For The Union-Tribune
December is gift-giving time, so how about gifting your besties (or yourself) a gift that will help them be their best gardener? Check out my recommendations for gardening gifts here. These gifts are perfect for any Southern California gardener!
Prepare for rain
We got some great rain in November. Long-term forecasts suggest that December will be dry, but you never know … If last month’s rain caught you off guard, prepare for the next (eventual) downpour.
Clean rain gutters so they don’t clog. When gutters and drains clog, water sheets off the roof onto the plants below and flattens them. Compost the debris that comes out of the gutters or use it as mulch.
Connect downspout cisterns either above or below ground. Cisterns can hold hundreds to thousands of gallons. Choose a size based on the size of your roof and your budget. You can expect to collect 62 gallons of water from every 1,000 square feet of roof. Use that water to irrigate plants — especially potted plants — during dry periods.
Alternatively, bank rainwater by capturing it in dips and swales in your garden. Those low, shallow spaces capture and hold water so it percolates into the surrounding soil. Plant roots then draw on that soil moisture after rains end spring. Swales are best lined in mulch or rock — not with landscape cloth nor weed barrier. Rocks allow water to filter through to the soil, while mulch absorbs and holds water as it penetrates into soil.
Weedcloth, landscape fabric and plastic sheeting prevent water and oxygen from reaching the soil, plant roots and beneficial microbes that live in soil. Your soil soon turns hard as concrete and all those beneficials perish.
The evergreen shrub lemonade berry (Rhus integrifolia) is one to consider adding to your landscape in San Diego County. It supports important pollinators such as butterflies and birds. (Adobe Stock)
Protect bare hillsides from erosion by stretching straw-filled or compost-filled wattles across hillsides. They act like speed bumps to slow water on its way downhill. Alternatively — or in combination — spread lengths of landscape burlap (also called “landscape jute fabric”) over the bare dirt.
Keep an eye on ice plant-covered slopes, not only because ice plant is invasive, but also because ice plant gets really heavy in rain. I’ve seen it pull down entire hillsides. Remediation is expensive and messy, so be proactive, not reactive. Remove ice plant and replace it with trees and shrubs that have deep, woody, stabilizing roots.
Prune overgrown or weakened trees so the weight of wet leaves doesn’t bend or break branches.
If there’s a long delay before the next rain, run your irrigation once every two weeks or once a month, depending on the types of plants each zone irrigates. As the seasons change, adjust the frequency of irrigation but don’t change the number of minutes each zone runs.
Empty water that accumulates in dishes under potted plants, buckets, containers and other places where the constant moisture can drown plant roots or become a mosquito nursery (this applies to all times of year, not just the rainy season).
After the rain, stay off wet soil for two days. Wet soil compacts easily underfoot, so rather than dig or weed or plant, do other chores like repotting plants, cleaning your toolshed, and planning for spring.
Be sure to water all your garden beds on the day before dry, Santa Ana winds are expected. Saturating the soil protects your plants from desiccation in the dry, hot winds.
A succulent tree, like the bottle tree (Brachychiton rupestris), is also a good, easy-growing choice for San Diego County. Its stout trunk — shaped like a wine bottle — is where it stores water. (Adobe Stock)
Update ornamentals
This is THE time of year to add new plants to your garden — or plant a completely new garden. Do your homework before you head to the nursery. Put together a shopping list rather than rely on impulse shopping.
Choose plants with narrow leaves, tiny leaves, succulent leaves, fuzzy leaves, silvery leaves, hard leathery leaves, and/or needles. These adaptations help plants conserve water to survive the hot months.
Here are some of my favorite plants for our region:
• Native plants like lemonade berry (Rhus integrifolia) and big berry manzanita (Arctostaphylos glauca) both evergreen shrubs that support birds, butterflies and their caterpillars, and other important native critters.
• Australian plants like kangaroo paws (Anigozanthos), a perennial whose flowers look like tiny kangaroo paws, and Callistemon ‘Cane’s Hybrid,’ a smaller evergreen tree with narrow green leaves and watermelon pink, brushlike flowers year-round. Hummingbirds and bees love these plants.
