Be mindful of heat, drought as summer gardens transition in September

Heat is ongoing. Drought compounds the heat, making for challenging gardening conditions. The entire state is in drought with almost half of us living under the most extreme or exceptional drought conditions.

The state issued emergency drought regulations in May, charging each water agency with implementing restrictions such as banning the irrigation of “nonfunctional” grass in commercial, industrial and institutional properties as well as HOA common areas. Check with your local water agency to find the restrictions for your garden.

Drought-proof your garden

If you still have a lawn, switch to high-efficiency, multi-trajectory rotating stream nozzles. These nozzles save at least 30 percent over old-fashioned spray heads. They screw on to replace old nozzles.

All other plants should be irrigated with inline drip irrigation and protected with a layer of mulch at least 3 inches thick. Inline drip looks like a long hose with holes in it. Inside, each hole connects to a very sophisticated emitter that releases water one drop at a time. This is the most efficient irrigation and the best way to get water to plant roots, which is the goal of all irrigation.

Since it releases water a drop at a time, inline drip needs to run a long time — 30, 60, 90 minutes or more — depending on your soil and how long it takes for water to penetrate all the way down to plant roots.

In vegetable beds, the soil needs to be always damp (not wet). Depending on where you live, your garden may need to be irrigated two or three times per week.

In ornamental garden beds, the soil should dry out between waterings. Water these beds no more than once a week. For mature drought-tolerant plants, natives and succulents, water just once every few weeks. Always water deeply and infrequently.

No matter the irrigation method, always water until the water penetrates deep into the soil to reach plant roots. After the irrigation runs, test how deep the water has gone by digging deep into the soil, using a soil probe, or sticking your finger as deep as it will go. Is it wet all the way down? If not, water again.

Match the mulch to the plant: straw mulch for vegetables; stone or rock mulch for succulents, including cactuses; wood-based mulch (but not bark chunks) for all other plants.

Figure out how often to water by using the Canary Test. Find it here.

Protect yourself

The sun and heat are still intense. Garden early and late in the day. Slather on high SPF sunscreen — and remember your toes!

Wear a lightweight, long-sleeved shirt with a high SPF rating. Get a good lightweight hat with a wide brim, too.

Liquids are essential for your plants and for you (but hold off on the alcohol until the sun dips low).

Vegetable gardening

Vegetables you planted in early spring — tomatoes, cucumbers and more — are at the end of their lifespan. As each stops producing, remove it. Put diseased plants (powdery mildew, root knot nematode and other issues) into the green waste unless you compost.

Take notes on how well each variety of vegetable performed. Which varieties were so good that you plan to plant them again? Which disappointed? Keep track.

Note the location of plants this year so you know where to plant next year. Plan to plant tomatoes, eggplants, peppers, tomatillos and potatoes in a different bed next year. In their place, plant melons, pumpkins, basil, sweet potatoes (Ipomea), okra, onions and other veggies that are not susceptible to these night shade plants’ pathogens.

Pick ripe fruits and vegetables to eat, to preserve, and to keep scavengers from eating them before you can.

Dehydrate surplus tomatoes to make tomato “raisins.” Find directions here.

Do your tomatoes split as they ripen? That’s a sure sign of overwatering. Water less, and the problem should disappear.

Feed melons and pumpkin plants. Remove any that have soft spots or insect damage.

Set melons, winter squash and pumpkins on a bed of straw or an upside-down yogurt container to keep them off the soil. If they grow on a trellis, support them with a sling made of old stockings or a cast-off bra (really!).

Harvest pumpkins, melons and winter squash when the stems turn brown and start to pull away from the fruits, the undersides yellow a bit, and they sound hollow when slapped.

Let peppers turn red, yellow, orange or purple before harvesting. They taste better and are easier to digest once they are fully ripe. They are prettier, too!

Late in the month, start seeds for fall veggies like cabbage, spinach, lettuce, cauliflower, etc. The seedlings will be ready to plant when the weather cools in October.

Buy seeds for cover crops to plant next month. Choose seeds based on your garden’s needs: some cover crops add nitrogen, others loosen compacted soil, some add organic matter, etc.

Watch for pests. Spray aphids with a sharp stream of water that will crush their soft bodies. Distract ants with boric acid-based traps. Wash off concentric white circles of giant whitefly eggs. Spray leaves top and bottom to wash away tiny orange spider mites and their webs.

Fruit trees

Pick figs only once they are fully soft and ripe. Unlike other fruits, figs stop ripening the moment they are picked.

Protect figs and other soft fruits from green fig eater beetles by covering them with nylon mesh drawstring bags. The bags are see-through, making it easy to monitor the fruits as they ripen.

Prune fig trees as soon as you pick the last fruit. Don’t be shy about cutting your fig tree back a little or a lot. It will resprout and fruit again next year.

Shorten the new growth on peach, plum, apple and other deciduous fruit trees now (you’ll prune again for fruiting and shaping in winter). Shortening branches keeps future fruits within reach. Visit to see how.

Pineapple guavas ripen and “self-harvest” this month. Wait for the oval green fruits to drop onto the ground. Gather them, cut them open and enjoy their sweet, cream-colored flesh.

