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Hobby Greenhouse Product

Posted by Jim Brown, Horticulturist on 5/16/2008

Cucumbers can be grown in the hobby hydroponic greenhouse with considerable ease. That is, of course, if the proper allowances for their rapid growth and production are planned before the crop is seeded. Hydroponic cucumbers require quite a bit of greenhouse space for proper growth. Under good growth conditions cucumbers can produce a fair number of cucumbers per week. Therefore, a bit of advanced planning in relation to the use or selling of the hydroponic cucumbers produced, before the seeds are planted, is suggested. A little planning and calculating ahead may direct you to go a little easier on the number of plants started, at least the first time.

Cucumbers make up a much larger part of the diet of people in countries outside the United States. Many people in the U.S. like cucumbers, however, and may find that they eat more of them if they have their own fresh supply.

Greenhouse Cucumbers

Seedless cucumbers are the most popular type grown in the greenhouse. The 14 to 18-in. European Seedless Cucumber is the best-known type of greenhouse cucumber. It has been marketed in many grocery markets within the U.S. for more than 20 years. The Beta Alpha or Mini cucumber is newer in the market and gaining popularity. It is also seedless but is more moderate in length. It generally ranges from 5 to 7 in. in length.

Seedless cucumbers are sometimes referred to as burpless cucumbers. The seeds in garden or field cucumbers are the source of the gas generation in the digestive system of most people who have problems when they eat cucumbers. If you avoid cucumbers for this reason, buy a seedless cucumber in the market and give it a try. You might like it and, in turn, it might like you and not give you any trouble. Test the theory before growing your own cucumbers in your greenhouse.

Seedless Cucumbers

No pollination is needed for seedless cucumbers, which makes them a good choice for greenhouse production. The plants have been bred and selected to have no ability to produce male flowers but produce female flowers that develop into fruit without being pollinated. The flavor of the fruit is similar to that of garden cucumbers. Seedless cucumbers virtually never have a strong or bitter flavor. They even seem to be slightly sweet.

Don’t grow any garden or field cucumbers in the greenhouse with seedless cucumbers. They have male flowers with pollen and could possibly cross-pollinate the seedless female flowers. Cross-pollination will then create seeds, changing the growth and flavor of the fruit. When seeds are set they may be inedible.

Growing seedless cucumbers outside is also not to be done. Pollen will probably be brought in from some place in the vicinity by bees or other pollinators, and your cucumbers will end up with some seeds and not be edible.

Greenhouse Cucumber Production Systems

Cucumber plants can be grown in the greenhouse in media like Sure to Grow, rockwool, or perlite. They seem to do better in a compatible medium than in a straight solution culture of NFT (Nutrient Film Technique). A bucket or slab system could be used with one of the media mentioned. Each system has its advantages and limitations. Much depends on your setup in the greenhouse and the flexibility of the greenhouse. Cucumbers are pictured growing in lay-flat perlite-filled bags and perlite-filled Dutch buckets.

The fertilizer used for cucumber production can be the same as for your tomato plants if you are also growing tomatoes. If you were growing several hundred cucumber plants in a commercial setup, the fertilizer plan would be adjusted for better production. For simplicity, a tomato fertilizer program is very satisfactory for cucumber plant growth and production on a small scale.

Greenhouse Environmental Conditions

Conditions in the greenhouse need to be within range for cucumber plants or they just don’t grow and produce. Night temperatures need to be kept up to a minimum of about 66 F for cucumbers to do well. If the night temperature gets down into the low 60s F each night, the plant growth and production rate will be drastically reduced. If the temperature gets a couple of degrees below the target a night or two when the outside temperature is the coldest, the plants will be slowed for a few days. But they should grow and produce as long as the temperature is kept up most of the time.

Cucumber plants like it a little warmer than tomato plants do. Some places in the greenhouse are usually warmer than other places. Keep this in mind when laying out the plant design for your greenhouse. Put the hydroponic cucumbers and other members of the gourd family in the warmer places of the greenhouse.

The greenhouse’s relative humidity should be watched and controlled. In the winter the relative humidity in the greenhouse can drop to where the cucumber plants do not grow properly. Because outside temperatures are low, the air has little moisture in it and becomes dry when it is brought into the greenhouse and warmed. An open pan of water may need to be put into the greenhouse when the relative humidity is below 50 percent.

If the air in the greenhouse is too dry, the plants will pump water up into their foliage and release it into the air at the expense of proper leaf growth. The cells of the leaf may not expand properly because the moisture sent to them is lost to the dry air in the greenhouse. Leaves affected this way will be small and puckered. They will not be capable of normal photosynthesis. The plant growth will, therefore, be restricted.

High relative humidity levels are not good either. Fungus spores need high relative humidity or free water on the plant tissue to germinate, grow, and gain entry to the plant tissue. During the warmer part of the year, and especially when the seasons are changing in the spring and fall, there can be wide swings in the relative humidity. Periods of time, several hours in length, during which the relative humidity is high can leave the plants at a higher risk for fungus disease infection. You need to manage the relative humidity more intensely when there are wider swings in the temperature.

Cucumbers have a high demand for light. They cannot be very successfully grown in or through the November through January time period in the U.S. without supplemental light. When the light levels drop, the plant growth slows and the fruit growth and development basically stops. Artificial light can be used to supplement the light needed by the plants during the low-light period.

