Not while they are still greenish in color. Wait until they have died back or you might not have many blooms next year.
Yes, it is recommended to cut back foxgloves after flowering to promote new growth and prevent self-seeding.
If you cut back the flowering stems of lupins after the flowers have faded you will get a secondary flowering. Any other cutting back should be to the ground in Spring when growth restarts.
You can ,but why would you? The right time to prune a Forsythia is immediately after flowering.
If you are referring to Spanish Bluebells, they do not have a relationship to trees. They are a perennial flower that grows from a bulb.
Normally after flowering
Can I assume you mean Wisteria? If that is the case summer pruning is the proper way to control it and encourage flowering. Shorten back the shoots that grow from the main stems after flowering.
Yes, you can trim them back to about 3 inches in this shape "^".
After flowering. Unless the plants have outgrown their space it is better not to prune them. You may lose the next years flower.
Cut it back to about an inch from the soil, give a light feed and water it and it will flower again in the Autumn.
Yes; cutting the stem back will produce more flowering branches. However, don't cut them when caterpillars are actively feeding. If you feel you need to cut them at that time, cut only 1/3 or so of the branches at once to leave food for the caterpillars.
Iris leaves should be trimmed back when they have brown tips. Cutting the flowering stalk to the rhizome will also discourage rot. The leaves usually don't need to be trimmed because they will carry on photosynthesis for next year's growth.
We need to cut back on power usage, the bill is too high.