Question
Hi Courtney,

I live just north of Toronto, Zone 5b, I believe. This past summer I planted a perennial Hibiscus that was producing huge flowers (one about every few days for a few weeks at the end of the summer). I am wondering now, do I have to prune it for winter like a regular perennial? It has 2 stems, that look pretty strong, but it is not a bush. Do you know what kind of look I should expect in a few seasons? I mean, will it get any "bushier"? Will it be giving more flowers?

I am a new gardener; I know by now that a lot of perennials should be pruned, but what about peonies? What about false sun-flowers (tall bushy plants with yellow flowers, not daisy-looking ones with brown centers - sorry, I am not even sure if I call them correctly)?

Thank you,
Oxana  

Answer
Hi Oxana.

I think the first plant you're describing is Hibiscus syriacus or "althea." This plant is hardy to minus 20 degrees Farenheit. This should tell you whether to expect any winter die back. You can use pruning to give a couple of different shapes depending on what you want to see. In my own garden, my altheas resemble small trees. They have a single trunk (3 inches thick) and branch out half way up. They don't get much taller than 9 feet. You can also get the althea to look more like a bush. Younger, multiple stems equal a bush, so you'll need to prune out older wood every year. Rather than winter, you get best pruning results if you do it in early spring--before leaf buds open. You'll get better bloom results this way.

I cut my peonies to the ground in late fall, when they've browned. In your area, you'll get best results by doing the same thing. This assumes you're talking about herbaceous peonies, of course, and not tree peonies (if they have flexible green stems, they're herbaceous; if they're woody, they're tree peonies--don't cut these to the ground!)

On the false sunflowers, you can prune them if you don't like how they look in the winter, or you can leave them and cut them back in the spring. This is another plant you'll get good results from my cutting it to the ground or near the ground.

I hope this helps you out. Congratulations on being a new gardener. Good luck!