Fertilize citrus and avocado. Use organic fertilizers and follow label directions. Pull back the mulch, apply the fertilizer and water it in. Replace the mulch.

If you live in north coastal and north inland San Diego County, please mind the citrus quarantine area so you don’t spread citrus greening disease, Huanglongbing (HLB). This is a serious situation. Citrus greening is transmitted by a tiny critter called the Asian citrus psyllid. HLB kills citrus trees. IF YOU LIVE IN THE QUARANTINE AREA, DO NOT MOVE CITRUS FRUITS, TREES, LEAVES or WOOD FROM YOUR PROPERTY. Learn the signs of citrus greening disease at


Thrips on your houseplants? Whiteflies? Put the plants outside in a shaded spot for fresh air and rejuvenation. The pests’ natural predators will eat them. Leave the plants outside until October.

If your houseplants are infested with tiny, flying gnats, reduce watering. Cover potting soil in an inch-thick layer of small round pebbles or marbles or other inert material. The pebbles block gnats so they can’t lay their eggs in wet potting mix. The gnats will disappear in a week or so.

Scale and mealy bugs are some of the most challenging houseplant critters. Scrape the scale away with your fingernail. Carefully dab mealy bugs with a cotton swab saturated in rubbing alcohol. Check the plant’s crevices for juvenile scale and mealy bugs. Alcohol kills them, too.

Ornamental plants

Collapsing agaves is usually caused by the agave snout weevil, a recently arrived invader that attacks agaves and their relatives. The female weevil chews her way into the base of the plant to lay her eggs in spring. When the eggs hatch, the larvae — which are grubs — feed on the core of the plant, leaving it vulnerable to rot from the inside out. Once the damage is visible, it is too late to save the plant. Seal infected plants and their plant parts in a plastic bag and place in the trash, not the green waste.

There’s still time to solarize grass and weeds to eliminate them IF you start at the beginning of the month. The sun must be high in the sky to superheat the soil to “cook” plants, weeds and seeds in the upper layer. This simple process involves clear (NOT BLACK) plastic and takes 6 to 8 weeks in the hottest months of the year. Beneficial soil microbes die in the process, so mulch afterwards to re-establish their populations. For directions, go to

Clean up dried-out foliage, dead branches, and other spent plant materials — in part for aesthetics but, more importantly, for fire safety. Dead, dry plant material is more flammable than living plants.

Wash dusty leaves using a Bug Blaster hose end nozzle. These round-tip nozzles put out a sharp but narrow spray of water to clean leaves and wash away pests. Spray leaves top and bottom, stems, branches, etc.

If your plants look a little droopy at the end of the day, don’t water. In the intense heat, some plants lose water to the air faster than their roots can take it up from the soil. Overnight, the roots catch up and the leaves get perky again. However, if leaves are still droopy in the morning, it’s time to water.

Plant spring-flowering South African bulbs such as species Ixia, Watsoniaspecies Gladiolus and His Ferrari.

Take a hard look at your trees, shrubs and perennials. After the spring and summertime growth, they might need a good haircut. Hire a certified arborist to do the work. Insist that the arborist remains on-site while the work is being done. Find certified arborists at

NEVER top a tree. Topping a tree disfigures it and leaves it exposed to decay and pests. Topping reduces the tree’s structural strength and shortens the life of the tree. It also stimulates rapid growth of new, weak wood. If a tree is too tall for its spot, it is the wrong tree. Replace it.

Plan for fall planting when the weather cools late next month. Photograph your garden beds, then examine each one to determine what needs to come out, what needs to be added, and so on.

Deal with pests

Aedes mosquitoes are almost invisible but bite aggressively during the day, especially on legs and ankles. They lay their eggs in standing water (as little as a quarter-inch deep) both indoors and out, so be vigilant about emptying water dishes, screening rain barrels, and running fountains to prevent standing water. Add mosquitofish to ponds. Fix torn window screens to keep the mosquitoes out of your house and be vigilant about wearing insect repellent when you head outside.

Floppy fronds on Canary Island palms are a sure sign of the deadly, invasive South American palm weevil. Once the damage shows, the palm is doomed. Have it removed by a professional arborist who knows how to dispose of infected palms without spreading weevils to other palms. Report infested palms to the UC Riverside Center for Invasive Species Research here:

Check for masses of tiny, disorganized webs on leaves and stems of trees and shrubs — the sure sign of spider mites. Use a sharp spray of water to wash them off.

Citrus scale and aphids appear when ants “farm” the critters, placing them on citrus stems and branches. The problem requires a two-pronged approach to control the ants and wash away the scale and aphids. Use a boric acid-based bait for the ants. Wash away aphids. Smother scale with a spray of light horticultural oil (Not Neem).

Support, learn, participate

Support the San Diego Botanic Garden by attending this year’s Garden Party from 4 to 8 pm on Saturday, Sept. 10. Learn more

Do you love to garden? Are you new to gardening? Are you an experienced gardener who just moved to the area? Please join the San Diego Gardener Facebook Group, to join our vibrant, local garden community.

Sterman is also a waterwise garden designer and writer and the host of “A Growing Passion” on KPBS television. More information is at and