The transition from spring to summer is often quick and hard in the Central Valley. Daytime temperatures rarely seem to slowly inch upward; they jump 20 degrees within a day or two and the average daytime temps remain 90 degrees and above for the next five or six months. Spring is over by late April when our summer begins.
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Spring-blooming annuals finish setting flowers as temperatures rise above 80 degrees. Pull out any remaining pansies, violas, snapdragons or Iceland poppies to allow room in planting areas for the root systems of summer-flowering annuals. A few spring-blooming annuals may act as perennials if conditions are good. Cyclamen and primroses can make it through a hot summer to bloom again next fall if they are planted in full shade, kept well-watered and well-mulched and fertilized lightly every month. Some spring-bloomers will seem to die out as temperatures rise but root systems, corms or rhizomes remain viable through the hot dry summer. Violets and calla lilies die back and disappear for the summer but new green leaves will sprout next fall when temperatures cool.
California poppies and Euphorbia characias are among the spring-flowering plants that vigorously self-seed. Take a photo of leaf patterns and shapes of plants that self-seed now to help you recognize seedlings that will show up in your garden next spring. The seeds may not germinate in the spots where they were first planted, but can be transplanted into a more desirable location when they are 4 to 6 inches high or first transplanted into pots to ensure better root development.
Cut off the last spent flowers from spring-blooming bulbs including daffodils, narcissus and tulips and sprinkle a tablespoon per bulb of bone meal or bulb food over the dying foliage of each bulb. The green leaves will provide food for the bulb’s growth, so don’t cut them back until they’ve turned brown.
The first two or three hot weeks are stressful for young transplants. Monitor your new plants daily for signs of wilting, leaf tip burn and pest insect problems. Try to provide afternoon shade to mitigate the effects of sudden high temperatures. Market umbrellas or shade cloth stretched onto a frame can be good temporary solutions.
Wash off pest insects with water from the hose or use sticky or pheromone traps to catch them. If insect problems persist, apply neem oil or jojoba oil to smother soft-bodied pest insects and their eggs. Insecticidal soaps kill insects only on contact. Avoid spraying any type of insecticide (or herbicide) when temperatures are above 90 degrees; high heat vaporizes the spray and there is a risk of leaf burn as well. Also avoid spraying any insecticides when you see bees, butterflies, hummingbirds and other pollinators foraging.
Automatic irrigation timers should be adjusted as temperatures rise-sometimes every day or two during hot spells. Check soil moisture levels with your finger or a trowel and irrigate when the top inch of soil is dry around new transplants. You may need to hand water between mandated watering days to keep the soil consistently moist.
Elinor Teague: firstname.lastname@example.org