The Monday Garden, Eco-gardening at its best
August 6, 2005, Issue 176
Hydrangea pom-poms are as sub/urban as the rhododendron, and golden retriever. However, did you know that of the 5 hydrangea varieties most popular here in North American, two are natives and only one (an Asian) turns color depending on the PH? If you are a sub/urban denizen, it’s good to know something about this ubiquitous plant, if only for making small talk at parties.
Picture: close-up view of a big-leaf hydrangea flower. Bedford Street, Stamford CT August 2005
Hydrangeas, part of the large Saxifragaceae (“stone breaker”) family, come in about 100 varieties and countless hybrids. Interestingly, hydrangeas are native only to the Americas and Asia (including Japan, Korea, China, the Himalayas, and Indonesia), yet a good part of the hybridizing, particularly early on, took place in Europe.
GROWING HYDRANGEA
Growing conditions: Garden hydrangeas, like many popular things suburban, are dependable and forgiving so they are a good “starter” plant for a new gardener. It is said that fossils of hydrangeas have been found in North America that date back some 40 to 70 million years; and that those found in Asia date back at least 25 million years. Accordingly, hydrangeas can survive just about anything. All you need to do to continue this tradition is duplicate hydrangeas’ natural edge-of-forest growing conditions. Plant in sun or up to half-shade, with well-drained soil with good organic matter, and give them at least average moisture, more in full sun. They are fairly drought hardy but do best with adequate moisture.
Like most garden plants, hydrangea benefit from a nice, cozy top dressing of 1 to 2 inches of organic mulch. Also, like many, many garden plants, if given enough sun and water, and mulched every couple of years, hydrangea do fine without any additional nutrients or fertilizers. You can save your money to buy a bird bath or a nice pair of pruners. (grin)
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Pictures: winter views of a bigleaf hydrangea. Stamford CT Winters 2004-2005; 2003-2004
Pests and problems: A healthy hydrangea will be just about pest –free. While such things as leaf spots, powdery mildew, aphids, and blight are possible, the diseases shouldn’t occur if the plant is in the right location, and, generally, the plant can recover from any minor infestations without help. If the plant is developing problems, move it to a more favorable location.
Deer: Deer eat hydrangea, particularly the native ones. (Keep in mind The Monday Garden cure for white-tail deer damage: plant some things that the deer will like to share with them, and ask that your local officials to fund deer population control efforts. If all gardeners put 10% of the resources we collectively spend on fending off the deer into population control, there would be no problem).
What not to do: Hydrangeas need space, so don’t over-crowd them. They don’t do full shade so make sure they get at least half day sun. While hydrangeas prefer adequate moisture, they don’t tolerate flooding well, so make sure that they aren’t left standing in water. Hydrangeas get cold, particularly in zone 6 north, so mulch well, and don’t plant in overly-exposed locations.
Pruning/flowering habits: Hydrangeas are valued for their med-to late season flowers. Hydrangea flowers come in three shapes: the big, round “mop heads”, the flattish “lace caps, and the conical “panicles”. Hydrangea carry their flowers in large clusters at the branch tips. The showy flower parts tend to be the big sepals or bracts of the sterile, outer flowers. Most hydrangeas will hold their flower heads all winter, if not dead-headed, and can be a major plus for the winter garden.
Some hydrangeas bloom on new wood; so they can be pruned at any time, and may bloom a second time if dead-headed. (Note: deadheading to force a plant to re-bloom, in my view, can sap the plant’s strength and interferes with its natural way of being, so if you’re going to do it, go easy – don’t do it every year or only do part of the plant.)
Some types of hydrangeas are said bloom on old wood, and, as such, it is said that they should only be pruned right after flowering. The old wood- new wood debate isn’t settled.
You can “split the baby” by pruning enough early in the spring to keep the plant small enough for the garden but save enough of last year’s buds to produce plenty of flowers. What works for me: I prune early in the season, leaving the bottom two or three sets of buds on “old wood” hydrangeas and get plenty of flowers.
picture: Late winter view of the same bigleaf hydrangea as above. Here you can see the as-yet-unpruned bud pairs. Stamford CT Winter 2004-2005
What not to do: Don’t prune off all of the flower buds, regardless of the time of year. In zone 6 and north, where winter damage is likely, don’t prune in the fall.
THE NATIVE HYDRANGEAS
Smooth Hydrangea
Oakleaf Hydrangea
THE IMPORTED HYDRANGEAS
BIGLEAF HYDRANGEA
PANICLE HYDRANGEA
CLIMBING HYDRANGEA
OTHER NOTES ON HYDRANGEA
Dried Flowers: Hydrangeas make great dried flower if you can bear to take them out of the garden. Hang up side down away from bright light. They can also be pressed for collages.
Medicinal and food use: Hydrangea leaves are seriously poisonous to most mammals, so don’t go chewing on them. Hydrangea flowers, though, are considered relatively low-pollen for allergy suffers, and will attract pollinators and other beneficial insects. There are many reports of the oakleaf hydrangeas’ seeds being eaten by wild life. In theory, at least, this should also be true for at least the smooth hydrangea. Medically, hydrangea root has been by herbalists to treat certain prostate and urinary problems.
Invasiveness: The Asian hydrangeas are not particularly invasive in the north due to lack of winter hardiness, etc. However, the native hydrangeas are said to be a problem outside of their native range in parts of the south and midwest, so check your local invasiveness before choosing a hydrangea for your garden.
