Hydroponic Culture Peppers (Part 1)
Colored, sweet, bell peppers are an important greenhouse crop. The most common colors are red, orange and yellow (Photo 1). These peppers are green initially and turn the color of the variety as they mature.
Greenhouse peppers are indeterminate or staking in growth similar to tomatoes unlike the field bush varieties. As a result, they must be trained vertically in the greenhouse supported by strings from overhead cables. We use special greenhouse varieties most suitable to greenhouse and hydroponic culture. Peppers are trained very differently from tomatoes and must be maintained to yield to their full potential. We want glossy colored blocky fruit.
The choice of cultivar depends upon your growing conditions and color preference. As with tomatoes, trials should be carried out with different varieties to determine those best adapted to your environmental conditions. Some of the more popular varieties we have found here for our climate and commercial growers prefer include:
Red: Cubico, Mazurka, Fantasy
Orange: Fellini, Narobi, Eagle
Yellow: Samantha, Lesley, Kelvin, Fiesta, Gold Flame, Bachata
For indoor hobby growing you might also consider regular garden varieties that are available in different colors and shapes. These will be bush varieties so you can change the crop more frequently than for the staking varieties that continue to produce for 8 months. You may purchase these seeds from a seed catalog such as Stokes Seeds or Johnny’s Selected Seeds to mention a few. Colored bells that mature within 72 days include: Scarlet King, White King, Purple King, Orange King, Lemon King and Gold King. There are ivory, purple, brown varieties as well. But, they normally change through 2 to 3 colors.
For example, Dove, an ivory variety (Photo 2), is initially ivory (green stage) that will mature through an orange and finally to red. Similarly, with Blue Jay that is initially purple (Photo 3).
The point is that when you harvest them prior to their fully mature red stage, their flavor will not be as sweet. In fact, in the ivory and purple stages of these varieties, the flavor is very bland, but less acidic than the green stage of other varieties. Some other hybrid sweet peppers include: Gold Finch – green/creamy yellow/pale lemon/red. Oriole – dark green maturing to orange; Canary – medium green/yellow; Blackbird – green/brown/black/dark red.
There are other varieties of different shapes and flavor. The sweet Italian Ramshorns are 2-lobed instead of 3 to 4 as are the others. These may be up to 8 inches in length. Several varieties include Sofia (red) and Super Shepherd (red). Of course, then there are the hot types of peppers. A popular greenhouse staking variety is Fireflame. Other field ones include Cayennes-red, yellow; Jalapeno (red); Habanero (green/orange/red) and many more. Please refer to various seed catalogs to select what you like most and determine which ones perform best under your conditions.
Peppers will tolerate higher temperatures than tomatoes or cucumbers. However, their optimum day temperature is 73 F (23 C) to 79 F (26 C) and night temperatures of at least 70 F ( 21 C). For initial fruit setting use 72 F (22 C) day and 65 – 66 F (18 – 19 C) during the night. These are optimum levels recommended for commercial growers. In your home you may not be able to regulate such precise temperatures; however, you will still get good production for your own use. We here at Cuisinart Golf Resort & Spa Hydroponic Farm cannot regulate temperatures precisely due to high RH and temperatures combined. In fact, our night minimum temperature is often between 75 and 80 F with daytime temperatures from 85 to 95 F. We still get good production, but expectedly less than optimum. Try to keep relative humidity about 75%. Light levels of 5500 lux (510 foot candles) for 18 hours per day is sufficient. Carbon dioxide enrichment of 800 to 1000 ppm will promote growth.
Ensure that when you purchase seeds they have been treated for seed borne viruses. Clean all propagation trays, and equipment with trisodium phosphate (TSP) or 10% bleach solution. When handling seedlings it is best to use a 10% skim milk powder (100 grams/liter of water) to clean your hands and any equipment. Germinate the pepper seeds in rockwool cubes, sowing one seed per cube. Be careful to thoroughly soak the cubes with water prior to seeding. After 10 to 12 days when the pepper seedlings have fully expanded cotyledons and the true leaves are beginning to emerge, lay them on their sides as we do for tomatoes (Photo 4).
Space them 28 per tray. Water the seedlings with half-strength nutrient solution as soon as the cotyledons are fully expanded. Keep the pH between 5.5 and 6.0. Keep the temperature of the nutrient solution about 75 to 77 F (24 – 25 C). Once the first true leaves are expanding to at least 1 inch in length you can transplant the seedlings to rockwool blocks. This will be about 7 to 8 days after laying down the seedlings and spacing them in the flats. Be sure to completely water the blocks with a mild nutrient solution (half-strength). Place the blocks in trays in a checkerboard pattern to fit 9 per flat (Photo 5). Within 3 weeks transplant the seedlings into the rockwool slabs or perlite system.
