Gardening Tips

Gardening Tips – September 2018

Eupatorium coelestinum

Wild Ageratum, Mist flower, Floss flower
Eupatorium coelestinum. (Conoclinium coelestinum)

Wild ageratum produces clusters of blue flowers in Autumn. This pioneer perennial is best for naturalistic settings, roadside plantings. A member of the Compositae (Asteraceae) family. Butterflies love this plant!

Wild ageratum blooms sparsely in the summer but fall is the best season. The plant has heads of tiny, velvety light blue flower clusters. Leaves are course, simple pubescent, triangular ovate leaves. They look like the cultivated ageratum we see in Spring but are taller and the plant is looser. Heights vary with growing conditions but average 10 –24″. Cut them back in spring for bushier, lower growing plants. They grow wild in my yard. This is a nice element of surprise since I never notice them until they start blooming.

They grow alongside other plants in full sun or part-sun. I don’t do anything to wild ageratum. They spread by underground runner, self-seed and may appear in unexpected locations. They are easily pulled when you find them where you don’t want them but should be left to seed in place for more plants and flowering. You may fertilize them some but they do fine without a lot of attention. They grow more aggressively in richer soil. They are not bothered by the freezes in our area.

While fall is the season for their best flower show, they may be planted in Fall and Spring. Young plants may be transplanted from March to May. Divide clumps in March for more plants. Water new plantings when dry to get them established but they don’t require much watering unless drought conditions occur.

Ageratum houstonianum is a lower growing cultivar. This annual produces tight flowers in blue, white and pink blooms in summer to fall. ‘Blue Blazer’, ‘Summer Snow’ and ‘Blue Danube’ are noteworthy.

Ageratum maculatum is taller, found in open spaces. Pink ‘Gateway’ has mauve- pink flowers, ‘Bartered Bride’ has white flowers.

Wild ageratum plants are available in nurseries in the fall as opposed to the cultivated ones which are available in spring.

Submitted by Karen Blackburn

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