• Succulent trees like dragon tree (Dracaena draco) that has a stout gray trunk topped in clusters of blue-gray, tongue-shaped leaves, and the bottle tree (Brachychiton rupestris) whose stout, water-storing trunk is shaped like a wine bottle. Both are extremely easy to grow, require little, if any irrigation, and thrive in full sun.
Prepare for cold
While we don’t get hard frosts (frosts so intense that the ground freezes hard), plants from coast to mountains can suffer frost damage on a cold night.
The flowers of perennial Anigozanthos look like tiny kangaroo paws, hence the name. (Adobe Stock)
Protect cold-sensitive plants like Plumeria, Fuchsias, bromeliads, many types of succulents, etc. Move potted plants under the eaves or under low branches of evergreen trees. Cover in-ground plants with floating row cover (not plastic and not a bed sheet). Use clothespins to secure the cover in place.
Do not cut off the damaged parts of a frosted plant — they protect the rest of the plant from the next freezes. Wait until February or March once all danger of frost has passed.
Fruit trees
Bare root season starts next month. Plan now for the new deciduous fruit trees you’ll add to your garden.
Match the variety of stone fruits, apples, pears and persimmons to the amount of winter “chill” your garden gets. Without enough cold, these plants don’t get enough dormancy to flower and/or fruit. Typical San Diego County chill ranges from 100 hours along the coast to 1,000 hours in Julian. Download a map of the county’s chill hours at bit.ly/ChillHoursSanDiego to use to select the right varieties for your garden.
Bare root blueberries, figs, grapes and pomegranates are already available in local nurseries. Chill hours are not important for these kinds of fruits.
What’s my favorite apple? Sundowner! This apple is sweet, tart and crisp. It is excellent eaten right off the tree and also makes great pies and apple sauce. And Sundowners ripen in October/November, which is after summer’s fruit is done, and before winter citrus.
This is the most important maintenance time for deciduous fruit trees like peaches, nectarines, Pluots, Apriums, apples and others that drop their leaves in winter. Between now and the end of January:
• Strip leaves off the branches of stone fruits, pears and apples if they don’t fall off on their own. Leaves can be infected with fungus and other pathogens that overwinter. Don’t compost them. Rake them up instead, then send them off in the greenwaste.
• Prune deciduous fruit trees, taking care not to cut off the fruiting wood. Different kinds of fruit trees form fruits on a different parts of their branches. Apples, for example, grow short spurs along the branches. Those spurs make flowers and fruits. Pomegranates and figs fruit at the end of branches. Pluots fruit along the length of the branch. Know what fruits before you cut.
My favorite pruning guide is “How to Prune Fruit Trees” by R. Sanford Martin. It’s a classic!
After pruning, spray fruit trees to kill overwintering pests and diseases. Spray each treatment once, wait two weeks, spray again, wait two weeks and spray a third time.
• Spray apple and pear trees with mineral-based horticultural oil to suffocate scale, whiteflies, mealy bugs and other tiny pests that overwinter in the bark.
• Spray stone fruits (peach, nectarine, plum, etc.) with liquid copper to kill the fungus responsible for the dreaded peach leaf curl. Spray mineral-based horticultural oil, too.
Every time you spray, coat all branches and trunks, from tips to base. The better the coverage, the more your trees are protected.
If you have lots of fruit trees, consider a battery-powered sprayer. Battery-powered sprayers are more expensive than hand pump but are easier to use, far faster, and much more effective.
Want to know more about fruit trees and shrubs? Watch “Incredible! Edible Waterwise Fruit Trees and Shrubs” at bit.ly/IncredibleEdibleWebinar.
Prune established ornamentals
Winter is time to prune deciduous ornamental trees and shrubs. Hire a certified arborist to remove weak or dead branches, check for borer infestations, structural integrity and so on. If you don’t have a favorite certified arborist, find one at treesaregood.org.
Before you prune, sharpen your pruning tools so they make clean, healthy cuts that don’t shred the wood.
Work clean. Disinfect pruning shears, saws, loppers and other cutting tools before and between plants to avoid spreading diseases and pests from one plant to the next. I use household disinfectant spray.
