Salty, savory, and satisfying… who doesn’t love snacks? Some of the best are not only homemade but homegrown as well. Common snack-producing plants such as sunflowers, peanuts, pepitas, and pickles can all be grown hydroponically and thrive in warm, protected environments. Some, such as pickle gherkins (a variety of mini cucumber), are well known as hydroponic crops, whereas pepitas and peanuts are a little more unusual but worth the effort to obtain a highly flavorful snack-food harvest.
Pepitas, also known as pumpkin seeds, are not only considered a health food due to a high content of protein (30 per cent), good fats, fiber, zinc, niacin, iron, and magnesium, but once roasted and salted are a crunchy and delicious snack. Growing and preparing pepitas is not difficult provided the correct cultivars are selected to start with.
Edible pumpkin kernels are only produced by particular varieties that develop dark green hull-less seeds inside the fruit’s seed cavity. This means there is no tough outer seed covering to remove to get to the edible kernel. Hull-less varieties are also called oil seed types as the edible kernels can be pressed to extract a high-quality oil with a number of culinary uses.
Once the pumpkin has been grown to maturity, the fruit are split open to reveal masses of hull-less kernels that only need to be scooped out, soaked, and rinsed to remove any remaining pumpkin flesh, then dried for storage. Many seed companies stock both modern hybrid and older heirloom hull-less pumpkin seed varieties for pepita or oil seed production, however, a good choice for hydroponics is Naked Bear F1 or Kakai.
Growing pepitas in hydroponics is similar to any other fruiting crop — the main requirements are warmth (64-79°F), high light levels similar to tomatoes and cucumbers, and sufficient space. Like melons, pumpkins can be trained upwards to maximize space in an indoor garden provided the heavy fruit are supported as they develop, or they can be left to trail along the floor.
Each plant should provide multiple pumpkins, depending on how long the vine is permitted to develop. EC levels for pepitas are similar to cucumber crops and these are easily grown alongside each other in the same system. An EC of 1.8-2.4 and pH of 5.8–6.0 with extra potassium provided during the fruit development stage is ideal. Substrate systems with good sized root volume such as the Bato bucket system suit pepitas and the crop responds well to a moisture-retentive substrate such as coconut fiber.
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Peanuts are a small, compact legume plant that performs well in hydroponics provided the correct conditions and substrate is provided. Peanuts are easily started from seed and there are a number of interesting and potentially gourmet-flavored types that smaller growers can experiment with to obtain the ultimate snack crop.
Of the commercially grown peanut types there are four main groups: Virginia (largest seeds), Runner (used for peanut butter), Spanish (smaller seeds for snacking), and Valencia (bright red with a sweeter flavor that performs particularly well in hydroponics). There are also a number of heirloom and speciality types available from some seed companies.
To obtain peanut planting stock, purchase raw seed that is still contained in its outer husk or pod, as this prevents drying out, and shell these just before planting out. Large, plump, raw (non-heat treated) peanuts, free of any signs of deformity or rot, are best selected for seed and germinated on a heat pad or at 72-84°F. The essential step with growing peanuts is to surface sterilize any nuts used as seed or treat with fungicide powder as these are prone to fungal attack during the germination stage and “damping off” disease as young seedlings.
The peanut plant produces its pods on the ends of pegs — long stems that develop from the aerial portion of the plant after flowering and self-pollination — then burrow down under the growing media to develop the young fruit (peanut seeds inside brown pods). For this reason, hydroponic systems for peanut plant production need to have substrate that is soft, friable, and light with the surface under the plant exposed for the pegs to grow down into. Finer grades of sterilized coconut fiber or blended coconut fiber and perlite make ideal substrates for this crop.
Peanut plants need a warm growing environment with reasonably high light levels for maximum growth, and good air flow up and under the crop as damp conditions favor fungal pathogen development. A well-grown peanut plant can have up to 40 pods, so a growing container or bed that holds at least two gallons of media is required when growing hydroponically. A standard vegetative nutrient formulation followed by a higher potassium fruiting formulation during the pod development phase at an EC of 1.2–1.6 is ideal under good growing conditions.
Outdoor peanuts are harvested when the foliage begins to turn yellow and die back, however, in a hydroponic system it is possible to dig back some of the growing substrate, observe the development of the young pods, and determine when the peanuts are large enough to harvest. Harvested peanuts then need to be dried inside the pods in a warm place for about four weeks before they can be stored.
The small pickle cucumber, or gherkin, is a more compact plant than the seedless European cucumbers commonly grown hydroponically and produces large numbers of crisp, seedless, and mild fruit that can be eaten fresh or processed in a spiced pickling solution to make an addictive snack. There is a wide selection of gherkin seed to select from, including varieties of green- and white-skinned types, however, the main characteristics to consider with hydroponic crops are compact plant size, wide disease resistance (particularly to mildew), parthenocarpic plants (fruit set without the need for pollination and with no seeds inside), size, and shape.
Pickling cucumbers need sufficient warmth (60-82°F), moderate to high light levels, and can be intercropped with tomatoes, capsicum, and other heat-loving crops. Since gherkin plants are smaller than other cucumbers, they can be grown two to three plants per planting space and trained upwards and along strings for wires.
Nutrient solutions should begin on a standard vegetative formulation at a moderate EC of 1.8–2.2 and pH of 5.8. This should then be switched for a fruiting formulation with higher potassium levels for maintenance of good fruit quality as soon as the first tiny fruitlets have formed, and maintained until the crop is finished. Under hot growing conditions, the EC can be dropped back slightly, particularly if the plants are wilting under overhead lights.
Cucumber vines are largely indeterminate, so they need to be carefully trimmed and trained to prevent them taking over the entire growing area; growth can be directed upwards to an overhead support and then downwards again so the maximum number of fruit can be obtained from a minimum of vertical space.
The small fruit only take a few days to develop to a suitable pickle size once flowering has occurred and need to be harvested frequently. Fruit can then be stored in the refrigerator until enough have been gathered to make the jars of pickles. Some keen pickle makers also grow various hydroponic herbs and spices to add to their jars of pickles for additional flavor, the most common being dill for the famous dill pickle flavor. However, hot chilies, lime leaves, basil, tarragon, and garlic can all be used added to the pickle liquid to give a unique flavor.
Sunflower kernels are another popular snack that can be eaten raw or roasted and salted, and have the advantage of also producing an attractive bloom to brighten up any growing space. Sunflower seeds may also be germinated and eaten raw as sprouts. As with pepitas, cultivar selection is vital and choosing a variety with extra large, easy-to-crack seeds will make snack preparation much easier on the fingers. Varieties such as super snack hybrid have been developed for edible kernel production and produce plants that are not overly tall.
Sunflowers, like other snack crops, prefer a warm, high light environment and will grow rapidly at 72-88°F. Plants generally don’t need support and are best grown in small groups to maximize space. Sunflowers have a strong root system, large leaves, and require high volumes of water, so are best grown in a moisture retentive substrate with frequent irrigation. EC levels in the range 1.8–2.0 with a pH of 6.0 are ideal.
Once the flowers form, they should be left on the plant for several weeks to allow the seeds to develop in the centre of head, once this has occurred the stem can be cut and the flower hung upside down to further dry before the seeds are removed for hulling.
Hydroponic snack crops provide some exciting opportunities to expand the options of home-grown produce and provide some truly unique taste sensations. Most of these crops are fairly similar to commonly grown hydroponic produce, so don’t need a lot of extra care or modifications, but do provide something just a little bit different to experiment with.