a family tree

One of my Christmas presents was a book about plant families, RHS Genealogy for Gardeners.  In just over two hundred pages it takes a brisk tour of the main plant families, from the oldest and simplest non-flowering species to the familiar plants we grow in our gardens.  It is a timely review from my point of view, since apart from giving an overview of all sorts of plants I don't know much about, the botanists have reclassified lots of species in recent years in the light of DNA evidence.  For a middle aged gardener like me, who finds themself resistant to the idea that what used to be Aster may now be Euribya or Symphyotrichum (or Almutaster, Canadanthus, Doellingeria, Eucephalus, Ionactis, Oligoneuron, Oreostemma, or Sericocarphus), it is helpful to be reminded that science and horticulture move on, and it's no good trying to freeze my plant terminology at about two years after the point that I left horticultural college.

The book starts with a family tree.  In the beginning came the Brypohytes, plants of damp places lacking roots or internal means of transporting water, then the Clubmosses and Ferns, and only then the flowering plants.  The earliest of those were the Gymnosperms, with their naked seeds, including modern day Cycads, Conifers, Ginkgo, and the Gnetophytes which are not generally found in gardens.  Then came the flowering plants, the Angiosperms, at which point I began to feel in more familiar territory, apart from when the botanists had moved things.

The family tree of the Angiosperms is designed so that close relatives in evolutionary terms sit closer together on the tree, at which point it becomes truly counterintuitive.  Who would have guessed that mallows and rock roses would sit on one half of a branch the other half of which was occupied by cabbage?  Or that stonecrops, witch hazels, peonies and saxifrages all lived at the end of the same branch?  Meanwhile, elders and honeysuckles are as far from cabbages as you can get, but heathers and primroses share a branch.  It's all come a long way from Victorian botanists counting stamens.

The Asparagus family, which used to be tiny clan, if not classed as merely a part of the Lily family, has risen to become one of the largest among the monocots, that group of flowering plants including grasses that have only one seed leaf, and generally strap shaped leaves with parallel veins.  Grasses, daffodils, daylilies, that sort of thing.  Meanwhile the Lily family, as well as losing asparagus, has also lost colchicums and melianthus to new families, and maples and horse chestnuts have been sent off to join lychees in the previously mostly exotic Sapindaceae.

It is interesting, though, being told which plants are closely related, and sometimes once it's been pointed out you start to see similarities that you didn't notice before.  Clematis, buttercups, columbines, larkspur and monkshood are all members of the Buttercup family, the Ranunculaceae, and when you think about it their leaves are often quite similar and many prefer it not to be too dry, while members of the Ericaceae tend to prefer acid soil.

The introduction contains keys to the major plant groups.  In theory botanical keys are a brilliant idea.  They pose a series of linked questions, and depending on whether you answer Yes or No you are sent on to one of two further questions, and so on until you arrive at the answer, so having confidently decided No, the plant is not a succulent, several questions later once you have said Yes to the proposition that the flowers are bilaterally symmetrical you have reached the point where you know it is a member of the Violet family.  The last time I tried to use one for UK native trees it told me conclusively that the twig in my hand was lime, the only problem being that I knew it was definitely hazel.