These radish sprouts are covered by an old grill grate. The second picture has some other metal grid thing on top, and so far, so good on keeping squirrels at bay.
This pot is filled with Green Leaf Gailen, which is a type of Chinese kale that is supposed to be a bit like broccoli but easier to grow. We're trying it this year, and it has sprouted, although it is hard to tell in the picture because the sprouts are still tiny.