(News article for February 13, 2021)
It sometimes happens that landscape beds are installed and, perhaps mulch is refreshed and pruning is performed from time to time, but little attention is given to replacing nutrients that have leached out of the soil with rain or irrigation water, or been removed in pruning waste. Over time, plants become less vigorous.
Late winter and early spring, as the aboveground parts of plants start growing again, are good times to fertilize many plants. This includes shrubs, small trees, and herbaceous perennials in landscape beds.
Taking a soil test and getting the results is preferable for knowing what amounts of different nutrients are needed and if soil pH needs to be adjusted. However, if there is no reason to believe that soil nutrient levels might be excessive, an application of a “complete” fertilizer – one containing nitrogen, phosphorus, and potassium – can be made at a moderate rate without one.
Fertilizing at a rate of 1 pound of actual nitrogen per 1000 square feet, or 0.1 pound per 100 square feet, is a rule of thumb for maintaining landscape ornamentals.
For example, you could use 0.7 pound of a 15-9-12 (15% nitrogen) product, 0.8 pound of a 12-6-6 product (12% nitrogen), or 1 pound 10-10-10 (10% nitrogen), per 100 square feet of bed area. These are just a few of many possible fertilizers that could be used.
Mixed fertilizers generally have a density of about 1 pound per pint, or per 2 cups, so 0.5 pound of fertilizer would be about 1 cup of fertilizer.
For landscape beds, a slow-release fertilizer that’s coated in such a way that nutrients are released slowly over time is preferred to one like 10-10-10 that’s readily soluble.
While it will soon be time to fertilize landscape beds, wait until April to apply any nitrogen-containing fertilizer to warm-season turfgrasses. Fertilizing turfgrass too early can promote winter weed growth and predispose grass to the fungal disease large patch.
Let me know if you have questions.
Contact Mary Helen Ferguson.
Late winter and early spring, as the aboveground parts of plants start growing again, are good times to fertilize shrubs, small trees, and herbaceous perennials in landscape beds. Pictured beds are part of the trial gardens at the Hammond Research Station. (Photo by M.H. Ferguson)
The LSU AgCenter and the LSU College of Agriculture