This big, ‘user-friendly’ hydrangea stands out for North Texas gardeners

·4 min read
Neil Sperry/Special to the Star-Telegram

My gardening friend, I introduce you to the most “user-friendly” hydrangea you’re ever going to meet here in North Central Texas. It’s a big one. It’s a shrub that, with some varieties, can grow to be five or six feet tall and six or eight feet wide.

Because its huge leaves loosely resemble those of a few species of oaks, it’s called “oakleaf” hydrangea, and that nomenclature even carries over into its species name. Oaks are all in the genus Quercus, and oakleaf hydrangeas are Hydrangea quercifolia.

Odds are you’re not even going to equate it to the pink or blue “mophead” hydrangeas you buy for Easter or Mother’s Day, because this one is sold with, and used as, a major landscaping accent shrub. Its leaves, and even its bare stems in the winter, are notably coarse-textured. Few plants that we grow will stand out as well from a distance. And when those leaves turn rich crimson red in the fall, they’re even more impressive.

But leaf size, texture, fall color, and the plants’ bark character in winter all pale in comparison to the real reason we grow oakleaf hydrangeas. It’s those magnificent flower heads that range from eight to 12 inches in length. They’re green as they begin, opening up to bright creamy white, then shading to pink or rose and on to chaffy brown after they’re finished. Some gardeners let them dry in place before harvesting them for dried flower arrangements. Others of us prefer to trim them off immediately after they finish flowering so we can reshape our plants and encourage good regrowth for next spring. Neither technique is right or wrong. It’s totally a matter of preference.

There is another great feature of oakleaf hydrangeas. They thrive in the shade. That’s typical of most hydrangeas, so we shouldn’t be surprised. However, unlike the others, these will hold up in morning sun. Either way, what they do require is highly organic planting soil that is kept uniformly moist at all times. Incorporate five or six inches of compost, peat moss, finely ground pine bark mulch and rotted manure into the top foot of soil, and be sure you’re not planting right on top of an outcropping of very alkaline white rock caliche subsoil. Black clay can be amended, but the caliche is eventually deadly to oakleaf hydrangeas. Iron deficiency will ultimately win out.

No plant will show signs of dry soil any faster than hydrangeas, oakleafs included. Let them be your early warning system for the rest of your landscape. When they wilt, everything is about to get dry as well. Soak their soil deeply, then wait until they’re dry before watering again.

NOTE: When an oakleaf hydrangea is sitting in full sun in springtime, its lush new growth will often start to wilt while the soil is still moist or even wet. There will be so much call for water to keep those big leaves plumped out that the conducting tissues can’t pull water through fast enough. Putting more water onto already wet soil won’t help in that circumstance. The plants will gradually adjust.

Because this plant has become more and more popular, named cultivars have come into the market. Your local independent retail garden center should have them. (But they sell out quickly). They’ll be in five-, seven-, and 10-gallon containers, and they’ll probably be in full bloom when you buy them. Some will have more compact growth habits for smaller urban landscapes. Others may have larger blooms, while some will have smaller heads but proportionately more of them. The selection ‘Ruby Slippers’ is very interesting, because its heads turn rosy-pink as they age.

In the 30 years that I’ve had oakleaf hydrangeas (probably 20 or more of them) in our local country landscape, I’ve never seen the first insect or disease bother them. In our alkaline soil, I am always concerned about the soil-borne fungus known as cotton root rot being a problem with any hydrangea (or almost any type of plant in general), but I add so much organic matter before planting them that it has been no problem for mine.

Iron deficiency is the only major concern. As I mentioned, if you’re going to try to grow this plant, you’re going to want to add a bunch of organic matter. That will lessen the chance of chlorosis. But, if you see the characteristic yellowing leaves with dark green veins starting to appear on the newest leaves, that would be the time to apply an iron/sulfur amendment. Keep all iron products off surfaces that could be stained.

Finally, to wrap it all up — if you do try a mophead (“florist”) hydrangea, it will require shade. No sun after about 9 in the morning. Give it the same highly organic planting soil, and it may need protection from extreme cold in the winter. A shaded alcove would be ideal. They struggle here anyway due to our alkaline conditions, and very hard freezes can finish them off.