Growing Cucumbers In The Greenhouse

Last updated on October 23rd, 2023 at 09:04 pm

Plant cucumber

Pre-plant cucumber
To allow optimal growth of cucumbers, we recommend that you preplant the plants in a pot starting around mid-March. You can do this on a windowsill or directly in the greenhouse. To do this, put three seeds in a flower pot with soil and choose special growing soil, which is already provided with the necessary nutrients. The pot should also have a diameter of at least 8 cm. We recommend direct sowing from the beginning of May only for more robust outdoor and pickling cucumbers.
Tip:
Cucumber seeds like it warm. Therefore, a temperature of 22-25 °C is ideal for germination.
Temperature
Time of sowing
The right time for sowing depends mainly on whether you have a heated or unheated greenhouse. In a heated greenhouse, you can start sowing as early as the end of March or beginning of April. In an unheated greenhouse, you should sow in May at the earliest. It is important to maintain a constant temperature of about 20 °C and uniform soil moisture. For greenhouses without heating, outdoor cucumbers are also suitable. You can simply plant these in the greenhouse and harvest them earlier than if you sow them outdoors.

Planting cucumber

Once the seedlings are 20-30 cm tall, you can plant them in the greenhouse at a planting distance of about 60 cm. Loosen the soil a little beforehand, then the young plants can take root particularly well. Make absolutely sure that the temperatures in the greenhouse do not fall below 10 °C, as young plants in particular react very sensitively to temperatures that are too low.

Tip:
If the greenhouse is not heated, you can also wrap the young plants with bubble wrap.
Location
A warm, bright location is ideal. Be careful not to plant the cucumbers directly by the door, because cucumber plants are very sensitive to wind. A location protected from the wind is therefore particularly important. If you want to give your plants the best possible conditions for healthy and rapid growth, you should also make sure that the soil is particularly rich in nutrients and has a pH value of between 5.5 and 7.5. Although cucumbers like it warm, they should be protected from too much sunlight. To do this, you can install a sunshade in your greenhouse. For example, a shade net is suitable for this purpose.

Types of cucumbers

Basically, we distinguish here between outdoor cucumbers and the so-called snake cucumbers or salad cucumbers, which you can grow in the greenhouse. Salad cucumbers are self-pollinating, that is, they produce only female flowers, and do not depend on pollination by insects. Ideal for sowing and growing in a greenhouse. Some cucumber varieties have even been bred specifically for greenhouse cultivation and are considered particularly resistant and easy to care for.

Tip:
Opt – if available – for F1 hybrids of the varieties. These have a particularly long harvest time, are often bitter-free and resistant to most diseases such as mildew.
We recommend the following – tried and tested and newly bred – cucumber varieties for your greenhouse:

Climbing aid

For cultivation, we recommend growing both outdoor and greenhouse cucumbers on a climbing aid. These keep the cucumber plant off the ground, ensuring that the leaves dry quickly and reducing the risk of diseases that could harm the plant. Climbing aids also help to make the best use of space, which is often at a premium, especially in smaller greenhouses. You can get climbing aids in the form of trellises and poles at any well-stocked hardware store, garden specialty store or online. Of course, a climbing aid can also be realized well in a DIY project. For this purpose, especially coarse wire mesh, bast ropes or simply sticks and rods made of wood stuck into the ground are suitable. Be sure to use a coarse surface here, so that the cucumber plants find the best possible grip.
After planting, the cucumber plant will need some support to hold onto the climbing aid: To do this, wrap some of the cucumber vines around the climbing aid. From here, the cucumbers should then climb the climbing aid on their own and grow upwards. Cucumber plants by nature want to reach high and can grow practically infinitely in height. Therefore, before the end of the climbing aid, they should be directed back down or regularly thinned out in the course of cultivation.

Cucumber plant – care
Not too warm, not too cold. Not too dry, not too humid – the cucumber is a plant with very specific requirements for its environment and requires special care. As explained in the previous section, they like it moist and warm, need a lot of water and are especially sensitive to strong sunlight and wind. But don’t panic, once you get the hang of it, you can enjoy tasty, homegrown cucumbers several times a year. Here’s what you should keep in mind when caring for your cucumbers:

Cucumber Fertilizer
Cucumber plants are so-called heavy feeders, which means they require more water and nutrients than other plants. Especially in the early stages of fruiting, the plants need the best possible support in their growth.
Before you move the plants into your greenhouse, you should therefore first prepare and pre-fertilize the soil there with mature compost, horn meal or mineral complete fertilizer. To do this, simply loosen the soil and introduce the fertilizer of choice. We recommend here a special fertilizer for cucumbers and vegetables, which you can get in the garden market or online. The advantage is the optimal composition of nutrients such as potassium and magnesium.
Fertilizing is done once when planting and again in the middle of the season, for example in July. When fertilizing cucumber plants, the following also applies: Less is more! The roots of the plants are very sensitive and react especially to very salty fertilizers. Signs of too generous fertilization are many leaves but few fruits.