Soak the rockwool slabs for 24 hours prior to transplanting with nutrient solution. Cut the slits in the bottom of the slabs just before transplanting as for the tomatoes. Transplant 4 to 5 plants per slab in the same spacing as for tomatoes. The slabs would be placed in a single row with two support wires above to train in a V-cordon fashion as was done for tomatoes.
If you use bato buckets of perlite, place two plants per bucket. However, several days prior to transplanting soak the perlite with Zerotol to sterilize the substrate. Zerotol is hydrogen dioxide and oxidizing agent, so be careful to use gloves. Use a dilution of 1:100 – 1:50 or 1 – 2 fluid ounces per gallon of water. Apply to the perlite substrate to the point of saturation (runoff). Just before transplanting soak the perlite with PlantShield, a beneficial fungus, at a rate of 1 to 2 tablespoons per 5 gallons of water or 3.5 gm/2 gallons.
Place one irrigation emitter per plant at the outer edge of the rockwool block. Attach the support string to the base of the plant with a plant clip (Photo 6). Remember that the pepper plants will each have two stems so provide sufficient strings for supporting them.
Peppers are the most difficult to train correctly compared to tomatoes or cucumbers. You must always select the side shoot that you need to cut back Permit the peppers to form two main stems (Photo 8).
After transplanting place one plant clip on the lower portion of the plant before it bifurcates. About 4 weeks after planting out, select two of the strongest stems and attach them to the support strings with plant clips (Photo 9).
It is preferred to alternate between winding the string around the stems and using plant clips. This helps to prevent slippage of the plant on the string. This has to be done at least every 2 weeks. A pepper should be allowed to set every two leaves. Prune all side shoots back to two leaves (Photo 10).
If sunscald occurs on the fruit you can prune back to three leaves per shoot to get more shading. Remove the crown flower where the first bifurcation takes place. The first fruit should be left on when there are four leaf axils above the first fork of the plant. Remove the first three side shoots.
It is very important to keep a correct balance between vegetative and generative phases of the plant. You need to be able to “read” the plant. That is to distinguish between vegetative and generative characteristics. Please refer to my book, “Hydroponic Food Production” for more details on these and other points of training. By “reading” the plant you can determine what changes to make in the environment to shift the plant from one phase to another. Three areas of focus include the plant head, leaves, and flowers.
Under high light conditions peppers tend to be generative, so often it is necessary to shift them more vegetative. To do this increase the irrigation cycles to at least 6 cycles per day. The correct balance of fruit is no more than 6 fruit forming per stem and no fruit set within 6 inches of the top of the plant. Increase the EC to shift to generative and decrease it to get more vegetative growth. You can also change the temperatures; raise night temperatures and drop the day temperatures by 1 to 2 degrees to make them more vegetative.
Peppers are not normally lowered as their stems are very brittle and will break easily. However, if you have low ceilings you may have to lower them. When they reach within 6 inches of the wire, lower the plants 6 inches, not a foot as that may break their stems. Lower them more frequently and less amount than what is done for tomatoes.
Remove lower leaves only if they are yellowing or if they get tangled up during lowering of the plants. However, do not remove more than 2 leaves at any time or during any week. Snap leaves with your fingers at the abscission layer (natural breaking zone) near the stem. Avoid cutting them with a pruning shears. Harvest the fruit with a sharp knife, not a pruning shears. They are generally too hard to snap off. Remove any sunscald or blossom-end-rot fruit when it is young and thin the fruit to 6 per stem to get larger size (Photo 11).
As plants approach the support wire and are heavily laden with fruit you can increase the watering cycle to 8 or more per day, but that is dependent upon the number of fruit forming. For your own use pick the fruit when it is 100% ripened as commercial growers will harvest at the 85% ripe stage to facilitate shipping. Storage temperatures below 41 F (5 C) will damage the fruit. Keep the fruit in the refrigerator at high relative humidity for best shelf life.
Pollination reduces the days from fruit set to harvest, increases the percentage of extra large and larger fruit, and decreases the amount of deformed fruit. While commercial greenhouses use bumble bees to pollinate that is not feasible for your indoor system. You can pollinate by vibration similar to tomatoes. Do this during the mid-day or driest period in your environment. Peppers usually set fairly easily unless growing conditions are not favorable, such as poor light or non-optimal temperatures, etc. that we spoke of earlier.
Articles Written by Dr. Haward Resh