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As we all do what we can to keep the pandemic at bay, one of the most personal things we can do is to keep ourselves as healthy as possible to boost our immunity. Boosting our immunity can be done through regular exercise but also by ensuring we are eating the freshest, most nutritionally-rich foods possible. The US’ CDC categorises 41 foods as ‘Powerhouse fruits and vegetables’ - those foods deemed to be the most strongly associated with reducing chronic disease by offering 10% or more of 17 qualifying nutrients per every 100 kcal of energy.
Four of the top ‘Powerhouse’ foods listed; watercress, chard, beetroot greens and spinach, all have a nutrient density score of 86% or more (watercress has a score of 100%) and are all vegetables you can easily grow now in a Greenhouse. Historic Glasshouse and Greenhouse manufacturer Hartley Botanic has been helping gardeners to ‘grow their own’ under glass for over 82 years. Here they share their essential tips for growing the most nutritionally dense, fresh vegetables.
Firstly, ‘grow your own’ powerhouse vegetables…
Growing your own is arguably the best way to access the healthiest fruit and vegetables, and using a Greenhouse you can do this all year round. Growing your own allows you to control exactly what sort of fertilisers or pest control measures are used, and it also means you can eat your food, the same day it is harvested. Numerous studies have shown that there is a connection between time after harvest and nutritional value lost. A University of California study showed that vegetables can lose 15 to 55 percent of vitamin C within the first week after they are picked. Similar studies have also revealed prepared, pre-packed fruit and vegetables have lower nutritional values.
1: Watercress - ‘powerhouse’ nutrient density score: 100 percent
Once considered a weed, watercress is part of the Brassicaceae family and packs an impressive nutritional punch - particularly vitamin K which is necessary for blood clotting and healthy bones. It is also a good source of vitamin C and antioxidants which may lower the risk of chronic diseases and cancer.
Watercress can be grown in a Glasshouse or Greenhouse all year round - albeit more slowly in mid-winter. This nutrition-packed crop doesn’t need to be grown under running water, it will grow well in pots or trays of compost which are kept moist. Pots must be kept continually moist and this can be done by standing them on capillary matting or in very shallow saucers of water. Change water regularly to keep it clean and oxygenated. Watercress can be started from seed or you can get perfectly good cuttings from watercress bought in the shops (you can even use microgreens). If you are using cuttings, insert each into wet compost, sharp sand or even just water. They will soon grow roots and then you will be ready to plant. When your plants start to run to seed, divide them up and start again.
2. Chard (or Swiss Chard) - ‘powerhouse’ nutrient density score: 87.27 percent
Despite its name, Swiss Chard originates from the Mediterranean. Like Chinese cabbage, chard is an excellent source of vitamin K. It is also high in antioxidants, including beta-carotene and flavonoids, which fight free radicals and may protect against disease. It is also loaded with fibre.
The growing process for chard is similar to spinach - although much easier. Chard needs a sunny spot in your Greenhouse and should be sown in moisture-retentive, free-draining soil. Sow in multi-cell trays around 2.5cm deep. The soil should be damp enough to encourage germination, not dry or cold and waterlogged, the seedbed firm and free of weeds and stones. In terms of temperature, a good rule of thumb is to be sure the soil is at least 50 F (10 C), which is warm enough for the seeds to germinate. A soil thermometer takes the risk out of sowing. Harvest your chard when crops are still young, don’t wait until they reach maximum size as the leaves will be less tender.
3. Beetroot greens - ‘powerhouse’ nutrient density score: 87.08 percent
Beetroot greens are the green leaves of the beetroot plant. Historically, they were used for their amazing healing properties as Hippocrates believed that the juice from beet leaf bindings would help heal wounds. They are bursting with vitamins and minerals including vitamin C, known to be a natural immunity booster, vitamin A for healthy skin and eyes and vitamin K. They are also rich in copper, manganese, iron, calcium and they are a good source of fibre. Their health benefits may help boost immunity, lower blood pressure, improve mental health and strengthen bones.
Beetroot is a versatile vegetable and can withstand cooler, and sometimes even freezing, temperatures although it is best to ensure soil temperature doesn’t fall below 7C (44F.) Beetroot can be sown in multi-cell trays or sown outside 5cm (2in) apart in rows 23cm (9in) apart. If growing a multi-germ type be prepared to thin seedlings. When the seedlings are large enough to handle easily, thin them out. If growing a multi-germ variety, thin the clumps to one seedling per station where wanted for roots. Thinning is less important if the plants are to be harvested as a salad leaf alone. Allow 10cm (4in) between roots for beetroot intended for salads or cooking. Water thoroughly, especially when the roots begin to swell. If you decide to plant them out, do it when the soil is sufficiently warm, hardening them off thoroughly beforehand by placing in a cold frame for a week or two prior to planting. Make sure plants are planted into their final positions before the roots start to coil around the compost in the cell and take care to disturb them as little as possible. Beetroot should be ready to harvest within about 12 weeks in the case of round-rooted varieties and 16 weeks in the case of the long-rooted types.
Harvesting - Lift grown beetroot carefully - long-rooted varieties will need a fork underneath them to aid lifting without damage since any bruises or cuts will bleed, draining the colour from the roots as they are cooked. To remove the leaves grasp them firmly above the root and twist with the other hand to prevent damage to the top of the root, again to prevent bleeding during cooking.
4. Spinach - ‘powerhouse’ nutrient density score: 86.43 percent
Spinach is well known for its nutritional qualities and has always been regarded as a plant with remarkable abilities to restore energy, increase vitality and improve the quality of the blood. There are sound reasons why spinach would produce such results, primarily the fact that it is rich in iron. Spinach is also an excellent source of vitamin K, vitamin A, vitamin C and folate as well as being a good source of manganese, magnesium, iron and vitamin B2.
First of all, choose the type and variety of spinach you would like to grow. Spinach comes in three main types; savoy, smooth leaf and semi-savoy. Spinach usually grows well in cooler temperatures so if you are planning to start sowing now, choose bolt-resistant varieties. Spinach likes well-drained soil which is neutral PH. It responds well to being fed so make sure the soil is rich with compost.
When sowing, space out the seeds well so they don’t compete. Each new spinach leaf can be carefully harvested with a sharp cuttings knife or secateurs; this gentle harvest pruning seems to encourage more leaves as long as you are not too eager and don’t damage the centre or cut off too many too soon. While wilted spinach disappears into tiny, tiny morsels, there’s something quite tactile about fresh and raw baby spinach leaves carefully extricated from the mother plants. Each perfect, heart shaped leaf has texture, substance and flavour left raw on the plate.
For more Greenhouse gardening help and advice, Hartley Botanic's online magazine offers a wealth of information.