Straw bale gardens are becoming popular with growers who are plagued with poor soil or limited garden space, said University of Missouri Extension Horticulturist David Trinklein. Straw bale gardening combines container gardening and raised-bed gardening into one, green thumb package. 

Many vegetables, fruits and flowers can be grown in a straw bale garden, said Trinklein. Cool-season varieties can be planted as early as mid-March if you cover plants with protective materials such as clear plastic or floating row cover. 

Use bales of straw, not hay, for gardening, said Trinklein. Hay contains weed seeds and is usually too dense for the best results. Choose bales held together tightly with twine. Farmers and local farm supply stores are good sources for straw. 

Avoid bales made from wheat or oats treated with an herbicide during production. 

To assemble a straw bale garden, first, choose a location that gets at least six to eight hours of direct sun. Once bales are watered, they become heavy and hard to move. If bales are placed on the ground, Trinklein suggests putting them on a base of thick layers of newspaper to control weeds. 

Set bales to that twine is on the outside and cut ends are face up. Place bales in single rows to allow best access, circulation and sun exposure. 

Successful straw bale gardening begins with conditioning the bales. This involves adding water and nitrogen to help bales partially decompose. Conditioning helps prevent nutrient tie-up once plants are added, said Trinklein. 

Nitrogen deficiency is common in straw bale gardening. This happens when the soil microbes take nitrogen away from garden plants as they break down the organic matter in straw. If leaves turn yellow, more nitrogen is needed. 

To condition bales, soak them with water daily for 12 days. On days one, three and five, add a half-cup of a high-nitrogen fertilizer such as urea, ammonium nitrate or a lawn fertilizer to each bale. If using lawn fertilizer, make sure it is not the “weed and feed” type, which contains herbicides that would harm garden plants. 

Continue to water to activate the microbes and break down the straw. On days seven and nine, add a quarter-cup of high-nitrogen fertilizer. On the 11th day, add one cup of a general purpose fertilizer such as a 12-12-12 mix to each bale. 

After the 12th day, touch the bale to check for heat, if it is cool to the touch, planting may begin. 

To plant, dig small pockets or holes into the straw and set plants into the holes. Fill the holes with soilless medium and cover the plant’s roots. Water the base of the plant to settle the medium around the root system. 

If planting seeds, put a layer of sterile potting media on top of the bale and tamp it down into the bale. Plant seeds according to package instructions. 

Straw contains few nutrients, so feed the plants regularly with a water-soluble liquid fertilizer solution. However, do not over fertilize plants growing in straw bales, said Trinklein. Otherwise, plants will be lush with abundant vegetative growth, but little fruit. 

Too much nitrogen causes pollen abortion, and flowers fall off. 

Be especially careful not to over fertilize vining crops such as cucumbers and melons. For sweeter-tasting melons, cut back on water when the fruits begin to size. 

Keep bales adequately watered during the growing season. Drip lines or soaker hoses may be helpful and eliminate hand watering. 

Straw bales provide conditions for good root growth, especially for tomatoes. You will see few weeds, but mushrooms may appear, said Trinklein. Discard them. Earthworms like the nutrient-enriched bales and help plants thrive. There should be fewer pests than in conventional gardening. 

Salad greens are a perfect choice for straw bales gardening, said Trinklein. You can enjoy greens up to frost, and even after frost with protection. Tomatoes, peppers and eggplant also grow well in straw. 

Although space in a straw bale garden is limited, avoid the temptation to crowd plants. Space them as you would if growing in soil. 

Unfortunately, straw bales last only one growing season. However, used bales make excellent compost.