Macroscale patterns of flowering and fruiting phenology in China

By Richard B. Primack

“If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundation under them.” - Henry David Thoreau in Walden.

Patterns of phenology are increasingly examined at larger geographic scales with on-line databases and digitized herbarium specimens. In a recent paper in the Journal of Biogeography, Chinese colleagues and I examined the timing of flowering and fruiting of over 16,000 plant species from China using over 1,300,000 records.

Spiranthes sinensis, the Chinese ladies tresses, is a herbaceous orchid species 
that grows in China. (photos courtesy of Du Yanjun)

We found that across the geographic range of China, plant species flowered earlier and fruited later at lower latitudes and lower elevations. In comparison with herbaceous plants, woody plants flowered earlier, showed stronger geographic trends, and needed a longer time for fruit development.  Variation in flowering was most strongly affected by mean annual temperature in woody plants and by temperature seasonality in herbaceous plants.

Antiaris toxicaria, the arrow poison tree, grows in Chinese forests.

These results suggest that woody plants and herbaceous plants will respond differently to climate change, though this needs to be confirmed by investigating individual species and specific locations in greater detail.

This study is noteworthy for the enormous number of species, observations, and geographical scale included.

A Flora of Home

By Tara K. Miller

After coming home during the COVID-19 pandemic, I decided to create a flora of the forest around my childhood home. A flora is a documentation of all the plant species in a location or region. 

Armed with 5-10 field identification books for trees, shrubs, herbs, and ferns, I spent hours wandering the forest, continually noticing new things in the woods where I grew up.

I picked out the tiny spring ephemerals, like spring beauties and trout lilies, that flourish before the trees leaf out.

Me and my field assistant with the spring beauties in early May

I waded through knee-high ferns, which I learned included wood ferns, lady ferns, and sensitive ferns.

I discovered that our forest boasts a few stray box elders and elms in an area dominated by maples, ash, and black cherry.

Black cherry trees are distinguishable by their “burnt-potato-chip-bark,” as my college ecology professor phrased it.

I ate wild strawberries, fought with invasive garlic mustard, and watched the eastern phoebes learn to fly.

Garlic mustard also makes a lovely pesto sauce

It’s never too late to gain a new appreciation of an old place.

Giant hibiscus flowers along the Charles

By Richard B. Primack

“How much of beauty - of color, as well as form – on which our eyes daily rest goes unperceived by us!”  -Henry David Thoreau in his Journal.

Thousands of rose mallow plants with huge flowers the size of dessert plates flower in early August on the banks of the Charles River in Newton, Needham, Waltham, and Dedham. The plants are typically 3 to 7 feet tall, and dozens of stems can grow in a clump.

Rose mallow plants emerging from the Charles River

Rose mallow flowers are usually pink, but some plants produce flowers that are darker pink, others lighter pink, and some are white. Many flowers have red markings at the base of the petals, forming a striking bull’s eye, and flowers can vary from 3 to 7 inches across.

White and pink flowers produced on neighboring plants.

Along the Charles River, about one in three plants produces flowers with a red center, and one in ten has white flowers, usually with a red center. Plants with entirely white flowers can be found but are rare.

A rare white-flowered plant.

Rose mallows are probably increasing in abundance along the Charles, as they colonize areas from which invasive purple loosestrife plants have been removed and places where beavers have cleared away woody riverside thickets.

Different plants produce flowers of different color and size.

August is a great time to be out on the river and see our spectacular native rose mallow plants growing in the wild. It is a world-class wildflower display right here in Boston.

An article about rose mallows along the Charles recently appeared in the Boston Globe.

Papaya trees growing in Newton

By Richard B. Primack

“Our circumstances answer to our expectations and the demand of our natures.”

-Thoreau in A Week on the Concord and Merrimack Rivers 

We know that climate change is already affecting what plants we can grow in the Boston area. In our Newton garden, we now have many fig trees, some of which survive outside through the winter with only minimal protection. And some day, we may be able to grow camellias and crepe myrtles in Boston. Crepe myrtles are already being sold in local garden stores in expectation of warmer years.

Crepe myrtle plants for sale in a Wayland garden store. 

However, this year we are extremely surprised to find dozens of papaya seedlings sprouting on their own in our vegetable garden. One fast-growing seedling is already 2 feet tall and is showing the distinctive deeply-lobed leaves of the species.

Papaya seedling growing in our garden. 

Papaya trees are strictly tropical, so what are papaya seedlings doing in our Newton garden? Even with our current warming climate, New England winters still have plenty of freezing temperatures and ice. The answer seems to be that last fall we added the skins and seeds of some papayas to our compost pile, and then mixed the compost into the garden soil. The round, black papaya seeds must have been deep enough in the ground to avoid freezing and may have even been warmed by the decaying compost. Now that the ground has been heated to tropical temperatures by the July sun, the seeds finally germinated.

These young saplings will certainly not be able to survive outside through next winter. Newton is not yet ready for papaya farms.