How to Grow Greenhouse Cucumbers – Ideal Cucumber Growing Conditions

Cucumbers are one of the most commonly grown crops in the world, from commercial greenhouses to small gardens. As a part of the cucurbit, or gourd family, cucumbers grow great outdoors, in row covers, and in controlled environments. Growing cucumbers in greenhouses lets growers extend their growing season, and produce larger, higher quality yields.

Cucumbers are a warm weather crop. Outdoors, growers usually plant cucumbers during spring time, once the danger of frost has passed. This allows the plant to flower and produce fruit in relatively warm temperatures, including soil temperature.

Greenhouse cucumber production can be year-round, depending on the level of control in the space. Cucumbers enjoy stable conditions and are susceptible to low temperatures and fluctuations in humidity. For optimal production, it’s important to avoid these two pitfalls.

What Are the Optimal Cucumber Growing Conditions?

There are numerous benefits to growing cucumbers in a greenhouse. You can provide the best conditions throughout the entire grow cycle. This ensures higher quality produce, larger yields, and lower rates of disease, molds, and pests.

Different varieties of cucumbers may have slightly different requirements. However, this guide should cover the basics for most common cucumber strains.

As a vining plant, cucumbers grow well both in soil and in a soilless environment. When planting in soil, it’s best to use a fertile soil, with a soil pH level of 5.5 to 6.8. Cucumber plants also need consistent watering. Under ideal conditions, you should water the soil with around an inch of water per week.

What Is the Ideal Temperature for Greenhouse Cucumber Production?

Maintaining the right temperature levels is one of the most basic greenhouse functions. Growing in a closed or semi-closed environment allows you to heat or cool as necessary and retain the right temperatures.

Like all crops, cucumbers too have a preferred temperature range. As a warm season crop, the ideal temperature range for cucumbers is generally 21-26°C (70-80°F). However, the plants can withstand a wider range, if necessary, ranging from 15-29°C (60-85°F). Like in nature, daytime temperatures may be higher than nighttime.

It’s important to note that cucumber plants are sensitive to frost. Low temperatures may cause frost damage, leading to wilting.

When it comes to cucumber germination, the ideal temperatures should be within the range of 15-29°C (60-85°F). Soil temperatures should be around 21°C (70°F), or higher, for germination to succeed. In general, germination occurs slower in lower temperatures.

Ideal Temperatures for Cucumber Cultivation:

• Vegetative growth and fruit setting – 21-26°C (70-80°F)
• Seed germination – 15-29°C (60-85°F)

What Is the Ideal Humidity for Greenhouse Cucumber Production?

Humidity is a major cultivation factor for any crop. Like temperature, every plant has its own ideal relative humidity or VPD range. Too high, or too low humidity can lead to several problems. It impacts growth, the plants’ ability to set fruit, and may lead to various disease or mold outbreaks.

In low humidity, plants experience stress due to heightened evaporation rates. This may lead to the plants significantly slowing down physiological processes, in order to retain water. So, when humidity is low, plants will struggle to grow and produce fruit. Low humidity may also increase susceptibility to various pests and diseases.

High humidity is generally favorable for growth. However, when humidity is too high, it can limit the plants’ ability to transpire, in turn slowing down growth as well. High presence of moisture can also lead to various diseases, including botrytis and powdery mildew.

Relative humidity may also have an impact on pollination and fruit setting. It can cause the pollen to dry out or be too damp. Cucumbers require the male flower to pollinate the female flower, so effective pollination is necessary.

Cucumber plants prefer a comfortable relative humidity range. However, they’re sensitive to fluctuations, so controlling humidity and providing consistent conditions is important.

The ideal relative humidity range for cucumbers is 60-70% RH. During nighttime humidity may be higher – 70-85% RH. In terms of VPD that’s 0.75-1.35 kPa during the day, and 0.35-1 kPa overnight.

Ideal Relative Humidity for Cucumber Cultivation:

• Daytime – 60-70% RH
• Nighttime – 70-85%

Optimal VPD for Cucumber Cultivation:

• Daytime – 0.75-1.35 kPa
• Nighttime – 0.35-1 kPa

How to Maintain Optimal Humidity in Cucumber Greenhouses

In any closed horticulture setting, humidity will inevitably rise to 100%. This is due to the plants’ transpiration.

Cucumbers are no different. Without removing moisture from the greenhouse, you will experience high humidity and water condensation. These lead to various diseases, mildews, and overall inefficient growth.

Traditionally, growers would reduce humidity by opening the greenhouse windows and vents to let the moisture out. This may be effective sometimes, but not always. It’s also highly inefficient, in terms of energy, as it allows heat to escape as well.

So, the most effective and efficient way to control greenhouse humidity is by using active dehumidification, such as DryGair.

To successfully control humidity, it’s also important to understand what affects it. For example, radiation, or lighting, can increase evaporation and transpiration, pushing humidity upwards. Higher temperatures will also increase the absolute humidity in the space, which can be dangerous when temperatures fall in the evening.

Using Air Circulation to Improve Humidity Control

Airflow is a great addition to dehumidification, and can help ensure ideal humidity levels for your cucumber plants. Air movement through the foliage helps disperse local pockets of humidity, known as microclimates. This is especially useful in dense or overlapping foliage, as moisture can easily get trapped.

Air circulation is a specific type of airflow. It’s non-linear, meaning it doesn’t just blow air in a single direction. Rather, it disperses air from the center of the space, in all directions, 360°. This creates a circular air pattern that ensures uniform conditions everywhere in the greenhouse.

All DryGair dehumidifiers come equipped with a patented air circulation mechanism, in order to provide total humidity control.

Additional Tips for Cucumber Greenhouses

Keep the Greenhouse Clean

It’s important to note that not all diseases are related to environmental conditions such as humidity or temperature. For example, cucumber bacterial wilt is often associated with pests, such as cucumber beetles, rather than environmental conditions.

You can help prevent many issues by keeping a clean environment. For example, organic matter on the soil is a hotbed for bacteria and pests. So, routinely removing any dried leaves and debris from the greenhouse can go a long way in preventing many common issues.

Use Thermal Screens to Retain Heat and Save Energy

Cucumbers prefer a warm environment. So in most cases, you need to heat the greenhouse to provide the ideal temperatures. However, heating can be very energy intensive and is associated with high costs.

Installing thermal screens is one of the most effective ways of retaining heat in the space, thus needing much less heating. Combining two or even three screens can drastically increase this effect.

One thing to note when using screens, is that humidity may build up in the closed space. However, using dehumidifiers solves this issue. It allows you to keep the greenhouse closed, retain heat, and maintain ideal humidity levels, all from inside the space.