The best way to keep your Magnolia and tulip, grape hyacinth and daffodil bulbs safe is to dig the grass out manually. Which of course is a big job, but it doesn't have to be done all at once. It can be done over a period of time. Another option would be to dig up some of the bulbs. You may not be able to get them all, but you can get a lot of them. Then take care of the grass with an herbicide, let the bulbs dry and re-plant in the fall. If you don't want to use an herbicide on the grass, you can cover the grass with landscape fabric or cardboard and leave it on long enough to kill the grass.

Following is a link to UMASS Extension article about Weed Management. The techniques for weed management are the same for grass. https://ag.umass.edu/greenhouse-floriculture/fact-sheets/weed-management-for-outdoor-cut-flowers
The article talks about non-chemical options as well as chemical options. There are some herbicides listed that are said to be safe to use around trees, shrubs and flowers. CAUTION: Not all tree, shrubs or flowers are safe. It is imperative to read the labels to determine if your Magnolia and bulbs will be safe.


I have attached pdf files which include the labels for two grass specific herbicides that indicate they are safe to use around flowers: Ortho Grass B Gon and Bonide Grass Beater. Check to see if they are safe to use around Magnolia and bulbs. There are other herbicides listed in the UMASS link above.

Bottom line, check the product labels of any grass specific herbicide you choose. Garden center and nursery workers can help.