Your Zone 9 December Garden Checklist: What to Plant, Prune, and Harvest Before the New Year
December is Zone 9’s second planting season. Here’s exactly what to sow, prune, and harvest — with the timing and reasoning behind each task.
December arrives and the rest of North America puts the garden to bed. In Zone 9, you do the opposite. While zone 5 gardeners flip through seed catalogs from the couch, your soil is 50–55°F and workable, your brassicas are sweetening in the frost, and you have a genuine planting window before the New Year.
Zone 9 spans coastal California, the Houston area, Arizona’s low desert, and parts of northern Florida — and December plays differently across all of them. Sacramento sees more frost than Phoenix; Houston stays warmer than both. What ties them together is a shared window: cool nights that improve crop flavor, deciduous plants entering dormancy, and six weeks to get garlic, peas, and transplants into the ground. Use this month’s checklist alongside the Year-Round Planting Guide to anchor your full 12-month calendar.
What to Plant in Zone 9 in December
Cool-season crops don’t just tolerate Zone 9’s December temperatures — they prefer them. Broccoli, cauliflower, cabbage, and kale transplanted now will head up in ideal 50–60°F conditions, slower and denser than spring crops rushing to mature in rising heat.
For root vegetables, direct sowing is the only option. Carrots, beets, and turnips develop a central taproot immediately after germination; disturbing the soil causes forking. Cherry Belle radishes return the fastest — 25 days from seed. Danvers carrots take around 70 days, putting a December sowing on track for a late January harvest.
Peas are December’s headline crop in Zone 9. Plant sugar snap or snow peas now and install your trellis at the same time — vines establish faster than expected, and digging around shallow roots once they’re climbing sets them back weeks. Expect harvest late January through February.
Garlic has a mid-December deadline. Choose softneck varieties — Silverskin, California Early, or Artichoke types — over hardneck for Zone 9. Softnecks initiate bulb formation with just 30–50 hours below 50°F, which Zone 9 winters reliably deliver. Hardneck varieties need 40–60 days of sustained cold; without it, they produce single-clove rounds rather than divided bulbs. Our garlic growing guide covers cultivar selection in full. After mid-December, wait until October.
Start peppers and eggplants indoors under grow lights now. Both need 10–12 weeks from seed to transplant-ready size — a December start produces robust plants ready for Zone 9’s last frost date in late February or early March. Tomatoes can wait until late December for the same spring timeline.
| Crop | Method | Ready | Notes |
|---|---|---|---|
| Broccoli, cauliflower, cabbage, kale | Transplants outdoors | Jan–Feb | Thrive at 50–60°F; plant now while temps are ideal |
| Lettuce, spinach, Swiss chard | Direct sow or transplant | 4–6 weeks | Light mulch retains moisture; outer leaves harvestable in 3 weeks |
| Carrots, beets, turnips, radishes | Direct sow only | 25–70 days | Taproots resent transplanting; radishes ready in 25 days |
| Sugar snap and snow peas | Direct sow | Late Jan–Feb | Install trellis at planting; harvest frequently once pods fill |
| Softneck garlic | Direct sow (last chance) | May–June | Mid-December deadline; hardneck varieties lack sufficient chill hours |
| Peppers, eggplants | Start indoors | March transplants | 10–12 weeks to transplant size; start now for last-frost timing |
| Pansies, snapdragons, calendula | Transplants outdoors | Immediate | Winter color and early pollinator support |
What to Prune in December (Zone 9)
Start rose pruning in mid-December and continue through the second week of February — this is the full Zone 9 window. Pruning while roses are still blooming is counterintuitive but necessary: removing top-growth forces the plant into dormancy by eliminating the energy sink of active shoots. An unpruned bush that grows through a warm December will push new growth from the top of existing canes rather than from the base — a 5-foot plant can hit 8 feet by May with blooms out of reach.
There’s a second reason not to delay: old foliage left on the plant through winter harbors Botrytis and black spot fungal spores. New spring growth pushing through that old material picks up the infection immediately. Remove spent blooms and fallen petals now to prevent spring reinfection. For full technique, see our complete rose pruning guide.
Deciduous fruit trees — peach, pear, apple, plum — can be pruned once leaves have fully dropped. The leafless structure makes crossing branches and weak angles visible that summer foliage hides. Remove dead, diseased, and rubbing branches first; then open the canopy to improve light and airflow.
Do not prune frost-tender plants or established citrus. Any pruning cut stimulates new growth, and fresh growth is the most frost-vulnerable tissue on any plant. If November frost damaged your citrus, wait until late winter — what looks dead now may still recover.
| Plant | Timing | What to Remove | Notes |
|---|---|---|---|
| Roses | Mid-December through February | Dead canes, spent blooms, crossing branches; reduce to 18–24 inches | Forces dormancy; removes overwintering fungal spores |
| Deciduous fruit trees | After leaf drop | Dead, diseased, crossing branches | Dormant pruning minimizes disease entry points |
| Spent annuals and perennials | Now | Spent stalks cut to 6 inches | Non-diseased trimmings go to compost |
| Frost-tender plants | Do NOT prune | — | Pruning triggers new growth vulnerable to frost damage |
| Citrus | Do NOT prune | — | Wait until late winter; frost damage extent may not be visible yet |
What to Harvest in December (Zone 9)
The best kale of the year is kale that’s been frosted. When temperatures drop below 50°F, cold-hardy plants activate an enzyme-driven conversion of stored starch into simple sugars — sucrose and fructose — that lower the freezing point of their cell fluids and protect tissues from ice crystal damage. For you, the result is kale that’s noticeably milder and less bitter than it was in September, Brussels sprouts with a sweet, nutty character, and broccoli with richer flavor. Two light frosts produce a clear improvement. Per Gardening Know How, the same conversion applies to carrots, beets, and turnips — all sweeter after exposure to sustained cold.
