Growing Courgettes in Ireland
Peter Dowdall, Irish horticulturist and broadcaster, explains when to sow and plant courgettes in Ireland, how to prepare the soil, protect young plants from slugs, and harvest consistently through the Irish summer season.
Growing courgettes in Ireland
Courgettes are one of the most productive crops you can grow in an Irish summer. One or two well-positioned plants will supply more than most households can use. The challenge is not making them produce. It is getting them started at the right time.
Courgettes are frost-tender and cannot go outside until the risk of a late frost has passed. In Ireland, that means late May at the earliest and early June in exposed or northern gardens. Plant too early and a cold night will set them back significantly or finish them altogether.
Courgettes are a warm-season crop that arrived in Irish vegetable gardens relatively recently but established themselves quickly as a reliable summer staple. They are generous, fast-growing and forgiving once established. The mistakes that most Irish gardeners make with courgettes happen before the plant goes in the ground: planting too early in the season, into cold or poorly prepared soil, or into a position without enough warmth and shelter. Address those three things and a courgette plant in Ireland will produce abundantly with very little further intervention.
The plants themselves are large. A single courgette plant in good conditions will spread to a metre or more in diameter. This surprises first-time growers who have planted two or three close together and find by July that the bed has become impenetrable. One or two plants, well spaced and well positioned, is sufficient for most households. The temptation to grow more than you need is understandable but resist it.
If you are growing courgettes in a raised bed, the advice on raised beds in Ireland covers soil preparation in full. A raised bed has the advantage of warming faster in spring and draining more reliably in a wet summer, both of which benefit courgettes.
When to sow and plant courgettes in Ireland
Timing is the single most important factor in growing courgettes successfully in Ireland. The plants are frost-tender and cold-sensitive. A late frost after planting out will kill or severely set back young plants. Even a cold night without frost will slow establishment significantly and delay first harvest by weeks.
Irish courgette growing calendar
Hardening off is essential and is often rushed. Move plants outdoors for increasing periods each day over ten to fourteen days before planting, starting with a few hours of shelter and building up to full exposure. Plants that have been properly hardened off establish significantly faster and show much less transplant check than those moved straight from a warm windowsill to an open bed.
Soil preparation and position for courgettes
Courgettes are hungry feeders. They need rich, well-structured soil with plenty of organic matter and consistent moisture. A plant growing in poor or thin soil will produce but will exhaust itself early in the season. A plant growing in genuinely well-prepared soil will keep producing steadily until the first autumn frost.
Choose the warmest, most sheltered position available. Full sun is essential. In Irish conditions, this typically means a south or south-west facing position, protected from cold winds. The plants are large-leaved and act as their own windbreak once established, but young plants are vulnerable. If your garden is exposed, a temporary windbreak during the first two to three weeks after planting out makes a real difference to establishment speed.
Prepare the planting hole generously. Dig a hole at least 30cm deep and wide, incorporate well-rotted compost, and improve the soil structure before backfilling. Understanding what your soil is doing before you start is useful: the advice on garden soil in Ireland covers the principles of structure and drainage that are directly relevant here. In Irish conditions, where summer rain is unpredictable, soil that holds moisture while still draining freely is particularly valuable for courgettes, which are susceptible to both drought stress and waterlogging.
Feed the soil before you plant
NutriChar is a certified organic biochar plant food, made using a patented process that locks nutrients into biochar structure rather than allowing them to wash away. Work it into the planting hole when preparing for courgettes and it improves how the soil holds both moisture and nutrients across the growing season, which matters particularly in the unpredictable Irish summer.
Courgettes benefit from a liquid feed once they begin to flower heavily. A seaweed-based feed applied every two weeks supports fruit development without forcing weak, lush growth that attracts pests. Do not over-feed with nitrogen-heavy products, which produce excessive leaf growth at the expense of fruit.
How to plant courgettes
-
1
Sow one seed per pot, on its side
Sow seed on its side rather than flat or pointed end down. This reduces the risk of the seed sitting in moisture and rotting before it germinates. Use a 9cm pot filled with good seed compost. Water in and keep at 18 to 20 degrees Celsius until germination, usually five to seven days.
-
2
Pot on once the first true leaves appear
When the first true leaves, distinct from the seed leaves, are visible, move the plant into a larger pot if planting out is still more than a week away. Courgettes grow quickly and a root-bound plant in a small pot will check badly at transplanting.
-
3
Harden off properly over ten to fourteen days
Begin with a few hours outside in a sheltered spot and build to a full day and night outdoors before planting. Do not rush this stage. Plants that have been properly hardened off establish in days rather than weeks.
-
4
Plant into a generously prepared hole
Plant at the same depth as the pot. Firm gently around the stem and water in thoroughly. Space plants at least 90cm apart, ideally more. If planting two, a metre and a half between them is not excessive for the spread they will achieve by August.
-
5
Protect from slugs immediately
Young courgette plants are highly vulnerable to slug damage in the first two to three weeks after planting. Apply sheep's wool pellets around the base of each plant immediately after planting and maintain the barrier as the plant establishes. A single night of unprotected slug activity can destroy a young plant completely.
-
6
Water consistently at the root, not on the leaves
Courgettes need consistent moisture, particularly once they begin to fruit heavily. Water at the base of the plant rather than over the foliage. Wet leaves in Irish conditions encourage powdery mildew, which becomes a problem on older plants later in the season.
