After a brutally warm August and September, we are all anxious for the cooler and shorter days later this month. Be patient. Don’t plant until the weather cools. And once it does, get going!

Why plant in fall? The sun is lower in the sky, so days are shorter and the air is cooler, yet the soil retains its warmth. Warm soil + softened sunlight + cool air = ideal planting conditions for nearly every ornamental plant.

Harvest melons, pumpkins and winter squash once their stems dry out and start to pull away from the base. Leave a few inches of stem attached as a handle. Rinse, dry and store in a cool, dry, dark location.

If your tomatoes, eggplants and squashes are still producing, you can leave them in the garden for about another month or replace them with cool -season crops.

Don’t compost old vegetable plants. Instead, send them off in the greenwaste. There, they’ll be “hot composted” to kill off pests and diseases.

Plant root vegetable (carrots, turnips, radishes, etc.) seeds directly into garden beds. Don’t buy them as seedlings; their long roots don’t transplant well.

Start seeds for kale, spinach, beans, cauliflower, lettuce and other leafy greens — either in the garden, or in containers to transplant in a month or so.

If winter gardening doesn’t excite you, give your garden a break by planting cover crops to improve the soil. Legumes like hairy vetch add nitrogen, grains add organic matter. Buckwheat chokes out weeds, builds organic matter and suppresses nematodes. Choose the best cover crop seed for your garden. Order and plant the seeds now.

Swap out warm-season herbs like basil for cool-season herbs such as dill and parsley.

Once the weather cools, plant permanent garden beds with perennial herbs from the Mediterranean: rosemary (shrub), bay (tree), oregano (perennial), marjoram (perennial), and thyme (perennial). These are the best herbs to cook with year-round.

Harvest pineapple guava. These egg-shaped, olive-green fruits grow on evergreen shrubs that reach 12 feet by 12 feet and make wonderful natural hedges. The plant’s botanical name is Acca sellowiana and it’s native to South America but grows across Southern California. You know the fruits are ripe when they “self-harvest,” by falling onto the ground. Simply pick them up, slice longways and scoop out the soft, sweet innards. YUM!

Plant the last of the year’s subtropical fruiting trees and shrubs like banana, citrus, avocado, cherimoya or tropical guava. Unless you live within a few miles of the coast, plant now or wait until spring.

Order bare-root deciduous fruit trees (nectarine, pluot, apple, etc.) from your local independent nursery. They’ll arrive in the nurseries in January.

Continue to water deciduous fruit trees for as long as they sport leaves.

Are your citrus trees’ leaves curled and distorted? Do the leaves look marbled? That’s classic leaf miner. It looks ugly but doesn’t hurt the tree nor diminish production. Don’t cut those leaves off. Cutting off infected leaves causes the tree to make new leaves, which will also get infected with leaf miner. Sprays won’t help. Just leave it alone.

In the shorter, cooler days, the sage (Salvia) family of plants puts on a big show of color and texture: bright purple flowering Mexican bush sage (Salvia leucantha), white and rose Salvia ‘Waverly’, yellow blooming forsythia sage (Salvia madrensis), copper-colored beach Salvia (Salvia africana-lutea), indigo blooming Salvia guaranitica ‘Black and Blue’ and more.

Plant drought-tolerant trees, shrubs and perennials native to winter rainfall regions of California, South Africa, Australia, the Mediterranean and western Chile.

Check your garden for emerging green spears of spring bulbs like Babiana, Watsonia and species Gladiolus. If you have bulbs you’ve been meaning to plant — do it now. They may not flower this coming spring, but they’ll bloom the following year.

Divide and plant irises including native iris and Pacific coast hybrids. Carefully separate the rhizomes (they look like tiny, jointed potatoes) at the “joints.” Use a sharp knife wiped clean with alcohol. Wipe the knife with alcohol again between plants so you don’t spread pests or diseases from one plant to the next.

Early in the month, shorten branches of scented geraniums and Martha Washington geraniums by a couple of inches. Next month, cut the long branches to force plants to grow new shoots at the base.

Feed roses with liquid fertilizer at midmonth. Inspect leaves for mold, rust or black spot. Remove infected leaves and put them into the greenwaste bin rather than into your compost pile.

Rake up leaves as they fall from fruit trees. Unlike ornamental plant leaves, send these leaves to the greenwaste, where they’ll be composted at a high temperature to kill bacteria, molds, etc.

