I’ve found that marrows suffer from a bit of an image problem. They’re often dismissed as watery and bland, but that’s usually because people grow them too large or don’t prepare them properly. A marrow harvested at the right size, around 20-25cm long, has a delicate flavour and firm texture that works brilliantly in traditional recipes. The key is knowing when to let your courgettes keep going and when to pick them. Let’s explore how to grow marrows.
How to Grow Marrows
Getting your supplies sorted before you start makes the whole process much smoother. I’ve grown marrows in various settings, from my first tiny balcony attempt in Bristol to my current allotment, and the basic requirements haven’t changed much. You don’t need anything fancy, but quality matters for a few key items. For more on this, see our guide on the complete guide to growing perfect courgettes.
Seeds and Growing Medium
You’ll need marrow seeds from a reputable source. I prefer heritage varieties like Long Green Trailing or Long White Bush, which give you proper traditional marrows. For starting seeds indoors, you’ll want seed compost and either 7-9cm pots or root trainers. Standard multipurpose compost works fine once plants are established, though I always improve it with well-rotted manure or garden compost. If you’re growing in containers, you’ll need large pots, at least 45cm in diameter, with drainage holes.
Site Preparation Materials
Marrows are greedy feeders, so you’ll need plenty of organic matter. I use a combination of homemade compost and well-rotted horse manure from a local stable. You’ll also want some general-purpose fertiliser for the growing season, preferably something balanced like blood, fish and bone. If you’re in an exposed area, some cloches or fleece will protect young plants from late frosts. A decent watering can or hose is essential because these plants drink like mad during summer. Finally, if you’re growing trailing varieties, consider some straw or cardboard to keep developing fruits off the soil.
Step-by-Step Instructions
Starting Seeds Indoors
I always start marrows indoors because they’re tender plants that won’t tolerate frost. From mid-April onwards, you can sow seeds on their edge (this prevents rotting) about 2cm deep in individual pots filled with seed compost. Place them somewhere warm, ideally 18-21°C. A sunny windowsill works perfectly, though I use a heated propagator in my unheated greenhouse. Seeds typically germinate within 7-10 days, sometimes faster if conditions are spot on. You might also find from seed to kitchen: growing marjoram successfully helpful.
Join the BFFD Community
Connect with thousands of UK growers, access our complete directory of farm shops and farmers markets, and get expert growing advice from our community.
Once seedlings emerge, make sure they get plenty of light. Leggy seedlings are a common problem if they’re too warm without enough brightness. I move mine to the greenhouse once they’ve got their first true leaves, gradually acclimatising them to cooler conditions. Don’t be tempted to sow too early. Seeds sown in late April will often overtake those started in early April because they grow faster in improving conditions and don’t get stressed by being pot-bound.
Preparing the Planting Site
Marrows need a sunny, sheltered spot with rich, moisture-retentive soil. I prepare my planting positions a few weeks before planting out, usually in early May. Dig holes about 30cm deep and 45cm wide, then fill them with a mixture of excavated soil and lots of organic matter. I’m talking at least a bucketful of well-rotted manure or compost per planting hole. This creates a nutrient-rich pocket that’ll feed the plant all season.
Space is crucial. Bush varieties need about 90cm between plants, whilst trailing types want 120cm or more. I learned this the hard way at my allotment in Wakefield, where I planted three trailing marrows too close together. By July, they’d formed an impenetrable jungle that harboured slugs and made harvesting nearly impossible. If you’re short on space, grow bush varieties or train trailing ones up a sturdy support, though the fruits will need supporting individually.
Planting Out and Early Care
Wait until all risk of frost has passed before planting out, typically late May or early June depending on your location. Northern gardeners should be more cautious than those in the south. Plant at the same depth the seedlings were growing in their pots, firm the soil gently around them, and water well. I always keep fleece handy for the first few weeks in case we get an unexpected cold snap.
