April to-do list
For the Mercury News
Here's the April to-do list for gardeners:
Fertilize citrus with nitrogen. A year-old tree needs about 1/10 of a pound; a 5-year-old tree will need 1 to 1½ pounds. It's best to divide feedings into three applications during April, June and August. Be sure to water well. Citrus leaf drop is normal, with some varieties losing thousands of leaves per day. But excessive drop can be caused by lack of water or an infestation of spider mites, which will show up as brown spots on the leaves; treat by washing them off with a strong blast of water from a hose.
If the weather cooperates, plant tomato seedlings. The soil temperature must have reached 65°F (and nighttime temperatures stay above 55°F). Some kitchen thermometers will measure temperatures in this range. Tomatoes can be planted vertically or horizontally. For vertical, plant deeply, up to the top few leaves (remove all leaves that will be underground). Or, dig a trench, lay the plant horizontally with all but the upper few leaves buried (again, remove all leaves that will be underground). Both methods provide for stronger plants by increasing the root system.
Remove poison oak -- carefully! -- if someone in your household is allergic to the oils in the plant. (About three-fourths of our population is allergic.) Plant removal should be done only by those who are allergy-resistant to this California native plant that provides shelter and food for many native birds and wildlife. Dig up the plant and/or apply herbicides. Caution: Poison oak should never be burned; the fumes can be highly toxic.
Check for codling moths, which can cause a great deal of damage to apples, pears, plums and walnuts by penetrating the fruit and boring into the core. On apples, look for brown-colored holes. If trees have low to moderate infestation, you can try nonchemical control such as sanitation, mass trapping, trunk banding or fruit bagging. With a heavy infestation you may have to resort to spinosad or carbaryl.
Treat powdery mildew, a common problem on many roses, dahlias, chrysanthemums, peas and squash. It produces a white powdery appearance on leaves. A homemade spray of baking soda, water and salad oil can be an effective, nontoxic treatment. But some roses are so susceptible that it may be easier to remove the plant and pick a disease-resistant variety.
What to plant now
Transplants: arugula, basil, beans, beets, broccoli, chard, lettuce, mustard, peppers, potatoes, radishes, spinach.
Seeds: arugula, basil, beets, carrots, chard, eggplant, lettuce, peppers, radishes, squash, tomatoes.
Have a question for Rebecca Jepsen or the other Santa Clara County Master Gardeners? Call the hotline, 408-282-3105, from 9:30 a.m. to 12:30 p.m. on weekdays or check www.mastergardeners.org.