Why Doesn't My Hydrangea Bloom?

"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 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 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!

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 blooms on old wood and late summer blooms 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 hydrangea needs soil with an acidic pH to allow aluminum uptake. In Pennsylvania, we have plenty of aluminum ions in our soils. We must lower the pH of the soil to 5.2 to 5.5 so that the hydrangeas can access the aluminum. Apply elemental sulfur or a soil acidifier to adjust the pH. Commercial growers use aluminum sulfate in the soilless potting media to create blue-flowered hydrangeas. Adding aluminum sulfate is unnecessary in our soil and may damage hydrangea roots. To promote blue flowers, avoid fertilizers with high phosphorus levels. Conversely, to encourage pink flowers, add lime and fertilizer with high levels of phosphorus to prevent the aluminum from entering the plant's system. The pH for pink flowers should be 6.0 to 6.2. 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 turn green with maturity, and can be cut back, if desired, anytime from autumn to spring. New varieties of H. arborescens, Invincibelle® Ruby and Invincibelle® Spirit, have naturally pink-rose flowers. This native hydrangea does not change its flower color based on soil pH.

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!

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.

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