This is my first year with Sir Thomas, so no doubt someone else will have some better information for you, but when I pruned back my enormous Harison's Yellow I waited until end of flowering and then cut one side back hard, and left the other side for the next year. The next fall I repeated on the other side. That way I still had a good crop of blooms each spring.

Where do you live? What zone? I usually recommend only hard pruning in the spring for most roses except once bloomers which should be hard pruned immediately after blooming. In the spring the rose is in high gear to grow so it seems to be the best time. In the fall, particularly in cold climates, the roses are slowing down in preparation for winter. I don't think that's a good time to crop them back. They need to store energy for the spring start up and they store that in the canes. If you cut them all off you cut off their early spring food source.

Excellent point, I forgot that Sir Thomas is a rebloomer. HY is a once bloomer, so I was told by the local plant center that it would only bloom on growth that it got going again after pruning and before winter.

I'm on the Cape in Mass. Think he flowered once. Does that mean i should cut back now or in the spring (not sure what ya'all said). Still not sure how far to cut back. He's about 12 feet tall and flowers n the top 4 feet

How good are you at IDing budeyes? I'd cut it back in the spring to about 4 or 5 budeyes per cane. I'm thinking that will be between two and a half and three feet, but it is the number of budeyes that can sprout new branches that matters.

What Mad said! According to HMF Sir Thomas is not a once bloomer. That means he blooms on new wood and can be pruned back in the early spring.

Once bloomer will only bloom on year old wood. That means last year's canes. If you prune off last year's canes in the spring you will get no bloom. For once bloomers you leave them alone in the spring until after they have bloomed. Right after they finish blooming you can prune them. Then just leave them alone until after the next spring's bloom. You want to let them grow back over the summer and leave that growth so it will bloom next spring.

But doesn't that give you much fewer blooms?

Sorry but i'm little confused. Can i go either way?

Seil, technically there are fewer blooms, but not a lot fewer, and the ones remaining are of higher quality.

Let's take Karl Forster for an example,

Most of what was pruned out was dying wood from underneath. It wasn't going to bloom anyway, and was only going to take energy from the plant. That's why it gets cut out. It you wait until summer to cut it out, you can't see it, and you run the risk of damaging a fair amount of young growth pulling it loose. If during the spring pruning, some buds get accidentally cut off, who's counting? This isn't a HT, even though it has halfway decent HT form, where every flower gets obsessed over.

Dale, prune it in spring. Fewer bugs.

Great photo Mad. I also love a natural shape where you let it go and do what it wants. Take your pick. They are both good.

So prune it in the spring and watch out for buds...