Grow kang kong

The scorching heat of summer takes its toll on most of my favourite leafy greens. Parched leaves of silverbeet drop to the ground, begging for mercy, while pak choy and other Asian greens burn – you can almost hear their crackle – and don’t even mention English spinach. But there’s a lovable leafy superhero that saves the day – the wonderful kang kong (Ipomoea aquatica). This tough perennial will nobly replace heat-sensitive greens in soups, salads and stir-fries.

If you’re not immediately familiar with kang kong, and you eat out at Asian restaurants, it’s quite possible you’ve had it before. It’s a common ingredient in many Malaysian, Vietnamese and Thai dishes – countries where it thrives. It has a mild flavour but, like many greens, is very good at taking on the flavours of ginger, garlic, chilli, spices and sauces. The best news is, it takes very little effort to grow and it’s a prolific producer.

How to grow kang kong

You don’t need potted plants, seeds or seedlings to get a crop of kang kong up and running. All you need is a bunch of kang kong, which you can buy from farmers’ markets or Asian grocers at this time of year. Cook up most of the bunch, but keep a few stems for propagation. Put these straight into a small container of water, and within a few days they will start forming roots.

As its species name (aquatica) suggests, kang kong likes to grow where there is plenty of water. It’s also known as water spinach, swamp cabbage and Chinese watercress. It thrives in boggy soils, and grows very well on the edge of ponds. One strong word of warning though – it grows like mad in the heat, and can take over, much like its close relatives sweet potato (I. batatas) and morning glory, the well-known bushland weed.

The kang kong vine has hollow stems that float, so it quickly chokes up the surface of a pond, and it drops roots at the nodes or leaf joints wherever they touch moist ground. So grow it in a container where you can keep an eye on it, and close to the kitchen, where you are likely to step out and harvest it often.

Closed containers are best (that’s right, no drainage holes!), because they allow you to create the kind of boggy conditions this plant likes. Fill your container with potting mix or compost to about 5cm from the top, then plant your cuttings and fill it with water until the level is just above the surface of the mix. Keep the container in semi-shade for a few days to allow more roots to develop. You could leave it there – it grows well in semi-shade – or move it into full sun. 

You can start harvesting in a few weeks – it’s hard to think of another crop that provides such a quick and trouble-free return. Cut stems back hard to just a few nodes above the surface. In the peak of summer, one 9L bucket with five cuttings can easily provide a weekly harvest of shoots for a stir-fry, if not more.

Plant care

Give the container a little top-up of water when needed. The plant won’t need much fertilising, because nutrients can’t leach away. If the leaves look pale, sprinkle with organic fertiliser, or water in some diluted liquid seaweed and fish emulsion. Don’t worry about pests and diseases – nothing much seems to bother them if you follow that basic care and harvest regularly.

Kang kong will grow all year in tropical climates, but dies back everywhere else as the weather cools. Keep your container in a warm, protected spot over winter; it often reshoots in spring. The old pot will be pretty full of roots and a little bit tired, so use these spring shoots to start a new container.

Header image credit: iStock

Want to learn more about kang kong?

Kang kong