I have grape hyacinths that are over-running flower beds and are getting into grass. What is the best way to get rid of them? How do they multiply (i. e. roots, seeds)?
Grape hyacinth multiply by either seed or bulblets. Your problem is with the seeds, though. Make sure to remove the flowers as soon as they have faded to keep them from spreading to areas that you do not want them in.
As for getting rid of them, unfortunately, you will just need to dig them up by hand. There is no selective herbicide for them.
I would like to transplant my grape hyacinths. When is the best time to do it, and what is the proper procedure to successfully move them where they can spread to their hearts content?
While typically this is done in fall, you can also transplant grape hyacinth in spring but try to wait until they have bloomed and then transplant, lifting as much of the dirt around them as possible without leaving any holes in the lawn/garden (during fall, you need only lift the bulbs). Prepare the new location before lifting the bulbs and water well after moving.
How do I store grape hyacinth bulbs until planting in the fall? Or can the bulbs be planted successfully in late May for blooms next spring?
Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/bulbs/bgen/preparing-bulbs-for-winter-how-to-store-bulbs-for-winter.htm
https://www.gardeningknowhow.com/ornamental/bulbs/bgen/storing-bulbs-in-south.htm
I would like information on how to plant, grow and separate grape hyacinth.
This article will help with that: https://www.gardeningknowhow.com/ornamental/bulbs/grape-hyacinth/planting-and-care-of-grape-hyacinths.htm
After a few years, should the bulbs be dug up and then get rid of weeds, which have accumulated over the years? Can the bulbs be put back in the same location? What time of the year is best to do this? Can this be done? My plants are 10 years old and are starting to look rather messy. Should I dig them up? When and how?
You can dig them up anytime if you’re simply relocating them to another area. However, you may want to consider using an organic weed killer or hand pull weeds once the grape hyacinth’s foliage has died back. This should not cause any ill effects on the bulbs in the ground.
I have just moved into a different house. I saw the grape hyacinths this spring but wanted other flowers in the bed. When I dug in the ground to plant, I dug lots of the little grape hyacinth bulbs. Some are quite tidy - a quarter of an inch. Can I replant them in another location now - or do I have to wait until fall? If I have to wait, how do I store the bulbs? Will the tiny bulbs actually produce flowers?
Yes, you can go ahead and replant these elsewhere. This article will help: https://www.gardeningknowhow.com/ornamental/bulbs/grape-hyacinth/planting-and-care-of-grape-hyacinths.htm
I dug up my bulbs to fix my flower bed, now I need to know how to store bulbs AND when to replant them. Can I replant them in clusters or one at a time?
These articles should help:
https://www.gardeningknowhow.com/ornamental/bulbs/grape-hyacinth/planting-and-care-of-grape-hyacinths.htm
https://www.gardeningknowhow.com/ornamental/bulbs/bgen/how-to-store-bulbs-that-have-sprouted.htm
https://www.gardeningknowhow.com/ornamental/bulbs/bgen/storing-bulbs-in-south.htm