Andrew The Arborist

Andrew The Arborist I'm an urban forester who is passionate about trees, native plants, and the natural world.
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Through my content, I aim to educate and inspire people to reconnect with and learn about the natural world around them.

04/29/2026

I recently joined my friend Connor for a soil scraping at a serpentine barren that he manages! This process involves scraping away the decades worth of accumulated organic matter that has piled up on top of the serpentinite soil that makes these ecosystems unique. By uncovering the mineral soil, we’re expanding habitat for numerous uncommon or even endangered grassland species that thrive in these tougher, slightly toxic conditions.

This is a fire-dependent ecosystem. Fire suppression over the last number of decades (or more) has resulted in the build up of organic matter in these grasslands as peripheral forests drop their leaves each fall. Over time, trees begin to creep in and take over the grasslands as they root into this new soil that lacks the toxic qualities of the serpentinite mineral soils. Thankfully, fire is regularly being used here now, with burns taking place almost yearly.

After the mineral soil has been uncovered, seeds in the seedbank at that layer may have a chance to sprout after decades of dormancy. Connor also collected and stratified seeds from numerous species on the barren which we then spread into this new area. He’ll continue to monitor this spot over the next few years as it establishes!

04/20/2026

My parents planted this beautiful eastern redbud (Cercis canadensis) about 15 years ago, and I’ve watched it grow quickly in my front yard. Each spring, it glows on warm spring days, attracting hundreds of buzzing pollinators. I make sure to take time each year to just sit under the tree and observe them.

Last fall though, I found a Ganoderma sessile conk at the base of the trunk. This fungus causes a rot in the butt (base) and in the roots of the tree, leading to a structural decline by weakening the wood. Eventually, this will probably lead to tree failure (falling over). The fungus infects stressed, wounded, or old trees.

Eastern redbuds don’t live for very long - usually 20-30 years in the landscape. I am growing seedlings from this tree, but in the meantime, I’ve planted its successor - a Shingle oak (Quercus imbricaria), which will get established as the redbud declines. It’ll be interesting to see how long the redbud will last!

04/14/2026

It was such a pleasure to visit a woodland full of native spring wildflowers. Unfortunately, this is fairly uncommon in southern PA!

While these spring ephemeral wildflowers are not as common as they used to be in our area, we can help them out by planting them on our properties or by removing invasive species around remnant populations.

Amazing work

04/10/2026

A Virginia’s Warbler was recently spotted near Philadelphia at the Riverbend Environmental Education Center and it has people traveling from all over the state to see it! It has been hanging around this same area for several weeks at this point, but with migration soon, it may get the itch to move.

It was interesting to spend some time looking for the bird and to notice its behaviors. It doesn’t stay in place for very long at all - eagerly hopping around from tree to bush, making it difficult to photograph. It seems to sort of loop around the woods at Riverbend before returning to the parking lot area / main trail, where most folks are spotting it.

You can join the PA Birds Discord channel for updates of this bird and other rarities in PA and all the different counties! The link is in my bio.
Thanks to my friend Adam who let me know about this bird a few weeks ago!!

03/29/2026

This isn’t my typical video style, but this was too egregious to not make a video about lol. This may be the worst pruning job I’ve ever seen, and on such a large scale.

Topping trees is generally not an acceptable way to prune. It creates an abundance of large wounds that are difficult for the tree to compartmentalize, it stresses out the tree by depleting it’s energy preserves, and it causes weak resprouts to grow. If you want to reduce the size of your tree properly, consider a crown reduction prune by an experienced team of arborists.

Why are we doing this to trees in tough, hot, dry parking lot conditions where the trees are already under a lot of stress? Do we not want parking lot trees to shade the giant asphalt heat island or our vehicles? This seems totally needless.

This is a really great program that Pennsylvania's DCNR started last year! Folks in PA can remove invasive species on th...
03/20/2026

This is a really great program that Pennsylvania's DCNR started last year! Folks in PA can remove invasive species on their property and get rewarded with a free native replacement tree or shrub! 🌳
Do you have a program like this in your state? If so, share it below!

