9 March 2023

On Monday 6 March 2023, Fran Bungert sent me an email to say that she saw snow trillium blooming at Cedar Creek Park the day before. She added that 5 March is the earliest she’s ever seen it bloom.

In my experience snow trillium (Trillium nivale) is usually the earliest spring ephemeral in southwestern Pennsylvania, traditionally blooming in late March or early April. The flowers persist for about four weeks so my observations circled below are not necessarily first bloom date. Nonetheless Fran’s 5 March observation in red is the earliest ever!

Inspired to see the flowers I visited Cedar Creek on Tuesday afternoon. Before I reached the snow trillium hillside, I found evidence of flash floods that cut the creek bank. It was a brown landscape compared to what I see in April.

Snow trillium dotted the hillside but blended into the fallen leaves because the white flowers looked like splashes of sunshine. How many flowers do you see in this photo?

The flowers were at various stages from barely to fully open, at top.

I found harbinger of spring (Erigenia bulbosa) leaves but no flowers.

As of 7 March only the snow trillium was blooming at Cedar Creek.

(photos by Kate St. John)

p.s. For my own notes, here’s a list of blogs that indicate when I saw snow trillium:

• 27 March 2011
• 3 April 2013
• 29 March 2015
• 27 March 2016
• 11 April 2018
• 6 April 2019
• 3 April 2020

8 March 2023

North American wildflowers face many threats to their existence including habitat loss, deer overpopulation and pollinator declines but there is another threat we didn’t see coming until now. As the climate heats up North American spring ephemerals will have no time to bloom and store food for the coming summer. Their existence is threatened by the Too Early Springs of climate change.

Forest wildflowers bloom before the trees leaf out because they are in a race to gather as much sunshine as possible before the canopy closes. When the trees reach Full Leaf the flowers stop blooming.

Wildflowers in deciduous forests often rely on leafing out before the canopy to create 50-100% of their annual carbon budget. Lead author and Carnegie Museum of Natural History postdoctoral research associate Dr. Benjamin Lee describes it “as if a person were to eat all the calories they needed for a year in the first three weeks.” 

— Climate Change Threatens North American Wildflowers

Ideally, wildflowers would merely advance their blooming schedules and all would be well but the study published last December in Nature Communications shows otherwise. Using herbarium specimens in North America, Europe and Asia, researchers compared wildflower blooming times and tree leaf out dates for the three continents.

Blooming early works in Europe and Asia because those trees leaf out later anyway. But in North America the trees and flowers use the same temperature trigger. We had a real life example of this in Pittsburgh in March 2012 when temperatures stayed in the 60s to 70s for at least two weeks. In that Too Early Spring everything happened at once.

I visited Barking Slopes on 25 March 2012 and I found both early and late spring wildflowers in bloom: Bloodroot (Sanguinaria canadensis) which normally blooms in late March or early April and large-flowered bellwort (Uvularia grandiflora) which normally blooms in late April.

The trees were leafing out, too.

June weather in March? What could go wrong?

Fewer spring wildflowers in the future.

Read more about the Too Early Spring of 2012 below. Will it happen this year? Only time will tell.

(photos by Kate St. John, diagram from Wildflower phenological escape differs by continent and spring temperature)

p.s. The time gap between bloom-time and leaf out is called the “wildflower phenological escape” hence the study’s name.

6 March 2023

This winter has been so warm in Pittsburgh that flowers bloomed and plants leafed out in February. Spring is early, but how early?

Some years I photograph bush honeysuckle’s early leaves and I can tell you that leaf out this spring is 23 days earlier than in 2015. But that’s only one year.

The USA National Phenology Network (USAnpn.org) tracks the progress of Spring using two indicators, bush honeysuckle and lilac leaf out and blooming times, and then compares them to the average in 1991-2020. The Spring Leaf Index Anomaly map for 4 March 2023 shows that this spring is astonishingly early.

The darkest red indicates 20+ days ahead of schedule. USAnpn called out a few examples in their 27 February report:

[As of 27 February 2023] Oklahoma City, OK is 9 days early, St. Louis, MO is 16 days early, and New York City is 32 days early. Phoenix, AZ is a week late. Seattle, WA is a week early.

— USA National Phenology Network — Status of Spring, 27 Feb 2023

How often does this anomaly happen? The darkest green on the map below shows that this is the earliest spring ever recorded in New York City while purple indicates the latest spring ever seen in southeastern Arizona.

Arizona might be even later now. Here’s snow in Tucson last Thursday morning just after dawn.

Click here to watch an animated map of spring’s advance through 4 March 2023.

(photos by Kate St. John and Ramona Sahni, maps from usanpn.org)

18 February 2023

Since a low temperature of 6°F two weeks ago, this month’s weather barely dipped below freezing (until this morning) and twice reached more than 70°F. This week I found signs of an early spring, some of which will survive today’s low of 22°F.

The swelling buds of daffodils, above, and tulip leaves, below, were evident six days ago. Both will probably survive today’s frost.

Yesterday I found early flowers that won’t fare so well.

• A few early blossoms of Cornelian cherry (Cornus mas)

• Some red maple (Acer rubrum) flowers

The swollen red maple buds are armored against frost if they’re not open too far.

Unopened American elm (Ulmus americana) buds are in good shape to wait out the cold.

These early signs are two weeks ahead of the earliest spring I’ve ever recorded. The spring of 2012 was so hot that all of April’s wildflowers bloomed in March.

Will we have a spring like that this year? Or is this just the temporary hot-cold yo-yo of climate change?

p.s. I also found piles of fluff from London plane trees (click here to see what that looks like).

(photos by Kate St. John)