Several people have written (below) of this problem. Before you can do anything you need to know what the problem is; here is our advice from below. See also the info under 鈥淧ests鈥 above:
鈥 There are also foliage-loving bugs. Go out after dark with a flashlight and examine your plant for slugs, earwigs, whiteflies, etc. (Google for photos or see our pest library). Once you identify the pest, you can figure out a control to deter it.
鈥 One possibility is that your soil has become depleted … trying enriching it, but not too much. If they are super cramped, they may need to be divided. Another possibility is that surrounding plants or structures may have changed since last year and your ladies are getting less sun.
鈥 Go out after dark with a flashlight and examine your plant for slugs, earwigs, whiteflies, etc. (Google for photos or see our pest library). Once you identify the pest, you can figure out a control to deter it.
鈥 If this happened overnight, it would normally be a deer or rabbit or animal. They usually leave the stem and go for the leaves.
Otherwise, look carefully at the leaves. Caterpillars tend to chew holes in the leaves. Slugs chews ragged, irregular shaped holes in leaves that cross the veins. See our pests and critter library to I.D. and learn more: http://www.almanac.com/topics/gardening/pests-and-problems
We hope this helps!