By Shirley Marken, Colorado State University Cooperative Extension horticulturist
Gardeners are an innovative bunch. If they want to grow something they'll find a way, even if space is limited.
A good way to compensate for lack of space is by gardening in raised beds. Doing so helps you overcome other problems, such as less-than-perfect soil and Colorado's short growing season.
A raised bed for vegetables can be as simple as raking the soil into flat-topped mounds a little higher than paths. Or, you can box the mounds with landscape timbers.
A convenient size for raised beds is about four feet wide and as long as space allows. Paths of 15 to 20 inches between the beds can be mulched to keep down weeds and allow a dry surface for walking. Pea-sized gravel, used carpeting, boards, grass clippings or straw make a good path.
Raised beds warm up earlier in the spring and dry out quicker. This allows the soil to be worked and planted earlier, extending the season a week or more. The wide edges of landscape timbers are handy to sit on while weeding or harvesting. Because the permanent paths need no water, fertilizer, soil amendments or tilling, costs and labor are reduced. Well-defined beds, such as those boxed with timbers, are less likely to be stepped on, so the soil stays loose and porous much longer and is easier to work each year.
Because the soil improved and there is no need to walk between plants,, vegetables can be spaced more closely. This increases the yield per square foot. Within wide beds, seed can be scattered randomly or sown in shallow furrows two or three inches apart. Thin plants enough to allow growing room. This works well for lettuce, spinach and root crops.
Beds three or four feet wide have space enough for two rows of large plants such as corn, bush beans or peppers. Tomatoes can be spaced two and one-half to three feet apart with the rows staggered.
Gardeners can borrow the idea of vertical space from skyscrapers. Sprawling plants, such as cucumber vines, can grow vertically on a frame or trellis. Pole beans, snap peas and small varieties of squash can climb a chain link fence or an A-frame from which fruits hang for easy picking. Tomato towers, purchased or homemade, are convenient for all climbing vegetables. An eighteen-inch diameter ring made from hog wire or reinforcing wire can cage a tomato or provide support for ten cucumber vines planted about six inches apart. Snap peas can be planted every four inches. Allow a foot or two between the cages.
Interplanting and succession planting increases the yield from a small plot. A common method of interplanting is to mix carrot and radish seeds in the same row or plot. As the early-maturing radishes are harvested, the row is thinned enough to allow carrots space to grow. Head lettuce or butter-head types can be sown thickly, then used as leaf lettuce until thinned enough to allow head formation.
Succession planting means using the same area to grow successive crops. For example, spinach is planted in early spring. When the weather and soil are warm enough for beans, squash or peppers, the spinach will be about to seed, so the warm crop can take over the plot.
Homegrown flavor and the fun of watching things grow can be even easier and more productive in raised beds.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010