I know, (from WP statistics), that many blog visitors are intrigued by my system for heating the greenhouse with air circulated through an external compost bed. And I’m overdue for an update on this, so fairly briefly I shall include my current system, which is primarily designed to maximise production of tomatoes, nectarines and apricots, during the summer, from the roughly 8 feet by 14 feet cedar framed structure. (Click here for all the previous posts on this subject).

• The heap definitely needs the addition of some wood  pulp or woodchip, in addition to chopped leaves as well as nitrogen in the form of pee and poultry manure, to achieve good temperature stability over the winter months. I had limited access to it this last winter, but it was fortunately very mild. I suspect about a third of wood chip to leaves, by volume would be adequate
• I now run the heap throughout the year.
• I’ve added a second run of perforated aluminium ducting to the fan blowing air through the heap, so that there is a double U on either side of the greenhouse, which then returns uninterrupted to the exit vent from the greenhouse, and back into the base of the external compost bed. This avoids the clumsiness of the previous set up, where I had to step over the ducting on entering the greenhouse. Both a bit of extra warmth, and also extra CO2 from the compost heap, are the benefits from keeping the system ticking over during summer.
• I’ve removed the side polycarbonate sheets, which has given added growing space. These sheets were then used to create early season protection for squash and courgettes – see later.
• I now use a flexihose on ‘shower’ setting for both damping down the central heat store path – on most sunny days during the summer, as well as for watering the tomatoes. Much is made of the benefits of using pre-warmed water, which I used to do, but frankly it’s bad on the back lugging such big containers about, so now the containers stay in the central channel, and I can sit on them, whilst working my way down the side of the greenhouse, soaking the compost – and avoiding anything going onto foliage; pulling off any diseased leaves at the first opportunity, and also pinching out side shoots. I realised early on, that tomato growing is very labour intensive.
• I’m now on the third year of growing the tomatoes in the same growing medium in pots – 12 or 15 litres, in double rows, slightly sunk into the two greenhouse beds. Initially a mix of soil and compost, all I now use, is the material from my greenhouse compost heap to top up, and to grow on the seedlings An old hand (I’m afraid he accompanied and chauffered the main speaker, so I don’t have his name), who gave some nuggets of years of wisdom last year at our garden club, reckoned the best tomatoes he’d ever seen, had been grown organically in the same bed for years and years – so I’m following his advice. By the end of the season the compost level has dropped 2 to 3 inches in the large pots, so this gets topped up after final planting out. The images below show the second potting on, into 2 litre pots, which I see was carried out on 27/04/2015. Note the loose un-sieved leafy compost, which doesn’t get tamped down. Also, because no weeds ever go into the compost heater bed, it’s almost entirely weed free – so no weeding of the tomatoes is necessary, once planted out.
• This year, they’ve had no supplementary feed, (other than the pretty rich compost) apart from a top dressing of sea weed meal at planting out, and I’ve also added crushed egg shells onto the base layer of compost again at planting out – a tip I gleaned from Alan Chadwick’s writings in the USA.
• The varieties grown are all from home saved seed, and this year, because of the turmoil in the house, they weren’t sown until about the middle of March. But by midsummer’s day, the foremost plants had 4 flower trusses forming, with fruit of this size on the lowest truss, and they’re nearly 6 feet high. Images below from 21/06/2015.
• Needless to say, I’m still using my pocket vibrator about every 2 to 3 days to pollinate the flowers, and also using the flexi ties (again now on their third year), to tie up the new growth to home grown miscanthus canes. So apart from the dried seaweed, it’s pretty much all sourced on site.
• I’m also trialling a couple of cucumber/pepper alternatives, (Achocha, from Real seeds), since I’ve failed miserably with growing the real thing, as well as sweet potatoes growing beneath the tomatoes. Too early to tell what cropping will be like, but they’re all certainly growing well. Again, notice the water filled bottles throughout the greenhouse – I’m convinced that this significant thermal store, helps smooth out day/night temperature extremes, which helps to promote growth.
• The apricots (cold weather cultivar ‘Tomcot’) and nectarines are fruiting well, and this year, my policy of gently knocking off all the petals from the apricots with my pollinating brush, once the fruit had obviously set, spared any young fruit rotting with botrytis/grey mould – interestingly the nectarines don’t suffer in the same way, with the petals drying and shrivelling, quite harmlessly.

I’ve added in 3 more line wires higher up, but I’m now at the point where I shall need step ladders in the greenhouse to reach new tomato growth and flowers, as well as to thin out this year’s fruit tree growth.

