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Water spinach: growing, harvesting & benefits
Water spinach is a versatile plant that offers a refreshing change from lettuce and spinach. In Asian cuisine, the vegetable is quite popular.
Water spinach (Ipomoea aquatica) did not get its name by chance: it is cultivated under very humid, often wet conditions. As delicious as it is, achieving a good yield from a UK garden takes some dedication. We explain step by step how to successfully grow water spinach. For die-hard lovers of Asian cuisine, it may be worth the effort, as freshly grown water spinach is hard to come by in Europe.
Contents
Water spinach: origin and properties
Like the sweet potato, water spinach belongs to the genus Ipomoea and the family Convolvulaceae. The vegetable has a few different names depending on the country, such as phak bung in Thailand and kangkong in Indonesia. As the epithet aquatica indicates, in its native habitat, water spinach is found in streams, ponds, rivers and flooded rice fields. Its range spans the tropical and subtropical zones. Nowadays it can be found in many different regions. In our latitudes, however, the herb can only thrive under artificial conditions such as in a greenhouse − it is simply too cold outdoors. In warm climates, the plant is perennial. However, as the plant is not hardy, Ipomoea aquatica‘s life span is limited to one year in locations with colder temperatures. In both cases, the vegetable usually flowers between June and early autumn.
Tip: Water spinach is sometimes called morning glory. This can lead to confusion, however, because many members of the Convolvulaceae family go by the same name. We will introduce you to an ornamental fire vine (Ipomoea lobata), also called Spanish Flag or firecracker vine, in another article.
The marsh plant has thick, hollow stems on which the leaves grow in an alternating pattern. Water spinach leaves can be ovate to lanceolate, and the leaf stalk is arrow- or heart-shaped and tapers to the end of the leaf. All water spinach varieties can be classified into two types depending on their leaf shape and site requirements:
- Green stem water spinach (Ching Quat): narrow, pointed leaves; adapted to moist, wet soil; can thrive in the garden, if it is kept constantly wet; bears white flowers
- White stem water spinach (Pak Quat): grows in an aquatic environment; broad leaves; bears pink flowers
The white to pale purple flowers are bee-friendly and attract butterflies. The funnel-shaped form is also characteristic to many other Convolvulaceae, such as hedge bindweed (Calystegia sepium). Its capsule fruits are ovoid, brown, seven to ten centimetres long and contain dark brown seeds. Whether creeping or floating, water spinach plants are fast-growing and can grow up to three metres long.
How to grow water spinach
Depending on the variety, water spinach is grown in water or soil.
For the most part, the plant can be sown indoors on a windowsill or in a greenhouse all year round. However, if you plan to cultivate your water spinach in the garden, it is best to pre-cultivate at the end of February or beginning of March. It is vital the plant gets plenty of sun. Water spinach also needs to be kept warm and protected from wind. In the UK, these conditions are easiest to provide in a greenhouse. Then, during the cooler months with less daylight, simply use a plant lamp in the greenhouse to make up the difference. For outdoor cultivation, be sure to use insulating boards made of wood or polystyrene to protect your water spinach against the cold. Use troughs as planters for hydroponics, and use raised beds for substrate culture.
As the name suggests, water spinach needs perpetually moist roots. While this is not a problem for water spinach grown with hydroponics, the soil of substrate culture should always be kept moist. Additionally, water spinach seeds need temperatures between 16 and 18 °C to germinate. For water spinach types that need substrate culture, the seeds should be soaked overnight in clear water before sowing them one centimetre deep in the soil.
Water spinach needs a soil high in nutrients. Our peat-free Plantura Organic Enriched Compost is a great match − it can be used both for the pre-cultivation and later in the garden bed. The pre-fertilised substrate ensures a good supply of nutrients and offers Ipomoea aquatica optimal development conditions with its neutral pH value. Keep in mind, as our compost is peat-free (for environment’s sake) and stores somewhat less water, the water spinach will need to be watered somewhat more frequently. In May, the plants can be planted outdoors in a sunny spot. We recommend planting your water spinach in a container or raised bed − this makes it easier to ensure and regulate the moisture levels.
