CUCUMBER CONUNDRUMS
For a fast-growing , high-yielding crop , you can ’ t go wrong with hydroponic cucumbers . These slender , green salad essentials produce a greater weight of fruit per unit area than peppers , tomatoes , or just about any other hydroponic crop when grown under optimal conditions . For those of us who are a little impatient , cucumbers are a satisfying plant that can fill an indoor garden within a short period and have young fruit hanging from the vine long before other plants have even managed to start flowering . While the crop ’ s growth and size may be rapid and impressive , cucumbers are not without their baffling problems . Thankfully , though , many of these issues are easily solved or prevented with a few basic steps and an understanding of the sensitivities of this popular crop .
GENETICS
Many of the common cucumber problems experienced by indoor gardeners can be prevented with the correct genetics . There are a range of different cultivars , but those most suited to indoor gardens are greenhouse hybrids that have been bred for productivity , fruit quality , and disease resistance . A resistance to common diseases like powdery mildew is particularly important . That ’ s because older , open-pollinated types of cucumber varieties are still extremely susceptible to developing mildew , even at a relatively early stage of growth .
EC LEVELS
Due to their rapid growth rate and large leaf surface area , cucumbers place a high demand on their hydroponic system , nutrient solution , and growing environment . They also have specific sensitivities that require a little more control and monitoring of the nutrient solution and root zone than many other crops .
An extremely common problem with first-time cucumber growers is the development of leaf yellow halo , which is a thin band of yellow coloring around the leaf margin . Typically , this will develop on cucumbers while all the other plants in the same hydroponic system are uniformly green and healthy looking . The leaf halo effect is caused by EC levels that have become too high for the plant in the recirculating nutrient solution or in the substrate . These high levels may also cause cucumbers to develop slightly drooping leaves . High EC levels can be caused by nutrient accumulation and salt buildup in some growing mediums , such as coco . These problems commonly occur under warm growing conditions where moisture evaporates from the surface of the substrate and a plant ’ s uptake of water exceeds its absorption of nutrient ions . High EC levels are also found in mixed cropping systems where EC levels are typically run higher to boost fruit flavor and compositional quality in salt-tolerant plants , such as tomatoes . Dropping EC levels back and leaching excess salts from the growing medium usually alleviates they symptoms of yellow halo and drooping leaves . The ideal EC levels for cucumbers are 1.7-2.0 during fruiting . When checking levels , however , keep in mind that EC should always be measured in the leachate ( solution draining form the root zone ); in substrates , the EC in the root zone may be higher than that in the feed nutrient solution .
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CUCUMBERS need a good-quality water supply that doesn ’ t contain high sodium chloride
( common salt ) levels .”
Cucumbers are sensitive to EC and can develop the yellow halo effect if levels are run too high .
A cucumber leaf covered by mildew .
Mites create fine webbing and foliar damage in cucumbers under dry , low humidity conditions .
Cucumbers can be grown in NFT , but be sure to check nutrient levels often .
134 Maximum Yield USA | December 2016