Because the mint bush was so thick the banksia has really been struggling and has long spindly branches with foliage only on the very tips of the branches. What little foliage it has seems to be healthy enough (considering...) but now it's competition is gone I've been thinking of trying to rejuvinate it by simulating a fire by removing it's branches down to the base (lignotuber) and allowing it to reshoot now that it has room to develop fully and making it more of a feature. The base of teh trunk is about 1 foot in diametre and the main branches seem to sprout form the swelling at the base (which I am assuming is the lignotuber). Before I do I would like some confirmation that what I am looking at is in fact a lignotuber because if I cut a non-lignotuberous banksia to the ground it is going to die on me. I'm 99.9% sure it is but if someone who knows could confirm it that would be great.

The flower (taken some during last winter):

If there are any tips in preparing a native plant for such an event I'd like to hear them too. It is developing new growth now so I assume it is in a period of active growth in preparation of the winter flowering season.

Cheers,

Simon

Isn't it great fun cutting back a garden to uncover hidden gems!

You'll be glad to know that this variation of Banksia spinulosa will respond well from coppicing to the lignotuber (yes, it is a lignotuber!). The only species of B. spinulosa that you will kill from cutting back is B spinulosa var. cunninghammii, as it does not grow from a lignotuber. You certainly don't have this variety as its leaves have more of a pronounced serrated margin (and yours is obviously growing from a lignotuber).

There's no need to simulate a fire before you cut it back, they respond just fine to hard pruning alone. I'd be cutting it back at the beginning of, or at some point during winter before it sets flower. This is when the lignotuber, essentially an energy storing organ, has the most stored nutrients in it, ready for flowering and growth.

If you wanted to, you could put down a VERY LIGHT feed of specialised protea fertiliser now in prep for it's cut back at winter's beginning, this should help it along.

This species also responds well to formative pruning when growing after a cut-back. It will give you a neater, and more dense shrub with more flowers. Don't be afraid to prune it as it grows is size after your cutting it back!

Good luck, I hope it all goes well and you uncover some more hidden gems in your garden.

Cheers,

Jim

I visited a nursery yesterday that had B. spinulosa var. 'collina' and mine is this one. 'collina' seems to have wider leaves than mine does and not quite so revolute. I think mine must be B. spinulosa var 'spinulosa'. Which ever way it goes it will look a lot better and be a lot more productive now it's enemy has been vanquished :)

Quick question... I live in Tasmania and the frosts we get here are fairly harsh and temps will get down to -6ish at night at head height (so lower at grund level). If I cut it back at this time do you think the frost will knock it around too much?

B. spinulosa is frost hardy to -10, so it should be fine. My advice would be to rake away any mulch from around the lignotuber, as mulched surfaces will frost heavier and more qucikly than unmulched surfaces.

Of course if you're really worried, you can keep a sheet of plastic or an old bed sheet outside that you can pull over the lignotuber when temps get really cold (but this shouldn't really be necessary).

And cutting it back now should be fine!

Good luck, Simon!