When I bought this stalk of Brussels sprouts, I wondered about the wild plant it came from. Did you know that cabbage, broccoli, cauliflower, kale, collard greens, kohlrabi and Brussels sprouts are all the same species? Every one of them is a cultivar of Brassica oleracea, also called wild cabbage.

Wild cabbage is a biennial that grows naturally on limestone sea cliffs in Europe. In its first year it’s a rosette of leaves. In its second year it blooms. As you can see by the flowers, it’s a member of the mustard family (Brassicaceae or Cruciferae).

Ten thousand years ago humans foraged for wild cabbage leaves. At the dawn of agriculture we began to cultivate them. One thing led to another, as described at Wikipedia:

• Our preference for leaves led to kale and collard greens as cultivars.
• We liked the tightly bunched leaves and the terminal leaf bud so we cultivated cabbage from the first-year rosette.
• The Germans liked fatter cabbage stems so they cultivated kohlrabi. It’s not a root, it’s a bulbous stem.
• People liked the tasty flower buds of the second-year plant so we cultivated cauliflower in the 1400s (flower is in its name) and then broccoli.
• In Belgium they preferred the small leaf buds that grow in the leaf axils, so they bred Brussels sprouts in the 1700s.

While they’re growing, Brussels sprouts are nestled in the leaf axils like this.

As the stem gets taller the lower leaves turn yellow and fall off. Farmers and gardeners usually remove fallen leaves or prune them back.

Sometimes the weight of the plant bowls it over.

Eventually the plant is harvested and we buy Brussels sprouts in the store. Mmmmm! Leaf buds for dinner!

p.s. Did you know that Brussels sprouts are sweeter if they’re harvested after frost? Alas, most are harvested before that.

(first photo by Kate St. John, remaining photos from Wikimedia Commons; click on the captions to see the originals)

Eastern redcedar or juniper (Juniperus virginiana) is a pioneer species that’s hard to find in Pittsburgh except where intentionally planted.

Junipers grow wild east of the Appalachians, offering their bluish berries to migrating birds. The berries are especially prized by robins, cedar waxwings, and catbirds.

(photo by Kate St. John)

What have we here?

Lichens are two organisms that operate as one, a symbiotic partnership of a fungus with a green or blue-green algae (sometimes all three).  The algae’s photosynthesis feeds the fungus.  The fungus gathers and retains water and nutrients and protects the algae.

Those that grow on trees are epiphytes, totally dependent on the surrounding air and precipitation for their nutrition.  As they take in air, their tissues absorb suspended elements in concentrations that mimic the air quality.

Lichens can thrive in some of the harshest habitats on earth but epiphytes can’t live in the presence of air pollution, so we were really surprised to find them on our Duck Hollow walk on 29 October 2019 when the air smelled of rotten eggs.

The smell is hydrogen sulfide from US Steel’s Clairton Coke Works, 8 miles away. On cold calm days the pollution creeps up the Mon Valley and blankets Pittsburgh’s East End, a reminder of Pittsburgh’s Smoky City days.

The pollution happens all too frequently, as shown in these screenshots from SmellPGH.org on 28 and 29 Oct 2019. (SmellPGH is a crowd-sourced app for reporting air pollution smells. Many dark red triangles mean the air smelled really bad that day. Click here for more info.)

We can smell hydrogen sulfide but not two dangerous air pollutants that travel with it: sulfur dioxide and particulate. Fructose lichens — the kind that stand out from the branch like those shown above — cannot survive in the presence of sulfur dioxide.

We were amazed. What have we here?

(photos by John Bauman, screenshots from SmellPGH.org; click on the captions to see the SmellPGH website)