In my youth, little old ladies dyed their hair blue and I am reminded of that when I consider the fluffy flowers of the endangered groundcover, Keys ageratum (Ageratum littorale A. Gray.) The old-fashioned blue flower is considered rare although it seeds readily. It can overwhelm a garden if new seedlings are allowed to grow. Like a number of things that have two truths, the ageratum is an oxymoron, both a beautiful flower and a noxious weed.

Ageratum comes from the Greek a geras which means non-aging, referring to the lengthy life span of the individual flowers. These puffballs come in clusters of 5 to 15 flowers and each flower has a misty ball of tubular florets.

Like the privileged old lady she is, the bloom sits up to six inches above the leaves on long stems. Not only a rare blue, the fragrant quarter-inch blooms can also be lavender, pink or white. Sometimes blooms literally cover the two-foot tall plant, attracting butterflies, birds and bees with their sweet nectar.

The second name, Littorale means "of the seashore." Sometimes called floss flowers, they are found in roadside ditches and along the shore. This native plant comes to the Keys from Mexico and Central America.

Unlike some of the little old ladies, this plant is fully toothed with leaves in inch-long triangles that are ¬½-inch wide. Leaves are positioned opposite each other. They are hairy, dark-green and connected to the stem on long petioles.

The plant creates tussocks and can survive near the ocean. While it has a high tolerance to salt wind, it does not have a high tolerance to inundation by salt water. It does re-seed, however. Our sandy porous soil suits it fine. It has a moderate to high resistance to drought so can thrive in hot dry areas as well as part shade.

The seed is inconspicuous. To propagate it must be transplanted carefully because if its roots are disturbed it will die. This plant is toxic to humans.

There are as many as 60 different plants in this genus Ageratum, a member of the Aster family that also contains sunflowers and daisies. Nurseries have created hundreds of hybrids from this flower.

The specimen that resides on the hill at the Key West Garden Club is in part shade. Iguanas don't seem to be attracted to it. True to its tropical heritage, Ageratum does not grow north of Windley Key.

This plant is readily available in nurseries. It is often used for borders around beds of flowers, edging to a lawn or path and in rock gardens. Ageratum pots up well in containers.

Imagine a grandmother out tending her rock garden with her blue hair bobbing among the floss flowers and butterflies darting about her head. ... just another blue beauty in the garden.

NOTES:

The Key West Garden Club welcomes volunteers to work on the historical fort, pull weeds, propagate plants and play in the sandy soil at the West Martello Tower from 9 a.m. to noon on Mondays.

Key West Master Gardener Robin Robinson was a columnist for the Chicago Daily News and syndicated with Princeton Features. Her books "Plants of Paradise" and "Roots Rocks and Rain: Native Trees of the Florida Keys," can be found at the Garden Club and on Amazon.com. This column is part of a series developed by the Key West Garden Club. For more information visit www.keywestgardenclub.com