To prune, first remove dead branches, weak wood, and crossing branches. Then prune for shape.
Make cuts in the right spot. Follow each branch to where it attaches to the trunk or to the next larger branch. Notice the swelling at the base of the branch? That’s called the branch collar. When you cut, cut up to the branch collar, leaving no stubs behind.
NEVER TOP A TREE. If a tree is too tall, replace it with one (or two or three) that doesn’t grow that tall.
Evergreen subtropical fruit trees like citrus, guava and avocado don’t need to be pruned the same way as stone fruits. Citrus are best left unpruned, though do remove dead and crossing branches. Leave their low branches — those are easiest to harvest from and they shade the trunk to keep it from sunburn, which can kill a citrus tree — though do remove branches so low that their fruit will touch the ground.
As you finish pruning each tree, spray your tools with disinfectant and dry them with a rag. When you are completely done with pruning for the day, disinfect again, wipe them dry and lubricate with mineral oil before storing.
Care for potted plants
It’s poinsettia time! Remove the fancy foil as soon as you get poinsettia home. Make sure its pot has drainage holes. If it doesn’t, move the plant to a new pot with drainage. Place it in a brightly lit room away from the heater vent and away from a cold window. Water enough to keep the soil damp but not wet. Click here for directions on how to care for your poinsettia plants.
Monitor potted plants. Feel the potting soil every few days and water before the soil gets too dry. Indoors, a humidifier helps keep air moist and plants from drying out.
Control pesky little black fungus gnats, which are attracted to the wet, decaying organic matter in the potting soil. The flies are easy to control without chemicals or sprays: 1) water less (your plants will be fine) and 2) use a 1/2- to 1-inch-thick layer of small pebbles, aquarium rocks, even marbles to cover the surface of the potting soil. That forms a barrier the flies can’t penetrate.
Watch vigilantly for scale and mealy bugs on plant leaves. Scale looks like small round, brownish spots along leaves and stems. Mealy bugs are bright white. Rub them off when you see them.
Edible gardens
Remove the last of the summer vegetable plants. Even if tomato or pepper or eggplants are still producing, next year they won’t be nearly as productive and vigorous. Pull them out and start seeds again in March or April (my “Easy Seed Starting: the Ultimate Seed to Harvest” course and workshops go on sale in January).
Plant winter root vegetable seeds (not seedlings) now: beets, turnip, radish, carrots, rutabagas, parsnip.
Plant greens and cabbage family plants from seed or seedling: spinach, lettuce, kale, broccoli, broccolini, cabbage, Napa cabbage and more.
Plant annual herbs in your vegetable garden: cilantro, parsley and dill.
Before you plant new seedlings, refresh the soil with compost, earthworm castings and vegetable fertilizer.
Mix permanent herb plants like bay, rosemary, oregano, thyme, marjoram and sage with waterwise ornamental plants, in full sun beds.
To harvest greens like lettuce, kale, spinach, bok choy and tatsoi, simply cut off as many leaves as you need, and let the plants continue to grow. Harvest herbs the same way.
Mulch
How thick is your garden’s mulch? Aim for a minimum of 3 inches layered over every garden bed. Be sure irrigation lines are under the mulch, not on top.
Mulch succulents with rock or gravel. Mulch nonsucculents with aged woody mulch or with fresh wood chips that are smaller than an inch. Larger fresh woodchips can bring deadly borers into your garden.
Aged wood chips are not problematic.
This month’s events
Dec. 4-6: San Diego Floral Association, 2025 Festival of Trees, room 101 Casa del Prado, Balboa Park; sandiegofloral.org/FOT.
Dec. 5-6: December Nights, Balboa Park; sandiego.gov/december-nights.
Dec. 20: Shop for bromeliads at the San Diego Society Bromeliad sale in room 101, Casa del Prado, Balboa Park, 10 am to 4 pm. SanDiegoBromeliadSociety.org.
Now through Jan. 4: Lightscape at San Diego Botanic Garden; sdbg.org/lightscape.
Sterman is a garden designer, journalist and the host of “A Growing Passion” on public television. She runs Nan Sterman’s Garden School at waterwisegardener.com.
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