By Doug Hackbarth
Broadview Florist & Greenhouse
I get a lot of questions about pruning trees, shrubs and all other perennial plants during the late summer and fall seasons, and they want to know which ones can be cut-back now. It is a very simple “rule-of-thumb”…DO NOT PRUNE anything from now until winter. Pruning stimulates new growth that will not have time to harden-off before cold weather arrives.
Guidelines for pruning…prune all trees, including fruit trees in late winter. Prune spring flowering shrubs immediately after they bloom, especially Rhododendrons and Azaleas as they start to set their flower buds for next year during the summer. Some flowering shrubs will bloom on current growth such as Rose of Sharon (perennial Hibiscus), Hydrangea and Potentilla so prune them hard in late winter/early spring as they grow fast and then bloom. Prune mid-summer to late summer flowering plants during late winter or early spring.
Root pruning is a little known procedure that can, in-fact bring new life to plants that seem to be “growing” nowhere. What happens is your plants root system grows out and gets old and tuff, and has a hard time absorbing nutrients. After root pruning, your plants will produce new, soft, fibrous roots that will be more capable of the absorption of nutrients.
To root prune, simply use a shovel at the drip-line of your shrub (closer for trees) and shove it into the ground as deep as the shovel will go. This can be difficult if your plants are well established. The best time of year for this pruning would be in the spring or early summer.
Specifically, stop cutting back your roses by the first of September, including the dead flowers…just leave them alone. No fertilizer after mid August as fertilizer also stimulates “soft” growth. Your plants need to harden-off before cold weather. Garden mums (“hardy” chrysanthemums) should be separated and pinched back in late spring (the end of May). After Thanksgiving (late November), you can cut off just the blossoms of your roses and garden mums but leave the stems until spring.