Regional Gardening Reports :: National Gardening Association

Southwestern Deserts

December, 2009
Regional Report

Buy Blooming Holiday Plants

Poinsettia, Christmas cactus, amaryllis, and paper white bulbs add festive color to the home during the holiday season. Place in bright light and maintain consistent soil moisture. Use a diluted fertilizer. Keep away from drafts, heating outlets, and fireplaces.

Plant Bulbs

There's still time to plant bulbs in the low desert. Bulbs need a well-drained environment or they will rot. Loosen soil to a depth of 12 inches, incorporate 4 to 6 inches of organic matter and an all-purpose fertilizer for blooming plants. A sprinkle of phosphorus, such as bone meal, in the bottom of each planting hole puts the nutrient where the bulb can immediately use it. As a general guideline for determining how deep to plant, dig a hole that is two times the size of the bulb.

Transplant Cool-Season Annuals

As soil temperatures cool, germination and seedling growth is often slower, so transplant from six-packs or 4-inch pots for faster color. Incorporate a fertilizer for blooming plants into the soil. The middle number, which represents phosphorus, should be the highest, e.g., 5-10-5 or 15-30-15. Phosphorus promotes flowering. 

Pansies, violas, snapdragons, calendulas, alyssum, stocks, primroses, Iceland poppies, petunias, and dusty miller provide long-lasting color.

Reduce Landscape Watering

Most native and desert-adapted landscape plants will probably be fine with just one deep watering per month during winter. Water should soak 1 foot deep for smaller plants, succulents, and groundcovers, 2 feet for shrubs, and 3 feet for trees. Water ryegrass every 4 to 10 days to a depth of 4 to 6 inches. Water dormant Bermudagrass monthly. Water citrus that has been in the ground up to 2 years every 2 to 3 weeks; established citrus trees monthly. Roses may need watering once every week or so. Maintain soil moisture two to three feet deep for roses.

Control for Powdery Mildew

This fungal disease appears as a grayish powder on leaves. It thrives in cool daytime temperatures with increased humidity, often after winter rains in the low desert. To prevent it, allow space for plants to reach their full size with plenty of air circulation and sunlight, as poor circulation contributes to it. If it appears, remove affected foliage immediately and dispose of plant debris. Also spray off plants with water, as this fungus is unusual in that it doesn't like wet conditions. If needed, apply dusting sulfur every two weeks.


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