Oakleaf hydrangea (Hydrangea quercifolia) is a slow-growing, deciduous shrub that produces cone-shaped sprays of white flowers each year in early summer. Because the flowers form on last year's wood, pruning the shrub too early or too late in the year will result in a total lack of flowers the following season. The best time to trim back the new green wood on an oakleaf hydrangea is immediately after it has finished flowering, usually from late summer to early fall.
Preparing to Prune
Sterilize the pruning tools by dousing a clean old rag in rubbing alcohol and thoroughly rubbing the cutting surfaces with the rag. Sterilizing pruning tools helps to reduce transmission of plant diseases.
Sharpen tools using a mill file, if necessary. Push the file away and diagonally away from you along the tool's cutting edge, lifting the file from the edge once the downstroke is complete.
Assess the oakleaf hydrangea to determine where the pruning cuts should be made. Start by identifying any dead or dying branches, as well as looking for canes that are diseased or insect-damaged.
Determine where to make thinning cuts or which branches to prune back in order to maintain the shrub's overall shape. Thinning cuts should be made in the interior of the shrub, whereas shaping cuts will be on new wood around the exterior of the hydrangea.
Pruning the Oakleaf Hydrangea
Cut back dead wood at the ground level.
Remove dying branches at their point of origin, either at ground level or where they originate from a parent branch.
Head back strong new wood by cutting off roughly half of the new growth. Make cuts at a 45-degree angle.
Remove no more than one-third of the overall new growth, which encourages larger flowers the following year.
About this Author
Michelle Z. Donahue lives in Washington, D.C., and has worked there as a journalist since 2001, when she graduated from Vanderbilt University with a B.A. in English. She first covered politics as a reporter for the weekly Fairfax Times newspaper, then for the daily newswire Canadian Economic Press, where she reported from the U.S. Treasury. Donahue is currently a freelance writer.