Dividing flowering bulbs and tubers
Another of the pleasure or late summer and early autumn is digging up and dividing your bulbs and tubers to aid their spread and also to share with friends and family. It can also revitalize plots that have begun to bloom sparsely because of overcrowding.
To begin with, let’s review the difference between bulbs, rhizomes, tubers and corms.
1) True bulbs (like daffodils or tulips) have papery skin like an onion and a basal plate (the spidery looking root thing on the bottom of the bulb). They divide easily by hand. Carefully break away the smaller bulb from the parents. These new bulbs may look more like giant cloves of garlic than a parent bulb which is teardrop shaped. Don’t worry, these will grow in size with time.
2) Tubers (like dahlias) increase in size every year but don’t usually form separate bodies. To divide a tuber you need to make sure that each section has a growing point (the pointy thing at the top that will become a stem) and you will likely need a clean knife to assist in the division.
3) Rhizomes (like cannas, bearded iris and ginger) run along the surface of the soil and produce new plants along their sides that can usually be broken apart by hand. In the case of some plants use of a knife may be necessary. Make sure that the blade is clean so as to not spread and diseases to new plants. Be sure that each division has at least one growing point.
4) Corms (like gladiolus, freesia, shamrock and crocus) look like small bulbs. They often produce more corms either above or beside or on the bottom of the parent corm which is sometimes wholly used up by the flower it produces. These are easily broken apart from one another. They should be stored in a cool, dry place for the winter, and replanted in the spring if there is any danger of them rotting because of standing water in pots or poorly drained soil. In many places they will naturalize and it will not be necessary to dig them up except when dividing is necessary.
5) Tuberous roots (like daylilies and peonies) are usually easily pulled apart. I do not however recommend dividing peonies until one absolutely has to—like once a century. Peonies prefer to stay in one place once they have found an ideal location. Any division should have at least three and preferably five ‘eyes’ on it. Daylilies, on the other hand, may be abused freely as they are very hardy and an excellent choice for a novice gardener since they will grow even in poor soil.
Dividing bulbs, tubers, rhizomes, corms or tuberous roots can be done any time after the foliage has died back naturally. It is best to wait until then so that the plant has extracted the greatest amount of benefit from its greenery and produced the strongest possible bulbs and tubers which are where they store their energy. It is also best not to disturb the roots of other annual or perennial plants that they may share a bed with until the growing season is through and plants are dying back or going dormant for the winter.
Some plants grown from bulbs, tubers and rhizomes will also produce seedpods. This can take energy away from the tubers and most gardeners prefer to remove them.