At a glance
- Melons are heavy feeders and love warmth. Below 5 °C they take damage, so with us they only move outdoors after the last frosts.
- Start seeds indoors in the warmth from mid-April · CW 16 to 18, plant out from mid-May · CW 20, harvest usually in August and September.
- A greenhouse or film tunnel makes the difference in many regions between green orbs and sweet fruit.
- Ripe muskmelons slip off the stem on their own, watermelons you recognise by the hollow knock and the dried tendril.
- Two to four fruits per plant are plenty. Fewer fruits set means more sugar in each single melon.
Melons in your own garden sound like the south of France, like heat and long summers. And for a long time they were considered a job for pros with a heated greenhouse. That has changed. Summers have grown warmer, the bred varieties earlier, and with a little head start on raising the seedlings you can harvest your own sun-warm melons even in a Berlin allotment or on a sunny terrace. They taste different from the supermarket ones: denser, more aromatic, because they are allowed to ripen instead of travelling half the world green.
Why melons need a warmth gardener
Melons belong to the gourd family, just like cucumber, zucchini and pumpkin. And like their relatives they are frost-sensitive through and through. Temperatures around 5 °C already slow growth, real frost means the end. Their true engine is warmth: only from about 18 °C soil temperature do the roots really get going, and for sweet fruit they need plenty of sun and warm nights over many weeks.
That is why you do not simply sow melons into the bed in April. They need a head start in the warmth and afterwards the warmest, most sheltered spot your garden has to offer. A south-facing house wall, a greenhouse, a film tunnel or a warm pot on the balcony are ideal. The cooler and rougher your location, the more important growing under glass or film becomes.
Cucumis melo
- Familie
- Gourd family (Cucurbitaceae)
- Standort
- full sun, warm, sheltered from wind
- Saison
- Sowing CW 16 to 18 · Harvest August to September
- Wasserbedarf
- evenly moist, reduce during ripening
- Frosthärte
- frost-sensitive, damage below 5 °C
Muskmelon or watermelon
In everyday life we throw everything into one pot, but botanically these are two different plants. The muskmelon (Cucumis melo), which includes cantaloupe, charentais and the smooth honeydew, is more closely related to the cucumber and the more rewarding choice in our climate. Its fruits stay manageable, ripen faster and forgive a cooler summer more easily.
The watermelon (Citrullus lanatus) comes from southern Africa and is even more warmth-hungry. It needs more space, more time and truly hot weeks to get the large fruits sweet. Outdoors it succeeds with us only in very good summers, in the greenhouse with early varieties it is surprisingly reliable.
- Muskmelon: the safe start
Fruits of 0.8 to 2 kg, ripe after roughly 80 to 100 days. Cantaloupe and charentais types succeed in a tunnel or against a warm wall. Recommended for your first melon year.
- Watermelon: the sun worshipper
Needs the longest, hottest season and plenty of space. Early, small-fruited varieties under glass are the best route to a successful harvest in cooler regions.
- Space and site
Both trail vigorously. In the bed reckon on about one square metre per plant, or train them up a string to save space.
- Pots and balcony
A container from 20 litres, dark and in full sun, works well for one muskmelon carrying two to three fruits. Watering regularly is a must here.
Raising seedlings: the head start decides
Melons need a warm start in the house, because otherwise the season is too short here. Do not sow too early: a plant raised in March turns into a leggy, root-bound, stressed seedling by planting-out time. Mid to late April · CW 16 to 18 is the right moment for most regions.
Sow into the warmth
Singly into pots of 8 to 10 cm, the seed about 1 cm deep and set on edge. At 24 to 28 °C melons germinate within a few days. A warm windowsill above the heating or a mini greenhouse with a heat mat is ideal.
Grow on bright and warm
After germination move them cooler, but never below 18 °C, and as bright as possible. Plants raised too dark become long and weak.
Harden off before planting out
About a week before the move outdoors, set the young plants outside for a few hours at a time so they get used to sun and wind. How to do this step by step is in the article on hardening off young plants.
Plant out after the last frosts
Outdoors only from mid-May · CW 20, once no more night frosts threaten. In a greenhouse or tunnel you can go one to two weeks earlier.
The simplest trick for more warmth is called film. A low film tunnel over the row or a fleece in the first weeks raises the temperature by several degrees and at the same time shields against cold wind. As soon as the plants flower, the tunnel must be open during the day so insects can reach the blooms. In a cool early summer this warmth head start often decides whether the fruits still ripen.
A late cold snap in May is no drama if you are prepared. Keep fleece ready and cover the freshly planted melons over cool nights. You can pull the protection back at any time, whereas a lost seedling costs you weeks.
Planting, training and watering
Melons are heavy feeders. A planting hole filled with ripe compost or well-rotted manure gives them the foundation for vigorous vine growth. Plant slightly raised on a small mound, then the sensitive root collar never sits in the wet and stem rot has fewer chances.
