Nasturtium officianale – Cultivation and Use
Geoff Aston

This is a native marginal, which has almost insignificant flowers but attractive and useful leaves. Naturally, it grows best in shallow, slightly alkaline flowing water. It is under fairly large scale commercial cultivation, but is not seen very often in gardens.

In a recent edition of Gardeners’ Question Time, Bob Flowerdew noted that although it can be grown in very wet soil/still water, it grows best in flowing water.

This gave me an idea to explore, as we do enjoy this plant on our plates and in sandwiches and soup -it is of course, watercress.
So far, we have stage 1 of our cress farm in production. This has proved the point but it is small and has only provided limited crops -yes, in some cases, bigger is better.

What I did was to use a spare cold water storage tank (central heating header tank size) and with a piece of aluminium angle, arrange for a non-perforated plant tray to lie on the top, inclined at about 5 degrees to the horizontal. Near the lower end of this tray, a hole was drilled through the base, and a piece of tube fitted tightly into this, the top being about 2 cm above the base of the tray. A small water feature pump was then installed to circulate water from the water tank to the top of the tray, thus maintaining a shallow depth and a flow down the tray as it drained through the pipe back to the water tank.

A layer of fine gravel was put into the tray.

A bunch of watercress was then purchased and some of the stems placed in a glass of water. After a few days, the leaves on these were dying off, but new leaves were forming and most importantly, roots were being produced from the nodes. These stems were then laid horizontally in the gravel and we stood back to await developments.

The leaves grew, and we used some of them and some side stems, then the plants began to flower and fade away. I cut off all the less happy looking bits and subsequently, stronger growth was produced, albeit with smallish leaves, and not as green as I would like, although edible and used for occasional garnish. On the positive side, it has been growing without attention apart from topping up the water, the occasional feed, and harvesting, for two or three months.

It clearly needs a high nitrogen feed, and probably a bit of lime in the water. Tomato feed has been tried (as it was handy), but has not been fully successful. So far it has been on the greenhouse bench (to access the electricity for the pump). It has probably therefore experienced higher temperatures than desirable, and may be a little low on light levels.

What next? Stage 2 will be larger, and will use a solar powered pump. This will simplify electricity supply, and I assume that flowing water will be most beneficial in the hours of daylight when the plant is growing. Location outdoors will aid temperature control. A nitrogen and lime feeding regime will be tried.

First published in the Shropshire Group Newsletter, January 2011
and subsequently in Cornucopia Issue 29.
© Copyright for this article: Geoff Aston

This article was taken from a copy of Cornucopia that was published in 2012. You could be reading these articles as they are published to a national audience, by subscribing to Cornucopia.