Clethra Summersweet – Pruning, Winter Care and Fertilizing

Clethra Summersweet

This plant in general will need a minimal amount of pruning.  Pruning can be rather important to the overall look of the plant. Pruning should be done in early spring before leafing out. Crossing, winter killed, badly formed or damaged branches should be removed back to a main branch, some shaping can be done as well. This plant blooms on new wood so you can “go nuts” if that is prudent.

This plant grows and develops best in acidic soil. Most of the soil, all of the rainwater and all of the ground water in southeastern Wisconsin is basic or alkaline. Therefore, for some plants to thrive, they need to have special care.

Initially, the soil the plant is installed into should be amended to make it more acidic and to increase the amount of organic matter in the soil. Over time, the soils acidity should be supplemented with an acid-based fertilizer. A liquid fertilizer, like Miracid works well. This liquid fertilizer is mixed with water and applied the same as you would water the plant (see product for specific details). This type of fertilization should be done three or four times per year, starting in April and ending by mid-July. Soil can also be acidified with soil sulfur, aluminum sulfate or cotton seed meal, however, these products will not fertilize the plant. Mulch is also important to acid loving plants. A 2-4″ thickness of bark or needle mulch should surround the plant at least as far out as its drip line.

These shrubs need little winter care but, should be occasionally checked for rabbit or other damage. If rabbit damage is found you can protect the plant with a fence formed with hardware cloth (looks like chicken wire but with small square holes). The branches of the plant should be tied in towards the center, then a circle of hardware cloth can be placed around the outside. The base of the hardware cloth should be buried in the soil or mulch. This protection should be installed in late November and removed in mid April.