Everyone loves Hydrangeas – they are a classic summer shrub for partially-shade parts of the garden, and their long-lasting blooms make a real impact for weeks and weeks – probably longer than any other shrub. They’re popularity, and the big market for potted bushes sold in flower, means that a lot of work has gone into breeding them, with many, many varieties available, and more arriving every day. This makes choosing the ones you want exciting, but the abundance of forms can lead to disappointed if you get something that isn’t what you expected. Some understanding of these shrubs, which have some unusual things going on with their flowers, will make it much easier to know what you are getting, and get what you want. So we are going to dip our toes into some botany and plant history, and find out what is going on. . .
The Basics – Mophead versus Lacecap
- Mophead hydrangeas have big, round heads of many large flowers
- Lacecap hydrangeas have a circle of large flowers surrounding many small, fluffy flowers
- Both come in shades of blue or pink, usually changed by the acid/alkaline balance of your soil
- Lacecap hydrangeas stand up to rain and wind much better than mopheads
- Both can be found in reblooming types, which is what you need in colder zones to get good flowering
- Hydrangeas you buy flowering in pots rarely do well in the garden – choose garden varieties from a nursery
Sterile and Fertile Flowers
Most of us have some basic knowledge of flower structure, often learned in school from some simple flower like a tulip. Petals, right? Those big colorful things that make up most of the flower, and attracts pollinators. Look in the center and you often see a bunch of fuzzy yellow things – stamens and pollen, remember?, plus a bigger thing in the middle where the pollen goes – the stigma. Down below is a little green ball, the ovary, that makes the seeds. . . ah, it’s all coming back now!
Trouble is, old Mother Nature is a fiendishly-inventive lady, and she doesn’t like sticking to the basics. Plants have evolved a multitude of variations on that basic plan, designed to attract some specific pollinator, and often ‘economy of effort’ is part of the planning. Making those big petals takes a lot of work, so you don’t find them on plants that don’t need ‘em. Many plants use the wind to carry their pollen, (as hay fever sufferers know all too well), which is why so many trees, and grasses too, have tiny flowers that don’t waste their time with pretty petals.
Some other plants – like our hydrangeas – do need to attract pollinating insects, but they figure, “Why give every flower petals, if I can attract all the insects I want with just a few?” Wild hydrangeas almost all gather their flowers into big clusters of tiny, petal-free flowers and then throw in some bait in the form of a few big flowers with petals around the edges. Insects arrive, wander around a bit, and the pollination is done – smart trick, huh? The ‘bait’ flowers are called ‘sterile florets’. They usually have four broad, flat petals, and since you don’t want the insect wasting time there, after landing, these flowers offer no pollen, and they don’t produce seeds – hence ‘sterile’. The remaining flowers are called ‘fertile florets’ and there are hundreds of them, each one with pollen, a stigma and ovary, but no petals. It turns out that the best design is to put the sterile florets around the outside of the flower head, and the fertile ones in the middle. So the basic form of hydrangeas is a ‘lacecap’.
Today there are many varieties of both types – you can see our current selection here. Worth mentioning that the plants in flower sold in flower shops and grocery stores have been developed as potted plants, and rarely do well when planted in gardens. Better to buy from a nursery, as those varieties have been bred to grow in gardens, not greenhouses.
The Introduction of Hydrangeas to Europe
So why, when most of us think, ‘hydrangea’, do we see that big ball of flowers we call a ‘mophead’? For that we can blame the neglect, indifference and colonial attitudes of early plant explorers, especially in Japan and China, where the first hydrangeas came from. Those countries had elaborate societies, and gardening had been a ‘thing’ for many centuries. If you have gardens, you need gardeners to grow the plants, and places to buy them. Many of those ‘intrepid’ plant collectors basically went down to the equivalent of a Garden Center, and purchased plants they had never seen before. These were shipped back home with great fanfare and introduced to a public eager for novelty. So it was with the mophead hydrangea.
The central figure in the first Western understanding of Japanese plants is Carl Peter Thunberg. This Swedish doctor got himself a job at a trading post at a time when it was virtually impossible for foreigners to enter Japan. He was also a botanist, and wrote the first book on Japanese plants, published in 1784. It was hard for Thunberg to travel around, but he did what he could – which was a lot. The hydrangea he described was a mophead we today know as the variety ‘Otaksa’.
It was developed in China from a Japanese species that was naturally a lacecap type, like all wild hydrangeas, and from there imported back into Japan, where it was a rarity in gardens. Thunberg almost certainly ‘found’ it being carefully grown a garden or nursery.
Getting in a book is one thing, getting the real plant is another. The first living hydrangeas in Europe arrived in England in 1788, from China, brought over by the botanist Joseph Banks. That plant must have also come from a nursery, as it too was a mophead type. James Edward Smith, another English botanist, named it ‘Hydrangea hortensis’, which is why many people still today call these plants ‘Hortensia’. Many years later that original plant was renamed as the variety, ‘Sir Joseph Banks’.
variety, ‘Sir Joseph Banks’ Thunberg’s original variety, ‘Otaksa’, didn’t get to Europe until the 1840s.
Amazingly, the wild form of these plants wasn’t ‘found’ by a westerner until Ernest Wilson, an Englishman who often worked for the Arnold Arboretum at Harvard, brought seed back in 1917. He found Hydrangea macrophylla f. normalis
on Oshima Island, off Tokyo. The rules of botanical naming mean that this wild plant has to be called a ‘form’ of the garden plant, which gets the simple Hydrangea macrophylla as its name today. That wild plant is of course a lacecap type, and not very showy – no wonder Thunberg spotted the mophead, and never saw the parent plant. It probably wouldn’t have been of much interest to Europeans. If it hadn’t been for Thunberg’s and Bank’s trips to the Garden Center, it is very unlikely we would be growing the profusion of hydrangeas we grow today.