Cane-growers or peripherals?

The Gardenist (the book) started out much bigger than that which was eventually published.  We deleted nearly half the word count a few months before pressing the ‘print’ button.  Each chapter was nearly as long again with stuff about how to care for each of the plant groups discussed – mostly info I wish someone had told me twenty or so years ago.

Hydrangea arborescens ‘Annabelle’. A classic cane-like grower

One of the bits I was sorry to see go discussed what I consider to be possibly one of the most significant factors by which shrubs can be divided into two groups.  The most obvious division in shrubs for temperate climates would be whether they’re evergreen or deciduous, which is little more than an aesthetic consideration.  But possibly one of the most useful divisions is whether shrubs are cane-like or peripheral in their growth.

English box – as peripheral a grower as you’ll find – here, the golden variegated form in new growth

(The other really useful division within shrubs is whether they flower on current season’s, or last season’s wood.  But that’ll make a post on its own.)

Yikes.  I can see that I’ve now backed myself into a corner of explanation that was never the point of this post.

Hydrangea paniculata in its autumn garb. Straight, unbranched canes clearly visible

As for the obligatory explanation:  The most obvious shrubs of primarily cane-like growth are roses and hydrangeas.  All really strong new growth comes from deep within the shrub – mostly from quite near the ground – and shows itself in long, initially unbranched shoots that head straight upwards, often puncturing right through the existing outline of the shrub.  Pruning shrubs of this form usually entails a slow but constant renewal of their fundamental structure by removing old, tired growth right down to where some younger shoot emerges.  It’s pruning from the inside, if you like.

This, of course, is entirely different to how you’d prune English box or Viburnum tinus, both example of shrubs that grow almost entirely by extension of the tip.  Pruning these shrubs is nearly always about trimming over their outline with hedging shears, or at least cutting them from the outside.

Some eccentric clipping in Bibury, Gloucestershire, of one of the variegated forms of Euonymus. You HAVE to use a peripheral grower for this sort of work. It’s always pointless trying to shape a cane-grower.

And now for the point I really wanted to make.   It was only when I was writing The Gardenist that it occurred to me that almost all evergreens are of peripheral growth.  There are very, very few whose growth is cane-like.

Leycesteria formosa – a plant very firmly in the naughty corner according to weed police

(There’s a converse leaning towards cane-like growth amongst deciduous shrubs, but there are far more exceptions)

The only two evergreen shrubs of cane-like growth I could think of at first were the once common-as-muck Abelia grandiflora, and Leycesteria formosa (Himalayan honeysuckle) which is hardly ever seen in gardens any more, but is something of a weed in high rainfall parts of the South-eastern Australia.  Later I thought of the semi-evergreen forms of Hypericum like ‘Hidcote’.  As I’ve been writing this post, I’ve added the evergreen buddlejas like B. globosa and B. salvifolia.  But so far that’s all I can think of.

 

Can you add any more?

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(Just thought of a few more myself:  Solanum, Nicotiana glauca, Iochroma.  Dang.  I’m almost nullifying my own point.  Then again, they’re all pretty warm-temperate and frost tender, and the numbers certainly appear to increase with the warmth of the climate of origin)

Yet another!  Leucothoe. I’ve gotta stop thinking about this, or I’ll delete this post on the grounds of it being self-contradictory

 

 

 

 

 

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6 thoughts on “Cane-growers or peripherals?

    • And I’ll join you there. I really like Leycesteria as well. And I’d love to grow it really properly, or carefully, and cut all those older canes out before they’re even past their best – keep it super-fresh

  1. So Michael as someone who has just taken up gardening, I have 2 small oak leaf hydrangeas. Do I prune them? I have not to date. They are 2 years old and not exactly thriving ( that could be the position).

    • There’s a tough decision to make with oak-leaf hydrangeas. They flower nearly exclusively on stems that branch off older wood. But they also get bare legs if left unpruned. So the decision is either for a nice, tight mound of their excellent foliage (which is achieved by annual hard pruning), or flowers atop gawky, rather leafless stems (when unpruned, or lightly tip-pruned, leaving plenty of older wood). I’ve sometimes worked my way around that by planting a double row and pruning the front row hard each year, but leaving plenty of previous-years stems on the rear row. If there’s only a single, large plant, I’ve tried pruning the front harder than the back, and that’s worked OK.

      But in your case, I wouldn’t prune at all. They either don’t like the position or the soil doesn’t suit. There should be plenty of good growth after two years if they’re happy. Either lift them and really work up the soil with compost and replant, or move them. They like part shade, but hate competing with tree roots.

  2. Interesting ideas, Michael. You could add Philadelphus mexicanus to the list as well… and to extrapolate on the theme- I guess bamboo- though of course we are talking culms and not canes. It is curious yet true that some clients fancy their bamboo ‘hedged’ (their words, not mine). Chacon a son goux (this keyboard doesn’t help!)

    • You’re right. Philadelphus mexicanus is a perfect example. It’s also, in my opinion, in very under-rated shrub. OK, it gets just way, way too big, and the flowers are virtually hidden. But there’s that incredible citrussy scent – all the more alluring from such a hidden source! The only thing it lacks (no, it’s we that lack) is a good management strategy to keep it fresh and manageable in the long term.

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