How to Grow Hydroponic Cucumbers Indoors and Outdoors

When it comes to growing cucumbers hydroponically, it can be indoors or out. It’s important to note, that some cucumbers will lend themselves better to being grown in a hydroponic system.

Let’s get started learning how to plant cucumbers in your hydroponic system and what the requirements are for growing them.

Quick Reference

cucumbers in a grow room
  • pH range 5.5-6.0 for optimal results.
  • EC 1.7-2.5
  • PPM 1190-1750

Cucumbers prefer moderate humidity

Good air flow is essential for plant vigor.

Cucumbers are prone to powdery mildew in high humidity.

80°F maximum is best for accelerated growth. Night temperatures should be no less than 65°F.

Nutrient Solution temperatures vary slightly see: Hydroponic Temperature.from drop down menu at page top.

8-12 hours of light daily optimal – minimum of 8 hrs.

Cucumber Varieties Best Suited for Hydroponics

In recent years there have been a number of new Cucumbers varieties introduced, many of which lend themselves well to hydroponic gardens. Some of the more popular indoor varieties include the Old World favorites such as Long English and Lebanese cucumbers.

Lebanese cucumbers over a white background.
Lebanese cucumbers

They are not as thin-skinned as common garden varieties found in most North American gardens. The common garden varieties such as American slicers which include Slice Master, straight 8, and Marketmore will also do well in a hydroponic garden. Persian pickles are another old-world cultivar, becoming popular in pickling.

They have varying sizes, shapes, maturation rates, and disease resistance characteristics listed. So long as you are not a seed saver, Hybrid varieties are generally best for hydroponic production.

Selection of the best cucumber cultivar can be somewhat bothersome, there are more than enough varieties within each cucumber category to select from. Cucumber types fall under the technical titles of:

  • Gynoecious Cucumber varieties produce mostly female flowers. They produce more prolifically than standard varieties and are more disease resistant.
  • Parthenocarpic Cucumbers will produce seedless fruits if grown isolated from other varieties. They differ slightly from Gynoecious in that pollination of a Gynoecious cucumber will not necessarily produce an undesirable fruit. Gynoecious cucumbers are also not necessarily seedless. Parthenocarpic cucumbers are nearly all gynoecious, meaning that they only produce female flowers. However, not all gynoecious cucumbers are parthenocarpic.

Burpless

Sweeter, thin-skinned, and Contain very little cucurbitacin which increases stomach discomfort and burping.

Bitter-free

Most varieties of cucumber will sometimes develop a bitter tastes if left on the vine too long. These won’t.

Spineless

Smooth skinned. Devoid of the white, prickly stubs.

With any all-female varieties, there are no male flowers present to pollinate. You do not need to constantly vibrate the flowers or hand pollinate, in most cases a gentle fan breeze and a light occasional shake will suffice.

Planting Cucumbers in a Hydroponic System

Cucumber seeds can be sown into individual cell pots with perlite, vermiculite, or a blend thereof. Oasis Cubes also work very well for seed starting, Blocks of Rockwool are also suitable, coco coir will suffice.

The seed should be placed deep enough so as to prevent it from drying out, this will also help the seed coat to release as it germinates.

Training Hydroponic cucumbers

Presoak all media{LCA, Rockwool, vermiculite…}in a pH balanced water for at about 45 minutes before using it. Dry media will soak up moisture from the plants roots.

Use straight water [pH balanced is preferable] for the first few days following germination until the embryonic leaves have fully emerged. By the 3rd or 4th day, use only a half-strength nutrient solution for about a week before graduating to full strength solution.

Germination

Germination periods vary depending on the variety and conditions. Temperatures around 80°F are best for accelerated growth.

Seedlings, once they emerge should be hardened off with a gentle breeze [fan] and temperatures around 73 to 75°F before planting permanently in your hydroponic system. The minimum night temperatures should be no less than 65°F

Spacing Requirements of Hydroponic Cucumbers

European cucumbers are generally spaced at 5-6 feet between rows by 16 inches between plants.

Bush varieties can be planted closer together – always consult the seed pack, as spacing varies from cultivar to cultivar.

Maintenance and Propagation of Hydroponic Cucumbers

Trellising Cucumber Vines

Cucumbers are generally vining plants and need to be supported not only for the health and yield of the plant but also to maximize the use of vertical space. Even bush varieties need support for optimal production and health. In a hydroponic set up they should be trained to grow upwards along supporting structures such as strings or wires, light trellises or mesh structures will also suffice.

Cucumber vines being indeterminate also need to be trimmed, trained, and maintained to prevent them from overtaking your entire growing area. Initially, the plant’s growth should be directed upwards on a wire or string support that leads to overhead support.

Once the plant has reached the overhead support – it should then be trained so that the majority of the cucumbers will hang downwards, thus using your vertical space as efficiently as possible to the benefit of a bountiful harvest.

Light Requirements for Hydroponic Cucumbers

Cucumbers only need a relatively moderate amount of light in comparison to other crops. 8 – 10 hours daily is sufficient, 12 hours is optimal. Post seedling and germination Temperatures should range anywhere from 65 to 85°F.

They can be grown two to three plants per planting space.

Hydroponic Nutrient Solution for Cucumbers

Mix your Hydroponic nutrients according to the package directions, and thoroughly water your plants with the nutrient solution. Nutrient solutions should commence with a standard vegetable formulation.

The optimal pH for cucumbers grown hydroponically is 5.5 to 6.0. For more advanced growers – EC ranges should be from 2.2 to 2.7 mS.

When the plant matures , prior to fruiting switch to a solution with higher potassium levels.

Cucumbers will also benefit from CO2 enrichment which will accelerate fruit production and increase yields.

See: Do it Yourself C02 generators.

Pests, Disease, Trouble Shooting

Insect pests of cucumbers are generally limited to sap sucking pests such as aphids, mites, thrips, whiteflies – which will reduce yields and fruit quality. Cucumber Beetles will generally effect cukes grown outdoors allthiough they can at times find their way into greenhouse and indoor grow rooms.

The most common disease is powdery mildew, which will decimate crops if not properly controlled.

Powdery Mildew, in conventional gardens, is prevalent under moist conditions. In a hydroponic setup – it is always wet.

The best defense is prevention, use resistant cultivars. Look for a “PM” designation on the seed packet. The PM code signifies that a particular variety is powdery mildew resistant.

Other diseases such as fusarium, verticulium, pythium and various wilts are not unheard of, but rare in hydroponic gardens.

Crooking is a problem that causes cucumbers to develop a bend. This is generally not a problem for home growers, as it generally only reduces the aesthetic appeal and shippability of the fruit.

Crooking can be caused by an object such as a training string or leaf or stem interfering with the fruits development or feeding damage from insects such as aphids or thrips. Excessive moisture, High or low temperatures, poor nutrient solution supply, or imbalances of essential mineral elements can also cause crooking.