03/18/2026

You can join me out here at Wildlands Conservancy’s Black River Sanctuary on April 19th for a Tree ID Hike, or check out the 7 showy spring trees that I wrote about in my blog post at the link 🔗 in my bio!

I first started learning how to identify trees and plants in these woods about 7 years ago, and I remember how exciting it was to start recognizing them wherever I went. I think tree and plant ID is an important skill that opens up many doors to appreciating the natural world. Whether you’re interested in foraging, studying galls or caterpillars, or exploring plant parasitic fungi, knowing how to identify plants is super important!

So here are some tips for identifying 3 trees that are typically considered more difficult!

03/10/2026

Bloodroot (Sanguinaria canadensis) should be a common spring ephemeral wildflower in the woodlands of eastern North America, but this is the only patch I’ve been able to find in my hometown. So my non-profit, teamed up with .pa and to target invasive plants like English ivy (Hedera helix), Japanese honeysuckle (Lonicera japonica), and garlic mustard (Alliaria petiolata) that were outcompeting the bloodroot.

We’ve done this event each of the last 4 winters, and have anecdotally noticed an increase in the size of the bloodroot population, but I’m going to actually count the number of plants this year so we can start recording some actual data.

We also fenced in a nice cluster of American prickly-ash, also known as Toothache tree (Zanthoxylum americanum), since the deer damaged the stand quite a bit last fall.

I encourage you to try a similar effort in your community to preserve higher quality ecosystem remnants in your area!

03/01/2026

Here were some of my favorite exhibits and activities at the 2026 Philadelphia Flower Show - Rooted: Origins of American Gardening!

The show provided me with a much needed break from the cold, snowy winter and has me looking forward to spring even more!

What were some of your favorites this year?

02/25/2026

Beech Leaf Disease (BLD) is rapidly spreading across the northeastern US and into Canada. It is believed to be caused by an invasive nematode that is native to Japan (Litylenchus crenatae subsp. mccannii). The nematodes feed inside the buds of American beech trees (Fagus grandifolia), and many other Fagus species and usually causes mortality within 5-10 years or less.

BLD is just the latest example of an insect, nematode, fungus, or other pest that has been accidentally introduced to our forest ecosystems and that will significantly alter their functionality. It is estimated that such pests cost our country $40 billion each year in lost ecosystem services, tree removal costs, crop losses, and more.

The largest cause of these introductions? The importation of live (mostly non-native plant material) from overseas. Shipping containers, especially those made of wood, also contribute significantly. To reduce these risks, we must demand that our governments implement better shipping regulations. We can reduce our individual roles by planting native plants in our landscapes and by reducing or eliminating items that we purchase from overseas.

My newest YouTube video covers this topic in much more detail. You can check that out below. This graph was generated using iNaturalist data for BLD observations between 2016 and 2025.
https://www.youtube.com/watch?v=7fjDNcX_VgM

Last summer, I came across an observation on iNaturalist.org of an emerging invasive grass in Pennsylvania - Wavyleaf Ba...
02/01/2026

Last summer, I came across an observation on iNaturalist.org of an emerging invasive grass in Pennsylvania - Wavyleaf Basketgrass (Oplismenus undulatifolius). This observation was made near State College, about 100 miles away from its known range in Pennsylvania.

After confirming its ID, I suggested that the observer submit their finding to PA iMapInvasives, a platform where invasive species sightings and management efforts can be recorded and shared. When she uploaded it there, the PA Department of Agriculture and PA Dept. of Conservation and Natural Resources were notified.

Less than a week later, foresters and land managers were sent to remove the entire patch of the grass before it could become established. They also searched the surrounding area for more.

This type of early detection, rapid response is ideal for emerging invasive species, and although we may not always be able to keep this plant from spreading, there's great value in delaying its establishment.

It's a good reminder that citizen science apps like iNaturalist and PA iMapInvasives are not only great learning tools, but can be extremely useful for conservation and land management. I recommend using these apps to document, learn about, and explore your local natural spaces!

Read more about it here:
https://storymaps.arcgis.com/stories/2caedb7bebf3420d98b78468e66182cf -n-XXRxAO

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Philadelphia, PA

Website

https://linktr.ee/AndrewConboy

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