This past weekend I dug up and moved a pretty perennial phlox to make room for an artichoke seedling that I bought at a plant sale. Transplanting perennials in spring gives the plants time to settle into their new spot and extend their roots into the soil before hot summer weather hits. It's an easy and an essential gardening skill to learn because most plants inevitably need to be moved sometime in their life.
Gardens by their very nature are mutable. They change from season to season and over time. I end up moving plants around my garden for a number of reasons:
They've outgrown their space. When you buy a little plant in a 4-inch pot, it's hard to imagine how big it will get. Even though I know better, I tend to plant perennials closer together than I should and they end up growing too big for their allotted spot.
Right Plant, Wrong Place. A couple of years ago I planted two sweetbox shrubs (Sarcococca confusa) in my front yard and by mid-summer their leaves turned crispy. Turns out the shade loving plants were getting way too much sun. In fall, I moved them to the shady side yard and they perked right up.
An Unfortunate Combination. If you decide that your planting of daylilies and Japanese forest grass really don't go well together, no worries. You can separate the duo and pair them up with plants that better compliment their color, texture, and form.
When To Transplant
Fall and early spring are the best seasons for transplanting because the weather is cool and the soil is moist, which means the plants are less likely to wilt. Along the same lines, transplanting in the evening is better than the heat of the day. Make sure the plant is well watered and think about where you want to move it before you dig it up.
How to Transplant
Loosen the Roots. Plants with a large root ball transplant best. To determine where to start digging, imagine where drops of water would land on the soil if they dripped off the plant's outermost leaves (this is called the plant's drip line). Then, drive a sharp shovel into the soil about 6 inches out from the drip line. Work your way around the entire perimeter of the plant, pulling back on the shovel's handle to loosen up the roots as you go.
Lever the Plant Out of the Soil. Once you've loosened up the roots, drive the shovel underneath the plant and lever it up and out of the soil. Keep the shovel under the plant to support its roots and then carry the plant over to its new home.
Dig a New Hole. Before you set the plant in the ground make sure the spot you've chosen provides enough room and gets the right amount of sunlight. Dig a hole with gently sloping sides that is about 1 1/2 times the size of the plant's root ball and the same depth; set the soil to the side as you dig.
Settle the Plant In. Place the plant in the hole. You want it to be at the exact same level it was growing before you moved it. I like to get down and eyeball things, making sure that the plant's crown—where the leaves emerge from the soil—is level with the soil line. Adjust the hole's depth if necessary and then take a step back and double check that the plant is positioned the way you want it.
Backfill the hole. Use the soil you set aside to fill in the hole, gently firming it with your hands as you go. Even though it seems like a good idea, do not amend this soil with compost or fertilizer. This practice discourages the plant's roots from extending out into the surrounding, less fertile, soil.
Finish Up. Rake the excess soil out around the plant, making sure not to pile it up against the crown and then water the plant in thoroughly with a hose or watering can.
Willi Galloway writes The Gardener column. She lives in Portland, Oregon and writes about her kitchen garden on her blog DigginFood. Her first book Grow. Cook. Eat. A Food-Lovers Guide To Kitchen Gardening will be published in January 2012