Thursday, July 18, 2013

Native Species Profile - Blue Vervain

Mid- to late-summer is one of the best times of the year to observe wildflowers in Mid-Michigan.  After the frenzied blooming of the spring ephemerals there is often a lull in blooms for several weeks.  It is not that flowers cannot be found, but they often cannot be found in the diversity and profusion of the spring.

However, once Summer arrives in force and there have been several weeks of hot weather then Mid-Michigan's second season of wildflowers truly begins.  The flowers of spring arrive in colors that match the coolness of their season- mostly white with others in pale shades of yellow, blue, and lavender.  In contrast, the flowers of summer and fall are often vibrant and bold in their coloration - pinks, oranges, reds, and most of all bright golden yellows and deep violet blues.

One of the deep violet shades is provided by Blue Vervain (Verbena hastata).  Also known as Swamp Verbena, Blue Vervain likes moist sunny habitats.  Often by late July - early August, many of the roadside ditches, meadows and shorelines in Mid-Michigan are covered with a violet blue haze. 

Blue Vervain with Spotted Joe-pye Weed, Yellow Rocket, and Boneset.

Each Blue Vervain plant is topped with a cluster of flowering spikes.  Individual flowers on the spikes begin flowering at the bottom of the spike and blooms progress to the top of the spike over time.  Each flower spike may grow to be six inches or more in length.  This blooming habit means that individual plants may bloom for a period of several weeks.  Individual plants may bloom any time between June and October. 

Flowering spikes of Blue Vervain - note that only a few few flowers on each spike bloom at any given time.

Blue Vervain flowers - flowers begin blooming at the base of each flower spike and progress upward over time.

With its large numbers of blooms and long bloom time, Blue Vervain is attractive to many native pollinatators - including butterflies, flies, and bees.  The Xerces Society identifies this plant as having special value to native bees.  If you want to attract more bees to you garden, this is a great plant to add.  While it prefers moist soils, it will grow equally well in dry soils.  But it is more likely to attain its maximum height of 2 to 6 feet in damps soils.  Because of the profusion of blooms, Blue Vervain produces large numbers of seeds (nutlets).  While some of these seeds are consumed by birds, many will drop to the ground and germinate.  If you include this plant in a garden be prepared for it to spread.  Removing the spikes after the flower has ceased blooming can help prevent this plant from spreading aggressively.

Blue Vervain can be be found growing in every state east of the Rocky Mountains.

Over much of its range, Blue Vervain shares habitats with the closely related White Vervain (Verbena urticfolia).  However, the White Vervain is much more likely to be found in shade and partial shade conditions than is Blue Vervain.  White Vervain attracts many of the same pollinators as Blue Vervain, but does not match the Blue Vervain in its overall value to pollinators due to fewer total blooms.

White Vervain

Close-up of White Vervain

White Vervain - may reach heights of 3 to 6 feet

Basic Information

Blue Vervain 
Verbena hastate

Height:  2-6’ tall

Habitat:  wet meadows, along streams, shorelines, wetlands

Flower Color:  violet-blue or blue

Bloom Time:  June – October

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