Seeding

Within a couple of days of cucumber seed sowing, the plants should be germinated. Temperature, moisture conditions, and seed position in the medium are all important.

When media like Sure to Grow and rockwool are used for starting cucumber seeds, it is important to put the seed into the medium so that the end of the seed from which the root will emerge is down. Although media like peat-based media mixes, perlite, and coco coir will give enough to let the emerging seedling pull the cotyledons up out of it, Sure to Grow and rockwool have a bonded structure that does not readily allow that process to occur.

The root of the germinating seed comes out the same end of the seed that was attached to the conductive tissue of the fruit in which it developed. That end should go down in the hole in the bonded medium. That way the seed coat and cotyledons will be pushed up as the root elongates. The seed coat may need to be picked off the cotyledons to free them.

If the cucumber seed is put into the medium so that the root comes out the upper end of the seed, the root will turn and grow down in response to gravity. Once the root is anchored in the medium, the crook will start to straighten to pull the seed coat and cotyledons up out of the medium. A loose medium like perlite or coco coir will give and let that happen. A bonded medium like Sure to Grow or rockwool will offer considerable resistance. A young plant could become strangled in the seed hole or the crook could break, leading to the death of the plant.

Once germinated, the young cucumber plants grow very rapidly as long as the environmental conditions are favorable. Within a week to 10 days of the time the cotyledons are spread you will want to have the final greenhouse growing space ready to be occupied by the plant. Flower blossoms should be removed up to the 10th leaf. This is required to allow the plant to develop vegetatively before being loaded down with fruit.

Cucumber plants will produce for three to four months once they start. It takes four to six weeks from seed sowing to get the first cucumber ready to pick. You can keep yourself supplied with your own fresh cucumbers by starting new plants before the old plants are removed. You have to allocate the space to do that in the planning stages.

Plant Training

Although there are many ways to train cucumber plants, we will only consider one with a few variations. The main idea is to get the plant growing vertically. That requires support, because the stem will not support the weight of the plant in the vertical position. Hang a piece of vine twine from a support wire or a part of the greenhouse support system. The vine twine can be tied in place, because it will not be moved during the growth of the plant.

Clips are placed on the vine twine and around the plant stem just below a leaf. In this way the plant is supported in the vertical position. Twist ties can be used if you don’t have vine clips. The twist tie should be first wrapped all the way around the vine twine so that it will not slide down the twine. Then the two ends of the twist tie are twisted together around the stem of the cucumber plant just below a leaf. The tie does not need to be tight around the stem; it is better if it is a little loose. Clips or twist ties should be placed every 10 to 12 in. up the stem of the plant.

Suckers and tendrils should be removed shortly after they appear. A sucker is a branch or lateral. We don’t want to let them grow when the plant is young. We will train the plant to one stem until it reaches the support wire or structure. The tendril is usually right beside the sucker at the node on the plant stem. The tendril is the plant’s natural support appendage. We remove them because they will wrap around anything, including a cucumber occasionally.

When the plants grow up to the support where the vine twine is attached, let it grow horizontally for a couple of feet before removing the growing point. Keep two of the suckers or laterals that come out from the horizontal portion of the stem. Let them hang down and grow. As cucumbers set on them they will be pulled down. When they hang down on the same side of the main stem it is easier to tell, at a glance, what belongs to what plant when you have a number of plants growing in your system. Let the first sucker grow on each lateral to replace it. When a lateral grows down to within 2 ft. of the floor, the growing point should be removed. Once all the cucumbers are picked off, it is removed back to its first sucker, which is growing to replace it on the plant.

English or European cucumbers will produce one cucumber per node. If more than one flower is produced at a node on a continuous basis, the temperatures are getting too cool for the proper growth of the plant. Beta Alpha or Mini cucumbers will produce more than one flower at a node as a regular practice. They will produce a new flower at a node after a cucumber has been picked from that node. As a result, the training of the plant does not get as far with the Beta Alpha cucumbers as with the European cucumbers. The plants do not grow as fast, because of the continued production of fruit on the older tissue.

Picking Cucumbers

When should the cucumber fruit be picked? This is the first question to be answered. The fruit usually have ribs that run their length. They usually elongate to almost their final length and then start filling out in diameter. The fruit should be picked before the ribs smooth out by the filling out of the diameter of the fruit.

The cucumber fruit can be cut from the vine with pruning sheers or it can be removed by lifting the fruit so that the blossom end points straight up into the air. This will cause the fruit stem to separate from the plant. The short stem can then be cut off, if you like. The fruit should not be removed by taking hold of it and twisting it. This can damage the stem end of the fruit.

Picked cucumbers should not be refrigerated. They should be stored at 55 to 65 F. European cucumbers should be wrapped with plastic stretch wrap to keep them from losing moisture and becoming rubbery. This should be done within an hour or so of their being picked. The Beta Alpha cucumbers have skin that, although still edible, does not allow the loss of moisture as rapidly. They can be kept for a couple of days without being wrapped, or they can be stored in a closed plastic bag.

Summary

The guidelines above should help you successfully include cucumbers in your hobby greenhouse along with the other plants you are growing. As you can see, they are fairly easy to incorporate into your program as long as you allocate enough space for them. Setting aside enough space for a plant that starts so small and so quickly becomes so large can be a challenge. But being able to top off your salad with some cucumber slices from your own greenhouse has nutritional and psychological rewards that are well worth the effort expended.

 

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