I’m lucky enough to have had a greenhouse for years, and I love it.

If I’m honest though, my ‘savings’ on Grow Your Own greenhouse fruits and veggies don’t come close to covering the cost of the thing itself.

The main reason is that we don’t heat it. However fond I am of it and the shelter it gives me from our valley’s frequent winds and seemingly incessant rain, it’s actually more like a supersized cold frame than a tropical glasshouse at Kew. I guess I could give in to temptation and bring out the paraffin heater over winter, but if you’re trying to reduce your carbon foodprint it’s a bit of an own goal to use fossil fuels to ripen your tomatoes a few weeks early.

My greenhouse has seen some great growing – the year I decided to plant a few spare courgette plants in there and couldn’t see the floor after a fortnight; my cherished rosemary plant, now over 15 years old (no mean feat for Moffat) and still growing strong; the single cucumber plant that was cropping a fully ripe mini cucumber every day for the whole summer (how I wish I could remember the variety).

It’s seen some disasters too – the long cold springs that put paid to my far-too-early tomatoes; that year when it was the only safe place I could persuade the hen and her newly hatched chicks to stay (oh, my poor topsoil!) – and don’t mention the ants!

Over the years I’ve done what most people do with an unheated greenhouse. Use it to give protection to early sowings and newly emerged seedlings, grown a few tomatoes and cucumbers and try it for overwintered lettuce and herbs.

But with the weather getting more unpredictable, it makes sense to try and get the most you can out of every bit of investment, and my old greenhouse is no exception.

So I was intrigued and ever so slightly envious when I came across Maddy Harland’s post on the Permaculture Magazine website the other week. Maddy is the editor of Permaculture Magazine and one of my eco-heroes.

Maddy has planted up her small greenhouse as a mini forest garden (I wrote about forest gardening in an earlier blog) using the small tree, shrub and herbaceous layers. There’s an espaliered peach on the back wall to create the small tree layer, a shrub layer of tomatoes, cucumbers and tomatillos and the herbaceous layer of capsicum and herbs. By using the technique of vertical ‘stacking’, the greenhouse isn’t just productive at ground level, but in three dimensions too.

Along with water butts and guttering to capture rainwater from the greenhouse roof, Maddy is using ollas for irrigation inside the greenhouse. These are buried terracotta pots (you can buy them specially or use a 10 inch terracotta plant pot with the drainage holes corked up and a plate over the top). The pots are filled with water. As the soil around the pots dries out, water seeps through the terracotta to keep the earth moist and the plants well watered, even if you do absolutely have to go on holiday.

If you have a greenhouse of your own, it’s worth checking to make sure you too are maximising its potential. Too often I walk past greenhouses that are stacked high with old plant pots and bags of compost, even the odd packet of Growmore, but very few plants, even in the middle of summer. Despite our slightly better summer of 2013, our weather is increasingly unpredictable so it makes sense to make the most of whatever shelter you have.

I love my newly planted outdoor forest garden and I’m now inspired to renovate the greenhouse to make one undercover too. Peaches (or apricots maybe?), kiwi fruit, a grapevine, Tumbler tomatoes in hanging baskets, herbs galore… bring out the catalogues, I’ve found my next project!

Have fun in your gardens this week.