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How to prune a clematis?

I've got a clematis that has never flowered and don't know what variety it is. It's recently burst into growth with greenery coming from low down the woody stems. Any idea when we should prune it

Comments (11)

  1. Grower

    Rachel the Gardener

    Hi Stephen,

    Oh dear, it's always a struggle when you lose the label, isn't it? (laughs, but sympathetically.)

    All clematis are bursting into new growth about now - well, they are, here in the south, apologies to Greenies in the north, of course! - so that doesn't help to identify it.

    When I'm faced with this dilemma, I start by asking when it flowered - but again, that won't help in this case as it hasn't flowered yet.

    The rule is that early-flowering clematis, ie the ones that flower before midsummer, don't get pruned now, as they flower on "old" wood, ie last year's growth, that tangled, unpromising, brown-looking stuff.

    Late-flowering clematis, ie the ones that flower after midsummer, can be chopped ruthlessly now, as they will flower on "new" wood, ie the growth they are about to start making now.

    And of course, if the owner gets them muddled up, they can easily end up with no flowers at all - although other reasons for non-flowering of clematis are that they are very young plants, or that they have been over-fed with nitrogen and have made lots of green growth and not enough flower buds.

    The fact that it hasn't flowered so far usually means that it's inadvertently been pruned "wrongly", so I have to ask if you can remember what you did to it last year? If you pruned off all the tatty dead brown stuff at about this time of year, then this might suggest it's an early flowerer, and should be left unpruned until after it has done its thing.

    If you can't remember, then I would suggest dividing it roughly in half, left and right. Cut one half down to about ankle height, cutting just above a strong new sprout of growth if you can. Leave the other half where it is. Then wait, and see which half flowers. Make a note somewhere, or take photos of it just after pruning, to remind yourself of what you did.

    Having pruned half of it, give it a good watering, and some extra potassium (K) to help the flower formation along. If you're a bit unsure about fertilisers, brace yourself for some chemistry. Ready?

    Shop-bought fertilisers contain the three main ingredients: nitrogen (N), phosphorus (P) and potassium (K) (there are lots of other minerals and stuff, which are also needed for good healthy plants, but we won't worry about them for now). They are always listed on the pack in that order, and you will often hear people talk about the N-P-K ratio.

    In broad terms, plants use nitrogen (N) for foliage, phosphorus (P) for good roots and fruit, and potassium (K) to promote flower development, and disease resistance.

    A "balanced" fertiliser such as "Growmore" is labelled 7-7-7 which means it has equal parts of the Big Three.

    Tomato feed (Tomorite is the main brand) is 4 - 4.5 - 8 so you can see that it has, proportionally, twice as much K (potassium for flowers) as N (nitrogen for green growth).

    So by giving it some tomato feed - diluted as per the instructions on the pack, and don't be tempted to make it extra strong, just follow the directions - you will give it a general boost, but with an extra helping of K. Repeat the watering and feeding once or twice a week and hopefully you will be rewarded with flowers!

  2. Grower

    Alison Clark

    Good advice to feed it. Just leave it and see when it flowers and what they look like, and do it right next year.

  3. Grower

    Rachel the Gardener

    Stephen, any chance of a couple of photos of the plant? I'm not suggesting that we can ID it from a photo, but you never know, there are some clever people on here...! A general view of it, and a closer view of the new growth might be helpful, you never know.

  4. Grower

    Angie's Garden

    Rachel, if there was an award for Clematis Pruning advise then you'd win it hands down! Your advice is the best I've ever read - easy to understand and reasons on why to do it.

    I agree that some Clematis would be difficult to ID from a photo but we can possibly narrow it down to species for you Stephen.

  5. Grower

    Rachel the Gardener

    Thank you Angie, (blushes), you're very kind! I'm happy to help.

  6. Grower

    Stephen Barnes

    Hi Rachel

    I hope this photo helps. And I like your tip about pruning half of the plant.

    Thanks

    Steve

    • How to prune a clematis?
  7. Grower

    Rachel the Gardener

    Thanks, Steve - "it's a clematis!" Joking aside, it's not a macropetala, which was what I thought it might be. Anyone else care to throw in an idea?

  8. Grower

    Alison Clark

    And I don't think it's C alpina either.

  9. Grower

    Angie's Garden

    Nor a montana - so between us we've managed to narrow it down to a few hundred!
    Rachel touched on feeding above and to my inexperienced eye I think it would greatly benefit.

  10. Grower

    Rachel the Gardener

    I agree - I very nearly said "ooh, intervein chlorosis" but it's hard to tell from photos, and having already suggested feeding it, I thought that might be one comment too far! The tomato feed should certainly help.

  11. Grower

    Hawthornes Clematis

    Difficult to tell what it is, but if it's not an Atragene group ( alpina, macropetala or koreana ) or a Montana group, then best to butcher it down to a few inches above ground, treat it as a Group 3 and identify it when it flowers in July.


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