Excerpts from Jim Conrad's
Naturalist Newsletter

from the April 14, 2007 Newsletter issued from Sierra Gorda Biosphere Reserve, QUERÉTARO, MÉXICO

For the last two or three weeks all across hot-weather Mexico in towns and along roads the Jacarandas have been blossoming into gigantic, lilac-colored bouquets. Even if you never look skyward the tree's blossoms are impossible to miss, for they strew the ground beneath trees with blue polka dots. I think the trees are most riveting when you stand beneath them looking up through their branches on dazzlingly sunny days such as we've had this week. Visualize translucent, purplish flowers against the deep blue sky, and freshly emerged, ferny leaves emerald green and wind- shaken, set among deliquescing, black-silhouette branches with sunlight-silvered edges. See this below:


The tree I'm referring to, growing up to 50 feet high, is JACARANDA MIMOSIFOLIA, in English often called Blue Jacaranda. It's a native of South America but planted worldwide in the tropics, even in southern Florida and places like Phoenix, Arizona. Besides being so pretty, jacarandas are popular because they can be grown easily from seeds or cuttings.

In size and shape Jacaranda's two-inch long, tubular flowers might remind Eastern North Americans of Catalpa or Trumpet-creeper blossoms. They should, because Jacaranda belongs to the same family as those plants, the Bignonia Family. Maybe half the species in that family are woody vines and the vast majority have opposite leaves. Jacarandas distinguish themselves in the family by being trees with twice-pinnately compound leaves, and having bluish flowers with five corolla lobes but only four fertile stamens.

The expected fifth stamen is reduced to a sterile, club- shaped "staminode" typically bearing a dense tuft of bristles. You can see this staminode, fuzzy at both its middle and its tip, on some dissected flowers, below:

flower of JACARANDA MIMOSIFOLIA dissected

In an online page of the American Journal of Botany I read that in our Blue Jacaranda the staminode's "bristles are critically important in keeping small pollen-foraging bees closer to the stigma, resulting in more frequent contact and pollen transfer." (http://www.amjbot.org/cgi/content/full/89/6/991).

About those lovely blue flowers that fall onto the ground once they're pollinated, the Desert-Tropicals website says of the trees that "The ground below them turns rapidly blue, and some gardeners might object to that quantity of litter."

What an amazing diversity of headsets we humans are capable of. It's scary sometimes.

Anyway, you can see that in this area several things are flowering and fruiting now, despite us still being in the dry season. I think the strategy of a good number of species is this: Have fruits mature at about the beginning of the rainy season, which arrives here next month, so seeds can germinate in well-watered soil.