The ideal temperature
Cucumbers like it tropical-warm, humid and protected from the wind. The ideal temperature for cucumber plants is between 18 and 22 °C. For seedlings it should be even a bit warmer: 25-28 °C is ideal before germination. However, too much humidity is counterproductive and should be avoided at all costs. If temperatures drop at night, dew can form on the plants, which in turn promotes diseases and fungal infections. It is also essential to ensure regular airing.

Proper watering
Cucumber plants are extremely thirsty comrades. Proper and sufficient watering is a crucial point for the successful cultivation and care of cucumbers with the highest possible yield. Depending on the growth phase, there are a few things to keep in mind:

Cucumber seedlings that you are currently pre-growing should be sprayed with lukewarm water twice a week. Young plants that have just been planted in the greenhouse should be watered with lukewarm water two to four times a week. In the case of great summer heat, of course, the interval should be increased accordingly. Although cucumber plants need a lot of liquid, you should definitely avoid watering your plants with cold water. This will not only make the cucumbers bitter, but the plants may even freeze to death from it, and there is a risk of cucumber wilt. Instead, we recommend watering your plants with warmed water in the morning.

Important:
Do not water the plants, but only the soil and the root area, as cucumber plants do not tolerate waterlogging. The leaves should always be dry, otherwise there is a risk of disease and fungal attack. Water containing too much lime and chlorine can also damage the plants in the long run.
Pruning
To ensure that cucumbers grow well, greenhouse cucumbers that grow upwards on climbing aids should be pruned out from a height of 20 cm. Culling means removing excess side shoots. In this way, the yield of the cucumber plants can be increased.

Here’s how it works: cut off all flowers and side shoots growing below 60-80 cm after the first leaves appear. This way, the plant’s energy is directed only to the main shoots and spent on their growth. At the same time, this also prevents the cucumber plants from getting wet in the lower part under the leaves and being affected by fungal diseases. Cucumbers that grow on the ground, as a rule, do not need to be thinned out. Here it is enough to regularly remove withered flowers and leaves.

Harvest
About three weeks after flowering, you can harvest the first fruits. There is no perfect moment for harvesting. Cucumbers are ripe when the skin feels smooth and the ends of the fruit round off slightly. Harvest too early rather than too late, and don’t let the fruit get too big or it will become bitter, unfortunately. To harvest, simply cut or clip off the stem above the cucumber. If the cucumber is already yellow, better off to the compost with it. Then the cucumber is already overripe and no longer really edible. With ideal care, you can even harvest up to four times a year!

Diseases and pests
Unfortunately, diseases and pests do not stop at the cucumber. The reason is often incorrect care. The following diseases or pests are common in cucumber:

Downy mildew:
Downy mildew causes yellow, demarcated spots on the leaves. Cold nights with dew are particularly conducive to this disease. You can prevent it by watering only the lower part of the plant and growing your cucumbers on a trellis. If your plant is infested with downy mildew, the only thing that will often help is removing and disposing of the infested plant (parts).

Powdery mildew:
In powdery mildew, the leaves are infested with a white, blotchy fungus. This occurs primarily after severe/prolonged drought. As a preventive measure, plants should be at least 60 cm apart. Regular airing in the greenhouse can also prevent disease. If your cucumber plant is infected with powdery mildew, the only remedy is to remove and dispose of the affected plant (parts).

Cucumber wilt:
Indications of cucumber wilt are droopy, drooping leaves and shoots. The reason is often incorrect watering, especially cold water harms the plant, cools it down and puts it into a certain rigor mortis. Lower water absorption is the result and the plant begins to wilt. Infestation with the so-called Fusarium wilt can also lead to cucumber wilt. In this case, a fungus invades the plant and clogs the conduits. The result: the plant can no longer absorb water and dies. If your plant is infected with cucumber wilt, you should remove and dispose of the plant. In addition, you should generously replace the soil.

Spider mites:
Spider mites infest the underside of leaves and can be identified by a fine, white web. The reason for a spider mite infestation can be insufficient humidity and too high a nitrogen content in the soil. Therefore, you should avoid nitrogenous fertilizers when caring for cucumbers. If your plant is infested with spider mites, generously washing the plant with lukewarm water will help. Then pack the infested plant in a plastic bag. This will create a moist, warm environment that will kill the spider mites. Another way to combat the infestation is to spray the plant with nettle broth.

Planting cucumber in a pot and in a tub
Cucumbers are also wonderful to grow in a pot or tub! Ideal if you are looking for a space-saving growing solution or the bed in the greenhouse is already occupied with other plants. And this is how planting in a pot or tub works:

1. even when sowing in a pot, the ideal time is between mid-April/early May. Again, it also depends on whether your greenhouse is heated or not. From the beginning, choose a pot as large as possible, because the plant will need enough space later. Feel free to use special growing soil. This is already mixed with all the necessary nutrients. 2.

