Cannabis Seeds in Ireland: Seed Types, Season Dates and How to Choose for a Wet Autumn

The decision that matters when you buy cannabis seeds in Ireland is not potency and it is not yield — it is finish date and mould resistance. Our season runs from a late-May plant-out to a harvest in the last days of September or the first days of October, and the wettest, dullest weeks of the year land on the flowering window. Pick varieties that finish inside that window with loose, airy flowers and you have already solved most of the problem.

Everything else — feminised or autoflower, indoors or out, east coast or west — follows from that one constraint. This article sets out the seed categories, the real calendar, the rainfall gradient across the 26 counties, and the mistakes that cost Irish growers a crop every year.

The four seed categories, and what each one actually controls

Seed labels describe two different things: whether the plant will be female, and what triggers flowering. Confusing the two is where most first orders go wrong.

• Photoperiod varieties, nearly all female, flower when daylight shortens
• Flower on age rather than daylight, short total life
• Selected for cannabinoid balance, timing varies by variety
• Mixed sex, used for breeding and seed saving

For a first outdoor attempt in this climate, the honest ranking is autoflowering seeds first, early feminised photoperiod second. The full argument, including how each behaves in a cool August, is in our comparison of autoflower and feminised seeds in Irish conditions, and the sexing question is covered in the guide to what a seed label controls and when to cull males.

Bottom line: Buy on flowering trigger and finish week, then check the sex label — not the other way round.

Ireland has no dry season, and that sets the whole strategy

Rain falls in every month here, with an autumn maximum, so there is nowhere on the island where flowering happens dry. Anyone promising you a dry finish outdoors has not grown through an Irish October.

That single fact makes botrytis — grey mould, which rots flowers from the inside out after prolonged wet — the real yield limit. Not cold, and certainly not heat. Open flower structure, thin leaf cover around the heads and a short finish beat every headline yield figure.

The wettest parts of the west can take more than twice the rain of the east

Annual rainfall, millimetres per year, by area, from Met Éireann monthly climate data:

The east is drier and sunnier, which buys you perhaps a fortnight of tolerance on finish date; the west adds Atlantic wind on top of the rain, so short, sturdy plants matter more there than big ones. It is a gradient across one temperate oceanic climate, not a set of different climates — the midlands carry the widest frost window and the heaviest ground, and the south has the longest frost-free season but the highest humidity. Our piece on mould resistance and strain selection by Irish region works through each of those.

Bottom line: Treat rain and humidity as constants and choose genetics that finish before the autumn maximum peaks.

The one genuinely good outdoor fact: seventeen hours of daylight

Ireland sits between 51.5 and 55.4 degrees north. Around midsummer that gives roughly seventeen hours of usable daylight, a real vegetative advantage that European growers further south do not get.

The same latitude is why the season shuts so abruptly. Day length collapses through September and light levels fall away fast in October, so a plant still filling out on 10 October is not going to catch up — it is going to sit wet.

The Irish outdoor calendar

1. Germinate indoors on a windowsill or under a light; do not sow outside.
2. Harden plants off in a sheltered spot for a week of days outdoors.
3. Plant out once night temperatures hold above about 10°C.
4. Defend young transplants from slugs, the pest that strips them overnight.
5. Use the long days: feed, train and build frame before flowering starts.
6. Photoperiod plants begin flowering; thin inner leaves to move air through the heads.
7. Inspect daily after rain and remove any browning or greying flower immediately.
8. Harvest, even if the plant would still gain weight in a drier climate.

Autoflowers break this rhythm usefully. Sown in two or three batches from mid-May, they finish in staggered waves from August onward, which spreads your risk instead of betting the whole grow on one week of weather.

Bottom line: End of May in, end of September out — anything that cannot fit inside those bookends belongs indoors.

Indoors, the problem is damp and cost, not heat

Ambient humidity in Ireland sits near 80% for much of the year, so an indoor room here fights moisture rather than temperature. A dehumidifier sized for the room, running through flowering, is the single most useful piece of kit you will buy — more useful than an upgraded light.

Electricity is also among the dearest in the European Union, as the Sustainable Energy Authority of Ireland energy statistics show, so running hours are a real cost line. Short-cycle varieties and a tent sized to the plant count, rather than to ambition, keep that under control.

Blue Dream Feminised is included here as an indoor pick specifically: it is named because its reported vigour suits a long vegetative run under lights, and because in a dehumidified room the flower density that would worry me in an Irish September stops being the deciding factor. Outdoors, in the open, I would choose something faster.

Common mistakes with Irish seed choices

• Buying on flowering weeks alone. A stated nine-week flowering time means nothing without a start date; a photoperiod plant that begins flowering in late August finishes in late October. Work backwards from 1 October and reject anything that does not fit.
• Choosing the densest, heaviest variety in the catalogue. Tight heads hold water at their core, and you will find rot only when you squeeze one open. Favour airy, open structure and inspect flowers by touch after every wet spell.
• Planting out too early. A May cold snap stalls plants for a fortnight, and stalled autoflowers never recover the lost time because they flower on age. Wait for nights above about 10°C.
• Ignoring slugs in June. The tell is a stem chewed through at soil level overnight. Ring transplants with a barrier and lift pots off wet ground.
• Storing seeds in the kitchen. Warm, humid air ages seed fast in this climate; our guide to storing cannabis seeds in a cool, humid climate covers containers and shelf life.
• Inventing an Irish heritage variety. Ireland has no cannabis landrace. If a description implies one, the rest of that description is unreliable too.

Ordering seeds and getting started

Order in late winter or early spring so you are germinating in April rather than waiting on post in May. Dispatch, tracking and Eircode issues are set out in our note on seed delivery in Ireland, and the shipping page lists current options.

Store what you do not sow. Most packs contain more seed than a single season needs, and a cool, dry, dark container keeps the remainder useful for the following spring.

Where to go next

You now have the two filters that matter in this climate — a finish inside the last week of September, and open flower structure that dries between showers. Run those against the catalogue with the strain finder, or start from the shortlist in strains selected for outdoor growing if you are planting in open ground. If you want the shortest exposure to autumn rain, autoflowering seeds are the category that gets you in and out fastest, and the step-by-step guide to choosing seeds for Irish conditions walks through a first order in detail.