The ageratum is a tiny, nearly true blue annual that is native to the Americas. It also comes in white or pink varieties. Because it only grows to a height of about 6 inches, it is perfect for the front of the flower border or for planting in containers. Ageratums prefer full sun to part shade and like a little shade during the hottest part of the day. The soil can be average or even poor. They are also tolerant of soil that tends to stay on the dry side.
Plant Ageratum from Seed
Prepare the seed bed. Turn over the top layer of soil with a garden spade, then rake the bed smooth.
Sprinkle the seeds on the surface of the soil. Do not cover; the seeds need light to germinate. Lightly press the seeds into the surface of the soil with the palm of your hand.
Water the seed bed with a hose end sprayer set to a fine mist. Check the seedbed every day and water as needed to keep it moist until germination occurs in about seven to 14 days. Thereafter, water only in times of extreme drought.
Thin the seedlings when they are about 2 inches high so they stand about 6 to 8 inches apart.
Mulch, if desired, to discourage the growth of weeds. Put down a 2-inch layer of straw or hay.
Remove faded blossoms for continued bloom until the plants are killed by frost.
Plant Ageratum as Small Bedding Transplants
Prepare the planting site by turning over the top layer of soil. This will aerate the soil. Rake the bed smooth when finished digging.
Dig a small hole with your garden trowel to plant each transplant. Space them 6 to 8 inches apart. Set the transplant into the small hole, back fill and firm the soil around the base of the plant.
Water each transplant with a hand-watering can after the entire bed has been planted. Thereafter, water only in times of extreme drought.
Spread a 2-inch layer of mulch, if desired to control weeds. Put down hay or straw to mulch ageratum.
Deadhead ageratum by cutting or pinching off the faded flowers. This will encourage them to continue producing more blossoms until they are killed by frost.