Pollination Collaboration

 Selby Vaughn

The Primack lab is investigating which pollinators are visiting plants around Newton, MA in order to determine if honeybees are outcompeting native pollinators. This work has been influenced by ongoing public debates about the keeping of honeybees and how it may promote pollination.  

A bumblebee pollinates a sundrop flower.

On June 22nd, we met in Newton with bee experts, Robert Gegear from University of Massachusetts at Dartmouth and Nick Dorian and his team from Tufts University, to learn from each other how to identify bumblebees and other species of native bees. 

The group collected and examined various bees to learn identification techniques.

The event included a lively discussion about the research of each lab group, and debates about the conservation value of pollinator gardens and other efforts to protect native pollinators.

A group photo taken in the Primacks' garden.

Late Leaves Live Longer?

Katia Landauer, Richard Primack, and Selby Vaughn

“If time is short then you have no time to waste.” Henry David Thoreau in his Journal.

With a warming climate, trees might become active earlier in the spring, and their new leaves might be at risk for being killed by a late frost. Even if a second crop of leaves is produced later, plant ecologists are concerned that the trees will not be able to grow as much or absorb as much carbon dioxide after losing their leaves. 

Normal leaves of a chestnut tree sapling

In a recent study by Zohner et al., potted tree saplings growing in greenhouse conditions underwent experimental cold treatments to simulate the effects of frost damage. The researchers found the surprising result that the second crop of leaves of beech and oak delayed chlorophyll breakdown in autumn; that is, they remained green longer than leaves on undamaged control plants. The extended longevity of second-crop leaves perhaps reduces the carbon budget effects of spring frost damage. 

Chestnut leaves several days after crushing to simulate the effects of a late frost

We decided to replicate this experiment under more natural conditions using oak, maple, sassafras, birch, and chestnut saplings growing in a forest in Newton, MA. To simulate frost damage, we crushed and later cut off the leaves of experimental plants; in contrast, leaves were left untouched on control plants. 

Over the summer and fall we will monitor plants for new leaves and chlorophyll content using a chlorophyll meter. 

Will second-crop leaves produced later in the summer last longer in the autumn? 

Here is the citation:  

Zohner, C.M., Rockinger, A. and Renner, S.S. (2019), Increased autumn productivity permits temperate trees to compensate for spring frost damage. New Phytol, 221: 789-795.

https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.15445

Are Male Trees Making Trouble?

Richard Primack

“There is absolutely no common sense; it is common nonsense.”  Henry David Thoreau in Reform Papers.  

For several decades, Tom Ogren, a horticulturist from California, has claimed that the worsening problems of allergy across the USA are due to government officials planting only male trees in cities.  In his view, “botanical sexism” has led to city trees producing an excessive amount of pollen with disastrous consequences for people suffering from allergies. 

As pointed out in a recent article in the Boston Globe, his theory is actually almost entirely wrong. 

First of all, many common city trees, such as lindens, Norway maples, oaks, birches, and flowering pears, do not have separate male and female plants. 

Oak trees are commonly planted as street trees, but do not have separate male and female plants.

Second, for species with separate male and female trees, such as some maples, ashes, junipers, and sassafras, government officials don’t just plant male trees as he claims. 

Thirdly, many common street trees, such as cherry trees, flowering pears, and crabapples, are insect pollinated, and don’t contribute to allergy problems. 

Flowering pear trees are insect pollinated, and don’t contribute to allergy problems. 

Finally, Ogren claims that planting more female trees would reduce pollen in the air because the female flowers would capture the pollen from the air. This is not tree, as the stigmas of the female flowers of wind-pollinated trees, such as oaks, probably only capture less than one in a million of the pollen grains released into the air.  

So while Ogren’s ideas are dramatic and lurid, they lack common sense. 

This article was published in the Boston Globe as: The theory of ‘botanical sexism,’ or 
planting ‘male’ instead of ‘female’ trees, debunked 
By Mike Damiano