I know ( from WP statistics) that many blog visitors are intrigued by my system for heating the greenhouse with air circulated through an external compost bed. And I’m overdue for an update on this, so fairly briefly I shall include my current system, which is primarily designed to maximise production of tomatoes, nectarines and apricots, during the summer, from the roughly 8 feet by 14 feet cedar framed structure. (Click here for all the previous posts on this subject).

• The heap definitely needs the addition of some woodpulp or woodchip, in addition to chopped leaves as well as nitrogen in the form of pee and poultry manure, to achieve good temperature stability over the winter months. I had limited access to it this last winter, but it was fortunately very mild. I suspect about a third of wood chip to leaves, by volume would be adequate
• I now run the heap throughout the year.
• I’ve added a second run of perforated aluminium ducting to the fan blowing air through the heap, so that there is a double U on either side of the greenhouse, which then returns uninterrupted to the exit vent from the greenhouse, and back into the base of the external compost bed. This avoids the clumsiness of the previous set up, where I had to step over the ducting on entering the greenhouse. Both a bit of extra warmth, and also extra CO2 from the compost heap, are the benefits from keeping the system ticking over during summer.
• I’ve removed the side polycarbonate sheets, which has given added growing space. These sheets were then used to create early season protection for squash and courgettes – see later.
• I now use a flexihose on ‘shower’ setting for both damping down the central heat store path – on most sunny days during the summer, as well as for watering the tomatoes. Much is made of the benefits of using pre-warmed water, which I used to do, but frankly it’s bad on the back lugging such big containers about, so now the containers stay in the central channel, and I can sit on them, whilst working my way down the side of the greenhouse, soaking the compost – and avoiding anything going onto foliage; pulling off any diseased leaves at the first opportunity, and also pinching out side shoots. I realised early on, that tomato growing is very labour intensive.
• I’m now on the third year of growing the tomatoes in the same growing medium in pots – 12 or 15 litres, in double rows, slightly sunk into the two greenhouse beds. Initially a mix of soil and compost, all I now use, is the material from my greenhouse compost heap to top up, and to grow on the seedlings An old hand (I’m afraid he accompanied and chauffered the main speaker, so I don’t have his name), who gave some nuggets of years of wisdom last year at our garden club, reckoned the best tomatoes he’d ever seen, had been grown organically in the same bed for years and years – so I’m following his advice. By the end of the season the compost level has dropped 2 to 3 inches in the large pots, so this gets topped up after final planting out. The images below show the second potting on, into 2 litre pots, which I see was carried out on 27/04/2015. Note the loose un-sieved leafy compost, which doesn’t get tamped down. Also, because no weeds ever go into the compost heater bed, it’s almost entirely weed free – so no weeding of the tomatoes is necessary, once planted out.
• This year, they’ve had no supplementary feed, (other than the pretty rich compost) apart from a top dressing of sea weed meal at planting out, and I’ve also added crushed egg shells onto the base layer of compost again at planting out – a tip I gleaned from Alan Chadwick’s writings in the USA.
• The varieties grown are all from home saved seed, and this year, because of the turmoil in the house, they weren’t sown until about the middle of March. But by midsummer’s day, the foremost plants had 4 flower trusses forming, with fruit of this size on the lowest truss, and they’re nearly 6 feet high. Images below from 21/06/2015.
• Needless to say, I’m still using my pocket vibrator about every 2 to 3 days to pollinate the flowers, and also using the flexi ties (again now on their third year), to tie up the new growth to home grown miscanthus canes. So apart from the dried seaweed, it’s pretty much all sourced on site.
• I’m also trialling a couple of cucumber/pepper alternatives, (Achocha, from Real seeds), since I’ve failed miserably with growing the real thing, as well as sweet potatoes growing beneath the tomatoes. Too early to tell what cropping will be like, but they’re all certainly growing well. Again, notice the water filled bottles throughout the greenhouse – I’m convinced that this significant thermal store, helps smooth out day/night temperature extremes, which helps to promote growth.
• The apricots (cold weather cultivar ‘Tomcot’) and nectarines are fruiting well, and this year, my policy of gently knocking off all the petals from the apricots with my pollinating brush, once the fruit had obviously set, spared any young fruit rotting with botrytis/grey mould – interestingly the nectarines don’t suffer in the same way, with the petals drying and shrivelling, quite harmlessly.

I’ve added in 3 more line wires higher up, but I’m now at the point where I shall need step ladders in the greenhouse to reach new tomato growth and flowers, as well as to thin out this year’s fruit tree growth.