Toxicodendron radicans; Anacardiaceae (sumac family)

It may be reviled by humans, but poison ivy is an important plant in our ecosystem: many birds eat the fruit, and some animals will eat stem and leaves, as well.  The flowers aren’t particularly remarkable, but poison ivy is one of the earliest plants to turn color in the autumn.  Watch for blazes of red going up into trees.  If it’s on your property in an out-of-the-way location, leave it be.  Spend your efforts rooting out invasive aliens instead.

Other plants in the sumac family: cashew, mango, and pistachio.  Yup.

Wikipedia has a decent article about urushiol.

Although I haven’t conducted a rigorous scientific experiment on myself (nor am I likely to), in my experience Tecnu is effective should you come in contact with poison ivy.  I always have a bottle on hand.  Use exactly according to instructions.

Flowers seen May 14 – May 31:

• blue-eyed grass
• bulbous buttercup*
• northern catalpa
• dwarf dandelion
• field hawkweed*
• daisy fleabane
• robin plantain
• hairy beardtongue
• honewort
• tall meadow rue
• mossy stonecrop*
• partridgeberry
• poison hemlock*
• poison ivy
• princess tree*
• puttyroot
• veiny skullcap
• squaw root
• stinging nettle
• strawberry bush
• tulip poplar
• Venus’ looking glass
• Virginia waterleaf
• broad-leaved waterleaf
• wild licorice

…bringing the year’s total to 153 species in 54 families, with Ranunculaceae in the lead, Brassicaceae a close second, and Violaceae, Rosaceae and Asteraceae in a 3-way tie for third.  Thirty two (about 21%) are aliens.

*alien

Later this year I’ll be scrambling for FOTD candidates, but for now I’m going through the spring backlog.  Here are two more golden flowers.  Alexanders are just about done but there should be cinquefoils around for awhile.

Zizia aurea; Apiaceae (carrot family): 

Potentilla canadensis; Rosaceae (rose family):

Hieracium venosum and Senecio aureus; Asteraceae (aster family)

In late March or early April the distinctively veined basal leaves of rattlesnake weed start emerging on rocky bluffs and drier soils along the Potomac:

 A month or so later the long stems start bearing the flowers:

  You’ll find rattlesnake weed growing alongside azure bluets and plantain-leaved pussytoes.

At about the same time, maybe a week earlier, golden ragwort will be in bud:

 Note how the basal leaves and stem leaves are entirely different from each other.  Its peak flowering will be well before rattlesnake weed’s.

Golden ragwort likes the wetter soils closer to the river.  You can find it on the eastern half of Billy Goat C.  Rattlesnake weed will be on the western half, near Carderock.

According to the USDA PLANTS database (plants.usda.gov), there are eight species of dogwood and ten of viburnum to be found in this area.  All have opposite, simple leaves (except the pagoda dogwood, which has alternate leaves).  All are small to medium sized understory trees or shrubs.  Some species have distinctive leaves,

Viburnum acerfolium (maple-leaved viburnum)

but most have very similar leaf shapes.  The dogwood leaves have different venation from the viburnums.

At first glance viburnum and dogwood flower clusters look alike, but the flowers themselves are quite different.

Viburnum dentatum (southern arrowood)

Viburnum prunifolium (blackhaw)

By the way, the blossom of the ubiquitous flowering dogwood (Cornus florida) is not actually a flower; those four showy petals are bracts, surrounding the tiny flowers in the center.  (A bract is a modified leaf that looks like a flower.)

 Cornus alternifolia (pagoda dogwood)

Viburnums are in the Caprifoliaceae (honeysuckle family), while dogwoods are in the Cornaceae (dogwood family).  Despite the apparent similarities, you have to go a few steps up the taxonomic ladder to find the common relation (which is the class Magnoliopsida, dicotyledons).