If you find that your shamrocks are over grown or think they died [over watering and under watering at the top culprits], you can easily propagate them.
Shamrocks grow from corms, or rhizomes that look like clusters of little bulbs. Dig them gently out of the soil. You can gently break apart the corms or rhizomes into smaller pieces to grow additional plants.
If you have coffee grounds, you can mix in a couple tablespoons in.
Then cover the shamrock rhizomes with a about an inch to an inch and a half of soil.