Can you please tell me if lupines are toxic to dogs?
Unfortunately, it really depends on the variety. This article may help:
https://www.ohsu.edu/oregon-poison-center/pet-poisoning
Lupines have finally got a hold in my garden, but I have other flowers in there and am wondering will it hurt the lupines if I cut the plants back after they have flowered to give the other plants a chance to be seen.
Lupines respond well to deadheading. Yes, you can cut the spent blooms and you may even get a second round of blooms if you do.
They are unsightly and if I remove them, does this prevent the plants from returning next year? Do they need to reseed from these pods to return? Thanks.
If they are unsightly, go ahead and clip them. You may even get additional flowers when you do. While some are considered annuals and others perennial depending on your locale, you can always save a seedpod or two (store in brown paper bag in cool, dry area) until next season just in case. Here is more info on these plants: https://www.gardeningknowhow.com/ornamental/flowers/lupine/growing-lupines.htm
I clipped my dead brown seed pods at the base last year after they were spent. The greens stayed healthy and green year round (even through the snow and I did not protect it in any way). As of last week I’ve got six new small to medium sized blooms... clip them!
The stalks are curling. . . as well as the leaves. There are, however, small flower blooms.
Curling is typically caused by a pest of some kind, such as aphids or whiteflies. Examine the plant closely to find the pests, they can be quite small. Treating the plants with a pesticide will help to clear it up.
Can I keep the seeds from lupines when flowering is over and set them out again?
Yes, you can harvest the spent blooms or dried seed pods from the plant and either save them for spring planting or direct sow them in the garden in fall. Some types do require soaking on water overnight prior to planting.
I am in zone 5a and I found plants that say zone 3. Will they do well in zone 5 (i.e. Lupinus perennis 250 seeds, Papaver glaucum Tulip Poppy, Tanacetum coccineum Double Mix)?
Plants typically have a range of zones they can live in, for example zones 3-8. These plants you are looking at will grow in zone 5 as well as zone 3.
I have moved some full grown Lupine plants to another part of my garden. They don't seem to be standing up as they should. Should I perhaps take some height off them to give them a chance to recover?
Yes, cutting back the foliage on a transplanted plant is always a good idea, to make up for the roots that were lost. This article has some insights into lupine care that you may find useful: https://www.gardeningknowhow.com/ornamental/flowers/lupine/growing-lupines.htm