December Garden Tasks for Zone 10: What to Plant, Prune and Harvest
Zone 10 December gardening is peak cool-season planting time. Here’s exactly what to plant, prune, and harvest this month — with zone 10a vs 10b timing notes.
While gardeners in zones 5 and 6 are staring at frozen ground, zone 10 in December is entering one of the best growing windows of the year. The brutal heat of summer has finally broken, soil temperatures have dropped into the sweet spot for cool-season crops, and you’re working with roughly 11 hours of daylight — enough to push leafy greens from seed to harvest in under 40 days.
That said, December in zone 10 isn’t without its nuances. The difference between zone 10a (minimum 30–35°F) and 10b (minimum 35–40°F) matters for a handful of cold-sensitive decisions. And gardeners in Southern California face a drier Mediterranean December than those in South Florida, where humidity and rain patterns shift what needs attention. This guide covers both.
Zone 10 in December: What the Climate Actually Looks Like
Zone 10 spans South Florida (Miami-Dade, Broward, Palm Beach counties), the lower Rio Grande Valley, and pockets of Southern California including parts of greater Los Angeles and San Diego. What they share: no hard freeze, average winter minimums above 30°F, and a year-round growing season.
What they don’t share: rainfall. South Florida’s dry season begins in November and runs through April — so December watering is your responsibility, not the sky’s. Southern California gets its limited winter rain but stays dry overall. Both regions see soil temperatures drop from summer highs of 85–95°F down to 60–72°F in December, which is exactly where cool-season crops want to germinate.
Zone 10a gardeners (minimum 30–35°F) in frost-edge areas should watch overnight lows in December. Cold snaps do happen and can catch tender crops off guard. Zone 10b gardeners in the heart of South Florida can plant and prune more freely — the thermal cushion is real.
What to Plant in December
December is zone 10’s prime cool-season window, and the mechanism is straightforward: soil temperatures have dropped below 75°F but remain above 50°F, which is the germination sweet spot for most brassicas, leafy greens, and root vegetables. According to OSU Extension’s germination temperature data, lettuce and spinach will sprout reliably at soil temps as low as 35°F, while carrots, beets, and radishes need at least 40°F — both well within December zone 10 ranges.
What you’re planting now will harvest in February and March, before summer heat arrives and bolts your greens. Don’t wait until January — every week of delay in December is a week of cool-weather harvest you’re giving up.
| Crop | Start Method | Days to Harvest | Notes |
|---|---|---|---|
| Broccoli | Transplant (4–6 weeks old) | 55–80 days | Direct sow is slower; use transplants for December |
| Kale | Direct sow or transplant | 50–65 days | Cut outer leaves; plants keep producing for months |
| Lettuce | Direct sow | 30–45 days | Fastest return; use cut-and-come-again varieties |
| Spinach | Direct sow | 40–50 days | Sow thickly; thin to 4 inches |
| Carrots | Direct sow | 70–80 days | Loosen soil 12 inches deep; thins poorly tolerated |
| Beets | Direct sow | 55–70 days | Harvest both roots and greens |
| Radishes | Direct sow | 22–30 days | Fastest crop in the garden; succession sow every 2 weeks |
| Peas | Direct sow | 60–70 days | Snow peas and snap peas both excellent choices |
| Swiss chard | Direct sow | 50–60 days | Heat-tolerant enough to bridge into spring |
| Onions (from sets) | Sets or transplants | 90–120 days | Short-day varieties for Florida; intermediate for CA |
| Garlic | Direct plant cloves | 150–180 days | Last call for garlic — plant now for June harvest |
| Cilantro, parsley, dill | Direct sow | 21–30 days to use | UF/IFAS recommends these as December priority herbs |
Indoor seed starting for spring: December is the time to start tomatoes and peppers indoors under grow lights. These crops need 8–10 weeks of indoor growth before they’re ready to transplant, which puts you at a February–March transplant date — right when zone 10 nights warm up and spring crops can hit the ground running. Start in 4-inch pots under 12–14 hours of light daily.
