At a glance
- The salad cucumber and the pickling cucumber are the same species in two roles: one grows long and smooth for the slice, the other small and warty for the jar. Decide before sowing what you want to harvest.
- Cucumbers are warmth-loving heavy feeders. Plant out only after the last frosts, roughly CW 18 to 22, into loose, nutrient-rich soil.
- A climbing support saves space, keeps the fruit clean and helps prevent disease. On a string the cucumber grows straight instead of crooked.
- Modern varieties are almost always free of bitterness. If a cucumber does turn strongly bitter, do not eat it: behind it sits the bitter compound cucurbitacin.
Few vegetables reward a warm summer as directly as the cucumber (Cucumis sativus). From a handful of plants you harvest basketfuls over weeks, and a sun-ripened cucumber from your own bed tastes fresher and crisper than any from the shelf.
The first decision comes with the seed: do you want cucumbers for the salad or for pickling? Both belong to the same species but pull you in different directions. Let us sort that out first, then move on to the spot, the climbing support and the question of why a cucumber turns bitter.
Salad cucumber or pickling cucumber?
The salad cucumber grows long, smooth and thin-skinned. In a greenhouse it easily climbs over two metres and delivers one cucumber after another. Many varieties flower purely female, so they crop especially heavily.
The pickling cucumber stays small, is often warty and is really harvested unripe, as soon as it is finger- to hand-length. That is exactly when it is firm enough for preserving. It is happy outdoors and carries all the more the more often you pick.
What every cucumber needs
Whichever type you choose, the basic needs are the same. Cucumbers are divas of warmth.
The four levers
- Warmth
Below 12 degrees the cucumber stops. Plant out only after the last frosts and protect young plants with fleece on cool nights.
- Nutrients
As a heavy feeder it wants plenty of compost and a steady supply through the season. A starved cucumber quickly stops cropping.
- Even water
Large leaves transpire a lot. Drought stress makes the fruit bitter and crooked, so water deeply and often, always at the roots.
- Something to climb
On a support the foliage stays airy and the fruit clean and straight. It is the simplest disease protection there is.
How to grow cucumbers
Pre-grow or sow direct
From mid-April raise cucumbers warm on the windowsill (CW 16 to 18), or sow direct into warm soil from mid-May. Direct-sown plants often catch the pre-grown ones up quickly.
Plant out after the last frosts
Only set the young plants out once no more cold nights threaten, roughly CW 18 to 22. Cucumbers hold a cold snap against you for a long time.
Put up the support from the start
A trellis, a net or taut strings: what matters is that the tendrils find a grip early. On a string you simply lead the main shoot upward.
Mulch and water
A layer of mulch keeps the soil moist and warm. Water evenly with tempered water, cold tap water shocks the heat-loving plant.
Harvest regularly
The more often you pick, the more the plant sets. Miss a fruit and let it grow fat and yellow, and it slows down the supply.
- Typ
- Annual fruiting vegetable
- Familie
- Cucurbits
- Standort
- Full sun, warm, sheltered
- Aussaat
- Windowsill from mid-April · CW 16 to 18
- Ins Freiland
- After the last frosts · CW 18 to 22
- Ernte
- July to September · CW 28 to 38
- Wasserbedarf
- Plentiful, even, tempered
Salad cucumbers are happiest in a greenhouse or against a warm, sheltered wall, because they dislike draughts. Pickling cucumbers do well outdoors and will also ramble flat over the ground if you put up no support. For the pickling cucumber it pays to set several plants at once, so that enough comes together for preserving in one go.
Training and pinching: how to keep the cucumber healthy
Like the tomato, the cucumber can be trained, and in the greenhouse especially that pays off. You lead the main stem up a string vertically and so keep the plant slim, airy and healthy. Freely hanging fruit grows straight and stays clean.
The trick is in the lower part: up to about 50 cm, you break out all side shoots and the first flowers. That steers the strength into growth and roots at first, keeps fruit off the damp ground and so prevents mildew. Higher up you let the side shoots stay and shorten them after one or two fruits. Once the main stem reaches the top of the support, you top the tip. That keeps the plant manageable and still cropping well.
Why does a cucumber turn bitter?
The bitter compound is called cucurbitacin and occurs naturally in all cucurbits. Modern edible varieties are bred not to form it, which is why shop-bought and most home-grown cucumbers are mild. Drought stress, extreme heat or cold can still trigger some bitterness in sensitive varieties, usually near the stem end.
Do not eat strongly bitter cucumbers
A slightly bitter cucumber can be peeled and generously trimmed at the stem end. But if a cucumber tastes intensely and persistently bitter, do not eat it and spit it out. A high cucurbitacin content can cause nausea, vomiting and diarrhoea. This matters especially with home-saved seed and when ornamental gourds stood nearby: if they cross in, the bitter compound can return.
Warmth, even water and a support. Drought stress is the most common reason for crooked, bitter fruit.
The core rule for juicy cucumbers
Frequently asked questions
My cucumber flowers a lot but sets hardly any fruit. Why?
Many varieties form male and female flowers. The male ones (without a little cucumber behind them) only serve pollination. If insects are missing in cool weather, the fruit fails to set. Purely female-flowering greenhouse varieties get around the problem.
Why do my cucumbers grow crooked?
Crooked fruit comes from uneven water, a lack of nutrients, or when the fruit catches on a leaf as it grows. On a support the cucumbers hang free and therefore grow straighter.
Can I use salad cucumbers for pickling too?
At a pinch, yes, but they soften quickly. Pickling cucumbers have firmer flesh and a thicker skin that stays crisp in the brine. The other way round, a pickling cucumber in a salad tastes a little firmer and less juicy.
White coating on the leaves, what should I do?
That is usually powdery mildew, a fair-weather fungus on the upper leaf surface. Remove affected leaves, keep the plants airy, and next time reach for a variety labelled as mildew-tolerant.
Greenhouse or outdoors?
Salad cucumbers reward you for the sheltered, warm greenhouse with a rich harvest. Pickling cucumbers and robust outdoor varieties do well outside. A relative is the zucchini, which as a cucurbit has very similar needs.
Rechtlicher Hinweis
This article is about growing cucumbers and does not replace professional advice. Take care with strongly bitter-tasting cucurbits: cucurbitacin can cause discomfort. When in doubt, do not eat bitter fruit.
Sources
- Cucurbitacins in zucchini, squash and cucumber, German Federal Institute for Risk Assessment (BfR)
- Julius Kühn Institute: growing cucumbers in the home and allotment garden
- Related in the magazine: Zucchini from variety to harvest and The garden in July
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