If you want an annual with soft blue or lavender blooms, then the enduring favorite Ageratum houstonianum is ideal. Also known as floss flower, ageratum features dense clusters of powder puff, flowers covering mounded plants from May through October. This dependable plant, which is native to Central America, is deer-resistant, moderately drought tolerant but prefers fertile, well-drained soil and full sun.
The shorter varieties of ageratum grow no higher than one foot and are wonderful filler plants, blending with others well. Their mounded appearance makes them especially suited as edging along walks, in front of borders, and in pots and window boxes. They are also great in rock gardens. The taller varieties can be used in mid-borders or in cutting gardens.
Some low-growing, dwarf varieties of annual ageratum include ‘Blue Danube,’ which grows to 6 to 8 inches high, or the early flowering ‘Blue Hawaii’. Others like ‘Blue Blazer’ and ‘Royal Delft’ grow to only 4 to 6 inches tall. The taller varieties such as Blue Horizon grow to 30 inches tall and are perfect cut flowers. A particular favorite is the ‘Artist Blue’ ageratum series. It thrives in full heat and full sun.
The soft blue flowers of ageratum combine well with pink in the garden, such as pink begonias, pink annual vinca, or pink lantana. Blue and yellow is another combination. Pair short yellow marigolds or yellow sulphur cosmos with tall blue ageratum for contrast. It is a great combination for sunny planters, too.
Here, I planted light blue ageratum as a facer flower in front of variegated boxwood. Behind the low shrubs are the upright delicate blooms of tall raspberry angelonia. Note the single plants of cherry-red annual vinca inserted occasionally in the bed. They add a colorful “pop” to the scene. This is a fun accent that can work anywhere. All deer resistant!
Lavender-blue ageratum mixes beautifully with the tall spikes of summer snapdragon (Angelonia angustifolia). These two annuals make a stunning blue statement in the sunny landscape.
Although various shades of blue are the most common colors of ageratum, pink and white selections are available to expand the possibilities. Now you can use white ageratum to accompany blue ageratum in a display.
‘Blackie’ sweet potato vine fills in large garden areas with deep purple foliage. The foliage is a bold accent to flowering annuals such as ‘Alaska Mix’ nasturtium, with its unique variegated and marbled foliage and light orange, edible flowers. I also tucked in white New Guinea impatiens to cool it all off.
‘Margarita’ sweet potato vine (Ipomoea batatas ‘Margarita’) has bright chartreuse leaves that turn pale green in partial shade. The heart-shaped foliage brightens any bed! Here in a half-sunny bed, I planted a tapestry of foliage and flowers with ‘Lemon Twist’ Swedish ivy (Plectranthus ‘Lemon Twist’) and the pink and purple flowers of calibrachoa.