Not many people realise that you can grow watercress really well in your greenhouse. In fact, it’s better grown under glass, because it grows much faster. The packet says you can start eating it in September. But grown in an unheated greenhouse, you can start cutting it at the end of April! And yes, we’re talking about the real watercress that’s normally grown in stream beds, not land cress or mustard and cress.
The method is as follows:
1. Get a tub about 3ft x 1ft 6in (0.8m x 0.4m) and at least 9in (22cm) deep.
2. Make sure it has some holes in it and put some polystyrene on the bottom for drainage.
3. In March, half fill it with muck, good soil or garden compost. Thoroughly water it.
4. Top up the tub with fine compost (peat based multipurpose is best).
5. Wet this compost and sprinkle a packet of Watercress seed on top (available from The Organic Garden catalogue under 'C' for Cress, for example). You might get away with only sowing half a packet, but I prefer to sow thickly –much thicker than they say on the packet.
6. Lightly cover the seed with sifted compost and dampen it.
7. Cover the tub with clear glass or plastic sheet.
8. In about 2 weeks it will germinate (faster if you sow later in the year or use a heated greenhouse) and after another 2 weeks it is ready to start cutting.
9. Once germinated, remove the glass. (At first, if the nights are still cold, you could put the glass back on in the evening). Now start to water daily. Water lightly at first, then thoroughly with a watering can when it gets really bushy. But don’t worry, watercress does not need to be constantly saturated –it just likes to be damp.
10. Carry on cutting (about half its length) as it grows. You can cut the same lengths when they re-grow too, but bear in mind that after 2 or 3 cuts the stalks start to get tough. You can feed it with an organic fertiliser after the second cut to give it some final oomph.
11. Sow a fresh packet in a new tub at the end of May to keep you going for another month.
Absolutely delicious and nutritious – and really cheap compared to the shops!