December Garden Tasks for Zone 5: Plant, Prune, and Harvest Before the Ground Freezes
Your zone 5 December window is closing: plant bulbs before hard freeze, prune fruit trees while fire blight is dormant, and harvest kale at peak sweetness.
December in zone 5 doesn’t feel like a gardening month. Temperatures hover between 20°F and 35°F during the day, the first hard freezes have likely arrived, and most beds are locked under a carpet of dead leaves. But there’s a narrow, productive window still open — and the gardeners who use it set themselves up for a much stronger spring.
This guide covers three categories of December tasks for zone 5 gardeners: what you can still plant before the ground seals, what to prune now while dormancy works in your favor, and what to harvest from beds you may have written off. There’s a table for each, so you can scan-and-act rather than read-and-forget.
Zone 5 spans a wide swath of the US — from northern Illinois and Indiana across Ohio, Pennsylvania, Minnesota, Wisconsin, and the Colorado mountains — where average winter lows fall between -20°F and -10°F. What you can do in December depends partly on whether your local ground has frozen solid yet. If it hasn’t, more options are open than most gardeners realize.
What to Plant in Zone 5 in December
The conventional wisdom is that December planting is over in zone 5. That’s mostly true — but not entirely.
Spring Bulbs — Last Call
If your soil is still workable, you have until roughly Christmas to get spring-blooming bulbs in the ground. Tulips, daffodils, alliums, and crocus all need a minimum of 10 weeks at 35–45°F to complete vernalization — the cold-triggered developmental process that allows them to flower properly. Skip that cold exposure and you’ll get stunted stems and weak flowers, if any bloom at all.
December planting is far from ideal; zones 3–5 should aim for late October to early November. But if bulbs are still sitting on your potting bench, planting them now beats waiting until spring. By March, unplanted bulbs will have desiccated beyond recovery. Push them 6–8 inches deep and cover with 3–4 inches of straw mulch to slow the soil from freezing too fast, buying a few extra weeks for root establishment.
Garlic — Possible, but Expect a Trade-off
Garlic still technically goes in during December if the ground isn’t frozen, but this is the last-resort window, not the ideal one. Penn State Extension recommends planting hardneck varieties in zone 5 by mid-to-late October. December plantings don’t build the same root system before the soil freezes, and the result is noticeably smaller bulbs at harvest the following July.
If you missed the fall window, choose a hardneck variety — Rocambole and Porcelain types are the most cold-hardy. Plant cloves 2 inches deep with the pointed end up, space 6–7 inches apart, and mulch heavily with 4 inches of straw. You’ll still get garlic; just plan a heavier October zone 5 planting session next year to avoid the trade-off.
Indoors: Microgreens and Forced Bulbs
December is when indoor growing justifies itself. Amaryllis bulbs potted now bloom in 6–8 weeks — right through the bleakest stretch of winter. Microgreens (sunflower, radish, pea shoots) grow to harvest in 10–14 days on a sunny windowsill without grow lights. A south-facing window handles either crop without any additional equipment.
| What to plant | Window | Best varieties/types | Notes |
|---|---|---|---|
| Spring bulbs (tulip, daffodil, crocus, allium) | Until ground freezes hard (late Dec) | Any hardy variety; plant 2–3x bulb depth | Mulch 3–4″ after planting; needs 10-week cold period to bloom |
| Garlic (hardneck) | While ground is still workable | Rocambole, Porcelain types | Expect smaller bulbs vs. October planting; mulch heavily |
| Amaryllis (indoors) | Any time | Any — soil-potted or waxed | Blooms in 6–8 weeks; no cold period required |
| Microgreens (indoors) | Any time | Sunflower, radish, pea shoots | Harvest in 10–14 days; south window or grow light |
What to Prune in Zone 5 in December
December is one of the best months to prune deciduous trees and fruit trees — and one of the worst months to prune about a third of what’s in your garden. Knowing which is which protects both your plants and your spring display.
