• Annuals. Take advantage of nurseries' wide selection of bedding plants this month and set out heat lovers such as ageratum, celosia, dahlia, gomphrena, marigolds, pentas, petunia, portulaca, salvia, sunflowers, verbena, vinca, and zinnia. Or start cosmos, marigolds, sunflowers, and zinnia from seed; they germinate quickly in warm weather and are easy to grow.
• Shade plants. The soil near walls in northern and eastern exposures is now warm enough for planting. For perennial color, try abutilon, clivia, fuchsia, hydrangea, and Plectranthus. In coastal areas, also consider shrubby begonias like B. fuchsioides; some bloom nearly nonstop. For foliage interest, choose from ferns, Japanese aralia, Japanese forest grass, lamium, ligularia, liriope, and wild ginger (Asarum caudatum).
• Subtropicals. In frost-free areas, plant fruit trees such as avocado, citrus, cherimoya, mango; flowering ornamental trees like bauhinia, crape myrtle, jacaranda, and tabebuia; or ornamental shrubs like hibiscus and princess flower. In colder climates, indulge in colorful foliage plants like Acalypha, bloodleaf (Iresine), coleus, and Persian shield (Strobilanthes); they'll bloom well into fall.
• Vegetables. Sunset climate zones 7-9, 14-24: Set out transplants of cucumbers, eggplant (except zones 17-24), melon, peppers, and tomatoes. Sow bean seeds; a new favorite in the Sunset test garden is 'Musica', a Romano-type pole bean that is meaty, tasty, and extremely productive. For information and sources for this and other beans, see "Best Beans". Also sow seeds of corn, cucumber, okra, pumpkin, and summer and winter squash. In the high desert (zone 11), sow seeds of corn, cucumber, melon, summer and winter squash, and watermelon.
• Feed actively growing plants. Roses, warm-season lawns, annual flowers and vegetables, and just about everything else that's actively growing in the garden will benefit from fertilizing now. But don't feed natives or Mediterraneans; they're entering a dormant period.
• Heat up tomatoes. A cool summer can make it difficult to grow tomatoes, especially along the coast. To improve your crop yield, try growing plants in large black plastic containers or in old tires along south- or west-facing walls. Also trim away some of the lower leaves so that sunlight can reach the soil more easily.
• Treat iron deficiencies. Azaleas, camellias, citrus, gardenias, and hibiscus that exhibit yellowish leaves with green veins at this time of year are probably suffering from iron deficiency. To correct it, apply chelated iron, either as a foliar spray or as a soil drench.
• Powdery mildew. Those foggy days known as "June Gloom" create ideal conditions for powdery mildew on roses, especially along the coast. Combat this fungus disease by hosing off foliage in the morning to cleanse roses of spores. You can also use a commercial fungicide or neem oil-based product. Or mix up this home remedy: Combine 1 1/2 tablespoons canola oil, 1 1/2 tablespoons baking soda, 1 tablespoon vinegar, and 1 tablespoon mild dishwashing detergent (without ammonia). Add to 1 gallon of water and spray leaves well.