My variegated weigelia is 2 years old this summer and I am enjoying it. I'm not so sure about the growth, though - but maybe it's just my own aesthetic preference: As you can see in the picture, it has a single, very tall vertical branch and I'm not sure it I should cut it back (next spring?) so that it is more compact - or if the rest of the bush will eventually catch up with the single stalk, so I should just leave it alone, even if it looks a bit strange at the moment?
It is a very good idea to prune them. There are several things to know before you do, though. This is not the easiest shrub to prune. Here is an article that will help:
https://www.gardeningknowhow.com/ornamental/shrubs/weigela/pruning-weigela.htm
This collection of articles will help also:
We have two ruby weigela bushes we planted late last Spring. They are doing well with lots of blooms but the branches are lying on the ground instead of upright. What’s wrong?
This is likely due to a few things. Some weigelas naturally have arching branches, especially when loaded with heavy blooms. Lack of pruning can also make branches too long and weak. To fix this, you can stake the branches or use plant supports to help them stand up. Prune them after they finish blooming to keep them strong and tidy. Also, make sure you're not overdoing it with nitrogen fertilizer, and water deeply but not too often. Mulching around the base can help too by keeping the soil in good shape.
https://www.gardeningknowhow.com/ornamental/shrubs/weigela/growing-weigela.htm
https://www.gardeningknowhow.com/ornamental/shrubs/weigela/pruning-weigela.htm
Then the leaves turned yellow, got brown spots and now the entire bush looks dead. I sprayed for insects but didn't help. My question is should I cut it back and try for next year or is it too late?
This can happen for a few reasons. Waterlogged roots, or disease caused by them. Fungal blights can cause these symptoms, too. Some can be controlled with fungicides and some cannot. Another cause that is common is root nematodes. They can destroy a plant pretty quickly. There aren't really any good cures for that one.
I would not plant in the area for a few years. This will get rid of most of the problems that it could be. Solarizing your soil wouldn't be a bad idea, either.
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/plant-problems/disease/root-rot-in-garden-plants.htm
t years spring bloom to prune? I planted young wiegelas from 2 gallon pots, and they have begun to flower. My intention is to control the size somewhat, but all instructions say to wait until late spring after the first bloom. Since they are flowering now, should I just wait until next spring's bloom is over and then prune? Also, are they supposed to flower this late in the season? I live in Zone 5B, Northern Illinois area. Thanks for your help.
Weigelas typically bloom in spring. Since yours was just planted in spring it got a late start. You are lucky it bloomed at all this year! It wouldn't hurt to lightly prune the ends after blooming, but it is getting late in the season and you want to be sure it has time to harden off before cold weather, at least six to eight weeks.
Weigelas bloom on "old wood" or the previous season's growth and that is why you prune after blooming and not before. You don't want to cut off next year's blooms.
This article should help:
https://www.gardeningknowhow.com/ornamental/shrubs/weigela/pruning-weigela.htm