GROW IN ABUNDANCE: Beat the Heat: Smart Fall Gardening in San Diego
By Sommer Cartier, for Lets Talk Plants! October 2026
Beat the Heat: Smart Fall Gardening in San Diego
Fall always gets me excited about the garden. I'm ready to start pulling out tired summer plants, refreshing beds and making room for lettuce, broccoli, carrots and all the other cool- season vegetables I love to grow. But if you've gardened in San Diego for any length of time, you know that just because the calendar says fall doesn't mean the weather always agrees.
September may be behind us, but that doesn't necessarily mean the heat is. October can still bring plenty of hot days, just as many of us are ready to get our fall gardens planted.
When that happens, our first instinct is often to water more. But getting our gardens through a fall heat wave isn't just about adding more water. There are several things we can do to reduce stress on our plants and help the soil hold onto the water we're already giving it.
Don't Rush to Plant
One of the easiest things you can do is pay attention to the forecast.
Before putting in new plants, look at the forecast for the next week or so. If you have a six-pack of beautiful fall seedlings ready to go, but the forecast is calling for 95, 98 and 100 degrees, hold off on planting them.
New transplants are much more vulnerable to heat than established plants because their roots haven't had a chance to grow into the surrounding soil. Waiting a few days for temperatures to come down can mean less transplant shock, less watering and a much better chance of those little plant babies getting established.
Sometimes waiting is actually the more water-wise choice.
Give New Plants the Night Shift
When you are ready to plant, try to do it later in the day rather than during the hottest part of the afternoon. Late afternoon or early evening gives your plants the cooler nighttime hours to begin settling in before facing another full day of sun.
It's also important to give new plants a good start. Make sure the root ball and surrounding soil are moist when planting, and water thoroughly once the plant is in the ground. Keep an eye on new transplants for the first several days, especially if temperatures are still high.
A new plant may need more attention while it's getting established. That doesn't necessarily make it a water-hungry plant. It's developing the root system it needs to become more resilient.
Give Them a Little Shade
If another heat wave sneaks up on you after you've planted, give those new little plant babies a little help.
Even plants that will eventually grow in full sun can benefit from temporary shade when they're young. Shade cloth works well, but you don't have to get fancy. A strategically placed umbrella or even a taller plant that blocks the harshest afternoon sun can help.
Don't Leave Your Soil Naked
One of my favorite tools for getting through the heat is mulch.
If you've ever touched bare soil that's been sitting in full San Diego sun all afternoon, you know how hot it can get. That heat also means we're losing moisture to evaporation.
Adding a layer of mulch can help protect the soil from direct sun, keep the root zone cooler and slow down any moisture loss. It can also help suppress weeds, which compete for water with the plants we actually want.
Wood chips, shredded bark, leaves, straw and other appropriate organic materials can all work, depending on where you're using them. Just remember not to pile mulch directly against plant stems or tree trunks.
You can feel the difference for yourself. On a hot afternoon, compare a patch of bare soil with the soil underneath a layer of mulch. You'll likely notice right away how much cooler and more moist the mulched soil feels.
Healthy Soil Makes Every Drop Count
What's happening underneath that mulch matters too.
Healthy soil also helps us make better use of the water we're giving our plants. Adding compost and organic matter when needed can improve the soil, helping it absorb and hold moisture while still allowing for good drainage and healthy root growth.
When a summer vegetable has finished producing and it's time to pull it out, that's a great opportunity to give the soil a little attention before planting your next crop. Add compost if needed, work it into the soil, and you'll be giving your fall garden a healthier environment to get started. Water-wise gardening really starts before we ever turn on the irrigation.
Right Plant, Right Place
Finally, remember that San Diego isn't one climate. What works in a coastal garden may not work exactly the same way in La Mesa, El Cajon, Poway or Escondido. We even have different microclimates within our own yards.
A plant next to a west-facing wall may get blasted by afternoon sun and reflected heat, while another plant around the corner gets gentler morning sun. Containers can heat up and dry out much faster than plants in the ground, and raised beds may need different attention as well.
So before assuming a struggling plant needs more water, look at the bigger picture. Is it getting too much afternoon sun? Is heat reflecting off a wall or patio? Is the container too small? Is the soil draining properly? Or is this perhaps the wrong plant for that particular spot?
Sometimes the answer isn't more water.
Work With the Weather, Not Against It
As we move deeper into fall, don't feel like you have to fight San Diego's October weather. Watch the forecast, give new plants a little extra protection, cover bare soil, build healthy soil and pay attention to the different growing conditions around your yard.
The goal isn't to give our gardens more water every time it gets hot. It's to create conditions that help our plants make better use of the water we're already giving them.
We can't control the next San Diego heat wave, but we can make it a whole lot easier on our gardens when it arrives.
Sommer Cartier
Master of Arts, International Development and Social Change
Clark University