Florida gardeners: The University of Florida IFAS Extension’s South Florida Gardening Calendar specifically flags December as the last reliable month to plant tomatoes and peppers for a late spring harvest. If you’re in Miami-Dade or Broward and want tomatoes this season, plant the transplants this month.
California gardeners: You have more flexibility with timing but drier soil to manage. Amend beds with compost before planting to improve moisture retention, and irrigate consistently — December rain can’t be counted on to do the job for you.
What to Prune in December
Pruning in zone 10 in December requires more nuance than most guides suggest. The general rule — “prune when dormant” — doesn’t apply to tropical and subtropical plants that never go dormant. The right approach depends on what you’re pruning and why.
| Plant | December Action | Timing Reason |
|---|---|---|
| Roses | Light shaping only — full pruning wait until January | Hard pruning now triggers growth flush; Zone 10a cold snaps can damage tender new canes |
| Citrus trees | Remove dead wood and crossing branches only | Harvest season; avoid cuts that stress fruit-producing wood |
| Bougainvillea | Skip December — prune after bloom flush or late February | Cutting during potential cold snap increases frost damage risk |
| Hibiscus | Light tip-pinching only; hard prune in February | Hard pruning now delays blooms; February timing aligns with growth surge |
| Perennial herbs (sage, thyme) | Light harvest-pruning fine | Encourages bushy growth; plants actively growing in December |
| Palms | Remove only brown, fully dead fronds | Green fronds store nutrients; over-pruning causes pencil-pointing and stress |
| Vegetable plants past their prime | Pull and compost; replant with cool-season crops | Lingering summer crops tie up bed space better used for winter vegetables |
The rose pruning question: Zone 10 gardeners who want roses blooming for Valentine’s Day (mid-February) should do a hard pruning in early December — roses typically take 8–10 weeks from a hard prune to full bloom. Remove all canes back to 18–24 inches, cutting just above an outward-facing bud at a 45-degree angle. If you missed the window or are in zone 10a where a December cold snap is possible, wait until January, which pushes blooms to mid-March and avoids the frost risk to new growth.
What not to prune this month: Avoid hard cutting of mango, avocado, and other tropical fruit trees until spring. Their wood is cold-sensitive, and fresh cuts into structural branches in December leave them vulnerable if temperatures dip. Light removal of crossing or dead wood is fine, but save any shaping for after last frost risk has passed.
What to Harvest in December
December brings some of the best harvest variety of the zone 10 year. Citrus peaks, tropical fruits ripen, and any cool-season crops you planted in October are now ready to pull.
| Crop | Ready When | Storage Tip |
|---|---|---|
| Navel oranges, early mandarins | Fully colored; a gentle tug drops ripe fruit into your hand | Refrigerator produce drawer; 2–3 weeks |
| Grapefruits | Full color reached; taste-test — skin color alone isn’t reliable | Leave on tree until needed; holds well for weeks |
| Limes (Persian) | Skin turns light green and yields to light pressure | Refrigerate; 2–3 weeks |
| Papayas | Skin turns at least 50% yellow; fragrant at stem end | Ripen at room temperature; refrigerate once ripe |
| Pomegranates | Deep color, metallic sound when tapped | Refrigerator; up to 2 months |
| Pineapple guava (feijoa) | Falls from tree when ripe; check ground daily | Refrigerate promptly; window is short |
| Broccoli (fall-planted) | Heads compact and dark green before florets open | Refrigerate in damp cloth; 1 week |
| Lettuce, kale, Swiss chard | Harvest outer leaves; leave growing point intact | Harvest morning; wash and refrigerate immediately |
| Carrots, beets, turnips | Finger-test the soil — roots should be 3/4-inch diameter minimum | Store in damp sand in a cool spot; weeks to months |
Citrus ripeness — the one cue that matters: Color change alone doesn’t indicate ripeness in zone 10’s warm climate. Florida citrus in particular can regreen (turn from orange back to green) when temperatures rise after color develops — the fruit is still ripe. The reliable test is flavor: taste one fruit. Alternatively, the gentle-tug method works for most citrus — a ripe fruit separates cleanly from the stem with a slight twist. Fruit that holds tight isn’t quite ready.
