A question about pruning

[GardenGeek]

Hi.

Why does pruning hard generally ensure more vigorous growth, while lighter pruning makes the look more compound?

May be it is stupid to think about such things but i think like that..lolz

[Chris]

It depends on the plant, but pruning hard back to a larger trunk or the crown of the plant will allow it to send up new, often thicker, canes or stems.

Whereas pruning higher will only encourage new stems from that point, which are likely to be thin and twiggy.

[hairycaterpillar]

Hi Garden Geek,
I think that's a good question I never really considered the reasons for the difference. I wonder if it's got something to do with the plant hormone auxin being produced in the shoot tips. I remember this part from college. When you take this tip away the side buds are allowed to grow, causing the plant to bush out.

I had a quick look on wiki it says that auxin causes ellongation of shoot tips and inhibits side shoots.

However. When cutting back hard you are taking away all side shoots aswell.
I'm only guessing but I think this is related to other plant hormones aswell as auxins. Something to do with the relationship between root and leaf being governed by the presence of a specific hormone telling the plant how it needs to grow when it's been cut.