Hydrangea serrata 'Blue Bird,' which is a fantastic summer presence. The clusters of blue flowers attract plenty of pollinators during the three to four weeks of bloom (from mid- to late-June well into July), and the light green almost chartreuse foliage is a great foil for other interesting foliage. Hydrangea serrata is a species native to eastern Asia (Korea and Japan), where it prefers the higher elevations, lending its common name, the Mountain Hydrangea. This species is closely related (some view it as a sub-species) to H. macrophylla, the Bigleaf Hydrangea, but H. serrata is more cold hardy, and has slender stems and smaller leaves. Hydrangeas are in the eponymous Hydrangea family, Hydrangeaceae.
Hydrangeas tend to bloom in mid-summer, which makes them a smashing addition to the shrub border, where most species bloom in spring. Hydrangea blooms range from the big, I mean HUGE globe-like puff balls of Hortensia types of H. macrophylla to the upright spikes of the wonderful native Oakleaf Hydrangea to the almost flat-topped clusters of our plants. A mixed planting of Hydrangeas is a great illustration of the diversity found within a genus, yet maintaining an obvious commonality.
The flower colors of H. serrata range from blue to pink, with mauve, purple and some other words for that range. Periwinkle comes to mind. As with most Hydrangeas, the flower color is very dependent on the soil pH. At more neutral to alkaline levels, the colors tend to pink, while acid soil brings out the blues. Unfortunately the most sensitive Hydrangeas can appear a strange mix of purple, pink, mauve and periwinkle at the same time. You might think that sounds nice, but try planting something next to it. It reminds me of trying to find drapes to match the eclectic crap in my old cabin in Kentucky.
I get asked all the time about pruning Hydrangeas, and I have given up on trying to get people to properly identify their species (I mean the species of their Hydrangea). Some bloom on new wood, or wood that is produced in the present growing year. Other species produce flowers on wood that is a year old. If you prune at the wrong time, you can be cutting off the flowering potential for a whole year, and as much as I love Hydrangeas, without flowers they lose their charm (the native Oakleaf Hydrangea DOES have a very good fall color though). So my best advice: if you are not sure what species you are growing, prune AFTER flowering and only prune for shape or size management. Don't cut your Hydrangeas to the ground in the spring UNLESS YOU KNOW IT BLOOMS ON NEW WOOD. If you can identify dead wood, in early spring remove
the dead wood from your Hydrangea but don't cut too low. You will not have to prune H. serrata, because it grows to three or four feet tall, with a spread of four feet, staying well-mannered and very presentable throughout the year.
H. serrata is hardy to USDA Zone 6, or even 5 with some protection. In really bitter winters, the cold will blast the flower buds (this tells us that H. serrata blooms on year old wood), but this is rare in our zone. Plant in partial shade, or full sun with good moisture. They will show some signs of drought stress if not given adequate water when planted in full sun. "Full sun" is a funny phrase. People from northern Europe
wouldn't say we get full sun, but what it means operably for us is at least six hours of unshaded sun per day. H. serrata likes afternoon shade (don't we all?), and well-drained average fertility garden soil. Found in pots or sometimes balled-and-burlapped at the better nurseries, plant them in spring after the soil has warmed a bit. H.serrata leaves contain a natural sweetener related to dulcin, which is hundreds of times sweeter than
sugar. Discovered just a few years after saccharin (in the late 19th Century), dulcin was touted for some time as a good sugar substitute and even better than saccharin because of a lack of bitter aftertaste. The specific compound in H. serrata leaves (pyllodulcin) makes it a very nice herbal tea base, and is used in Korea and
Japan. In the latter country, Amacha Tea is used in the celebration of Buddha's birth.
The larger but sterile outer flowers surround the fertile perfect (having both male
and female parts) inner florets, giving this and other Hydrangeas the common
moniker Lace-cap. Bees, butterflies and all kinds of pollinators abound on our
plant on sunny days.