Don’t leave broccoli past its window: Once the florets in your broccoli head begin to separate and show yellow flower buds, the clock is running. Flavor deteriorates fast at this stage. Harvest broccoli when heads are tight and the color is deep green — if you see any yellowing on the florets, cut immediately and use within two days.
Other December Garden Tasks
Switch to a winter irrigation schedule. Your summer watering frequency was driven by heat load and evaporation. In December, soil moisture holds much longer — you can typically cut irrigation by 30–50% compared to August. Overwatering in winter is the leading cause of root rot and fungal disease in zone 10 cool-season beds. Check soil moisture 2–3 inches down before irrigating; if it’s damp, wait.
Mulch actively planted beds. A 2–3 inch layer of organic mulch does double work in December: it insulates roots from the occasional overnight dip in zone 10a, and it slows the moisture loss that dry-season winds accelerate. Use shredded leaves, straw, or pine bark — keep mulch 2 inches away from plant stems to prevent collar rot.
Monitor for pests — they don’t always slow down. According to UF/IFAS Extension, some pest populations actually increase in cooler months despite what you’d expect. Aphids, whiteflies, and caterpillars can still run through a broccoli or kale planting in December. Check the undersides of leaves weekly and knock off aphids with a strong water spray before reaching for anything stronger.
Prepare for unexpected cold in zone 10a. Keep frost cloth or old bedsheets accessible. A brief dip to 28–30°F won’t kill established broccoli or kale but will damage tomato transplants and tender herbs. If a cold front is forecast, cover sensitive plants the evening before — not the morning of.
For a full month-by-month breakdown of what zone 10 gardeners should be doing year-round, the Year-Round Planting Guide covers every month with zone-specific timing. If you’re planning ahead, January’s Zone 10 task guide shows exactly what comes next — including when it’s safe to do the heavy rose pruning if you held off this month. If you’re newer to gardening in this climate, the Florida gardening guide covers the broader seasonal patterns that shape how zone 10 works differently from the rest of the country.
Frequently Asked Questions
Can I plant tomatoes in zone 10 in December?
Yes — but act now. UF/IFAS Extension flags December as the last reliable month to plant tomatoes in South Florida for a spring harvest. Use transplants (not seeds), choose a variety with 70–80 days to maturity, and get them in the ground by mid-December for the best results. In California zone 10, you have a slightly wider window into January due to cooler, drier conditions that slow maturity.
What should I do with summer annuals that are fading?
Pull them. A summer annual hanging on in December is taking up space, often hosting pests, and producing little. Clear the bed, add a 2-inch layer of compost, and plant cool-season crops. The turnaround time from bare bed to harvestable lettuce or radishes is just 4–6 weeks.
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→ View My Garden CalendarIs it too late to plant garlic in zone 10?
December is the last practical window. Garlic planted now will harvest in May–June as temperatures rise. Plant individual cloves 4–6 inches apart, 2 inches deep, with the pointed end up. Zone 10 gardeners should choose softneck varieties (Silverskin or Artichoke types) — they’re better adapted to mild winters than hardneck types, which need a longer cold vernalization period.
Sources
University of Florida IFAS Extension. South Florida Gardening Calendar (ENH1191/EP452). UF/IFAS Extension.
Oregon State University Extension Service. Soil Temperature Conditions for Vegetable Seed Germination. OSU Extension.
Sow True Seed. Zone 10 Monthly Garden Calendar: Chores and Planting Guide. sowtrueseed.com.
Soule, J. Zone 10 December Garden Tasks. gardeningwithsoule.net.
Harvest to Table. December Vegetable Garden — Zones 9b–11. harvesttotable.com.
