I am soon to acquire a greenhouse, sadly this has to be sited on concrete. I shall be wanting to grow tomatoes, peppers and aubergines and will probably have to use growbags. I have considered using ring culture, but know little about this method. Can you help?
Ring culture involves growing your tomato plants in large (22-26cm or 9-10in), bottomless pots that are filled with compost and stood onto a water retaining, though free draining aggregate base.
Washed builders ballast and sand (80:20mix) makes a good aggregate base.
Although ring culture pots are available, any large (22-25cm or 9- 10in) container with the bottom removed is suitable, providing that it has adequate capacity (6.5kg or 14lbs). On a solid floor, build a retaining wall to hold the 10-15cm (4-6in) of aggregate mix. The ring culture method encourages the development of 2 root systems; fibrous roots in the ring culture pot supply the plant with food, the taproots reaching down into the aggregate take up water.
Gently remove your tomato plants from their pots and place in the centre of the ring culture pot. Add compost and firm around the root ball, leaving 4cm (11/ 2in) to allow for watering. Place on a bench and give each plant 600ml (1 pint) of water. Do not water again for a week, then provide 300ml (1/2 pint) every other day for the next 2 weeks.
After 2 weeks move the pots to their cropping position on the aggregate base, ensuring that there is good contact between the base of the ring and the aggregate. Water the aggregate daily. After 10-14 days check that the roots are pushing down into the aggregate. Once the tomatoes are around cherry size apply tomato feed to the plants 2-4 times weekly.
Organic tomato compost, organic grow-bags and ring culture pots are available from The Organic Gardening Catalogue