Hydrangea Care and Perennial hibiscus et. al. - Knowledgebase Question

Name: Lily Adu
Avatar for ladu
Question by ladu
September 25, 2005
I was smitten this summer with the beauty of hydrangea flowers at the nursery and couldn't resist buying quite a few. It occurred to me as the season wore on that the hydrangea I bought last year - of the 'Endless Summer' variety - did not live up to its name and never quite bloomed at all this summer, let alone all summer. There were a few and far between semblance of petals now and then but nothing like the profusion of blooms I saw on the plants in the nursery. I would like to know what I can do to my hydrangea shrubs between now and next summer to ensure that they bloom all season long, like they are supposed to. Among other care instructions, I would like guidance in pruning, and in soil treatment to change color of blooms. Speaking of which I also bought the hydrangea limelight bush - can the color of the blooms on those be changed as well, and if so how?

My 2nd question pertains to perennial hibiscus. I bought this unique perennial hibiscus from one of your distributors last year. It has really fine leaves, almost like the Japanese Maple, and big red petals (but not quite as big as the Luna hibiscus - it is quite special and made my yard the talk and envy of my neighborhood. So much so that, my neighbor would like to have it in her yard, but I haven't seen it in the nursery this year. (Ash's Flower has a similar kind this year but with slightly bigger, fuller flowers and bigger leaves). I would like to know if it is possible to divide the clump and give a piece to my neighbor. Or would this ultra-altruistic gesture kill my beloved, one-of-a-kind perennial hibiscus?

Answer from NGA
September 25, 2005
Your zip code places you in zone 6A which is getting very cold for growing Hydrangea macrophylla successfully. Most varieties bloom on the old wood from the year before. If winter kills off the branches or if spring frosts damage the early buds, then the plant will not bloom. (And if you prune it in fall, winter, or spring or early summer, it will not bloom for the same reason.)

The Endless Summer variety however is able to bloom on both old growth and on new growth of the season. If the winter kills off the old growth, it can still bloom later in the summer and into the fall on the new growth. In climates where the plant does not die back at all in the winter, this can make its bloom season seem "endless". In climates such as yours where it is normally too cold in winter to bloom these hydrangeas, the late blooming on new growth allows the plant to bloom nonetheless.

To try to maximize the bloom potential of your hydrangeas, they should be grown in a spot that is a warm microclimate, sheltered and protected from the winter wind. You might consider a wind break if it is in the open. Hydrangeas need some direct morning sun or very bright dappled light all day in order to grow vigorously and set flower buds. The soil should be organic and humusy and evenly moist yet well drained like a wrung out sponge. You should mulch with several inches of organic mulch in a flat layer over the root area all summer, and add to that in late fall after a few freezes. (Do not heap it over the stems however.)

In the spring, trim away any winter killed wood but minimize your pruning as much as possible. If a late frost is predicted, cover the plant to protect it.

Ideally you would fertilize based on soil test results, but an annual top dressing of good quality compost along with some slow release 10-10-10 in granular form should be adequate. Read and follow the label instructions. To some extent the color is affected by pH. In your area it should be naturally acidic enough to bring out the blue color. It is better to wait until your plant has been in the ground for a few years and see what color it settles into. Some plants will shift a bit until thoroughly rooted in the native soil. Then if you want to adjust it you can do so, but be sure to do it slowly to avoid shocking the plant. Usually it is better to enhance the natural pH than to try to fight it.

The perennial Hibiscus can sometimes be started from root cuttings in early spring before it starts to grow, or can be rooted from tip cuttings taken in the summer. The tip cuttings are less stressful on the parent plant, so that is what I would suggest.

If possible, you are welcome to ask as many questions as you'd like, but please limit to one question per Q&A entry -- thanks!

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