Fatsia Japonica Cut Back ?

I grew some Fatsia Japonica from seed, a few years back. I now have two in my garden which are over 6 feet tall. A little to big for the location. How and when can I cut these plants back? I need to reduce them by about a third.
TIA

 

Hiya HarryS
Yep, they do...suddenly it seems...grow quite large
Need to reduce by a third? You can prune one in 3 main stems back hard to the ground. Or, as I have done, simply cut back all the stems...if you do this, use secateurs to cut to shoots on every stem

 

I usually do mine at this time of the year, gives you some new growth this summer, so cut back a bit lower than you want the plant to be, but I cut mine back last year and it struggled a bit with the dry summer.

 

Thanks Verdun and Pete
So I will cut back each stem to above a leaf node, and now is the time to do it. That's a job for tomorrow.