Cucumbers: Cultivation of cucumbers in greenhouses/outdoors

Cucumbers, botanically called Cucumis sativus, belong to the pumpkin family (Cucurbitaceae). Actually, their fruits should be called berries, since their seeds are embedded directly in the pulp. Cucumbers originally come from India and have been cultivated there for over 3000 years. in the 19th They also came to Europe in the 19th century and have been cultivated in our greenhouses ever since.

sowing

Cucumber seeds can be sown in a heated greenhouse from around mid-March. Cucumbers intended for outdoor cultivation can be grown on the windowsill or in the cold frame. However, sowing should not take place before mid-April so that the young plants do not become too large before they are planted out in the bed.

• Only half fill the seed pots with substrate
• put two or three seeds on each
• cover with about 1 cm soil
• Substrate: potting soil
• Minimum temperature: 20 degrees
• keep evenly moist
• set up bright
• protect from the midday sun
• Germination time: 3 to 4 days

Let all the seedlings grow until the leaves of the strongest plant protrude over the edge of the pot. All weaker plants are removed. Then fill the seed pot with humus-rich, well-drained soil. In this way, the cucumber plant forms additional roots (adventitious roots) at the bottom of the stem. These ensure better water and nutrient supply and more stability.

Preferred plants

In addition to seeds, grafted cucumber plants are also available in specialist shops. Pumpkin seedlings serve as a base. The advantage lies in the vigorously developed root system of the plant and its resistance to fungal diseases. The base provides the cucumbers with nutrients and water in a particularly reliable manner.

Location

Cucumbers love a warm location with lots of sun. The optimal temperatures are between 20 and 25 degrees. However, the plants should be protected from the blazing midday sun - especially in the greenhouse. Some caution is required in the case of moisture. Because dew or rainwater on the leaves increase the risk of fungal diseases. Although cucumbers need a lot of warmth, care must be taken to ensure good air circulation. Outdoors, cucumbers prefer a warm, rain-protected wall.

• as warm as possible
• full sun outdoors
• in the greenhouse lightly shaded in strong sunlight
• good air exchange
• protected from rain
• sheltered from the wind
• not below 10 degrees

Floor

The soil for cultivating cucumbers should be crumbly and loose. Compacted or wet soils are not suitable because the plants are very sensitive to waterlogging. Increase the humus content before planting with about five liters of compost per square meter. This is how you create ideal conditions.

• humorous
• relaxed
• finely crumbly
• well permeable to water

Crop rotation and mixed culture

Cucumbers should only be planted in the same spot several years apart. Usually about four years are necessary. In order to avoid having to replace the soil for the constant culture, it has proven useful to place the cucumbers in large tubs or in sacks with substrate in the greenhouse. The soil is then distributed in the rest of the garden or on the compost after the cucumber season. It is also important with which neighbors the cucumbers are planted together. With a good mixed culture, the plants support each other and ideally keep pests away.

Good neighbors:

• beans
• dill
• Garlic
• Kohlrabi
• spinach

Unfavorable neighbors:

• Peas
• cabbage
• Beetroot
• celery

planting

Young cucumber plants in particular are still quite sensitive to cold. Therefore, they can only be planted in an unheated greenhouse or even outdoors in late spring. Temperatures should be above 12 degrees at night. The planting time therefore does not differ between outdoor planting and planting in an unheated greenhouse. When planting out, the cucumbers should already be over 20 cm high. Choose the warmest place in the greenhouse or in the garden for the plants.

• Time: from the end of April into the heated greenhouse
• unheated greenhouse and field: from mid-May
• Planting distance: 50 to 60 cm
• plant only in well-prepared soil
• Mix in 60 g horn shavings and 100 g potassium magnesia per square meter

Cucumbers also like warm temperatures in the root ball. To increase the soil temperature, you can cover the soil with black mulch film. It is important to provide slits or holes so that the irrigation water can penetrate through the foil into the soil and at the same time good air circulation can take place.

climbing aid

If the leaves of the cucumber are lying on the ground, they are quickly attacked by mold or mildew. And the fruits also rot quickly when they come into contact with moist soil. Vertically erected steel mats or other latticed frames such as wire mesh have proven useful as climbing aids, to which the shoots are guided upwards and possibly tied. The cucumbers slip off smooth plant stakes and break easily, especially when fruit is already hanging on the tendrils.

balcony

If the cucumbers are planted in a bucket of at least 20 liters, they can also be cultivated on the balcony. Make sure the pot has holes in the bottom to allow excess water to drain. The same conditions apply to maintenance as in the field.

Care

Cucumbers are no friends of extremes. This applies to both the temperatures and the water supply. If the plants are exposed to great stress in this regard, the flowers can fall off, the young fruits die or grow deformed.

shading

Shading is necessary in the greenhouse on sunny or hot days. For this purpose, when planting, wires are stretched under the roof for internal shading, into which mats or fleece can be inserted. Alternatively, it is of course also possible to place a brushwood mat or fleece on the roof of the greenhouse in the midday hours.