Photo credits: Sue Sweeney © Sue Sweeney 2005
Comments (7)
Hi! Nice to hear from you.
Actually, you can start now -- early August. Many people cut the iris leaves back to a fan of about 4" to 6". I don't know if cutting the foliage back is helpful to the plant but it looks neater.
The important thing with iris is to keep the tops of the corms (roots) above ground. Usually it's best to NOT water for a few days after transplanting. It's best of any cuts in the roots have had time to heal over before major watering or you could get rot.
Sue
Posted by S. W. Sweeney | August 10, 2005 7:35 AM
Posted on August 10, 2005 07:35
I just ran across your site while looking for a good on-line place to buy bulbs. I could not find a physical address on your main page and wonder what is your gardening zone? My live in Houston, TX in zone 9 and gardened in clay soil when I had a yard. My daughter lives in MA and gardens in zone 5a in mostly subsoil put in my the contractor after he blasted off the top of a hill to make her house site.
I am interested in finding plants we can both grow as we share a love of gardening.
As I was reading this article, I wondered if she could grow hydrangeas. I know I can BUT I always think of them as shade plants or plants to put along the north side of the house here in our strong, hot sun. I've never seen climbing hydrangea grow here either. Can it? What hydrangeas will grow in 5A?
I read several of your articles and enjoyed both them and the pictures and have bookmarked your site. But if you could add information on what zones we can grow the various plants in, that would be helpful or at least identify your location as to zone.
Thanks,
Marilyn Kircus
Posted by Marilyn Kircus | August 10, 2005 7:54 PM
Posted on August 10, 2005 19:54
Marilyn--
I am Southern CT, zone 6, but plant for zone 5.
I try to include some idea of zone information. If I've left it out, see Floridata.com which is a great source for information about plants that will do better in the hotter parts of the country.
With hydrangeas, the climbing hydrangea is said to be the hardiest and should go north at least as far as Boston. According to the "experts", most hydrangeas won't go north of Zone 6, perhaps with shelter and mulch. A better test than the "experts",though, is to look around town and see what's growing.
On the south end, you're right that in Texas hydrangea is a shade plant. The "experts" think Zone 7 is pretty much the cutoff. I'm wondering, though, how the oakleaf hydrangea, a Southeast native, would do down by you. Do you see much of it around your area?
Sue
Thanks for your reply. After I responded to the article, I looked at the links and found zone information.
We have a lot of hydrangeas south of I-10 in the end of zone 8 and the beginning of zone 9. However most of the old ones - I think the bigleaf ones- are in Louisiana where the soil is acid. I think the only problem to growing them in Houston is the heavy clay soil which would have to be amended with lots of compost and the beds raised.
I do see lots of Oakleaf hydrangeas used in commercial landscaping. I only recently realized it was a native.
Marilyn
Posted by S. W. Sweeney | August 21, 2005 7:41 PM
Posted on August 21, 2005 19:41
From the S.CT Master Gardeners web site (posted there by Chris Reid, an extraordinary gardener:
When you get a query regarding a hydrangea that has a funky
flowering year and pale leaves/wilt easily, here is some info that
may not cross your mind right away. Too much fert. can actually
interfere with flowering in hydrangeas, so even though pale leaves
might sound like a nitrogen deficiency alone, sounds like it's
important to get a a SOIL TEST and asking that they check for salt!
This tip is from the Hydrangeas Plus newsletter:
Winter tip - salt and hydrangeas
If you salt your drive and walk ways, the run off could be harming
your hydrangeas and other plants. We recommend using non sodium
chloride based salts like calcium chloride, sawdust, fireplace ashes
or gritty sand. There is a new product on the market called CMA
(Calcium Magnesium Acetate) that will actually help your plants by
replacing important trace elements. You may have to sweep the
residue of some salt alternatives after the ice is gone but your
plants will be much happier.
Salt overdose wont appear until later in the growing season. Plants
will slow their growth and leaves will pale and be much more
susceptible to the sun. Hydrangeas may or may not bloom after a salt
overdose but if they do bloom, petals will be smaller and bloom time
will be curtailed.
If you must use salt, some tolerant varieties of plant material are
Day lilies, Junipers, Spruce, and some varieties of Sedium and
Syringa lilacs.
Posted by S. W. Sweeney | February 9, 2006 4:06 PM
Posted on February 9, 2006 16:06
Can I grow Hydrangea's in Lutz, Florida?
(Close to Tampa, Florida) I'm not sure which Zone I am. I think it's either 9 or 10.
Posted by tampa1307 | April 20, 2006 11:58 AM
Posted on April 20, 2006 11:58
You sure can!
According to www.Floridata.com, which is headquartered in Florida (and a bunch of very nice people), no problem to grow hydrangeas in Zones 9 and 10. However, you need to shade the hydrangea from the extreme heat of afternoon sun.
enjoy
Sue
Posted by S. W. Sweeney | April 23, 2006 10:23 AM
Posted on April 23, 2006 10:23
Rich --
Floridata.com is Florida-based and according to their site, the oak leaf hydrangea grows wild as far south as the Florida panhandle and they rate it good for Zone 9. They also advise the Southerners to plant oak leaf hydrangea in part shade with only morning or evening sun
Sue
Posted by S. W. Sweeney | June 9, 2006 6:50 AM
Posted on June 9, 2006 06:50