DIVIDING PERENNIALS

Dividing plants at the proper time ensures good success.  For spring-blooming perennials, it is best to divide them just after they have  finished blooming, or in early fall.  Fall perennials can be divided in early spring or fall, as well, after their bloom cycle is over.  They each have things I like best about that:  In early fall it gives the plants time to establish a good root system before the cold, winter weather arrives.  It gives the plants a jump start for the spring.  It also helps to clean up the beds in the fall (although I cut down most everything in the fall anyway) so spring clean up goes faster and is much easier.  But, if the plant doesn't get a good root system established, you'll most likely lose that plant.  Spring is easy because perennials will still be in a dormant stage, and the ground is usually softer and easier to remove the plant and its root system.  Some plants I prefer to divide in the fall are monarda, obedient plant, mums, 'steppable' ground covers,  bleeding heart, Jacob's ladder, lady's mantle and  iberis.  Spring is a good time to divide hosta, before they 'unfurl' their fingers.   July and August are the best times to divide your iris.  Just make sure you never divide a plant just before it's ready to bloom.  If you do that, you risk losing it because all of its energy is going to the bloom and not the roots.

These are some guidelines to follow when dividing your plants

• Never divide plants when it's hot, dry weather (like now!)
• Divide plants on a cool, or at least cloudy, day early in the spring
• When dividing in spring, divide plants before they have grown 5 inches or more--the earlier usually the better
• Don't plant too late in the fall or you'll risk losing the plant due to non-established roots
• If you know when you're dividing, soak the plant thoroughly for a few days
• If you're dividing in the fall, cut down the plant beforehand, it will make handling the plant much easier.
• Make sure the area you're going to move it to is well prepared so that you can quickly plant the new plant so its roots won't dry out.
• If you CAN'T plant immediately, pot it up and keep watered, or give to a friend who can plant it in their garden quickly. 
• Make sure the area you're planting in gets the proper amount of sun or shade, and water.
• If any of the plant is diseased, cut that portion out when dividing
• Make sure divisions are healthy, ensuring the best possible outcome for your transplant.
• After preparing your new area, make sure the plant is 'watered in' to help the soil settle and remove all the air pockets.  If there are air pockets, you risk the roots drying out and this could seriously stunt, or even kill the plant.

I'm always anxious to cut back, cut down, or transplant in the fall.   I watch the newly transplanted plants closely to make sure they don't dry out.  I mark them with plant labels and note any changes on my master list  of the beds.  Doing this also enables me to see where I've put my "temporary markers" for fall plantings of bulbs, etc.   This makes spring clean up much more manageable as well.