If you’re limited by a tight budget but have plenty of time and patience, you can cut costs by growing your own new perennials. But thrift isn’t the only motivation for bringing new perennials into the world. After you fill your own garden to capacity, you can share your bounty with friends and neighbors. Most perennials multiply as rapidly and as easily as field mice.

Multiplying Perennials By Division

A young perennial starts out with only one tuft of leaves and one set of roots. Many perennials reproduce themselves by sending out a length of root or stem from which a whole new plant grows. Eventually, a cluster of loosely connected but separate plants forms. The process of pulling clumps of perennials apart to create new ones is called dividing. Each piece then grows into a new clump that you can divide, and so on.

Reasons to divide

Producing more plants is the main reason to divide your perennials, but it’s not the only reason. Some types of perennials reproduce themselves so quickly that they can overrun the whole flower bed if you don’t intervene. Whenever you feel the need to restore order, dig up these miscreants, put a piece of them back where you originally planted them, and give the remaining pieces away.

A few perennials die out in the center of their clumps as they spread, creating a noticeable bald spot. Instead of contemplating some sort of a floral toupee, you can easily correct the problem by digging up the whole plant and dividing it.

Perennials that don’t tolerate division

Division works best on perennials that grow into colonies — groups where each new plant develops its own set of roots and leaves. Similarly, most bulbs reproduce by forming clusters of new bulbs, which you can divide in exactly the same way that you divide colony-forming perennials. Perennials with a single, large taproot and those with multiple stems arising from a single crown don’t like to be divided. The following perennials don’t tolerate division well:

• Monkshood (Aconitum napellus)
• Butterfly flower (Asclepias tuberosa)
• Basket-of-gold (Aurinia saxatilis)
• Blue wild indigo (Baptisia australis)
• Pinks (Dianthus)
• Bleeding heart (Dicentra spectabilis)
• Gas plant (Dictamnus albus)
• Globe thistle (Echinops exaltatus)
• Baby’s breath (Gypsophila paniculata)
• Candytuft (Iberis sempervirens)
• Sea lavender (Limonium latifolium)
• Blue flax (Linum perenne)
• Lupine (Lupinus)
• Oriental poppy (Papaver orientale)
• Balloon flower (Platycodon grandiflorus)
• False lupine (Thermopsis carolinian)

A lesson in division

You can divide perennials whenever the ground isn’t frozen, but the best time of year for division is a couple of months before severely cold or hot weather sets in. You want to give newly planted sections a chance to settle in and get a strong start before they have to cope with weather extremes. If you live in a cold climate, divide your perennials either in spring, when the newly emerging foliage is up several inches, or in late summer, six to eight weeks before temperatures are expected to drop below freezing. In warm-winter regions, divide your perennials in the fall.

To divide perennials, follow these steps:

• Soak the ground a few days before you plan to work, if the soil is hard and dry.
  Ideally, the soil should be soft enough that you can dig into it easily with a shovel or spading fork, but not so muddy that it sticks to you or your tools.
• Cut all the stems down to 4 to 6 inches (10 to 15 cm) from the ground.
• Dig up the whole clump.
  Cut a circle a few inches outside the edge of the clump you’re planning to divide. Don’t worry if you cut roots — they grow back.
• Place the whole clump on a tarp or an old sheet and look it over.
  Some plants come apart as easily as pull-apart cinnamon rolls. Others are impossibly dense and tangled.  ....read more