Suburban Gardener—

Ask Anyone Who Has Tried_To Grow Them: Not All Hydrangeas Are Equal

By Gerry McCabe

Regardless of how many articles are written on the Hydrangea, it never ceases to amaze me that the same questions always arise over and over again. Why didn’t mine bloom? How do you get the flowers to turn blue? Why did mine die during the winter? I picked the flowers to dry for arrangements and they withered and died, why?

If there was one universal answer to these queries it would be “Not all Hydrangeas are created equal.” The species you plant may have been that globular blue beauty you received as an Easter gift back in April, but did you check the fine print an the accompanying tag? Chances are that particular plant was Hydrangea macrophylia or Big Leaf Hydrangea, which does have some cultivars that will survive a winter in zone 6, but most of the supermarket varieties sport a hardiness zone of 8, which equals the likeness of northern Florida. That’s why it died. Buyers beware.

Of the Hydrangeas hardy for our zone 5-6 winters, Hydrangea macrophylia does offer some beauties that with a little TLC in winter, will reward you with glorious summer-sky blue globes of magnificent inflorescence.

The old favorite, which I have, is ‘Nikko Blue.’ This hydrangea sports huge deep blue flower clusters atop a vigorously growing plant that can reach six feet high. I doubt I’ll ever see mine grow that tall for one good reason: Theses hydrangeas set their flower buds on last year’s woody growth. Being the cold sensitive nature of this particular species, if you don’t protect the woody growth you see growing outside right now, all you’ll get next summer is a flush of lush green foliage…no flowers.

I try to keep mine of manageable size of four by five feet and when Thanksgiving rolls around, I enclose the entire plant with chicken wire and proceed to cover it with layers of oak leaves, which will not mat or decay quickly. Then around the second week of April I slowly remove the leaves about a foot every two days and Viola! — I have saved last year’s wood from harm and can look forward to a blossoming frenzy.

Of course to get that cherished blue color you must amend the soil with the mineral aluminum but that is not enough. This plant is tricky. You can dump sacks of trace minerals containing aluminum all round this plant but just like a stubborn child it will not eat it unless the soil pH is perfectly acid in the range of 5.0 to 5.5.

Try the combo Aluminum sulfate available in most garden centers. Seems like a lot of work, but not really. After a while it becomes second nature.

Also falling under this species is the blue lace-cap hydrangea. ‘Blue wave’ is the most vigorous and a stunning variegated leafed (white edges) blue lace-cap, while ‘Mariesii Variegate’ can steal the show when in full bloom. Both of these, which I have grown well in sun to part shade, need winter protection.

On the other side of the coin are the Hydrangeas paniculata and arborescens. These bloom on the current year’s growth, meaning the flower buds form on any new wood growing from the crack of spring. No winter protection is needed. These guys can be pruned hard in late winter and as a matter of fact, they love it.

My Hydrangea arboescens  ‘Annabelle’ was stooled, or cut right to within 4 inches of the ground, this April and it rewarded me with most colossal 12-inch wide white flowering blossoms that I thought were only pictured in cottage gardens and fairy tales. Easy to grow, non-fuss ‘Annabelle’ needed a bit of shelter from the hard afternoon sun lest her leaves would wilt in despair but with a little water and cool evening temps she bolted right back to the special lady she is.

Hydrangea paniculata, or the “Cemetery Hydrangea” which I call it, is the hardiest of all. In contrast to arborescens, paniculata can grow anywhere, sun, shade rich soil, poor soil and if left to be, it can grow rapidly to 25 feet tall. Basically needing no special care, this plant has been a popular specimen in low maintenance areas such as cemeteries and public parks.

Blooming late in the season, the modified cone shaped flowers open as tender cream white then to a blush of pink to full pink and finally to brown. The flowers will stay on the plant though the winter for seasonal interest. These are the drying hydrangeas. Do not cut them until the pink blush covers at least third of the flower head. Any earlier and they will wilt.     

So now, with this abbreviated primer on the Hydrangea favorites in hand, see what you can do and be brave with the “blues.” It is fun to see your patience rewarded.

(When she isn’t tending to her garden at home, Gerry McCabe spends some of her time continuing her gardening education at Naugatuck Valley College in Waterbury. Gerry, a certified master gardener in Connecticut, can be reached at TNGCATS@aol.com.)