Before you plant anything new, be sure your garden has a solid infrastructure:

1. Water the plant in its pot and let it drain. Gently pull the plant out of its pot. Dig a hole as deep as the rootball is tall, and slightly wider. Make the hole square instead of round, and rough up the edges. Add a few handfuls of worm castings to the hole, but no other amendments. Fill the hole with water and let it drain.

2. Carefully loosen the plant’s roots (except for Bougainvillea or Matilija poppy, Romneya coulteri). Set the plant’s rootball into the hole, just barely higher than the plant sat in the pot. Refill the hole with soil you dug out. As you refill the hole, wet the soil and tamp it down to eliminate air pockets.

3. When the hole is full, make a shallow moat around the stem or trunk. Set your hose to trickle water into the moat until the soil is saturated. Layer 3 or 4 inches of mulch onto the soil surface, starting at the outer edge of the moat. Continue the mulch to cover the entire planting bed.

Bougainvillea and Matilija poppy can die when their roots are roughed up at planting. To plant, then, complete step No. 1 above, then turn the pot on its side and gently cut out the bottom of the pot. Use your hand to support the bottom of the plant in its pot, and carefully move it into the prepared planting hole. Slice down two sides of the pot, then start to refill the hole. After a few inches, gently pull away the remaining portions of pot. Follow step No. 3 above to finish planting.

With the sun lower in the sky, plants need less water, so adjust your irrigation clock to water just as long but less frequently. If you have a smart irrigation controller, check to make sure it is making the necessary adjustments. If your controller isn’t “smart,” set the water to run less often. Don’t change the run time.

“Smart” irrigation controllers adjust your irrigation seasonally, zone by zone, depending on the type of plants each zone waters, your garden’s location, type of soil, slope, sun, shade and so on.

When you plant natives and other Mediterranean climate plants, irrigate them with in-line drip irrigation. In-line drip has emitters embedded in the lines and delivers water directly to the soil, where it penetrates down to the roots. The entire root zone gets evenly wet just as rain wets the soil evenly. Natives do great with this kind of drip irrigation.

Replace individual emitter-style drip. These kinds of systems are neither durable nor reliable.

How long should you water? Always water long enough to saturate the plant’s deep roots. Use your fingers or a soil probe to feel how deep the water has gone. Adjust your watering schedule so water reaches the deep roots every time. For drought-tolerant plants, let the soil dry out several inches down before deep watering again.

Organic mulches act like a sponge to hold water, keep moisture in the soil and protect soil from erosion. As the mulch breaks down, it feeds the micro flora and fauna that help build healthy soils to support plants. Research shows that mulch can protect plants from soil pathogens, too.

Renew your garden’s mulch using organic mulch (made from leaves, bark, wood, etc.) for nonsucculent plants. Mulch succulents and cactuses with rock or decomposed granite. Whichever you use, keep the mulch at 3 to 4 inches thick.

While mulch should cover the soil surfaces in your garden, leave several bare spots for native, ground-dwelling bees — very important garden pollinators that rarely sting.

Sadly, we are still dealing with citrus greening disease (aka Huanglongbing or HLB), spread by tiny Asian citrus psyllids. There is a quarantine zone in north coastal and north central San Diego. If you live in the quarantine zone, DO NOT MOVE citrus fruits, leaves, wood or any other part of citrus plants off your property. Do not compost fallen leaves, branches or any prunings. Instead, seal them in a plastic bag and place in a closed greenwaste can for collection. Find the quarantine map here.

South American palm weevil is still killing Canary Island date palms and beginning to spread to other kinds of palms. Once the center blades start to droop, the palm is doomed. If you notice the giant weevils or your palm starts to look sad, there is a chance you can save it, but you have to act fast. Find information here.

Agave snout weevil is another large black weevil, but this one attacks Agave, Agave relatives, golden barrel cactuses, and even some Opuntia. It attacks the plants from the center so often, the first you notice of their presence is a collapsing plant. Explore further and you’ll find a cesspool of rotting roots and plant crown at the base. As SOON as you notice the plant failing, dig it up along with the rooting plant parts and any weevils or giant weevil grubs you can find. Seal it all in a plastic bag and place in the trash — not the greenwaste. Act fast, before the weevils spread to nearby plants.

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

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