I need to prune after the plants froze. Each plant is eight feet tall. There is no new growth on the top, but one plant has new growth at the base. Should I prune severely? They look like crap.
Cut off any brown or yellow leaves, as these will not come back. Then let the rest recover for a season before pruning for looks. This article will also help:
https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-of-paradise-pruning.htm
I have three Bird-of-Paradise plants (don't know what type, but the flowers look like the ones pictured on this website) that have grown to enormous proportions (very tall and wide). It takes me two days and much angst to cut out the dead leaf and flower stalks each year. Is there any way to reduce the size of these plants without damaging or killing them? Can they be divided and transplanted? If so, is this the right time of year to do those things?
You can divide them. This article will help you with that:
https://www.gardeningknowhow.com/ornamental/flowers/bop/dividing-bird-of-paradise.htm
One of our Strelitzia's foliage is turning yellow and the leaves are developing small black spots. We live in southern Spain and have had an unusually cold and wet winter. Do you think this is the problem?
Wait until spring is fully here and cut back the plant. Remove the yellow foliage, as they will not come back. Do not remove any greens. These articles will help you as well:
https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm
https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-of-paradise-pruning.htm
My BOP finally bloomed, but now that it is done and the flower is dry, should I cut that stem, cut the pod where the flower was, or leave it alone?
You can do any of these. All will not hurt the plant. Just do the one that works best for your personal aesthetics regarding your BOP.
My Bird of Paradise has all these leaves that are torn and they look bad. It is a white Bird of Paradise. How much do I prune off the leaf?
This article will help you: https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-of-paradise-pruning.htm
How far to plant apart and how deep?
The planting hole should be dug about 2 to 3 times the diameter of the root ball with plants spaced about 2-6 feet apart.
Please advise me on how to trim back (rather severely) the Bird of Paradise.
Cut back the plant by no more than 1/3 per year. Cutting back anymore than that will kill it. Another option would be to divide the plant.
These articles may help you:
https://www.gardeningknowhow.com/ornamental/flowers/bop/dividing-bird-of-paradise.htm
https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-of-paradise-pruning.htm