With our increasingly unpredictable weather, it makes sense to make the most of your greenhouse. I used to use mine for growing seedlings started in a heated propagator, a crop of tomatoes and indoor cucumber in the summer, perhaps some oriental vegetables like mibuna and mizuma sown in early autumn for a winter crop if the tomatoes had finished. I also bring on potatoes in pots, hoping for waxy new potatoes at Christmas if hard frosts were avoided but at best my greenhouse was mainly busy in spring/summer with just two crops.
Now I ‘stack’ every vertical space possible to imitate a mini forest garden with a tree, shrub and herbaceous layer. Full size forest gardens can incorporate seven layers (see diagram) but it is amazing how productive a mini forest garden under glass can be with at least three layers.
This year, in my 10 x 6ft greenhouse, I am growing an espaliered peach on the back wall, my small tree layer (see main photograph). The peach is an own root stock variety. The stones were given to me by Achim Ecker at ZEGG ecovillage in Berlin and I have managed to germinate a few, another is in the forest garden. At ZEGG, near Berlin, there are hot summers and very cold winters and Achim's peaches thrive outdoors and are peach leaf curl resistant. My outdoor peach is not so happy in rainy England. The outdoor specimen is healthy and fairly vigorous, however, requiring a fairly hard prune every spring. We fertilise the flowers with a sable paintbrush and this year we have 41 peaches ripening. They grow large and juicy. Can't wait until August!
My ‘shrub’ layer consists of tomatoes, cucumbers, tomatillos (Physalis philadelphica). I grow cherry, plum and beefsteak tomatoes and favour traditional varieties of cucumber with spiky skins. They are crispy and taste delicious.
My herbaceous layer consists of capsicums and herbs. I grow sweet pepper and chillis. I have also planted year-round perennial herbs like thyme, flat-leaf parsley and tarragon and add annual basil once the danger of frost has passed. The parsley starts growing in early spring and the thyme and tarragon thrive once the greenhouse heats up. I don't have to coat the glass either to prevent leaf burn in full summer. All the plants create enough shade to prevent burn but not too much to inhibit growth. The secret is not to overcrowd them. That said, every vertical available space is almost filled. I am thinking of growing strawberries and trailing tomatoes in hanging baskets from the roof next year.
Outside the greenhouse is guttering that harvests rainwater into a water butt. It is so useful to have a water source right by the door. Inside, I also use ‘Ollas’, a 4,000 year-old irrigation system originating in Africa. It comprises of 10 inch buried porous terracotta pots with plates for lids. The drainage holes are plugged with a wine cork and the pots are filled with water. As the surrounding area dries out, water is sucked through the terracotta into the soil. The roots of the plants wrap themselves around the pots. Evidence is that it is working. This system is a simple and cheap way to irrigate the greenhouse and can be used in any veggie bed. I hope it will prove especially useful when I am away on holiday for a few days.
I am always looking for other ways to stack layers and functions in my greenhouse but so far the idea of mimicking three layers of a mini forest garden is working well.
Maddy Harland co-founded and edits internationally acclaimed, Permaculture magazine – practical solutions for self-reliance.