Prune Now: Deciduous Trees, Fruit Trees, and Roses
When trees enter full dormancy — signaled by leaf drop and halted sap flow — they handle pruning with minimal stress. Cuts don’t trigger the vigorous compensatory growth that spring pruning provokes, and the branch structure is fully visible without foliage in the way.
For apple and pear trees, December pruning carries an additional disease-management benefit: fire blight bacteria (Erwinia amylovora) are dormant inside cankers during winter and cannot spread through pruning tools. That means you can remove infected wood without sterilizing your blades between cuts — a significant advantage over growing-season pruning, where active bacteria travel easily on contaminated equipment. Cut 6–12 inches beyond the visible canker edge into wood at least two years old, and burn or bag all removed material before spring.
For roses, December is right for a light tidy: remove dead, damaged, or rubbing canes and trim any overly long growth that wind could whip around, causing crown damage. Hold structural pruning — cutting roses back to their framework — until late February or March in zone 5, when the risk of a hard freeze is lower. See our full zone 5 rose growing guide for timing specifics by rose type.
Skip These: Spring Bloomers, Bleeders, and Old-Wood Hydrangeas
Three categories of plants will punish a December pruning. First, spring-flowering shrubs — lilac, forsythia, rhododendron, azalea, magnolia — have already set their flower buds in the current season’s wood. Cut now and you remove next spring’s bloom. Wait until two to three weeks after they flower instead.
Second, bigleaf, lacecap, and oakleaf hydrangeas bloom on old wood — the canes that grew last summer. December pruning eliminates those canes and the summer flowers with them. (Panicle and smooth hydrangeas bloom on new wood and can be pruned in late winter without consequence.) If you’re not sure which type you have, check our zone 5 hydrangea guide before cutting anything.
Third, bleeder trees — birch, maple, and willow — lose significant sap from winter cuts, which attracts borers and other pests. Prune these in early summer after the leaves are fully out.
| Plant | Prune in December? | Reason |
|---|---|---|
| Apple, pear trees | Yes | Fire blight bacteria dormant; no tool sterilization needed between cuts |
| Oak, beech, hawthorn and other deciduous trees | Yes | Fully dormant; structure visible; stress-free cuts |
| Roses | Light trim only | Remove dead/damaged canes; structural pruning wait until late Feb/March |
| Lilac, forsythia, rhododendron, azalea | No — prune after bloom | Flower buds already set in wood; December trim = no spring flowers |
| Bigleaf/lacecap/oakleaf hydrangea | No | Blooms on old wood; cutting now removes next year’s buds |
| Birch, maple, willow | No — prune in early summer | Heavy sap bleed in winter attracts borers |
| Cherry, plum trees | No — prune late summer | Cold, wet cuts invite canker disease in these species |
What to Harvest in Zone 5 in December
December looks empty, but some crops actively improve after a hard freeze — and a few will still be waiting under mulch right through the month.
Frost-Sweetened Crops: Brussels Sprouts, Kale, Carrots
Cold temperatures trigger one of the more useful processes in vegetable gardening: starch-to-sugar conversion. When temperatures drop below freezing, cool-season crops convert stored starches into soluble sugars that act as internal antifreeze, lowering the freezing point of their cellular fluids and protecting cells from ice crystal damage. The flavor change is immediately apparent — Brussels sprouts become nutty rather than sulfurous, kale loses most of its bitterness, and carrots taste noticeably sweeter than the same variety pulled in September.
In zone 5 in December, these crops are at or near peak flavor. Brussels sprouts planted in May are still harvesting from the bottom up — pick the lowest sprouts first while the upper buds continue to size. Kale can stay in the ground and be picked as needed; it tolerates temperatures into the low teens °F. Carrots left under 6–8 inches of straw mulch can be harvested right through December and often into January — pull back a section of mulch, harvest what you need, and replace the cover.