Citrus is at peak season in Zone 9 December. Navel oranges, tangerines, lemons, and grapefruits are all in the harvest window — but color is not a reliable indicator of ripeness. When nights cool, citrus de-greens: the skin’s chlorophyll breaks down, revealing underlying yellow and orange pigments. This happens because of temperature change, not because the fruit has developed full sweetness. A fully orange navel orange in early December may still be watery and bland; the same tree in late December may be perfect. Always sample by cutting one fruit open before picking the rest of the tree.
For greens, practice cut-and-come-again harvesting: remove outer leaves of chard, lettuce, and mustard greens at the stem base, leaving the central growing point intact. These plants will produce multiple harvests across December and January.
Peas planted in October or early November are sizing up now. Pick every 2–3 days while pods are plump and the skin is still smooth — once the pod wall turns papery and the peas inside press visibly against it, the sugars convert to starch and production slows.
| Crop | Sign of Readiness | Harvesting Tips |
|---|---|---|
| Kale, Brussels sprouts, collards | After 1–2 light frosts | Frost-sweetened: sweeter and less bitter after cold nights |
| Broccoli, cauliflower | Compact, dense heads before flowering | Cut central head; side shoots continue producing for weeks |
| Citrus (navel orange, tangerine, lemon) | Taste test — not color | De-greening (color change) is temperature-driven, not ripeness-driven |
| Carrots, beets, turnips | Check root diameter; don’t rush | Leave in ground as cold storage until needed — flavor improves |
| Swiss chard, lettuce, mustard greens | Outer leaves 6+ inches | Cut-and-come-again: leave center intact for continued harvest |
| Peas (planted Oct–Nov) | Plump pods, skin still smooth | Pick every 2–3 days to prolong production; papery pods = too late |
Soil Prep and Garden Maintenance
December is the best time to amend beds you’re not currently using. Spread 2–3 inches of compost or aged manure over harvested or empty areas and work it into the top 6 inches. A December application gets 10–12 weeks of microbial breakdown before spring planting, with winter rains incorporating nutrients into the soil profile. Spring-applied amendments added days before planting don’t have that time — the difference shows in April.
If you haven’t tested your soil recently, December is the right time. Submit samples to your state university extension lab (typically $15–20; results in 2–4 weeks) in time to adjust pH or add targeted nutrients before your spring schedule begins. Many Zone 9 soils trend alkaline at pH 7.5–8.0, which locks up iron and manganese and causes yellowing even in fertilized beds.
Empty beds not designated for immediate planting benefit from a cover crop. Crimson clover or Austrian winter peas sown now fix nitrogen and suppress winter weeds through February, improving both soil structure and fertility.
Frost Protection in Zone 9
Zone 9’s average first frost falls around December 15, but that average masks real variation within the zone. Houston rarely drops below freezing at all; Sacramento can hold below 32°F for several consecutive nights; Arizona’s low desert gets brief, sharp cold snaps that damage tender plants more than prolonged cold does.
Apply frost cloth when the forecast drops to 32°F — but remove it the next morning as soon as temperatures rise above 40°F. Frost cloth over plants on a clear, sunny December day creates a miniature greenhouse: interior temperatures can reach 90–100°F within an hour of sunrise, heat-stressing the plants you’re trying to protect.
For established citrus trees, string lights draped through the canopy provide 2–4°F of warming, enough protection when temperatures stay above 26°F. Below that, combine a frost blanket with a supplemental heat source. Young citrus transplants need blanket coverage at 32°F regardless of size.
Low tunnels over brassica rows extend your harvest window through hard frosts and are worth setting up in northern Zone 9 before the first cold spell arrives.
Frequently Asked Questions
Can I still plant garlic in December in Zone 9?
Early December, yes — choose softneck varieties like Silverskin or California Early. After mid-December, the remaining season is too short for cloves to develop full-sized bulbs before summer heat arrives. Wait until October for next year.
Is it too late to plant vegetables in December?
No. For Zone 9, December is one of the best planting months of the year. Cool-season crops planted now will produce through February and into March before the heat triggers bolting.
Stop missing your zone's planting windows.
Select your US zone and month — get a complete checklist of what to plant, prune, feed, and protect right now.
→ View My Garden CalendarWhat comes next after December?
January brings the full rose pruning season, bare-root fruit tree planting, and the first spring seed-starting decisions. See the Zone 9 January garden task guide for what to schedule as the new year begins.
Sources
- Arizona Garden in December — Growing In The Garden
- Zone 9 Monthly Garden Calendar — Sow True Seed
- December Rose Care: Start Pruning — Sacramento Digs Gardening
- Zone 9 Winter Gardening Guide — Everyday Homesteading
- Why Do Root Vegetables Get Sweeter With Cold — Gardening Know How (cited inline above)
- Monthly Vegetable Gardening Tips — UC Master Gardeners Sacramento County
