MANHATTAN, Kan. – Using a starter solution (root stimulator) to "water in" new vegetable and flower transplants is – and yet can sometimes not be – a good gardening practice.

Using a starter solution has been a standard recommendation for years in garden stores and books.

"But recent research has shed more light on just how useful it is in a variety of situations. Those research results could be important to gardeners’ success with transplants in weeks ahead," said Chuck Marr, horticulturist at Kansas State University.

Several companies produce retail starter solutions. These products basically are a weak fertilizer mix that contains some nitrogen and phosphate.

"When soil is cold in early spring, its nutrients aren’t readily available to plants," Marr said. "So, starter solution mixed with water and applied near plant roots can provide the needed food. And plants really will seem to establish roots more quickly."

As soils warm, however, their nutrients become more accessible to plants. In turn, root stimulator use becomes less effective.

"Studies have shown that in warm, fertile soils, starter solutions don’t make much difference at all. In fact, too much starter solution when the weather’s very warm may actually hurt plants because it can make the concentration of nutrients too high," said Marr, who is K-State Research and Extension’s vegetable crops specialist.

He advises gardeners to use starter solutions with caution – or not at all – from late spring through early fall.