Pour

Cucumbers have a fairly high water requirement, but they do not tolerate waterlogging. Therefore, it is preferable to keep the soil slightly moist and always water it when the upper substrate layer has already dried slightly. In hot periods, watering twice a day may be necessary. Always water directly onto the root ball and not over the leaves. Use only tempered watering water and no cold water from the garden hose. The cucumbers do not tolerate the temperature shock at the roots particularly well.

• water only with preheated water
• for example from the rain barrel
• preferably in the morning and not in the evening
• a layer of mulch prevents excessive evaporation

humidity in the greenhouse

On the one hand, cucumbers need a relatively high level of humidity, because if the air is dry during the growth period, the fruits are rejected by the plant. On the other hand, the humidity must not rise too much. In this case, there is a risk of dew forming on the leaves when it cools down at night, creating an ideal breeding ground for fungal spores.

Fertilize

Cucumbers need relatively high amounts of nutrients for their rapid growth. However, it should be noted that the plants are sensitive to lime and salt. Therefore, mineral fertilizers are not recommended. They do better with organic fertilizers in the form of compost, horn shavings or slow-release fertilizers for vegetable plants. With particularly fast-growing varieties, it is advisable not only to fertilize when planting, but also in the About four weeks apart with an organic fertilizer in liquid form once or more to fertilize.

Cutting/Pruning

As soon as the cucumber has reached the end of the trellis or the greenhouse roof, the shoot tip is cut off. A maximum of six cucumbers may be left on the main shoot. The bottom cucumber should hang at least 60 cm above the ground.

• Remove all side shoots up to a height of 60 cm
• shorten all other side shoots
• Greenhouse: leave only one or two fruit buds per side shoot
• maximum 6 to 8 fruits per plant
• Lead cucumbers in the greenhouse mainly upwards
• For outdoor cucumbers, cut off the main stem after the sixth leaf
• this stimulates the formation of side shoots
• Let side shoots grow a little longer
• Cut after the third set of fruit

harvest

Cucumbers ripen very quickly, the first cucumbers can be harvested about two weeks after flowering. With early sowing and cultivation in the greenhouse, it can be as early as the end of May. With outdoor cucumbers, depending on the weather, you usually have to be patient until around mid-July. Cucumbers taste better when they aren't quite the size of the ones you get in the supermarket. Cucumbers are harvested by cutting off the stem of the fruit with a knife. Ideally, fresh cucumbers can be harvested twice a week until late summer. At a storage temperature of 13 degrees, the cucumber fruit can be kept for several weeks.

Proven Varieties

With cucumbers, a distinction is made between outdoor cucumbers and those varieties that can only be grown in a greenhouse. The varieties for the greenhouse are generally referred to as cucumbers or cucumbers. Modern varieties of cucumbers for the greenhouse form exclusively female plants, so they do not need pollination to form fruit. These are so-called virgin cucumber varieties. Peeling and pickling cucumbers are primarily suitable for the open field. There are both classic long cucumbers and short variants. F1 hybrids have proven to be productive. Not only do they have a long harvest period, they are also resistant to mildew and do not produce any bitter substances.

For the greenhouse

• 'Eiffel': cucumber up to 35 cm long
• 'Dominica': snake cucumber, up to 35 cm long
• 'Fitness' F1 hybrid: Cucumber, self-fertile
• 'Helena': Cucumber, self-fruiting with long, smooth fruits
• 'Picolino' F1 Hybrid: Mini Cucumber
• processed cucumber varieties

outdoor varieties

• 'Gergana': almost smooth-skinned cucumber for outdoors
• 'La Diva': refined house cucumber, suitable for outdoor and greenhouse use
• 'Printo': relatively cold-tolerant, mini cucumber, suitable for balconies and containers
• 'Tanja': mixed flowering landrace

diseases and pests

The humidity in the greenhouse should not be too high at night. This usually happens when the water is poured in the evening and the temperatures outside drop afterwards. In this case, dew forms on the leaves, preferring fungal infection. In addition to good ventilation, a resistant or refined cucumber variety also helps against many diseases. In addition, cucumbers in the greenhouse are often attacked by pests such as aphids, spider mites and thrips. Regular checking of the undersides and axils of the leaves is therefore essential in order to identify the pests at an early stage. In this case you can fight them with beneficial insects, sticky boards or other environmentally friendly measures.

snails

Outdoor cucumbers often fall victim to slugs. Young seedlings in particular are very popular with the snails. So be sure to use good snail prevention so you can expect a bountiful harvest.

mildew

There are now a number of varieties resistant to powdery mildew. Downy mildew infestation occurs especially on cool nights and the associated formation of dew. Good air exchange is necessary for prevention. If the leaves are too close together and prevent drying, some of them should be removed. Powdery mildew tends to appear after a dry period in the greenhouse.

Conclusion

Since cucumbers are heat-loving plants, they grow particularly well in a greenhouse. Only robust varieties should be used for outdoor cultivation. Growing cucumbers is very easy if the most important points in care are observed.

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