Easy to grow and available in a host of colours, carnations appeal to many gardeners. Like other perennials, carnations spread, invading the turf of neighbouring plants and sometimes crowding them out. Left untended, the oversized carnation plant begins to suffer, producing anaemic leaves and fewer flowers. For the health of your carnations and of your garden as a whole, divide your carnation plants every two to three years.
Score a circle on the ground around the carnation plant with a long-handled garden shovel. Draw your circle so it corresponds to the drip line, the farthest edge of the plant where rainwater drips off the leaves. This reduces the chance of damaging the plant's roots.
Place your foot on top of the shovel blade. Push down and under the carnation plant. Repeat all around the circle until the plant's root system is loose. Lift the plant with the shovel or a garden fork.
Clear away the excess dirt clinging to the plant's roots by rinsing them with your garden hose set to a gentle spray. Carnation roots are often tangled tightly together; to minimise damage to the roots, you must see as much of the root system as possible before you begin dividing it.
Pry the carnation plant's roots apart gently with your fingers or a small garden hand fork. Separate the roots into two or more clumps, depending on the size of the original plant.
Move the clumps to their new location and plant them immediately. If you must postpone planting the divided carnations, store them in brown paper bags, cardboard boxes or buckets in a cool, dark place such as your basement or garage. Cover the plants with damp newspaper to keep them moist until you are ready to plant them.
Enrich the soil of the carnations' new location with compost or manure. The rule of thumb is one wheelbarrow full of organic fertiliser for every wheelbarrow full of plants.
Never leave your divided carnation plants lying on the ground in full sun while you go off to have lunch or get a cold drink. Out of the soil, these plants are vulnerable and could wither while you are away. If you must step away for more than a few minutes, place the divided plants in full shade and cover them with damp newspaper.