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Index : Vegetable Gardening
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- 8. Winter Fertilization of Gardens and Container Plants - Top
- Our landscape plants are in a dormant state during the cool winter months and won’t start new growth until well into March. They don’t need, nor should they be fertilized until spring growth begins. But that’s not the case with winter lawns, seasonal vegetable and flower gardens, and patio container plants. All need a regular supply of nutrients, in the form of fertilizer, to keep them flowering, fruiting, and growing during the winter.
For those who have winter lawns, monthly fertilization with nitrogen is a must. To keep your cool season perennial ryegrass green and growing, apply one-half pound of actual nitrogen for every 1,000 square feet of lawn area. For a typical lawn fertilizer containing about 20% nitrogen, this translates to two and one-half pounds of fertilizer per 1,000 square feet. Most lawn fertilizers will tell you how much to use and how to set your fertilizer spreader. If the lawn product you select has some timed-release nitrogen, all the better! Timed or slow release nitrogen will feed the lawn evenly, providing a more consistent green color.
Vegetable gardens also need nitrogen through the winter months. Cool season veggies include leafy types like lettuce, spinach, chard, cabbage, broccoli and cauliflower. If plants are growing too slowly or are yellowish, nitrogen should be applied. If your vegetables are planted in rows, spread a dry fertilizer down the row at the outer edge of the leaves. Ammonium sulfate (16-20-0) or a complete vegetable fertilizer can be used at the rate of one-half cup fertilizer per 10 feet of vegetable row. If your fertilizing individual vegetable plants, apply one tablespoon of fertilizer for small plants like lettuce and spinach and two tablespoons for broccoli and cauliflower. After spreading the fertilizer, scratch it in to the top few inches of soil, then water.
Flower beds of pansies, petunias, stock and other winter annuals should be fertilized every 6 weeks after planting with ammonium phosphate or a flowering plant fertilizer. Apply one pound (approximately 2 cups) of fertilizer for every 100 square feet of bed area. Or you can use a water-soluble plant food such as Peters or Miracle Gro every 2 weeks, diluted according to directions.
For flowers or vegetables planted in containers, I prefer using a timed-release fertilizer. They’re sold in bags and plastic bottles. Most are resin-coated products which break down slowly, releasing their nutrients over a 2 to 3 month period. You just sprinkle the fertilizer beads over the soil and with each watering, a small amount of the nutrients are released. For other plants growing in containers, I prefer a water soluble plant food for winter feeding. Potted cactus won’t need any winter fertilization. For perennials and woody ornamental plants growing in pots, just feed them if they seem to be yellowing from a lack of nitrogen. Then as spring approaches, apply a timed-release plant food.
Winter yellowing can occur on a number of plants. Some, such as Citrus and Aleppo pines are normal for the season. For these trees, cool temperatures result in an inability to absorb sufficient nitrogen to keep leaves and needles green. Citrus trees will have a scattering of yellow leaves. With pine trees, the yellowing or browning occurs on the outermost shoots. When warm weather returns in the spring, nitrogen is again absorbed by the roots and this temporary winter ‘yellowing’ disappears.
Garden centers and nurseries here in Tucson and throughout Southern Arizona stock a wide array of plants. Not all of them are well-suited to the desert. In fact, a large number of the varieties of plants for sale are not true desert plants and may require significant amounts of water to survive our harsh, often drought-stressed environment.
Before purchasing plants this spring, do your homework. Find out whether the plant(s) your thinking about purchasing are desert native, desert adapted or water-dependant exotic species.
Desert native plants will require the least amount of care. Once established these plants can survive on what Mother Nature provides in terms of water and nutrients. Even during periods of drought native plants will survive; either by going drought dormant or by self-pruning to reduce moisture loss. Prickly pear cactus shed their outermost pads. Palo verde drop leaves, stems, sometimes even branches to reduce their water needs.
There are a wide variety of Southwest desert natives to choose from. Selections of trees include; Blue, Foothills, and Desert Museum Palo Verdes, Arizona Rosewood, Catclaw Acacia, Texas Honey Mesquite and Ironwood. Some good choices of desert shrubs are; Creosote Bush, Chuparosa, Autumn Sage, Fairy Duster, Texas Rangers, and Brittlebush.
Desert-adapted plants are those able to tolerate our desert environment in terms of heat and drought tolerance. But during hot, dry periods they will require periodic irrigation. Selections of these desert-adapted trees include; South American Mesquites, Texas Honey Mesquite, Sweet Acacia, Western Soapberry, Gregg Ash, and Kidneywood. Some desirable desert-adapted shrubs include; Yellow Oleander, Red and Yellow Birds-of-Paradise, Emu Bush, Feathery Senna, Poverty Bush, Bush Lantana and Mexican Honeysuckle.
In addition to trees and shrubs for low water use desert landscapes, cacti and succulents are also great choices. Native Saguaro, Barrel, Hedgehog and Prickly Pear Cacti need little attention after establishment. Agaves are also great drought-tolerant plants for desert landscapes. Some of the best for home gardens include; Octopus Agave, Hauachuca agave, Twin-flowered agave and Holly agave.
For landscape color, there are many desert perennials to choose from. Those that can manage on just one watering per month during hot weather include; Penstemon, Angelita Daisy, Desert Marigold, Desert Zinnia, and Paper Flower. Perennials that need a little more frequent watering (every week or two) include; Peruvian Verbena, Calylophus, Chocolate Flower, Golden Dyssodia and Guara.
In general, plants that use the most water are annual flowers like petunias, geraniums, zinnias and marigolds. It’s best to limit the use of these flowers to a few pots for seasonal color on the patio. Summer vegetables like tomatoes are also high water users, so if your planting a garden, limit it’s size or grow your vegetables in containers.
When shopping at local garden centers and nurseries it’s best to avoid unfamiliar varieties of plants that don’t have the ‘desert look’. Plants with lots of large, soft leaves are probably not adapted to desert conditions. Many of these plants come from wholesale nurseries in California and are best suited to their milder growing conditions.
Consult reference books and internet sources for listings of additional recommended desert plants and their watering requirements. Among the best books to consult are: Landscape Plants for Dry Regions, by Jones and Sacamano; and Plants for Dry Climates by Duffield and Jones. An on-line data base of recommended desert landscape plants for Southern Arizona is available at: www.ag.arizona.edu/pima/gardening.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona,
520-626-5161. - Updated: December 25, 2005
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