Expert: C.L. Fornari - 7/22/2009

Question
QUESTION: I have 3 hydrangea plans that get very tall (about 3-1/2 feet, lots
of green large leaves but very few blooms.  The blooms I get are huge,
beautiful color but very few.  I tried last year not to cut the stems back at the
end of the season.   I only trimmed them to the first node.  What am I doing
wrong.


Answer
Victoria,
Did you not get my reply about this sent yesterday?  Since you asked this as a followup to your question about petunias, my answer would have come back with the petunia subject matter.

In any case, I'm assuming that you're talking about the blue and pink blooming hydrangeas we call "mop heads" - these bloom on what we call old growth - that is, the flower buds form the previous year and bloom the following year. If those buds get cut off, or zapped in cold winter or spring temperatures, the stalks don't bloom the next year. (Note that there are a few types that bloom on both old and new growth - Endless Summer and Penny Mac are examples.  If these are cut down or freeze down in cold winters, there will be fewer flowers.  That said, here are the reasons that hydrangeas may not bloom:
1. cut down short at any time of the year - this cuts off those future flower buds.
2. If the temps get too cold in the winter - if it goes to zero or below the buds get frozen and die - happens most on upper parts of the canes.
3. Cold April temperatures - if there is a warm spell in March, followed by cold winds in April, those swollen buds that have started to grow in march get zapped with the cold April winds. This happens frequently in the Northeast coastal areas.
4. Too much nitrogen - if the hydrangeas are near the lawn, and the lawn gets even one application of fertilizer (which is high in nitrogen) this promotes leaf growth on the hydrangeas at the expense of the flowers.
5. Too much shade - hydrangeas need at least 3 hours of direct sun in order to bloom well.

I hope this helps,
C.L.