School gardens are an excellent way to teach students how to grow their own healthy fruits and vegetables. Most schools throughout South Carolina, however, are not built on land ideal for vegetable gardening.
Due to compacted or poorly drained soil, some school garden sites may flood periodically, posing potential health hazards if flooded crops are consumed. While there seems to be plenty of room around schools to till up a new garden, the downside is there is always a large bank of weed seeds lurking in the soil ready to sprout. Without mechanized or chemical weed control methods, school gardens can quickly become weedy and unsightly. Raised beds help school gardeners minimize weeds, extend the growing season, and lessen the work associated with growing vegetables in traditional tilled gardens.
When gardening with students in a school setting, safety is the top priority; therefore, the following building materials are recommended for use in raised bed construction for school gardens:
Raised beds may be constructed of a vast array of materials, limited only by the gardener’s creativity, aesthetics, and budget. Due to safety concerns using treated lumber, landscape timbers and recycled plastic composite lumber are not recommended for school gardens. Creosote soaked railroad ties and rubber tires should never be used.
The safest choice is untreated cedar which typically lasts between 5 to 7 years in our hot southern climate. If you choose to build your own raised beds, make sure no nails, screws, or other hardware will pose a threat to student safety.
When gardening with young children, raised beds should be no more than 2 to 4 feet wide so students can reach into the center of the beds without stepping into them. Raised beds should be 4 to 6 feet long to ensure students and busy teachers do not have to walk too far to get to the other side of the bed.
Paths between beds should be 2 to 4 feet wide or as wide as necessary to accommodate one to two students and walkers or wheelchairs. This will also allow space for wheelbarrows or garden carts to maneuver the paths as well. Mulch the walkways to minimize the need for mowing and trimming weeds around raised beds.
Construct or purchase raised beds that are at least 12 to 18 inches deep. Building deeper beds that hold more soil will initially cost more. You will need more building materials and soil to fill the beds, but the garden will require less irrigation and, plants will be more productive with less water stress.
Raised beds are essentially large containers, so it is fine to use a soilless growing media. These may be purchased bagged or in bulk. Common blends found on the market contain ground pine bark, sand or vermiculite, limestone, slow release fertilizer, and compost. Weeds, diseases, fertility, and drainage issues can be reduced using soil free media. Avoid using peat-based potting soil that can dry out easily. Avoid the temptation to fill beds with low cost compost. Plants may thrive for one or two seasons in straight compost, but nutrients are lost quickly and won’t provide long term support for a healthy garden.
Sheet composting or lasagna gardening also works well in raised beds. Begin with a layer of cardboard directly on the ground under raised beds to smother weeds and encourage microbial soil activity. Add layers of carbon and nitrogen rich sources inside the bed. Begin by putting pats of alfalfa hay down first, then 1 to 2 inches of compost, followed by nitrogen rich fruit and vegetable scraps, another layer of compost, rotted leaves, more compost, and finally bagged garden soil on top. Moisten each layer well before proceeding and plant in the final layer.
Replenish garden soil regularly. Additions of compost and fertilizer in the gardens, and mulch around the beds will keep your school garden productive and low maintenance for many years.