- Perfect for all crops and ornamental plants with a high nutrient requirement & for raised beds
- Improves soil quality & promotes healthy root growth
- Peat-free & organic soil: CO2-saving composition
In hydroponics, the cultivation takes place in water. To get started, you will need a metal net that stretches over your chosen, water-tight container. It is important that the holes in the net are very small. You can either place the seeds on the net immediately, provided they do not fall through, or use already grown cuttings with well-formed roots. Simply place the young plants on the wire − the roots will find their way down to the water and, eventually, the plants will adjust into standing upright.
As an alternative to wire netting, you can grow your water spinach on expanded clay. Get a container with drainage holes, set it on a plant saucer, and fill it with already expanded clay. Plant the water spinach seedlings in the expanded clay and fill the planter partway with water.
The right care
It is important that the water spinach plants are always kept moist or wet. Also, water spinach grows and branches out from its base leaves, so if you wish to have multiple harvest, be sure not to cut off the base leaves when harvesting or pruning your water spinach.
For a rich harvest, fertilise: hydroponics requires a special fertiliser − soil fertilisers are not suitable here. For substrate culture we recommend an organic, nitrogen-rich, liquid fertiliser such as our Plantura Liquid Flower Food. Not only does it stimulate water spinach’s leaf and shoot growth and protect against over fertilisation, but it can be easily applied when watering as well. Apply this type of fertiliser every couple of weeks. Between applications of fertiliser, water with clear water only.
- Perfect for all flowers & balcony plants
- Liquid fertiliser for a lush blossom throughout the season
- Quick & easy application - child & pet friendly
Do not forget: Regularly changing the water in hydroponics is important to inhibit the development of harmful germs.
If you would like to overwinter your water spinach, be sure to cultivate your plants in a container you can easily move. Cut back the water spinach plants and place them indoors or in a greenhouse. It is important that their overwintering location is bright and warm. A temperature of around 20 °C and consistent watering are ideal. Only harvest or fertilise your water spinach in winter if the heating and additional lighting are proving to provide good growing conditions. The containers can be put outside again from mid-May onwards, after the last frosts.
If you only have room to overwinter one water spinach plant, do not despair. In spring, simply take cuttings from it to grow more plants.
Harvesting and preparing water spinach
Under optimal conditions, you can harvest water spinach after four to six weeks. However, in most cases, harvest is later. Apart from the base leaves previously mentioned, everything can be cut off. Radical pruning encourages the plant to sprout and branch. When the side shoots reach a length of about 15 cm, the next pruning can take place.
Water spinach recipes: From the tender stalk to the leaves, every part of the water spinach plant can be used. That said, removing older stems prevents the vegetable from becoming bitter. In Asian cuisine, the mild-tasting water spinach finds a place in salads and wok recipes. Simply fry the water spinach briefly in oil, and serve it with chilli, garlic and/or other sauces. It also pairs well with other vegetables such as onions, tomatoes and mushrooms. Just like leaf spinach, water spinach can also be boiled. In addition, water spinach is often combined with tofu.
Is water spinach healthy?
Water spinach is very low in calories and consists of 90% water. Despite the high water content, this vegetable is nutritious: its dry matter contains about 24 % protein and 48 % carbohydrates. In contrast to household sugar, the human body can only break down and absorb these longer, complex carbohydrate chains slowly. This means that, after consumption, the body’s blood sugar levels remain relatively constant. Subsequently, including more vegetables like water spinach into your diet should help to counteract diseases like diabetes. Lastly, water spinach also contains vitamins C and A − both are beneficial antioxidants that help the body stay healthy.
It is not only water spinach that is considered a healthy and tasty crop. Check out this overview of the healthiest fruit and vegetables.
