My roses often have branches that shoot up a foot or two above other growth
Usually, this is a sign that your rose is trying to revert back to the rootstock. Simply remove these any time that you see them.
https://www.gardeningknowhow.com/ornamental/flowers/roses/removing-rose-suckers.htm
I planted a Glenfiddich rose thirty years ago - it thrived for ten years - then not a single trace of it at all - until today when I was tidying the garden where it had suddenly grown up again, sprung into life and bears a beautiful bloom. How can this be explained?
A portion of the roots may have remained alive, but the top growth died out. Rose die back is common. It is amazing, though, that it took that long to regrow. It also could have dropped some seed, which finally grew.
I’ve let them get about 3 feet tall.
This is a very difficult subject, as it depends on where the sucker originates. This will be best explained by an article which will help:
https://www.gardeningknowhow.com/ornamental/flowers/roses/removing-rose-suckers.htm
Here is information on growing roses from seed. We don't sell any plants or products; we only provide free gardening information.
https://www.gardeningknowhow.com/edible/fruits/grapes/witch-finger-grapes.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/growing-roses-from-seed.htm
I have not planted them. It's unusually hot here (Peterborough, NH). I water every night -- the leaves are turning yellow. I probably watered too much--what should I do to stop the leaves from yellowing and get it back to a healthy plants.
I suspect one or both of the following: Overwatering
or heat stress. Both are treatable.
Overwatering or sitting in water can lead to yellowing leaves in roses because it causes root rot and deprives the roots of oxygen. This prevents the roots from absorbing nutrients properly, resulting in nutrient deficiencies and yellowing leaves.
On the other hand, heat stress can also cause yellowing leaves as it can lead to excessive transpiration and dehydration of the plant.
To correct these issues, it is important to ensure proper drainage for the plants and avoid overwatering. Additionally, providing adequate shade and reducing heat exposure by putting them in shade on occasion can help prevent heat stress. Regularly monitoring the moisture levels in the soil and adjusting watering accordingly, as well as providing appropriate temperature and humidity conditions, can help restore the health of the plants and prevent further yellowing of the leaves.
This article will offer more information:
https://www.gardeningknowhow.com/ornamental/flowers/roses/yellow-rose-leaves.htm
Had tenants in the house 2 years during covid, Rose bushes were un-tended but still doing great .... but too huge now. How far can I cut them down, and how? Should I fertilize after I cut? They have great gorgeous flowers & scent, but now being eaten by tiny green "slugs" on underside... should I spray w/ horticultural oil after cutting? Thank you.
Rose bushes can take a severe pruning in stride. If your bushes go dormant in the fall, wait till then to prune. Many people prefer to cut roses back in spring. You can spray Neem oil on the pests now. Here is more:
https://www.gardeningknowhow.com/ornamental/flowers/roses/pruning-roses.htm
With the hot weather my rose bush has lost all its flowers but has left me a lot of green buds and I wondered if they can be regrown in any way thank you
Shrub roses bloom off and on all summer so if that is what you have, the green buds should bloom. Some types of roses only have a spring flush but sometimes bloom again in late summer. It just depends on your rose. You don't need to do anything extra to make it bloom.
Here is more info that should help:
https://www.gardeningknowhow.com/ornamental/flowers/roses/different-types-of-roses.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/what-is-shrub-roses.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/roses-that-are-hard-to-kill.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/no-blooms-on-roses.htm