How To Get Hydrangeas To Bloom

Why Doesn't My Hydrangea Bloom?

Big-leaf hydrangea (Hydrangea macrophylla) Photo courtesy of Penn State Master Gardener Program

"Why doesn't my hydrangea bloom?" It wasn't until I became a Master Gardener that I ever thought about this question. I have always been familiar with the four main types of hydrangeas: the peegee (Hydrangea paniculata 'Grandiflora') tree that came with my parents' house in 1946; the 'Hills of Snow' variety (Hydrangea arborescens) between my parents' and the neighbor's backyard; my Uncle Joseph's gorgeous oakleaf hydrangea (Hydrangea quercifolia) near State College; and Mrs. Russell's pink and blue hydrangeas (Hydrangea macrophylla) in Cape May, New Jersey.

So, why doesn't my hydrangea bloom? Usually because of poor pruning by humans or by Mother Nature.

I have learned to ask for more information before I give a complete answer. "Did you receive the hydrangea for Easter or Mother's Day? Did it have pretty foil or plastic around the pot?" If so, the plant may be a "florist's" or "gift" hydrangea. It is simply not winter hardy in our area. Mother Nature freezes the flower buds and/or the stems each year destroying the future flowers. The hydrangea roots may be hardy, but the top of the plant is not. Usually, these plants are a big-leaf hydrangea (Hydrangea macrophylla). Most varieties bloom on "old wood," i.e., wood that grew and produced flower buds during the previous year. Therefore, early or late freezes or bitter winters may damage the flower buds. The other reason that hydrangeas don't bloom is pruning at the wrong time. If you cut back a hydrangea between the autumn and early spring and it blooms on old wood, you have trimmed off all the future flowers!

Hydrangea macrophylla

Look for a newer variety of Hydrangea macrophylla that blooms on both old and new wood. Read the plant tag and ask for help at a nursery. Try the Endless Summer® or Let's Dance® collection of re-blooming hydrangeas. You get early bloom on old wood and later bloom on new wood (current season's growth).

A bonus with the Endless Summer® series is that the pH of the soil determines the color of the flowers. To produce blue flowers, the plant needs a soil with an acid pH to allow aluminum uptake. Apply aluminum sulfate, one tablespoon per one gallon of water, to the soil each month of the growing season. Take care to water well before treating, as this chemical can burn the roots. Avoid fertilizer with high phosphorus levels. To encourage pink flowers, add lime and fertilizer with high levels of phosphorus to prevent the aluminum from entering the plant's system. It may take more than a year to see a change in color. Be aware that lime may leach from house foundations and sidewalks. In these areas, blue flowers may be difficult or impossible.

How about taking the easy way? Plant a native, like Hydrangea arborescens. 'Hills of Snow' or 'Annabelle' are hardy here, produce beautiful white flowers that green with maturity and can be cut back, if desired, anytime from autumn to spring.

Hydrangea arborescens 'Annabelle'

Another great native option is Hydrangea quercifolia, the oakleaf hydrangea, with four seasons of interest: huge white flowers that mature to shades of pink, gorgeous red leaves in the autumn, an open shape with brown exfoliating bark during the winter, and green, oak-leaf shaped foliage in the spring. Wow!

Hydrangea quercifolia

Perhaps you don't have room for a bushy hydrangea. Try a tree form of Hydrangea paniculata 'Grandiflora', or peegee. They bloom on new wood so one can trim off the new growth to the standard (trunk) each year, if desired. The huge flowers mature to pink and are easy to dry for winter bouquets.

Hydrangea paniculata

There is one more thought to consider about non-blooming hydrangeas. Those green mounds are lovely all by themselves! Just love them for what they are.