Now add two or three seeds to the pot and cover them with a layer of soil. Note: There should be at least 20 cm of space between the cucumber seeds. For smaller pots, it is therefore better to plant only one seed per pot.

3. the germination phase follows: make sure that the temperature does not fall below 20 °C.
4. if at least five leaves are visible, remove the lower two leaves. This will give your plant enough strength to form the main shoots.
5. cucumbers in pots or tubs should also be given a climbing aid at best.
6. now take to heart the above tips when caring for and growing cucumber and soon you will be able to harvest the first fruits.

The pot with the cucumber plants, of course, you can move outside to the balcony or terrace. Just make sure that the cucumbers are placed on a wind-protected side of the house, are protected from too much sunlight and are not placed outside before the “Ice Saints”. Also, go for outdoor cucumber varieties that can handle the lower temperatures better than greenhouse cucumbers.

What goes well with greenhouse cucumbers?

Not only with the optimal location, but also with its neighbors in the bed, the cucumber is rather picky and, unfortunately, does not get along with all plants. If it is placed in the greenhouse together with the wrong plants, there is a risk of crop failure for at least one of the plants. Absolute no-goes here are tomatoes, potatoes or even radishes. The reason here is quite simply the different requirements for climate and care. The tomato, for example, does not like the warm and humid climate that is ideal for cucumbers.

If you still want to plant cucumbers and tomatoes together in a greenhouse, you should make sure that the greenhouse is large enough (at least 8-12 m² floor space), that the cucumber and tomato plants are as far away from each other as possible, and that the tomato is planted in a cool, well-ventilated place in the greenhouse, ideally directly by the door.

Good partners for the cucumber, on the other hand, are lettuce, cabbage varieties, onions, leeks, beet or even peppers. Also various herbs, especially dill, basil and caraway, are wonderfully suited to be planted in the immediate vicinity of the cucumber. Practical side effect: as so-called underplanting directly under the cucumber plant, the herbs keep unwanted vermin and diseases away from the cucumber plant.

Here are the suitable and less suitable neighbors again in the overview:

Growing cucumbers – this is how it works

Growing cucumbers in a greenhouse is a great gardening project. To make it a success, we have once again summarized the most important tips for sowing and caring for the plants. So nothing stands in the way of a rich and tasty cucumber harvest:

The right variety:
Opt for salad cucumber or snake cucumber varieties, ideally a resistant F1 hybrid.
The ideal location:
Warm, bright & protected from wind. Also, protect cucumber plants from excessive sunlight.
Fertilizer to help them get started:
Especially in the initial phase, an adequate supply of nutrients to the cucumber plants is of great importance: pre-grow the plantlets with special growing soil and fertilize the soil in the greenhouse with mature compost, mineral complete fertilizer or, at best, special fertilizer for vegetables before moving the young plants there.
Proper watering:
Cucumbers are very thirsty. Water – especially young plants – two to four times a week with lukewarm water and avoid waterlogging.
Provide assistance:
Cucumbers want to grow tall. Therefore, give the plants enough support while growing with a climbing aid/trellis.
The ideal temperature:
Cucumbers like it moist and warm. The temperature should always be between 18 and 22° C.

Frequently asked questions

Here you will find answers to questions that we are often asked.

What temperature do cucumbers need in the greenhouse?

Cucumbers like a tropical, warm and humid climate. The ideal temperature here is between 18 and 22 °C. For seedlings it should be even a bit warmer: 25-28 °C is ideal before germination.

How do I care for cucumbers in the greenhouse?

Cucumbers like it warm and humid. The temperature should therefore always be between 18-22 °C. Avoid too much sunlight and protect the plant from wind. Cucumber plants need a lot of water and should be watered two to four times a week, depending on the temperature. It is essential to avoid waterlogging. Otherwise, there is a risk of fungal attack and crop failure.

How to water cucumbers in the greenhouse?

Cucumber seedlings should be sprayed twice a week with lukewarm water. Young plants that have just been freshly planted in the greenhouse should be watered with lukewarm water two to four times a week. However, never water with cold water. This not only makes the cucumbers bitter, but also promotes disease. We recommend watering the plants in the morning with warmed water. Also, avoid waterlogging and water only the soil.

What suits cucumbers in the greenhouse?

Cucumbers are picky and do not accept every greenhouse neighbor. Especially well suited are lettuces, cabbage, peppers or even herbs. However, you should avoid a direct neighborhood with tomatoes, because both vegetables have different requirements for climate and care. Otherwise, there is a risk of crop failure.

Why cucumber on climbing aid?

The climbing aid offers several advantages:

Prevents diseases, as the plant is kept away from the ground and dries faster.
Space is optimally used, as cucumber can grow well in height.
Allows for easier, especially back-friendly harvesting while standing.
What types of cucumbers greenhouse?
We recommend special types of salad cucumbers and snake cucumbers such as Helena, Eiffel or even Picolino. Feel free to reach for special F1 hybrids. These are particularly resistant to diseases and provide a high yield.