Young plants are slug magnets. I use a combination of beer traps, copper tape around pots, and evening patrols with a torch. The first few weeks are critical because slugs can demolish a young marrow plant overnight. Once plants get established and develop rougher leaves, they’re less vulnerable. Water regularly but avoid wetting the leaves, as this encourages powdery mildew, which is a persistent problem with marrows.
Feeding and Watering Through Summer
This is where many gardeners go wrong. Marrows are incredibly thirsty and hungry plants, especially once they start flowering. I water mine deeply every two to three days during dry weather, giving each plant at least 10 litres. Shallow, frequent watering encourages surface roots that are vulnerable to drought. Instead, you want to encourage deep rooting by watering thoroughly but less often.
Start feeding once the first fruits begin to swell. I use a liquid tomato feed every 10-14 days, following the packet instructions. Some gardeners feed more often, but I’ve found this can lead to excessive leaf growth at the expense of fruit. If leaves start yellowing, increase feeding frequency. The plants will tell you what they need if you pay attention.
Pollination and Fruit Development
Marrows produce separate male and female flowers on the same plant. Males appear first on long, thin stems, whilst females have a tiny marrow-shaped swelling behind the flower. Early in the season, you might only get male flowers, which is perfectly normal. Female flowers appear once the plant is established and growing vigorously.
Whilst bees usually handle pollination, I often help things along, especially early in the season when bee activity is lower. Pick a fresh male flower in the morning, remove the petals, and gently brush the pollen-laden centre against the stigma inside a female flower. You’ll know pollination was successful when the tiny fruit begins swelling rapidly. Unpollinated fruits turn yellow and rot within a few days.
Harvesting and Storage
Here’s where growing marrows differs from courgettes. Instead of harvesting small and often, you leave fruits on the plant to develop properly. For eating, I harvest marrows when they’re 20-25cm long, whilst the skin is still relatively soft and can be pierced with a fingernail. At this size, they’ve got good flavour and texture without being watery.
For exhibition or storage, leave fruits to mature fully on the plant. The skin will harden and develop its characteristic shine. Cut marrows with a good length of stem attached, using secateurs rather than twisting them off. Handle carefully because bruised marrows don’t store well. A properly cured marrow with hard skin will keep for several months in a cool, dry place. I store mine on slatted shelves in my garage, checking regularly for any signs of deterioration.
Common Mistakes to Avoid
Planting Too Early
The single biggest mistake I see is planting out before conditions are right. Marrows are subtropical plants that simply won’t grow in cold soil. Even if they survive a late frost, cold-stressed plants never really recover and produce poorly all season. I’ve seen this at my allotment repeatedly, where enthusiastic new gardeners plant out in early May, only to watch their plants sit there sulking whilst mine, planted three weeks later, quickly overtake them.
Wait for warm soil and settled weather. If you’re desperate to get going, warm the soil by covering planting areas with black plastic or cloches for a couple of weeks beforehand. Better to plant later and have vigorous growth than plant early and struggle all season.
Inadequate Watering and Feeding
Marrows can’t produce large fruits without adequate resources. I’ve found that inconsistent watering is particularly problematic, leading to bitter-tasting marrows or fruits that rot at the blossom end. This blossom end rot is actually a calcium deficiency caused by erratic water supply, even if there’s plenty of calcium in the soil. The plant simply can’t transport it properly without consistent moisture.
Similarly, trying to grow marrows in poor soil without feeding is a recipe for disappointment. These plants evolved to grow on rich, composted ground. Skimping on preparation or feeding will give you small, poorly flavoured fruits and plants that succumb quickly to disease. It’s not a crop you can neglect and expect good results.
Overcrowding Plants
Giving plants proper space seems wasteful early in the season, but it’s essential. Crowded marrows compete for resources, create humid conditions that encourage disease, and make harvesting difficult. I learned this watching a friend’s garden in Durham, where tightly packed plants developed severe powdery mildew by mid-July. The lack of air circulation meant the disease spread rapidly, and she lost most of her crop.
