The care information provided in this section represents the kind of practical advice is available for all the plants in this web site if you subscribe to the monthly customized newsletter Yardener’s Advisor.
Oakleaf hydrangeas tolerate some dryness better than most other hydrangeas as long as they are planted in healthy soil with lots of moisture retaining organic matter in it and are mulched. However, they always need generous watering for several weeks after they are first planted and just before the ground freezes in the winter. During prolonged droughts in the summer or if they are in poor soil or are unmulched they will need periodic supplemental watering. Run your sprinkler or a drip system for about one half hour weekly.
Hydrangeas wilt when the temperatures heat up. They lose moisture through transpiration faster than their roots can take it up. So it's possible to water them well one day and find the plants wilting in the noonday sun the next. However, if the plant remains wilted in the morning, it should be watered immediately.
For more information see the file About Watering Equipment
Hydrangeas are fairly heavy feeders. If they are not planted in soil rich in organic matter and mulched regularly they will appreciate some fertilizer in the spring or fall. Sprinkle slow-acting granular fertilizer--either all-purpose or a product for acid-loving plants--on the soil under the shrub in the early spring for the rain to soak in. Follow label directions. Do not fertilize in the summer, because the new growth that will result will still be too tender to withstand early fall frosts. For more information see the file About Fertilizers
Spread a 2 or 3 inch thick layer of organic mulch on the soil under each hydrangea shrub. Chopped leaves, wood chips, pine needles, or shredded bark discourages weeds and helps retain soil moisture. Over the winter it insulates soil from temperature extremes, protecting the shrub from soil heaving caused by alternate freezing and thawing. The mulch layer decomposes over time, adding valuable organic matter to the soil around the hydrangea. Renewed periodically, the layer of mulch also harbors beneficial insects to help keep your shrub healthy.
Click here for more information on About Fertilizers.
Oakleaf hydrangeas do not need routine pruning. However, over the years it is advisable to cut back to ground level some of the oldest, weakest canes periodically to rejuvenate the shrubs. Do this thinning in the early spring. Do not prune individual stems later in the summer or you will remove the buds for next year's flowers. Pinching off faded flowers is optional, since the faded flowers left to dry on the shrub are so beautiful even into the winter. You may leave them for winter interest in the landscape or cut them over the fall for dried bouquets indoors. For more information see the files on Pruning Shrubs and Choosing Pruning Tools.