By Peyton Ellas
UCCE Master Gardener
Planting: If you can, wait until cooler weather to add new plants. The exceptions are heat-loving edible annuals, and some water-and-heat-loving small perennials. I have planted plenty of plants in the summer, but you must have your irrigation system ready to go and monitor soil moisture reliably for at least two weeks. It’s more work, takes more dedicated time and the risk of losing the plants is greater. It’s not for the faint of heart or the time-challenged! Plant only in the early the morning or, even better, at dusk, and don’t let the root ball dry out while transplanting. Saturate the soil and mulch around the plant. Hose the plant off with a light mist. Do not use any fertilizer either in the planting hole or around the base of the plant. You may need to construct temporary shade structures, since heat waves will be inevitable this month. When the nighttime temperatures remain in the 70s, plants cannot cool themselves off well. Breezy hot days are very stressful to plants, so don’t plant at all if wind is forecast in the next week.
Expect some wilting, yellowing and dropping leaves. The plant should recover within two weeks. The soil should remain moist but not completely water-logged, since roots do need some oxygen to grow. Avoid planting species that are susceptible to root and crown rots. This includes many low-water, woody shrubs and perennials like Ceanothus, manzanita, woody sages, lavender, rosemary, buckwheat, cactus and some succulents, flannel bush, desert mallow, Hesperaloe and coffeeberry. You can plant California fuchsia and goldenrod for some late summer and fall color, since they like heat and tolerate over watering in warm soils. You can also plant fall-flowering crocus, Lycoris and Sternbergia right through summer.
Edibles to plant in July include tomatoes, basil, peppers and artichoke from well-developed seedlings, and from seed: corn, winter and summer squash, radish, peas, bulb and green onion and fall-harvested vegetables like broccoli, cauliflower, chard, kale and cabbage.
Maintaining: Monitoring watering is the biggest maintenance job in July. Because of our late-season precipitation, many plants have put on extra growth and flowers. That extra first-season vegetation needs to stay hydrated. Established ornamental trees and shrubs should be deep watered, but on a less-frequent schedule than smaller perennials and new transplants. The edible garden, including fruit trees, should receive a consistent supply of water sufficient to replace water lost through transpiration. That doesn’t necessarily mean the ground should be wet all the time. Let the first inch or more of soil dry out between watering. If a heatwave is predicted, water a day or two in advance, and then not again until the soil dries out a little. Roots need oxygen as well as water and nutrients, so water-logged soil leads to stressed plants. Monitor and test your irrigation system at least once during summer, especially if you will be gone more than a few days. You don’t have to overwater your garden plants in summer. The goal is to keep them alive and healthy, but winter and spring-blooming plants should produce seed in the summer but not grow much, if any, foliage. Many plants, especially California-native and other Mediterranean-climate species, go dormant or partially dormant during summer. Learn about your plants so you won’t accidentally kill them by over watering a plant that displays dormancy by showing a lot of brown foliage. Plants in this category include bush lupine, monkeyflower, bush anemone, many woody sages, some lavender species, gumplant, blue-eyed grass and native iris.
Avoid overwatering lawns. If your lawn is water soaked, disease and pest insects are almost guaranteed in valley-floor soils. Water does not cool the grass, it only replaces what the plant transpires during the day. Plants don’t sweat the way mammals do. Use a moisture monitor or poke your fingers down into the crown of your lawn to see if it’s lacking moisture. Fescue lawns can suffer heat stress, sunburn and warm-season diseases, and all of them may look like you need to water more.
Continue dead-heading roses and daylilies. Remove spent flower heads and the entire flowering stem from hydrangea, leaving only a few buds per stem for next year. You can begin to divide bearded iris in July or wait another month if they still look lush and green. If you decide to divide: Lift the entire clump. Use a sharp knife to separate the rhizomes. Remove and discard the old rhizomes and only replant the younger, smaller rhizomes that grow off of the older stems. Trim leaves to about 6 inches. Set exposed sections in the sun to dry for a few days to callus over any cut sections. Plant the rhizomes (that big gnarly root-like mass) just below the soil surface, water well and mulch. Prune spent berry canes to the ground after harvesting. Trellis new canes as they emerge. Pinch new growth on chrysanthemums. Lightly prune bougainvillea to promote more flowers.
Major pruning should wait until the weather cools, unless it’s for safety. You can lightly prune in the cool morning or evening hours, but not if a heat wave is predicted in the next few days. Don’t fertilize anything during July with high-nitrogen products, including lawns. Fertilizing itself is stressful to plants. July is a good month to let the garden rest. Weeds are a year-round challenge, so keep up with those heat-loving weeds. Monitor and control rodents and insect pests. You don’t have to eliminate pests, just control their populations. Hose off plants as a first treatment. Insecticidal soap sprayed in the evening is the second treatment. We are all busy and would rather do a one-time-and-done style of pest management, but gardening is like caring for other living beings: Steady observation and small corrections are the key to a garden full of beneficial wildlife, happy plants and happy humans.
Conserving: Healthy plants can tolerate quite a bit of damage. Chewed leaves may be from grasshoppers, but if you find caterpillars, try to identify them before removing or reaching for the chemicals. Try to tolerate damage from native species in order to support native moths and butterflies. Tobacco or tomato horned worms and other exotic pest larvae are easy to handpick. You can use Bacillus thuringiensis (BT) if pest caterpillar populations are out of control, and then return to monitoring and handpicking as needed. Don’t use pesticides as a preventative, especially broad-spectrum poisons. Pesticides are a remedy to a specific problem you have identified. Native bees and wasps are active in the summer months. Most of these tiny insects are hardly noticed because European honeybees are also active. Leave flowering (“bolting”) plants like radish, onion and carrots for beneficial insects, and if you can, leave a little bare dirt here and there for ground-nesting solitary bees.
Summer months are also good for planning. Spend some time in the shade of the garden and start making your notes on changes you want to do when the weather cools. Who knows? Maybe this will be a short summer. We can dream. Happy Gardening!
The UCCE Master Gardeners will be available to answer your gardening questions each Saturday at the Visalia Farmer’s Market in the Sears parking lot from 8 to 11 a.m. Also, on Thursday, June 27, they will be at the Porterville Farmer’s Market at Sierra View Hospital from 8 to 11:30 a.m.