Answer: Squirrels can smell the fresh bulbs in the ground and are also curious to see what you are burying there. Once the bulbs have been in the ground all winter, squirrels seem to leave them alone. You may have to try a combination of tricks to outwit the squirrels.
If you are planting a large bed that doesn't have any obstacles to work around, you can cover the area with chicken wire as a barrier to prevent digging. For smaller areas, try placing a big saucer or a board over the newly planted spot. Surface barriers need to stay in place until the ground freezes and be removed before the bulbs sprout in spring. Some gardeners have had success with repellents such as blood meal. Another trick is to dip the bulbs in TreeGuard before planting them. Covering the bulbs with a few handfuls of sharp gravel is a good deterrent because it hurts the squirrels' feet. And if you can't get the squirrels to leave your tulips alone, try planting daffodils - they don't like them.
As for keeping weeds down, as long as you remove weed barrier in the late winter, the bulbs should be fine and you'll have minimal weeds. Another approach is to spread a 3-4" layer of organic matter over the area after planting your bulbs. The bulbs will work their way through the compost or bark but the weed seeds won't be able to germinate.
Best wishes with your garden!
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