Fire & Spice - Growing Hydroponic Chiles
By Dr. Lynette Morgan, Maximum Yield Magazine

Hot chile peppers have become a popular hydroponic crop grown by both hobbyist and commercial growers all over the world. Much of this popularity has arisen from an increasing interest in spicy and strongly flavored ethnic foods, combined with the fact that chiles are one of the most colorful and rewarding crops to produce. While most people recognise the fiery nature of chile peppers, many hydroponic growers of these plants also discover the complex and fascinating flavor profiles that different chile varieties can produce. Chile pepper fruit provide not only heat of varying degrees, but also intensive color, flavor, aroma and texture, making them one of the most versatile small plants for hydroponic systems.

Chile Fire and Flavor
When eaten with certain foods, hot peppers have the effect of stimulating saliva and causing the release of endorphins which creates a sensation of pleasure. Chiles heighten the mouth's sensitivity and as a result the taste buds perceive the food to be more flavorful than it actually is, this is why chiles are often used to spice up otherwise bland and starchy ingredients such as corn and beans. The 'heat' experienced from eating chiles comes mainly from compounds called 'capsaicinoids', although other pungent compounds have recently been identified in hot capsicum fruit. The sweet bell peppers contain very little of these heat producing compounds, although they are similar in regards to their production requirements. Capsaicinoids are extremely concentrated and powerful compounds, and even a drop of a solution of 1 part to a million imparts a fiery kick to the taste buds. Of the five major capsaicioids that have been isolated from chile fruit, each has its own characterized 'bite' sensation in the mouth. Some capsaicinoids produce a numbing effect, some burn in the back of the mouth, some on the centre of the tongue, some burn the lips rather than the tongue and others are extremely painful at first but then leave behind a warm sensation.

Capsaicinoids have no flavor or odor - the ability to sense it depends entirely on the physiological action of the compound (i.e. burning) on the tongue. The pungency or heat factors are caused by the stimulation of pain receptors in the mouth. For this reason, human taste panels were used in 1912 to develop the 'Scoville Organoleptic test' which is still used today to measure the heat of pepper fruit (expressed in Scoville heat units). Sweet bell peppers have zero Scoville heat units, the Anaheim peppers have 1000, while the Jalapeno and Cayenne can range in heat from 2500 to 25 000 heat units.

The pungency of the fruit of any chile plant is influenced greatly by the environmental conditions, with the concentrations of capsaicin increasing with plant stress factors such as drought, high temperatures, high EC and high salinity. This gives a hydroponic grower great scope to influence and manipulate the flavor quality and heat of their chile fruit. Capsaicin concentrations also increase through out the development of the fruit and are always highest at maturity.

Chile Pepper Varieties
Within the capsicum genus there are over 300 different chile peppers grown around the world. Most fall within the Capsicum frutescens or the Capscium annuum species, although others do exist. Chile varieties can range from the mild Hungarian wax to the explosively hot habanero. Habanero chiles, the hottest in the world, come in green, yellow, orange or red and these are used extensively in food preparation in central America and the Caribbean. Congo peppers and Scotch Bonnets are also types of habaneros. The yellow Hungarian wax is a large, fleshy chile with mild to medium heat and a good flavor. Cayenne peppers are long, thin tapering chiles which change from bright green to intense red at maturity these are used in many Asian and Indonesian countries and are also used crushed and powdered in dry form as Cayenne pepper. Jalapeno peppers are small very hot chilies with dark green fruits, turning red at maturity - these are popular peppers in Mexico and California for cooking. Serrano chiles are more popular in Texas and South America to make savory hot pickles and fiery sauces. Thai hot peppers have a distinctly hot flavor and are used in many Asian dishes. Tabasco chiles which are the main ingredient in the famous hot sauce, are used in Creole cooking. Tabasco chiles have a unique hot, dry, smoky taste and a distinctive flavor making them a popular choice for many hydroponic growers. There are many other less commonly grown chile types such as the Bulgarian carrot chile, large hot cherry, Filus blue, fire cracker piquin chile, the strangely shaped peter pepper, variegated chiles, Jamaican hot and rocoto-Manzano chiles to name a few. Most vegetable seed supplies have a good range of hot chiles to chose from and seed mixtures containing a range of different varieties are often a good way to start a chile plant collection and select the best types for a hydroponic garden.

Growing Hydroponic Chiles
Chile pepper plants are easily raised from seed for hydroponic cropping. These are best sown into cells of inert media such as oasis or rockwool, or into small pots for later transplanting into hydroponic systems. Chiles have a high heat requirement for germination - in the range 22 - 28 C, with an optimum of 25 C. At 25 C chile seeds will take about 6 days to show the first signs of germination. Some varieties of chiles are slow to germinate, but this can be overcome by storing freshly harvested chile seeds at 24 C for 2 - 3 weeks before sowing. Slow emergence in chiles can also be prevented by delaying extraction of the seeds from the fruit for 10 days after the fruit have become fully ripe. For example, seeds from the Tabasco pepper can have germination rates increased from 40% to 70% by storage of the seed for three weeks prior to sowing.

