatively high in organic matter. They should be planted with the top of the soil mass from the pot at soil level, leaving the tuber half exposed on top. If the tuber is buried, it will likely rot. The dormancy period is opposite that of most perennials. Cyclamen defoliate when the weather warms up around June, and they start growing again in cooler weather around September. If planted in a cool location, some leaves and flowers may be present through summer. Do not be discouraged if you plant your cyclamen in late spring, and the leaves immediately fall off. If the tuber is still firm, it is experiencing a healthy dormancy, waiting for cooler weather. Cyclamen should be fertilized when active growth begins, but because they grow through winter, monthly applications should be about half what summer perennials get. Cyclamen prefer part shade and are ideal under large shrubs where shade prevents other perennials from being planted. Because the plants are active during the winter, the shelter of shrubs or trees is also useful for frost protection. Tony Tomeo can be reached at 358-2574. [ Back to Contents Page | Los Gatos Weekly-Times Home Page | Archives ] This article appeared in the Los Gatos Weekly-Times, December 16, 1998. ©1998 Metro Publishing, Inc. All rights reserved.