What gardener can resist providing a little treat to help plants grow vigorously? If you’re installing new plants, growth stimulants help them to become established more quickly. Or you may want to enhance the performance of a plant already in the garden. Natural growth stimulants increase the performance of your plants without jeopardizing their health with excessive amounts of fertilizer. That means stronger and healthier plants capable of increased fruit and flower production. Just what we want!
Appropriate timing is important when using growth stimulants. Attempting to force a plant out of dormancy is a mistake that can result in stunted spring growth, just the opposite of what you want. Wait for signs that the plant is ready to grow and has begun a growth cycle. At the end of winter, the swelling buds on woody stems are a signal that natural growth stimulants are stirring within the plant. Longer days and rising temperatures trigger the manufacture of plant hormones, a sure indication that new growth will soon be underway. Stimulants can safely be offered when buds have opened and the first flush of foliage is underway. New plants you purchase through the spring and early summer benefit from growth stimulants, but don’t use stimulants after the first week of August on established plants or new plants. Tender new growth produced late in the season might not have enough time to harden before deep frost arrives.
Plant growth stimulants provide a key hormone or organic element that influences growth in a particular way. They’re different from fertilizers you use to provide a supplemental meal for plants, although some stimulants may also contain plant nutrients. Stimulants can be applied to any kind of plant and have no toxic properties. If you use them for spring planting, be sure to follow the instructions and amounts recommended on commercial packages or in the notes below. You can also provide the same amounts of stimulants to established plants already in the ground.
Bone meal, super phosphate and triple phosphate are rich sources of phosphorus, and stimulate root growth and bud set. Phosphorus is one of the three main plant nutrients in standard fertilizer formulas (nitrogen—phosphorus—potassium). Bone meal is extracted from steamed animal bones and has the lowest phosphorus content (expressed as 0–11–0) and won’t burn roots. It can be mixed into a planting hole to provide slow-release rooting stimulation over several months. Super phosphate (0-22-0) and triple phosphate (0-33-0) are extracted from rock and have sufficient phosphorus to burn roots if not carefully applied.
Granular transplant fertilizer is a commercial product sold as dry granules that are soluble when mixed with water. The formula is very high in phosphorus (often 10-52-10) and stimulates root growth and bud set.
Liquid concentrate transplant solution has a lower amount of phosphorus (10-15-10), and most contain indole butryic acid (sometimes referred to as IBA), a rooting hormone plants manufacture naturally in spring. It’s a powerful root stimulant and helps plants overcome transplant shock.
Alfalfa is a nutritious grass used for animal feed. It provides sufficiently mild amounts of nutrients (5-1-2) that won’t burn roots when mixed into planting holes. More important, it contains triaconatol, a fatty acid that is a potent stimulant of overall plant growth. Alfalfa grass can be purchased in bags, tied in small bales, or in compressed pellet form from animal feed companies or urban pet stores. Any of these forms is suitable for planting holes.
Kelp meal and seaweed extract solutions are rich in growth-promoting hormones called auxins, gibberellins and cytokinins. They increase blossoms and yields in fruit, vegetable and flowering plants, as well deepening petal colour and enhancing scent. Kelp and seaweed also improve seed germination, increase storage life of fruits and vegetables, strengthen frost resistance in hardy plants and build resistance to insects and fungus diseases. Dig kelp meal into soil around plant roots, or dilute seaweed extract in water and deliver as foliar feed by spraying it on leaves several times during the growing season.
Willow tea is also a good source of auxins, gibberellins and cytokinins. In spring, cut six-inch (15-centimetre) lengths of willow tips with swollen buds (the buds contain the hormones), crushing them slightly with a hammer, and soak them in boiling water. When the water has cooled, strain out the twigs and use the tea to soak seeds and water plants into their new holes. Use the willow tea immediately or freeze for future use. Because this is a homemade material it’s difficult to control or measure potency, but try working with a ratio of one thick handful of willow tips to two quarts (two litres) of boiling water. Any specie of willow has the same strong rooting hormones.