I can't lie, the last month of weather here in Southern California has been strange, to say the least. We've had days in the 40s and just about as many in the 80s, which makes for not only strange attire choices but also a feeling like you're growing in two seasons at once. Your brassicas might be thriving, or bolting, depending on what your weather has been like. You might already have thriving tomatoes and perennial fruits starting to flower. No one Zone 10 March garden is identical, because all of our microclimates are a bit different, but regardless of your garden's makeup one thing is true: there is a ton to do this month.
Last month I told you February was the work nobody sees. Well, March is when all of that invisible work becomes very, very visible, and it can happen fast. You're harvesting cool-season crops, transplanting warm-season starts into the ground for the first time, direct sowing things you missed or didn't get around to, and still trying to squeeze in a few more rounds of lettuce before it bolts. The sheer volume of things you can plant this month is longer than any other month of the year.
This is also a great time to take stock of your cool-season garden, really look at what worked, what didn't, and what you'd do differently next fall. Those observations are easy to forget by September, so write them down now while the evidence is still in the ground (speaking from repeat first hand experience). Then take a breath, make a list (check it twice), and let's get into it.
Plant Your Seedlings or Support Your Nurseries
In my garden right now I've got a wide variety of tomatoes already planted, but not as many as I'd like. Same goes for eggplants, peppers, zucchinis, and a handful of other summer crops I direct sowed. The point is, they're in the ground and growing, and if yours aren't yet, now is the time. Not "should I start thinking about it" time. Not "maybe next weekend" time. Now is the time to party.
Tomatoes, peppers, eggplant, squash, cucumbers, melons, beans, corn, whatever summer crops excite you, this is your window to get them planted. If you started seeds back in February, your tomato seedlings should be six to eight weeks old, stocky, and ready to move outside (gradually). Plant them deep, bury them up to the first or second set of true leaves, because every bit of stem below the soil line will develop roots and give the plant a much stronger foundation. Set up your cages or stakes at planting time, not later when the plant is already sprawling and you're trying to wrestle it into shape. I usually procrastinate, and then end up having to prune and mangle my tomatoes more than I’d like.
And if you didn't start seeds, or your seed starting didn't go as planned, go support your local nurseries. Not only is buying transplants a great way to get things moving quicker in your garden, but it's also a great way to support local businesses and plug into your gardening community. Big box stores are fine if that's all you've got, but oftentimes you'll find that local nurseries are a great place of education too. The people working there usually know your zone, your soil, and your microclimates like no other.
Cool Season's Last Stand
While the warm-season garden is just getting started, the cool-season garden is winding down, and this year confirmed something I've been feeling for a while now: in my very warm Zone 10a, I think I'm breaking up with large brassicas. My cauliflower and broccoli have bolted, and I'm pulling them out. It's not that they can't grow here, it's just that the window is so tight and the results are so inconsistent compared to cooler zones that I'd rather use that space and energy on crops that thrive without a fight.
That said, I'm hanging on to my kale and cilantro and the smaller, more forgiving crops that can still produce in warmer conditions. Kale in particular is a survivor here, it doesn't really bolt in my area, and it'll keep pushing new growth well into the warmer months if you just harvest from the outside leaves and let the center keep going. Cilantro and spinach, on the other hand, tend to bolt first once the days get long and warm enough, and arugula and mustard greens aren't far behind. Standard lettuce varieties will start sending up flower stalks too, though if you planted slow-bolt or heat-tolerant types like Jericho, you can stretch the season a bit longer. Now, cilantro is a deep love of mine, so I will fight that bolt until the day I die, and that's just the reality of being a gardener sometimes, there are fights worth fighting and some that aren't.
For everything that's bolting or looking tired, pull it. The bed space is more valuable than one more week of bitter lettuce.
Direct Sow What You Missed
If there are seeds you didn't get around to starting indoors, or crops you just forgot about, March is a forgiving month for direct sowing. Beans are easy, just poke them in the ground and keep them watered (especially snap peas, but I’m biased). Corn needs to be planted in blocks (not single rows) for proper pollination, so plan for at least a three-by-three grid if you have the space. Both of these want soil that's at least 60 degrees, so if you're in a cooler microclimate, you might wait until early April.
Lettuce, radishes, and other quick-growing greens can still be direct sown now too, especially if you go with heat-tolerant varieties. Succession planting is your friend here, because even though the window is narrowing, a small sowing every couple of weeks will keep you in salads longer than one big planting will.
Meanwhile, peppers and eggplant that are still growing indoors need warmer soil than tomatoes (closer to 70 degrees) and won't go outside until early April. If you started them in February, they should be putting on good growth but aren't ready for the outdoors yet.
Feed Your Soil
March is when the whole garden wakes up, and waking things up means they're hungry.
Start by feeding your citrus if you haven't already. I actually started fertilizing mine back in February, because finding a regular cadence with your citrus rather than treating it as a one-time event is a great way to get things cranking. Every 2-3 months is what works best for me.
Beyond citrus, this is the time to feed everything. Work a couple inches of compost, some worm castings, and a well-rounded organic granular fertilizer into beds as you clear cool-season crops and prepare for warm-season planting. If you grew heavy feeders like brassicas in those beds over the winter, the soil is probably a little depleted, so don't skip this step. Your perennials could use a feeding too, and speaking of perennials, my dragon fruit is putting out a ton of new growth right now, which is always a good sign that things are waking up and the soil is warming. My pomegranate tree is showing its first buds of the season too. If you have tropicals or subtropicals in your garden, they should be starting to move, and a feeding now helps them push strong.
Refresh your mulch across the garden while you're at it. Three inches is the sweet spot for most beds, enough to retain moisture and suppress weeds without suffocating the soil. This is less urgent than feeding, but you’ll be glad you did it as summer heat creeps closer.
Flowers and the Supporting Cast
If you planted flowers in February, you should be starting to see some of them come to life, and March is the time to keep that momentum going. Sunflowers, cosmos, marigolds, nasturtiums, and borage can all go in now. If you didn't plant milkweed for monarchs yet, this is a good time (I love getting mine from my local nursery). My popcorn cassia (seen at the top of this post) is absolutely thriving right now, which is one of those perennial legumes that I always recommend for Zone 10 gardens because it fixes nitrogen, feeds pollinators, and looks stunning doing it (just be warned, once it gets going you might never want to give up that space).
As for summer flowers like zinnias, this is where your specific climate matters. If you're feeling ambitious and you live in a slightly drier Zone 10 where powdery mildew isn't as much of a concern, go ahead and get them started. But given the erratic weather here in Southern California specifically, I'm probably going to wait another month so they don't get wiped out by mildew before they even get going. Your call, but just know the risk if your springs tend to run damp.
Companion planting gets real this month too. As you plant tomatoes, tuck basil and marigolds nearby. As beans go in, add some summer savory. These aren't just garden aesthetics, they're functional relationships that support pollination and help manage pests. The more you integrate flowers into your vegetable garden rather than keeping them separate, the better everything performs.
Wrapping Up
March is a lot, as both seasons are running simultaneously, your to-do list is longer than any other month, and there's a real temptation to try to do everything at once. If that's your energy right now, great, channel it. But if you're feeling overwhelmed, just focus on getting your summer crops in the ground and clearing out whatever cool-season crops are done. Everything else can happen on your schedule.
Next month we'll talk about the handoff, when the warm-season garden takes over completely, cool-season crops say their final goodbye, and your job shifts from planting to supporting what's already in the ground. See you in April!
