Wow, time flies! I've been trying to be good about posting and then suddenly I look up from what I'm doing and it has been THREE WEEKS! Where does it go?!?
My Hydrangea macrophylla varieties are beautiful this year. They're usually the most prone to damage by early frosts and in the Nashville area we usually have one good Hydrangea macrophylla year out of every five. But it's the Hydrangea serrata cultivars that are truly remarkable. Words just can't describe how loaded with flowers they are! Hydrangea serrata 'Blue Billow' has outshined anything else in the garden by far and Hydrangea serrata 'Beni' is proving itself to be an exceptional plant. If you're unfamiliar with the "serratas", the plant resembles our common garden hydrangea (Hydrangea macrophylla), but the leaves are typically a little smaller and usually have a matte surface to the leaf rather than the glossy or semi-glossy leaf of the "macrophyllas". The other difference is that the "serratas" are almost all lace-caps, with their delicate flowers seeming to float just above the plant.
I am frequently asked about the proper culture for hydrangeas. Generally speaking, they prefer moist, rich, well-drained soil and plenty of water. In my estimation, one of the most common mistakes is planting them in too much shade--even in the South. At minimum, they really need to be sited in morning sun and the more sun you give them, the better they will usually flower. Sunlight helps to ripen their semi-woody stems late it in the season and the more ripened and hardened off they are before winter sets in, the more likely those stems and the buds they carry are likely to survive the winter to flower the following year.
Wilting vs. Flagging. I think it's very important for gardeners to know the difference between a plant that is "wilted" and a plant that is "flagging". A wilted plant is one that has drooped because the soil around it has become dry and it can no longer pull water from the soil. Water is pulled out of the leaves and into the stems for storage--a defense mechanism to try and stay alive. A plant that is flagging has plenty of moisture at its roots, but is responding to another environmental factor--usually sun (especially with hydrangeas), but it can also be a response to a dramatic change in air pressure or humidity.
How do you tell the difference? Easy. Does the plant stand back up and look "normal" once the sun is no longer on it (or after the weather front passes)? If so, then the plant has just "flagged" in response to some change in its environment. Openings on the back of the leaf, called stomata, have closed in order to conserve water inside the plant and the plant droops. Hydrangeas, specifically, may flag every day if they're in the sun, but as long as they have moisture at their roots, they'll be fine. If, however, your plant has wilted from being too dry, the leaves won't perk back up, even after the sun is off of the plant or the weather has finished changing. If you have hydrangeas that wilt in the afternoon sun but do not perk back up once the sun has gone down, they probably need a thorough soaking around their roots.
In the fall, usually around Labor Day weekend, I stop watering my hydrangeas altogether--only supplementing them if they wilt and stay wilted for more than 3 or 4 days at a time. This is a little bit of "tough love", but I want their woody stems to ripen and harden off and a little bit of stress helps to do this. I don't go overboard and will give them some supplemental water if their wilting persists for more than a few days, but I've found that this "hardening off" process helps me to have more reliable blooms the following season.
Guess I had better sign out for now, but I'll be back again in a week or so! Hope your hydrangeas are outdoing themselves this year!