GARDENING: Linn Mills

     Gloriously warm spring days make April gardening a pleasure. This month is a good time to plant almost any kind of tree or shrub.
      First, take a tour through the Desert Demonstration Garden at 3701 Alta Drive and see some of the water-conservation plants that are so beautiful. Surprisingly, you'll find many colorful plants that are available to incorporate into your landscape.
      After planting, water thoroughly -- even if it's a low-water-use plant -- until it's established. Here are some things to "fool" around with in your garden this April:
      Recondition plants. Condition your plants for the summer stresses ahead by watering everything deeply but infrequently. This will encourage deep rooting and leach away the salts. If dry spots appear in the lawn, aerate and soak the turf.
      Iron problems. If plants can't obtain sufficient iron, their leaves turn yellow on new growth and the new leaves will become stunted. In the early stages, the veins of these leaves remain green and may turn brown and eventually die. Spray liquid iron onto the leaves of affected plants for short-term results; but for a long-term control, apply iron chelates.
      Holey poplar leaves. If the leaves on your cottonwood trees look like someone blasted them with a shotgun last year, you had leaf mining insects called "shield bearers." They lay eggs on the leaf, which turn into larvae that burrow into the leaf to make a BB-size hole. When adults emerge, the leaf covering drops out to create the shotgun effect and the leaves prematurely drop. Spray with a systemic insecticide to correct the problem.
      Dead limbs. Suspect flatheaded borers if you find small, egg-shaped holes on the branches and trunk. Peek under the bark. If you find galleries packed with sawdust, you have borers. Borers attack weak, run-down trees and shrubs. Therefore, a vigorously growing plant is the best control. Paint the exposed trunks with a white, water-based latex paint to deter the insect.
      Stop pollen. Olive trees begin shedding pollen this month. Prevent fruit set by spraying trees with Florel when blossoms first open and repeat as needed to abort the flowers. Also, drench blossoms with a jet of water each morning to prevent pollen from flying.
      Check sprinklers. Turn on water and check for leaks and plugged or twisted nozzles and make needed repairs. Check drip system and clean as needed.
      Save your tomatoes. A disease called curly top virus causes tomato leaves to curl and become stunted. It also deforms the fruit. An insect called the sugarbeet leafhopper causes this virus. The good news is the insect doesn't like shade. Therefore, place a shadecloth over the plants. If you have infested plants, remove them to prevent contamination of other plants.
      Stop crabgrass. It's time to apply the second application of crabgrass control to catch the late-germinating crabgrass.
      Stop the wind. I know you can't, but you can build a windbreak. Research out of Arizona found flowers and vegetables exposed to wind mature later and were 60 percent smaller than sheltered plants. Wind reduces their ability to take up water, causes leaf pores to close, reduces water movement and slows photosynthesis.
      Roses. It will soon be "show time" for roses. Enjoy them, because summer roses will be much smaller. To encourage another round of blooms, remove fading flowers while leaving enough foliage to produce the next cycle of blooms. Fertilize after bloom with a balanced rose food. Add iron as needed. Use the proper chemicals to control aphids and other insects.
      Mums. Clean out last year's dead growth. Follow with a feeding of nitrogen. Propagate new mums by digging up old plants and separating out the new starts. Establish the new mums in an open, highly organic soil.
      Flower power. For color through the summer, plant these sure-fire flowers: verbena, cosmos, gaillardia, ornamental pepper, salvia, gloriosa daisy, portulaca, zinnias and marigolds. Remove spent flowers to encourage more blooms. Sustain earlier-planted flowers by fertilizing monthly for continued performance in the summer.
      Bulbs. Fertilize spring flower bulbs as the blooms fade to help replenish root reserves and ensure a healthy bloom next year. Plant summer-flowering bulbs (agapanthus, callas, dahlias, daylilies, cannas, gloxinias, etc.) for added summer color.
      Container gardening. Containers -- including hanging baskets -- require extra watering, perhaps twice a day during the hot windy weather. Apply enough water each time to leach away the salts. But frequent irrigations deplete the fertilizer, so use a slow-release fertilizer or apply a half-strength of fertilizer to the soil every two weeks.
      Veggies. Plant onions, radishes and beans before the 15th. During April, plant tomatoes, peppers, eggplants, okra, sweet corn, cantaloupes, melons, squash, pumpkins and zucchini. Thin vegetables to their desired spacing and follow with a feeding of fertilizer.
      Feed turf. Feed lawns with a turf-type fertilizer using amounts suggested on the label and repeat as suggested throughout the season. Follow each feeding with a deep irrigation.
      Bermuda grass. Bermuda lawns are greening up now. If you overseeded with rye last fall, make a smoother transition back to the summer lawn by lowering the mower blade a half-inch with each mowing so the lawn will green up faster.
      Shrubs. Cut back all ornamental grasses, such as pampas and fountain grasses now to encourage new growth. After enjoying the blooms of spring-flowering shrubs (lilac, cassia, etc.), remove the faded blossoms and train plants. To control the weeds, use a mulch or herbicide.
      Fruit trees. It's time to make a second application of nitrogen to your fruit trees. It will assist in the development of new fruit bud formation for the 1998 crop. For larger fruit, thin the fruit early to redirect nutrients to the saved fruit. Check for aphids in the new unfolding leaves. Use Malathion or Diazinon for control. Remove any developing sucker growth in trees.
      Mulch. Mulching has become a lost art. It conserves moisture, smothers weeds and cools the soil. Spread 1 to 3 inches of bark chips, compost, wood shavings or other organic materials under flowers, shrubs, trees, vegetables and in containers. Replenish later, if necessary.
      Learning opportunities. If you would like to learn how to grow orchids, plan to attend "Orchids, Simply Elegant," presented by master gardener Greg Dalton at 9 a.m. Wednesday at the Desert Demonstration Garden. And to learn more about gardening in the desert, attend "Beginning Desert Gardening" by master gardener Bob Stauffer at 9 a.m. Saturday at the garden. For more information, call 258-3205.
     
      Linn Mills is a horticulturist for the University of Nevada Cooperative Extension.