Posted: 17/01/2013 at 20:04
I would use the paving slabs for the path for you. A dwarf wall of on edge concrete walling blocks, or bricks if you prefer, would increase the head height and volume (growing space) of your greenhouse. You could use pressure treated timber, or sleepers, instead if you accept a shorter life. A completely solid floor inside has something to recommend it giving freedom from slugs, snails, worms etc. and can keep the humidity down in winter, but I would use very coarse sand. It drains well, it will wick away excess water from pots by proper contact with the compost in the pots, something gravel does very poorly. If you want to grow plants in the ground then you treat it like the garden, accepting it may need refreshing from time to time, or treating for bugs or diseases. Grow bags or large pots or raised beds, on a concrete base sort of give you the best (or worst?) of both systems.