Apply organic mulch on most established ornamental plants in mid- spring when the soil has warmed sufficiently for active root growth.

If applied before this time, the mulch will keep the ground cool and root growth of ornamental plants may be slow.

Apply organic mulch around newly set ornamental plants after they are put into place and thoroughly watered.

How deep to apply organic mulches

For best results, apply mulch at least 2 to 4 inches deep over the whole area during spring, summer and early fall, but avoid covering the crowns of very low-growing ornamental plants.

Tender ornamentals that need winter protection may require an additional 1 to 2 inches of mulch around the crowns or bases of the plants during the winter. In the spring, this added mulch should be fanned out or away from the stems or crowns of the plants before more material is added for a summer mulch.

Fertilizing organically mulched plant material

As indicated previously, mulching with many organic materials means you must apply extra fertilizer around the plants to reduce the chance of nitrogen deficiency or starvation.

Apply 1/4 pound of ammonium nitrate or ammonium sulfate for each bushel of mulch material used on the bed, or two pounds per 100 square feet of a complete fertilizer such as 5-10-5, 12-12-12 or similar analysis. This fertilizer should be applied to the plants before the mulch is placed on the soil, or in early spring before more material is added to plants already mulched. If the lower foliage yellows and the plants lack vigor during early summer, apply additional fertilizer.

Do not over mulch

The roots of the plants need a constant supply of oxygen at all times. Over-mulching kills the roots of shallow rooted plants by suffocation.

Symptoms of too much mulch include chlorotic foliage (symptoms often resemble those of iron deficiency), abnormally small leaves, poor growth and dieback of older branches. Disease organisms that are active under conditions of low oxygen and excessive moisture can become active and attack the roots.

Sometimes the old root system will be rotted as the plant tries to send out new roots into the mulch layer. Excessive amounts of mulch applied around tree trunks can lead to cankers and tree injury.

Curt Peterson, Ph.D., is a landscape designer and garden specialist from Union Springs. He can be reached at curt.peters@hotmail.com