Self-Watering Plants
At this time of year, my thoughts always turn towards edible water plants. A British summer guarantees one of two things – plants that have been parched by long periods of dry weather, or plants with waterlogged roots from a complete absence of dry weather. I figure that water plants, safe in their ponds, would probably cope with either extreme!
An obvious choice is water mint (Mentha aquatica), which is as easy to grow as any other mint, but likes keeping its feet wet. Tasty, scented and with pretty flowers that will attract beneficial insects, it can really justify its place in the pond. It is closer in flavour to peppermint than spearmint, and its leaves can be used to brew a herbal tea. And I keep meaning to try growing Ipomoea aquatica, an edible Morning Glory that’s related to both bindweed and sweet potatoes. It will be quite happy in the pond during the summer, although (unlike the mint) it won’t be hardy. In southeast Asia the leaves are widely used in a similar way to spinach, and called kangkong. Like watercress, kangkong can transmit a parasite to humans if it is harvested from contaminated areas, but at home in your pond this is nothing to worry about.
Some of the species that have struggled in my garden over this dry summer would love a spot on the edge of the pond, doing the plant equivalent of dipping their toes into the water. My Vietnamese coriander (Persicaria odorata) has proved very difficult to keep happy, frequently wilting between waterings, even in the shade. It turns out it is phenomenally thirsty, and I finally found the key to keeping it alive is a pot with a built-in water reservoir. As long as it doesn’t get missed out when I do the watering, it’s now fine for several days at a time. When it’s happy, it’s a pretty plant, its green pointed leaves livened up with a charismatic purple chevron.
The Chameleon plant (Houttuynia cordata) has an even greater water requirement. Although it is supposed to be happy when planted in a bed, in a container it needs a constant supply of water and I have popped mine in a bucket – in effect it has its own, personal pond. It’s probably the best way to keep it under control, as left to its own devices it can spread a little too enthusiastically. With its strikingly colourful leaves, Houttuynia is frequently grown as an ornamental plant. If bought as such it won’t be safe to nibble on the leaves until it has ‘detoxed’ for a season in the your garden – ornamental plants can be sprayed with chemicals that aren’t safe to use on food crops, but fresh growth next year will be good to eat. Unlike the Vietnamese coriander, Houttuynia will flower, and so would make a very decorative choice for your pond.
My wasabi (Wasabia japonica) would also probably be happier on the edge of a pond. In Japan it is grown in flowing streams, in much the same way watercress (Nasturtium officinale) is grown in the UK. It can be happy in a pot, with a regular supply of water, but it needs a shady spot. It rapidly fades even in the insipid English sun. And, of course, you could have watercress in your pond. It, too, can be kept happy in a damp pot, but you just know it longs for the clear, flowing waters of the chalk streams it hails from.
There are other edibles that can be planted in a pond, or along its margins, but many of them are a little too large for the average garden. Space for a lotus might be nice, but water chestnuts are a more realistic option. Chinese water chestnuts are Eleocharis dulcis and can be grown as a pond plant or bog plant (if you can get hold of some live ones to plant). The water caltrop, Trapa natans, can be grown as a water chestnut substitute, and is a pond plant happy in water up to 2 feet (60 cm) deep. It may be an easier species to source.
Sagittaria sagittifolia, arrowhead, is an edible water plant with a Hollywood connection – one of its common names is Katniss, and it is this plant from which the leading lady in the Hunger Games books and films takes her name. Edible, starchy tubers are found at base of the plant as it dies back in the autumn, and a little digging around in the mud gets you a harvest that can be roasted like potatoes.
I think there are far more intriguing, edible species than I could safely squeeze into my pond, so perhaps it’s best that it is merely a fantasy – for now. Maybe next year I’ll finally get around to building it into the garden, so I can sit back and dabble my feet during the hot days of summer, and leave behind the stress of watering the garden!
Emma Cooper is an author and ethnobotanist, based in Oxfordshire. Her blog, at emmacooper.org, records a mixture of her gardening exploits and experiments, her general excitement about plants, and her love of eating them.