What to plant in December in Ireland

Worked out for 14 cities from their own weather and frost dates, by zone.

What to sow and plant in December in Ireland, by zone: frost possible, highs below 10 °C (Dublin, Cork and 12 more): garlic, broad bean, peas, onion, spinach and 4 more.

In Ireland, December is winter.

Frost possible, highs below 10 °C: Dublin, Cork, Galway, Limerick and 10 more

In December, on average, these cities have highs of 8 to 10 °C and lows of 3 to 6 °C, 85 to 148 mm of rain on 14 to 20 days; the day lasts 7 h 14 min to 7 h 48 min (on the 15th).

December falls in the frost season: frost-tender crops wait. Average first frost: Bray (7 December).

How	What	Where
plant cloves	Garlic	all
sow direct	Broad bean, peas, spinach, radish, cabbage	all
plant sets	Onion	all
start indoors, plant out in February or sow direct	Broccoli	all
plant bulbs	Crocus, daffodil, hyacinth, tulip	Dublin, Cork, Limerick and 7 more

Compared with November: no longer sown — arugula and turnip.

Not starting in December: tomato (no month outdoors by these rules), bell pepper (no month outdoors by these rules), zucchini (June, sown direct), green beans (June, sown direct) and lettuce (March, started indoors) — dates for Dundalk.

Ready to harvest in December in Dundalk, if sown in the right month: broad bean (September), peas (October), spinach (October), lettuce (October), radish (November), cabbage (August), broccoli (September) and Swiss chard (October).

How we work it out

For each city we use its average weather in December and the months after (highs, lows and rain for 2016–2025, ERA5 reanalysis via Open-Meteo) and its average frost dates. A crop starts in December if the month's mean temperature reaches the minimum soil temperature for germination on its card (we use the mean air temperature as a stand-in for the soil's) and if, over its first months (up to three), the average highs stay within its group's range, with no frost for crops that cannot take it. Crops started indoors count from the month they are planted out.

Temperature groups from Colorado State University Extension: cool-season crops prefer 16–27 °C and lose quality in heat; hardy ones grow in days as cool as 4 °C, semi-hardy ones from 4–10 °C (we use 10 °C); warm-season crops need days above 13 °C, and the most tender (tomato, pepper, aubergine, melon, watermelon, squash) above 16 °C, up to 35 °C. Crops the guide does not name go into the stricter group by their frost hardiness. Broad beans, which the guide does not name, count as hardy: hardy varieties are sown in autumn and overwinter (RHS). Garlic and bulbs: a month before the first frost, and later only while the ground is not frozen (as on each city's page).

Courgettes and French beans: GIY Ireland sows courgettes and succession-sows French beans outdoors in June, so we list them in June wherever June has no frost.

This is a general rule from averages: your garden can be a week or two earlier or later, and a greenhouse or a cold frame brings the season forward. Greenly works out the dates for your location.

What to plant in December in Ireland

Frost possible, highs below 10 °C: Dublin, Cork, Galway, Limerick and 10 more

How we work it out

Other months in Ireland