That depends on where you live. If you live in a cold winter area where it is often below 30 degrees than I suggest you gather the best of the crocosmia bulbs from the ground in the fall and store them indoors in a brown paper bag. Plastic bags can hold too much moisture. Then in mid spring replant the bulbs into fresh soil. If you just want to thin out an overgrown patch then early fall is a fine time to dig in and dig out the weakest plants with the corms or bulbs still attached to their roots. The crocosmia will form a new corm under the old worn out corm from the summer. So when you dig out the entire grassy clump you can remove both the old and new corms often by pulling up one stem. Once you have one plant for every one foot of garden space that plant will no longer have to compete for food and water and you will enjoy stronger more vigorous plants. Thanks for the reminder. My crocosmia patch has fewer blooms and less foliage this summer. A sure sign I need to dig in and thin out my own crocosmia. Keep Growing, Marianne Binetti