If the China doll plant likes for its roots to be root bound, when would it be advisable to repot it?
Never repot a plant until it is fully acclimatized to its environment. Also, plants generally don't need to be repotted unless they require watering more frequently than every three days, and then to a pot only 1-2" larger. Over potting frequently leads to over watering, which in turn causes root rot.
I have two China dolls that are about 3 years old. They are about 5 feet tall and still in the same pots in which I purchased them. They are getting too tall and too wide for their indoor location and I have not been able to find any instructions for pruning them to keep them to the size I want. Will pruning damage the plants? Your website does not recommend repotting but what about transplanting them to an outdoor location?
Pruning can be done at any time. A healthy stem can be cut back to any point on that stem. The new growth will emerge just below the point of the pruning cut, so prune back to the place where you want new growth to come in. If your plant is healthy and you are able to keep the soil properly moist, then there is no benefit to repotting or replacing soil. If you live in an area where cold winters are not a problem, then it can be transplanted outdoors. They can not survive winter outdoors.
I have a 20+ year old China Doll plant that has flowered this summer. Is this normal? I read that these don't have flowers.
It does not normally flower, especially of it is grown indoors, but it is possible. You are very lucky to have seen a flower on the plant. Enjoy. :)
I received my China Doll plant as a gift about five years ago, and we have, for the most part, followed the tips on your website (which I just found today, lol). One thing, however, we didn't know about - we have repotted the plant into a bigger pot twice. For the most part, the plant is fairly healthy, although it does lose a lot of leaves. My concern, however, is that the plant is enormous. It's over six feet tall, and so slender that it is collapsing under its own weight. Should we be pruning it? If so, please give specific instructions - this is the first plant I've ever had to really care for, and frankly I'm clueless.
Pruning can be done at any time. A healthy stem can be cut back to any point on that stem. The new growth will emerge just below the point of the pruning cut, so prune back to the place where you want new growth to come in.
Is China doll (Radermachera sinica) poisonous to dogs or cats?
This plant is considered non-poisonous. For future reference to poisonous plants, these articles should help: https://www.gardeningknowhow.com/plant-problems/environmental/plants-toxic-to-cats.htm
https://www.gardeningknowhow.com/plant-problems/environmental/plants-poisonous-to-dogs.htm
https://www.gardeningknowhow.com/houseplants/hpgen/keeping-your-pet-safe-identify-poison-plants-in-your-house.htm
I purchased a 4-inch potted China Doll last year. It is now about 4 inches in diameter, but has one lonely branch that is over 4 FEET tall. How do I get this plant to 'fill out', along with the growth. If I cut this long, tall branch, will the rest of it die? Please help, as this is the only China Doll I have ever owned in 25 years, which actually stays alive for me. All others have only lasted a month or less.
Pruning of China doll plants can be done at any time. A healthy stem can be cut back to any point on that stem without harming it. The new growth will emerge just below the point of the pruning cut, so prune back to the place where you want new growth to come in.
I have a 2-year old China Doll in a 16-inch pot on the floor. It's very happy and has reached the ceiling. Its new pair of leaves and the main stem are still trying to grow and are smashed against the ceiling. Should I top it or prune it back, and if so, how much? Also, it recently developed a sucker at the base. Can I root that?
Yes, you can prune it. A healthy stem can be cut back to any point on that stem by 2/3 to 1/2. The new growth will emerge just below the point of the pruning cut, so prune back to the place where you want new growth to come in. As for rooting another plant, this article should help with that: https://www.gardeningknowhow.com/houseplants/china-doll/china-doll-plant-propagation.htm