Gardening is wonderful! What other hobby can give you such an amazing return on your investment? Plant a daffodil bulb for instance, and before you know it, it has begun to make new little plants. In a few years, you will divide your now crowded clump, replant the divisions and pretty soon, you will have even more daffodils. With so many kinds of daffodils to choose from, there is certain to be several you will want to try – yellow ones, pink ones, bi-colored ones, double flowered ones, tiny ones for the rock garden, the list goes on and on. Probably the best thing about all this proliferation is that when friends visit, you can share your bounty with them.
Some of my most cherished plants are ones friends gave me when I visited their garden. I am sure you have noticed that gardeners are among the most generous of people. You need only to ask the name of that pretty flower over there, and your friend will grab a shovel and a container and start digging up part of it for you to take home. Sometimes you can get a real treasure that way. I have been the glad recipient dozens of times, and have been the donor at least as often.
There are some plants that can be left in the ground almost indefinitely without dividing them and they will still come back faithfully year after year. Herbaceous peonies are like that. Others need division every two or three years, and still others can wait four or five years. Perennials will often signal when they need to be divided. Perhaps the flowers have become smaller or stop blooming at all. Sometimes the stems and branches get so crowded that they become tangled with each other or the center dies out, leaving a dead zone ringed with new shoots. In some cases the plant has simply become too big or needs staking even though it never needed it before.
Other plants send out underground runners that root and sprout new shoots, sometimes far from the mother plant. Division will keep it from crowding less rampant growers or from leaping out of the border entirely and racing into the lawn! Plants described as “vigorous”, “a fast-growing groundcover“ and even “easy to grow” usually will need to be divided often, giving you plants for other areas of your garden, to offer at plant sales or to give away to visitors and friends.
Most horticultural organizations, plant societies and garden clubs hold spring or fall plant sales. This provides a way to acquire divisions of plants you do not have and to sell your own extra divisions. Usually a portion of the proceeds from such sales go to benefit the organization and you get to keep the balance from your own sales.
Of course, the reason the societies have spring and fall plant sales is that those are the best times to divide most plants. There is a “rule” that says fall-blooming plants should be divided in the spring -- early enough for the roots to settle in before hot weather -- and that spring blooming plants should be divided in the fall well before your first frost. There are other exceptions – bearded iris, for one, should be divided in summer, just after flowering is finished or by August. (When you do, it is recommended to cut back the foliage to about six inches high, divide the rhizomes leaving one “fan” of leaves on each division (discard sections of the rhizomes that are one year or older), and replant them high so the sun can shine on the rhizome. This helps to eliminate soft rot and if drainage is a problem, be sure to dig grit and compost into the soil before replanting the divisions.)
It is easy to see where to divide plants when the foliage is up only a few inches in spring. However, the reality is that most plants can be divided when you have the time and energy to do it. Just keep things moist if you have waited until mid-May or so and the sun is getting hot. September is usually a good month – or about one month before your first frost date -- if you are dividing plants in the fall. Try to pick an overcast day.
After deciding what to divide and when, you will need water the plants to be divided thoroughly a day or two before you begin. Then gather your tools, making sure they are sharp! Depending on the plants you are dividing, you will need a spade, one or two forks and an unserrated knife. Also, provide yourself with pots to put the divisions in or, if they are to be replanted in your own garden, either dig the holes in advance or place the divisions in a shady spot and cover them to keep the roots moist until they can be planted.
Dig up the whole clump. Use a garden fork inserted a few inches to about a foot, (depending on its size) from the edge of the clump, and gently work it out of the ground. Trim stems and foliage back to about six inches to lessen the chance of moisture loss. Shake or hose off some of the soil so you can see what you are doing. Perennials with spreading root systems -- many slender matted roots that originate from several locations with no distinct pattern -- can sometimes be pulled apart by hand if the plant is small enough. If it is large or has an extensive root system, it is better to use a knife. Examples of these plants include asters, bee balm, purple cornflowers and many other common perennials. Very large plants or ones with fleshy root systems – hosta, daylilies, ornamental grasses, etc. -- will need more muscle. Insert two forks back to back in the center of the clump and pry them apart. The idea is to end up with two clumps and little damage to the roots. Replant the divisions as soon as possible in soil that has been amended with sand and/or compost to enhance drainage and water them in well.
Daffodils develop little bulblets around the mother bulb and remain attached. These young bulbs need to be separated and replanted every three or four years or the whole clump will stop blooming. They are supposed to be divided in the fall, but by then, it is extremely hard, if not impossible, to remember where they are in the border. The foliage has long since yellowed and died, having fed the bulbs below with the essentials they need to re-bloom next year. You could try marking them somehow with colored stakes or some other method, but that has never worked for me. So, before the leaves disappear, I dig up several clumps and divide away. Here's a tip to hide the dying foliage of other bulbs (anemone, Dutch iris, perennial tulips, allium, etc.) as well as the daffodils: plant them next to strong, assertive plants such as hosta (especially variegated hosta) and let the yellowing foliage of the bulbs become mulch as the perennials emerge and grow.
Speaking of hosta, division may never be necessary. If you decide to divide them to gain additional plants, they are tough enough to survive being dug even in summer – provided they get enough moisture. They may flop, but will probably return strongly next season. Divide astilbes and many ornamental grasses in the same way.
Daylilies have fleshy roots too, and the larger varieties can be challenging to divide. The good news is the older cultivars rarely need division. The newer hybrids, however, may need division every four to five years. They are traditionally divided in spring or fall, but also can be divided in summer like hosta. Use the double-fork method; divisions with three or more shoots will bloom sooner.
Late summer or early fall is a good time to lift lily clumps. Do not be surprised if the bulbs are deeper than you originally planted them. If necessary, to find sufficient nutrients, the bulb's roots will pull them deeper in the soil. Separate the larger bulbs and pull the small bulblets away from them. The clumps of some varieties may be a bit difficult to break apart; do not be afraid to use a twisting motion to separate them. Before replanting, completely remove this year's stem from of the top of the bulb and replant four to six inches deep. The larger bulbs should be planted deepest and the smaller bulblets only one to two inches deep. The little ones probably will not flower for a year or two.
Sedum 'Autumn Joy' and other sedums are easy-care, usually pest free and need little in the way of TLC. Leaving them alone to enjoy the summer heat and sun is what they really like and these tough plants can be easily divided almost anytime during the season. If they flop over, they may be getting to much water or fertilizer and is often a signal that division is needed.
Dahlia tubers should be cut apart with a sharp knife, leaving a piece of the original stem and a growth bud attached to each division. They can then be stored for the winter or replant them if you live in zones 8-10.
There are a few plants, such as butterfly plant, columbines and Oriental poppies, that resent division. It is best to avoid dividing these if possible.
Plants divided in the fall may need protection during their first winter to prevent heaving caused by alternately freezing and thawing of the soil. Use an airy mulch such as pine needles, pine boughs (Christmas tree trimmings are excellent) or chopped leaves after the ground has frozen.
Divide and conquer – and share, of course!