When watering the rule is: evenly and always at the root, never over the leaves. Wet leaves are the invitation for powdery mildew. During the growth phase the plants need plenty of water, but as soon as the fruits reach their final size and begin to ripen, you deliberately cut the watering back. A little drought stress in the last two to three weeks concentrates the sugar in the fruit. Too much water shortly before harvest makes it watery and bland.
Leave every fruit on the plant and you harvest many mediocre ones. Cut back and you harvest a few really good ones.
Gardener's wisdom
If you train the muskmelon upward, for example on a string in the greenhouse, it saves space and the fruits stay clean and well aired. Heavy fruits then need a net or an old nylon stocking as a hammock, otherwise they tear off under their own weight. Melons grown on the ground are best laid on a board, a tile or a little straw so they do not rot on the damp soil.
Flowers, pollination and the right fruit set
Melons carry separate male and female flowers on the same plant. You recognise the female ones by the small fruit set, a tiny melon directly behind the flower. For anything to come of it, pollen has to travel from the male to the female flowers, and normally bees and bumblebees do that.
In a closed greenhouse the pollinators are often missing. Then you had better help out yourself: on a dry, sunny morning pick an open male flower, remove the petals and dab the pollen directly into several female flowers. It sounds fiddly but takes only minutes and decides your harvest. Once a fruit sets and grows visibly, the pollination has succeeded.
Once two to four fruits per plant have set well, you may be consistent: pinch out further fruit sets and the shoot tips. The plant then puts all its strength into the remaining melons, and these turn out noticeably larger and sweeter. Leave everything hanging that sets and you end up with many small, barely aromatic orbs that may not even ripen in time.
The knock test: when is the melon ripe
The big question of every melon year. Unlike an apple, a harvested melon does not really ripen further, so it pays to wait for the right moment. The good news: both melon types give you clear signals.
With the muskmelon the scent is your best ally. A ripe cantaloupe or charentais smells intensely sweet and floral at the blossom end. On top of that comes the so-called slip: when ripe, many muskmelons come away from the stem almost on their own, a small crack shows all around, and a gentle press is enough. The base colour also shifts from greenish to creamy or yellowish.
With the watermelon the classic knock test helps. Knock on a ripe fruit with your knuckles and it sounds low and hollow, almost like a muffled drum. An unripe melon sounds bright and hard. Two more sure signs: the little tendril right at the fruit stalk is dried and brown, and the ground spot the melon lay on has turned from white to creamy yellow.
Note the date of pollination or hang a small label on the tendril. Most varieties need about 35 to 45 days from fruit set to ripeness. Together with the knock sound, the scent and the dried tendril you will then hit the harvest moment almost every time.
When it does go wrong
Melons are robust when warmth and water are right. The most common problems almost all come down to cold or wet. Yellow, stalled plants in early summer usually simply suffer from nights that are too cool, and here only patience and warmth protection help. If a young fruit rots away black at the end, the pollination was incomplete and the plant sheds the set. That is normal as long as enough other fruits are sitting.
Powdery mildew, a white, floury coating on the leaves, is the most common serious enemy of the melon, especially in a greenhouse with muggy air. Water only at the root, provide air movement and remove affected leaves early. Standing wetness at the root collar leads to stem rot, which can topple a whole plant. Prevent both with the planting mound and dry material under the fruits.
One good last piece of advice for your first melon year: start small. Two or three muskmelons against a warm wall or in a tunnel bring you more of a sense of success than half a bed full of watermelons that stays green through a cool August. Once the first sun-warm slice of your own is cut, you know why the effort is worth it.
Frequently asked questions about melons in the garden
Can I grow melons outdoors here without a greenhouse?
Muskmelons yes, in a normal to warm summer at a full-sun, wind-sheltered spot, ideally against a south wall and with a film tunnel in spring. Watermelons need more warmth and succeed outdoors reliably only in very good summers. In the cooler north or at altitude a greenhouse or tunnel is almost always the better choice.
When do I sow melons and when do I plant them into the bed?
Sow in the warmth from mid-April · CW 16 to 18, not earlier, or the young plants get too big and weak. They only go outdoors after the last frosts from mid-May · CW 20, once no more night frosts threaten. In a greenhouse you may plant one to two weeks earlier.
How do I tell that a melon is ripe?
The muskmelon smells clearly sweet at the blossom end and, when ripe, comes away from the stem almost on its own, often with a small crack all around. The watermelon sounds low and hollow when knocked, the tendril at the stalk is dried and the ground spot is creamy yellow. Harvested melons barely ripen further, so it pays to wait for these signs.
How many fruits does a melon plant carry?
Two to four fruits per plant make sense. Technically it sets more, but then they all stay small and barely sweet. Once two to four melons have taken hold well, you pinch out further sets and the shoot tips so the plant concentrates its strength.
Do I have to hand-pollinate melons in the greenhouse?
Often yes. In a closed greenhouse bees and bumblebees are missing. On a dry morning use an open male flower to dab the pollen into several female flowers, recognisable by the small fruit set behind them. If the house stands open during the day and insects come in, pollination usually takes care of itself.
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