Root Crops Under Mulch
Parsnips, turnips, and leeks are all still harvestable under proper mulch cover in zone 5. Parsnips require a hard frost to convert their starch, so December is their flavor peak — they’re genuinely better now than they were in October. Turnips hold down to about 20°F. Leeks are the most cold-hardy of the three and can stay in the ground until the soil freezes completely solid.
| Crop | Cold tolerance | Frost sweetening? | Harvesting method |
|---|---|---|---|
| Brussels sprouts | Into teens °F | Yes — peak nutty flavor after freeze | Harvest from bottom up; leave tops to mature |
| Kale | Into low teens °F | Yes — noticeably less bitter after hard frost | Cut outer leaves; plant keeps producing |
| Carrots | Down to ~15°F under mulch | Yes — noticeably sweeter than September harvest | Pull as needed; replace mulch after each dig |
| Parsnips | Into single digits °F | Yes — frost required for best flavor; peak now | Harvest through December; top flavor window |
| Leeks | Down to about 20°F | Mild improvement | Pull whole; freeze surplus if supply exceeds use |
| Turnips | Down to about 20°F | Mild sweetening | Harvest while ground is still workable |
Essential December Protection Tasks
Mulch After the Ground Freezes, Not Before
The timing of winter mulch trips up even experienced gardeners. The goal isn’t to prevent the ground from freezing — it’s to keep it frozen consistently. Freeze-thaw cycling is what heaves shallow-rooted perennials out of the ground, tearing roots and leaving crowns exposed to wind and cold. Apply 3–4 inches of straw or shredded leaves after the ground takes its first hard freeze, not during the mild spells earlier in fall.
For newly planted perennials or marginally hardy plants, 4 inches of mulch provides meaningful insulation. Avoid going deeper than 5–6 inches — dense mulch can trap cold rather than insulate against it, and delays the soil warming that perennials need in spring to break dormancy on schedule.
Protect Young Tree Trunks
Wrapping the lower 18–24 inches of young tree trunks (under three years old) prevents sunscald, where bark warms on sunny winter days and then refreezes rapidly at night, cracking the tissue. It also deters deer antler rubbing, which can girdle a young tree. Use commercial tree wrap or a cylinder of hardware cloth — avoid materials that trap moisture against the bark, which invites fungal issues.
Switch De-icing Products Near Beds
Rock salt (sodium chloride) applied to walks near garden beds changes soil chemistry and damages roots through salt burn. Calcium chloride and potassium chloride are both more plant-friendly and more effective at lower temperatures. If your beds border a treated path, switch now and make it a standing policy.
Stop missing your zone's planting windows.
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→ View My Garden CalendarPlan While the Garden Rests
December is the only month when almost nothing is pressing outdoors. Order seed catalogs now — the most popular tomato and pepper varieties sell out by February. Review your season notes: which varieties performed, where spacing was wrong, what you’d grow differently. Starting seeds for onions and leeks in early January (the next task on the zone 5 calendar) requires having those seeds in hand, and that means ordering this month.
The year-round planting guide maps out the full zone 5 sowing calendar from January through December, so you can see exactly how December’s indoor starts connect to your spring timeline and what seeds to prioritize in your catalog order.
Key Takeaways
December in zone 5 is brief and the list is short — but the tasks on it matter. Get spring bulbs in the ground before the soil locks. Use the dormancy window to clear fire blight cankers from your fruit trees without the disease-spread risk of growing-season pruning. Step outside and harvest Brussels sprouts and kale that taste better now than they did six weeks ago. Mulch after the ground freezes, not before. Everything else — the planning, the catalog orders, the indoor starts — can happen from the kitchen table.
Sources
- Why Do Root Vegetables Get Sweeter With Cold — Gardening Know How
- Growing and Using Garlic — Penn State Extension
- When to Plant Spring-Blooming Flower Bulbs — Longfield Gardens
- 4 Plants to Prune in December – and 4 to Skip Until Spring — Gardening Know How
- Apple and Pear Disease – Fire Blight, Dormant Removal of Cankers — Penn State Extension