After germination, temperatures can be reduced to 20 - 25 C to harden the seedlings off before transplanting into the hydroponic system. Chile plants are fairly temperature dependent, and good vigorous growth will only be achieved under warm conditions with high light levels. Generally night temperatures need to be lower than the day temperature (25 C day/ 18 - 20 C night are ideal), for good plant growth. High night temperatures cause problems with flower and fruit- let drop, although this is largely dependent on the type of chile being grown. Seedlings can be given a half strength (EC 0.8 - 1.0) vegetative nutrient solution from the time of the development of the seedling leaves until a week before planting out. Full strength nutrient (EC of 2.0) should be given to seedlings before planting into the hydroponic system to assist with hardening the plant off. Seedlings raised under artificial lighting only should be exposed to maximum light levels in the week prior to transplanting if possible to give the plants time to adjust before establishment into the hydroponic system. Where chile plants are to be grown under grow lights only, the smaller, more compact varieties have been shown to perform well and make the most efficient use of both light and space.

Most chile plants, like the larger capsicums, are rather slow growing in the early stages (30% slower than tomato plants in fact), but they can be kept growing and producing for many months as a perennial crop if conditions remain warm enough. Chile plants are best pinched or pruned to create a compact bush shape in hydroponic systems which then does not require support or further training. Once the plant has become established in the hydroponic system flowering will occur early on in the plant's life and most chile varieties will produce large numbers of flower buds and fruit. While pollinators such as beneficial insects and bees are not required for fruit set in chiles, the plants do benefit from pollination assistance - tapping or gently shaking the plants when in flower will release pollen and promote fruit set.

Once the chile plants have begun to set the first fruit, the nutrient formula can be gradually changed over to a full strength 'bloom' or 'fruiting' formula to support the development of the fruit. While this is beneficial, many chile plants have been grown on a standard general purpose nutrient formula in mixed systems containing salad greens, herbs and other plants. A good nutrient formula which will support maximum levels of vegetative and fruiting growth in hydroponic chile plants would contain the following levels of nutrients:

Nitrogen 302 ppm, Phosphate 103 ppm, potassium 364 ppm, magnesium 96 ppm, calcium 330 ppm, sulphur 174 ppm, iron 4.90 ppm, manganese 1.97 ppm, zinc 0.25 ppm, Boron 0.70 ppm, Copper 0.07 ppm, molybdate 0.05 ppm.

Most varieties of chile plants will produce large numbers of individual fruits, however the number and size of these depends on the type grown. The large fruited Hungarian wax, obviously will produce less fruit than a cultivar such as 'Thai Hot' which has many small (5-10 mm) fruit. The heat and flavor of hydroponic chile fruit can be influenced by the grower - chiles grown in warmer conditions produce more 'heat' or fiery compounds in the fruit flesh than those grown under cooler conditions. High light also promotes color development in the red and orange varieties (carotenoid pigments) and this increase in color is associated with strong flavor. Chile plants grown with inadequate light will have a more diluted color, flavor and pungency. High levels of potassium are required to produce firm, crisp fruit flesh and also assist to prolong the shelf life of the harvested fruit. Potassium also plays a role in the flavor of the fruit. Running moderately high EC levels in a chile hydroponic system will have a noticeable effect on the fruit, as will maintaining a slight moisture stress in media based or flood and drain systems. Both high EC (above 3.0) and moisture stress, which can be maintained by allowing the media to dry slightly between irrigation's of nutrient solution, have the effect of concentrating the flavor and heat in chile fruit and this technique is well worth the chile connoisseur experimenting with.

Pests and Diseases
Hydroponic chile plants are prone to much the same pests and plant diseases as other hydroponic crops. Whitefly, aphids, caterpillars, mites and thrips can call cause problems on chile plants. Some species of caterpillars will chew large holes into chile fruit, the heat of the fruit flesh does not deter these insects since they don't have the same ability to taste hot compounds as we do. Control of most of these pests can be obtained with the usual pesticide products - Neem oil is particularly effective if used on a regular basis and safe to use on food crops. Soap and oil sprays which smother soft bodied insects are also another safe option for small numbers of plants.

Chiles are also prone to diseases such as damping off (Pythium), Botrytis under conditions of high humidity, fusarium, bacterial leaf spot and soft rot and certain virus diseases Generally growing chile plants in a warm environment and preventing excessive humidity levels (above 90%) will prevent many fungal diseases. Keeping the foliage dry at all times prevents many of the bacterial and fungal pathogens from become established and preventative sprays of sodium bicarbonate and silica products will also give a good degree of disease prevention.

Hydroponic chiles are generally a trouble free and highly rewarding crop to grow. They take up minimal amounts of space and provide the greatest amount of culinary 'heat' per plant than just about any other crop. Chile plants are also highly ornamental with a spectacular range of shapes, sizes and colors making them an essential for any hydroponic garden.

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