I’ve come to the conclusion that a tunnel house or greenhouse is almost more useful in the winter than in the summer in Wellington. On a sunny day with a big southerly blowing, it is of course the perfect place to hide. I don’t heat my tunnel house so I’m not about to produce summer crops throughout the year. It just means that winter crops grow more quickly and are protected from wind, rain and bird damage. My priorities for the space are seed raising in pots, herbs and salad. If I can fit in a few other root crops I will. I find brassicas and leeks grow well enough outside. A few early peas are a bonus, but they need to be out in time for the summer crops. I dig up some mint, chives, thyme and tarragon from the garden and plant them in the tunnel house to give me herbs through the winter when they die down outside.
Here’s how I get my tunnel house ready for winter:
1. remove summer crops and weeds
2. clean the plastic inside and out
3. water well
4. test the soil pH and sprinkle lime if necessary
5. aerate the soil with a garden fork and level it.
6. spread a layer of potting mix
7. sow seeds.
You won’t need to water much during the winter but if it’s sunny the soil can dry out. Keep a mouse trap set along the edge of the tunnel, as it’s a snug place for mice to winter up too. If you don’t want to grow an edible crop, sow a green manure and dig it in to improve the soil in spring. Think about where the sun will be in winter and try not to grow taller crops where they’ll shade smaller ones. I grow salads and herbs I pick every day near the paths and put root crops and spring onions near the back, as I don’t have to reach them as often. I’ve just sown mibuna, mizuna, chicory, white turnips, radishes, claytonia (miners lettuce), endive, carrots, cos lettuce, coriander, perpetual spinach, spring onions, welsh onions, parsley, spinach, basil (not sure it will be warm enough for this to germinate), beetroot, rocket, pak choi, broccoli ‘green lance’, plus some snow peas. I’ve got similar crops outside too, so I should have a succession through winter and spring.