If space is genuinely limited, grow one or two plants really well rather than cramming in more. A single well-grown marrow plant can easily produce 5-8 good-sized fruits, which is plenty for most households.
Expert Tips
Choosing the Right Variety
Not all marrow varieties perform equally well across the country. Bush types like Green Bush work brilliantly in smaller gardens and are more manageable generally. They produce a concentrated crop over a shorter period, which suits people who want to harvest, cook, and freeze in batches. Trailing varieties like Long Green Trailing or Table Dainty produce over a longer period but need more space.
I’ve had particular success with Long Green Trailing in my Leeds allotment. It’s a vigorous grower that handles our unpredictable northern weather better than some of the newer hybrids. For those wanting something different, try Custard Marrow varieties, which have an unusual shape and excellent flavour. They’re particularly good for stuffing because of their round form.
Managing Powdery Mildew
This fungal disease is almost inevitable on marrows, especially from mid-summer onwards. The white, powdery coating on leaves looks alarming but doesn’t necessarily spell disaster. The key is managing it rather than trying to prevent it entirely. Good spacing helps enormously, as does watering at the base of plants rather than overhead.
Once it appears, remove the worst-affected leaves to improve air circulation and slow the spread. Some gardeners spray with milk solution (one part milk to nine parts water), which has antifungal properties. I’ve had mixed results with this, though it’s worth trying. By late summer, my plants usually have some mildew, but they continue producing acceptably as long as they’ve still got plenty of healthy leaf area.
Extending the Season
Marrows are naturally a mid to late summer crop, but you can extend production slightly at both ends. Starting seeds indoors in mid-April gets earlier fruits, whilst protecting plants with fleece during early autumn cold snaps keeps them productive longer. I’ve harvested marrows well into October by draping fleece over plants on cold nights.
However, there’s a limit to this. Once overnight temperatures regularly drop below 10°C, plants slow dramatically. Rather than struggling to keep tired plants going, I harvest remaining fruits (even small ones) before the first proper frost and use them promptly. Young marrows can be used like courgettes in most recipes.
Dealing with Excessive Production
A thriving marrow plant can produce more than most households can use. Rather than letting fruits grow enormous (which reduces overall yield and quality), harvest regularly at a usable size. I pick mine at 20-25cm for eating fresh. You can also harvest some as large courgettes, which gives you versatility.
Marrows freeze reasonably well if prepared properly. I peel, deseed, and cut them into cubes, then blanch for 2-3 minutes before freezing. They’re not quite as firm after freezing but work perfectly in soups, stews, and bakes. Alternatively, make marrow chutney, which uses up large quantities and stores for ages. My marrow and ginger chutney has become a proper staple.
Frequently Asked Questions
Can I grow marrows directly from seed outdoors?
You can sow marrow seeds directly outdoors from late May onwards, once soil temperatures reach at least 12°C. However, I’ve found this approach less reliable in most parts of the country. Direct-sown seeds are vulnerable to slug damage, cold, wet conditions that cause rotting, and uneven germination. Starting seeds indoors gives you stronger plants that establish quickly and start producing earlier. If you do sow directly, use cloches to warm the soil first, sow two seeds per station, and thin to the strongest seedling once they’re growing well.
Why are my marrow plants producing only male flowers?
This is completely normal, especially early in the season. Marrow plants typically produce male flowers first, sometimes for several weeks before female flowers appear. The plant needs to establish a strong root system and plenty of foliage before it has the resources to support fruit development. As long as your plant is growing vigorously with healthy leaves and you’re watering and feeding adequately, female flowers will appear. Stress from cold, drought, or poor nutrition can delay female flower production. Be patient and maintain good growing conditions. Once female flowers start appearing, they’ll continue throughout the season.
How can I tell when a marrow is ready to harvest?
