harvested , the square can be replanted with another crop . So a radish square may become a lettuce square in its second go-around .
The organized and clean look of the square-foot garden is what makes it attractive for many , but it also saves space and produces more . Weeds are easy to keep at bay because they fall outside the pattern of the plants and can be easily identified and plucked .
Once you have your raised bed built , it needs to be sited in a location that gets a minimum of eight hours of daily sunlight and preferably much more . Some sort of weed barrier should be placed underneath to prevent weeds and grass from making their way up , but if you balk at the cost of landscape fabric then consider two or three layers of cardboard . The advantage of cardboard is that it will eventually decay , allowing worms and other helpful organisms access to your garden from below .
Once in place the structure needs to be filled with soil . A good soil mix retains moisture , air and nutrients . Although there are many prepared container mixes available , I like to blend my own using an equal volume of vermiculite , peat and compost .
I use a large block of peat ( 107 litres or 3.8 cubic feet ), a large bag of # 2 expanded vermiculite ( 118 litres or 4 cubic feet ) and four bags of manure ( 4 × 10 kg or 22 lbs each ). The manure or compost should be a mix of different types : steer , sheep , mushroom , worm castings , or whatever you can get your hands on . The more variety the better .
Today ’ s horticultural vermiculite is not the same product as was blown into attics in the 1950s as insulation . There has been controversy about the safety of vermiculite because the primary producer during the 20th century , a mine in Montana , sold product contaminated with asbestos . That mine has been closed for nearly twenty years and Canadian suppliers have been sourcing their vermiculite from alternate producers for years . For those who still harbour concern , a suitable substitute with similar aeration and moisture-retention properties is Perlite .
Sample Raised Beds
Another advantage of a raised bed is that it is easier to access for those who have difficulty kneeling or bending . A bed with a height of 12 ” to 16 ” can be tended from a comfortable stool or bench . Wheelchair accessible gardens should be 18 ” to 24 ” in height and have a minimum of four feet of space surrounding them . Tabletop beds should be built 36 ” off the ground to allow a wheelchair to fit underneath .
The final step in raised-bed gardening is choosing and planting your crop . In Alberta many seeds can be sown in April , but some of the more sensitive plants should wait until after the last risk of spring frost . By mid May virtually all seeds are safe to sow , although having a plan to cover delicate seedlings in case of a late frost is prudent .
Once established , keep your bed well watered , as it will tend to dry out more rapidly than a typical in-ground garden . If you want to take your garden to the next level , consider a simple irrigation system attached to a rain barrel .
Whether you favor a row of radishes , a plot of parsnips or a square of squash , raised beds make urban gardening gratifying .
Jane Thrall is a self-taught amateur gardener . You can follow her blog about gardening in zone 3b at www . gardeningrrl . wordpress . com
news & views SPRING 2015 | 33