Slug protection for courgettes in Ireland
Slug damage is the most common cause of failure with courgettes in Ireland, particularly in the critical first two to three weeks after planting out. A young courgette plant has soft, substantial leaves and stems that slugs find highly attractive. One night of significant slug activity on a newly planted courgette can leave nothing but a stump.
The approach is barriers rather than treatments. Sheep's wool pellets applied around each plant immediately after planting give reliable protection through the establishment period. They need to be maintained, checked after heavy rain and topped up if the ring has been disturbed. As the plant grows and the stem becomes woodier, it becomes less vulnerable, but maintaining the barrier through the first month is essential. If you are dealing with persistent slug and pest problems across your garden more broadly, the plant problems Ireland page covers the ecological approach to diagnosis and long-term management.
For ground-level planting
- Sheep's wool pellets in a ring around each plant
- Refresh after heavy rain or if the ring has been disturbed
- Maintain for at least the first four weeks after planting
- Go out after dark with a torch in the first two weeks to check and remove any slugs that have crossed the barrier
For raised beds and containers
- Copper tape around the inside rim of the bed or container is effective and persistent
- Combine with sheep's wool pellets around individual plants within the bed
- Raised beds with good sides reduce slug access significantly compared to ground level
- Check underneath the bed frame and around the edges regularly
Never use chemical slug pellets. They disrupt the natural balance of predators, including ground beetles, hedgehogs and birds, that provide ongoing biological control. A garden with a healthy predator population manages slugs better long-term than one that relies on chemical treatments.
Harvesting courgettes
Pick courgettes regularly and while they are still young, at 15 to 20cm long. This is not just a matter of taste, though younger courgettes are generally better to eat. It is about maintaining production. A courgette plant that has been allowed to produce one or two large marrows will slow down noticeably, as the plant interprets the large, mature fruit as reproductive success and reduces its effort to produce more.
Check plants every two to three days during the main season. The plants are large and leafy and it is easy to miss fruit that has been hidden under the foliage. A courgette that was 15cm long three days ago will be a 40cm marrow if you do not check. Harvest generously and consistently and the plant will continue producing through to the first frost.
Managing the end of the season
Courgette plants will continue producing until the first frost, which in most of Ireland falls in October or November. As temperatures drop in September and October, production slows and the plants become more susceptible to powdery mildew, which appears as a white coating on older leaves. This is normal at the end of the season and does not affect the fruit. When production stops and the plants are showing significant mildew, remove them completely and compost. Do not leave them over winter as they can harbour disease.
Rotate courgettes and other cucurbits to a different part of the vegetable garden each year. Growing in the same ground repeatedly increases the risk of soil-borne disease building up over time.
Questions gardeners ask about growing courgettes in Ireland
My courgette flowers but produces no fruit. What is wrong?
Courgette plants produce separate male and female flowers. The male flowers, which have a plain stem, appear first, often two to three weeks before the female flowers, which have a small embryo fruit at the base. It is perfectly normal to see flowers with no fruit in the early weeks of the season. Once both male and female flowers are open simultaneously, pollination occurs, usually by bees and other insects. If the weather is cold or wet and there is little insect activity, you can hand-pollinate by transferring pollen from a male flower to a female flower with a small brush or by removing a male flower and touching it directly to the female. Poor pollination, not poor soil, is almost always the explanation when a plant flowers without fruiting.
Can I grow courgettes in pots or containers?
Yes, but the container needs to be large enough to support a plant that will eventually spread to a metre or more. A minimum container size of 40 to 50 litres is needed for a productive plant. Use a rich, well-draining compost mix and feed every two weeks once the plant begins to flower. Containers dry out faster than beds, so watering needs more attention, particularly in warm spells. The advantage is that containers can be positioned to maximise warmth and shelter, which is valuable in an Irish context.
Why are my courgette leaves covered in white powder?
This is powdery mildew, a fungal condition that commonly affects courgettes and other cucurbits in Ireland, particularly later in the season as days shorten and conditions become cooler and damper. It does not typically affect the fruit. Good air circulation around the plant reduces the risk of it appearing early, and watering at the root rather than over the foliage helps. By September most courgette plants in Ireland will show some mildew. This is a sign that the season is drawing to a close rather than a problem requiring treatment.
How many courgette plants do I need?
One well-grown courgette plant will produce more than most households can use at peak season. Two plants of different varieties, one standard and one yellow-fruited or round, gives variety without overwhelming production. Unless you are preserving or cooking for large numbers, three or more plants will produce more courgettes than any household needs in July and August.
Is it too late to plant courgettes in June?
No. A courgette planted in early June in Ireland will still produce a full and productive harvest before the first frost. Even a plant put in the ground in mid-June will crop well through July, August and into September. The season is long enough that a June planting date is not a disadvantage. If anything, a plant that goes in the ground during a warm period in June often establishes faster than one planted in a cold late May.
That is the general picture
But your garden has its own conditions, its own slug pressure and its own microclimate. Tell Ask Peter what you are working with and get advice specific to your situation.
Ask Peter about your gardenRelated growing guides
More from the vegetables, fruit and herbs section of the Garden Q&A.