For eating, harvest marrows when they’re 20-25cm long and the skin can still be pierced with your fingernail. At this size, they’ve got good flavour and firm texture. For storage or exhibition, leave fruits to mature fully until the skin hardens and develops a characteristic shine, usually when they’re 30-40cm long. The fruit should sound slightly hollow when tapped. Harvest before the first frost by cutting with secateurs, leaving a good length of stem attached. Check fruits regularly because they can grow surprisingly quickly during warm weather. Don’t leave marrows on the plant too long thinking bigger is better, as overly large specimens tend to be watery and bland.
Why do my developing marrows turn yellow and rot?
This happens when flowers aren’t properly pollinated. The tiny marrow behind the female flower will only develop if pollination occurs. Without successful pollination, the fruit turns yellow, softens, and eventually rots. This is particularly common early in the season when there’s less insect activity or during cold, wet weather that keeps pollinators away. You can solve this by hand pollinating. Pick a fresh male flower in the morning, remove the petals, and brush the pollen-laden centre against the stigma inside female flowers. This simple technique dramatically improves fruit set, especially early in the season. Once the weather warms and bee activity increases, pollination usually happens naturally.
Do I need to remove leaves from marrow plants?
Generally, you shouldn’t remove healthy leaves because they’re the plant’s energy factories. However, removing a few leaves can be beneficial in specific situations. Once powdery mildew appears, remove the worst-affected leaves to improve air circulation and slow disease spread. You can also carefully remove leaves that are completely shading developing fruits, as marrows colour and ripen better with some sun exposure. Later in the season, removing old, yellowing lower leaves tidies plants and reduces disease pressure. Always use clean, sharp secateurs and don’t remove more than a few leaves at a time. The plant needs plenty of healthy foliage to support fruit development.
Can I grow marrows in containers?
Yes, marrows grow successfully in large containers, though you need to be realistic about pot size and maintenance. Use containers at least 45cm in diameter and depth, filled with good quality multipurpose compost mixed with well-rotted manure or garden compost. Bush varieties are more suitable than trailing types for container growing. Container-grown marrows need more frequent watering than those in open ground, sometimes twice daily during hot weather. They also need regular feeding because nutrients leach from compost quickly. Despite the extra work, container growing works well if you’ve only got a patio or want to grow marrows in a sunny spot on otherwise unsuitable ground.
If you’re looking to take the next step, explore our full resource hub where we cover practical growing guides, seasonal advice and sustainable farming insights in greater depth.
You can also join the conversation inside our community forum, where growers, allotment holders and small-scale farmers share real experiences, challenges and solutions.
For those ready to plan ahead, our Growers Calendar provides structured monthly guidance on what to sow, plant and harvest, helping you stay aligned with the British growing seasons.
Final Thoughts
Growing marrows successfully is largely about understanding their basic needs and providing consistently good conditions. These aren’t difficult plants, but they won’t tolerate neglect or poor soil. The key points are warming the soil properly before planting, providing rich growing conditions with plenty of organic matter, watering and feeding generously throughout summer, and giving plants adequate space. Do these things right, and you’ll have more marrows than you know what to do with.
I’ve watched marrow growing become fashionable again after years of being dismissed as old-fashioned. People are rediscovering that a properly grown and prepared marrow is actually rather good. Whether you stuff them, make chutney, or simply roast them with garlic and herbs, homegrown marrows have a flavour that shop-bought ones rarely match. The satisfaction of growing something substantial from a single seed never gets old. Start small with one or two plants, get the basics right, and you’ll soon wonder why you didn’t grow them sooner.
Author: Megan Walker
Megan focuses on seasonal food, kitchen garden growing, and how households can reconnect with where their food comes from. Her writing blends practical growing advice with ideas for cooking and eating in season. With a passion for fresh ingredients and sustainable living, Megan’s articles help readers make the most of local produce while supporting British farms.