Sunday, June 23, 2013

Roadside White Shrubs

Blooming on the side of the road right now is a trio of shrubs with flat, cream colored flowers. For each of these shrubs, the “flower” is officially known as an inflorescence that is composed of many small flowers.  Zooming along at 35-55 miles an hour, it is hard to distinguish them, but I’ve got some pictures that might help.

Elderberry (Sambucus nigra ssp. canadensis)
On sunny roadsides, even highways, you are most likely to see elderberry (Sambucus nigra ssp. canadensis) which can be a large sprawling shrub. While elderberry is happiest in damp areas (ditches are a good spot), they can be found in drier areas as well. In my experience, the bloom size can vary quite a bit – I’ve seen them as large as dinner plates! I’m sure that soil moisture can affect the size.

Elderberry (Sambucus nigra ssp. canadensis)

Each bloom is composed of dozens of tiny flowers. Each flower offers a bit of nectar and pollen to the insect that visits, so imagine what a feast each cluster represents. Pollination allows each flower to turn into a small juicy berry that will be popular with birds (and humans like them too). Compound leaves are arranged opposite one another along a pale brown stem dotted with round lenticels.

Silky dogwood, Cornus amomum
Another shrub that you might see on moist, sunny roadsides (often smaller roads, not highways) is dogwood. Not the large-flowered dogwood (Cornus florida) you might be used to, it is one of the shrubby dogwoods that have tiny, star-shaped flowers arranged into a cluster. Shrubby dogwoods tend to grow in large round mounds and have leaves that are opposite one another on the stem. I think the one found most often around me is silky dogwood, Cornus amomum

Cornus amomum
The flowers turn into blue berries, quite different from flowering dogwood’s red berries that so many of us recognize. The flower clusters are consistently about 2-3 inches in size.   

A few sterile flowers on Hydrangea arborescens

On roadsides that are partially shaded and composed of rich, moist soils you can find the third of these shrubs: smooth hydrangea (Hydrangea arborescens). The stems of this shrub reach out from roadside embankments, creating a graceful tumble of foliage and flowers that brighten the area. Again leaves are oppositely arranged, but look carefully and you can see distinctive flaky bark on the older growth.

Hydrangea arborescens

The dense clusters of flowers attract a variety of insects. Recently I saw a bee cavorting happily through the tiny flowers, almost drunk it seemed. Other times I have watched beetles carefully stepping from flower to flower.

Hydrangeas have both sterile and fertile flowers. The sterile flowers are likely a way to attract insects from afar, but of course humans fall for that too. Cultivars like ‘Annabelle’ and ‘Incrediball’ have most (if not all) sterile flowers and would not benefit pollinators; they attract gardeners instead.

Note: a similar flower blooming at this time is the non-native Queen Anne's lace (Daucus carota). You can distinguish it by noticing it is a flower with very thin foliage on mostly single stalks. There is no woody growth as it is a biennial plant.

Non-native Daucus carota


  1. I have noticed a lot of Elderberry along the roadside around here. Great post as always!

  2. Thank you so much for the elderberry photos. I wondered what that was!