Robin-Lee

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Knees of the Mysterious Trees & Bees

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Bloodroot poking out at Bartram’s Garden

Green has returned to Philadelphia, which means I’ve been setting out to Bartram’s Garden, amongst other places, to see if my Sweet Annie’s returned as well. Sadly, my lovely lass is inexplicably nowhere to be seen amongst the dead stalks of yesteryear, but there’s plenty of other curiosities to seek out in the Garden, particularly alongside the planked boardwalk leading to the Schuylkill River’s edge — the more interesting, at least botanically, forested acre of the Bartram property.

At first glance, they could be taken as new tree growths — albeit flared, sometimes chunky, and more dead than alive in  appearance — rising from the waters that swell into the swampland that supports other hydrophilic plants such as jewelweed.

Pointed, gnarly knees rising up around a bald cypress
Source: Wikipedia

But they’re not quite new growths and definitely not saplings. Bald cypress trees have been known for their unusual “knees”, woody extensions arising from underground roots both near and well out from the tree’s base. In 1819, Francois Andre Michaux, the same man who around 1790 gifted the now-gnarled yellowwood tree on the property to William Bartram, wrote, “No cause can be assigned for their existence.”

Farther along in the history of botanical studies, cypress knees were thought to have a role in retrieving more oxygen for the oft swamp-submerged tree. Yet, other scientists found that even cypresses in year-round dry conditions produced these mysterious structures. Moreso, the knees lacked lenticels and inner structures necessary for transporting oxygen throughout the tree’s interior – lenticels being the slits or holes we see in other species like silver birch and cherry tree varieties, respectively.

Other theories came about, my favorite (as in interesting, not feasible) being nutrient acquisition in which various above-ground cypress structures might snag dead tree matter and digest the degrading biomatter (sort of like the mechanism used by pitcher plants). One tauntingly puts forward the idea that these knees once served a purpose that is no longer required, much like how the hardness of avocado pits was specific to the able, crushing power of the teeth of a now-extinct mammal.

A very attractive plant, Fothergilla, in Bartram’s Gardens. The “flowers” actually lack petals and are really a cluster of aromatic stamens (the male fertilizing organ of a flower). Many of this species appear throughout Philadelphia.

A stronger theory has held on: the knees are providing better anchorage and stabilization for the tree, which tends to grow thin and tall in aquatic environments, which also happen to be places of strong and damaging winds.

Further buttressing the argument, a report by Arnoldia Arboretum states that “researchers have agreed that it is average water depth that determines the height of knees, and one observer, Mattoon, reported that the knees on trees growing in softer soils were larger than those produced by trees growing on firmer land.

The report goes on to say, incredibly, that “the tallest on record is a knee fourteen feet in height seen on a tree growing along the Suwannee River, which flows through Georgia and Florida”

So, if you’re ever wandering the meandering the riverside wooded areas of Bartram’s Garden, take some time to admire and wonder about these knees poking out of the soggy earth – having been around since at least the Upper Cretaceous period, there could be more than meets the eye and current climactic situation.

Another aromatic plant, Mountain Mint (Pycnanthemum). This one in Bartram’s Garden had a scent twice as strong as other mints.

Farther up the slope of the garden on drier land, bees swarm the bottle brush plant (Fothergilla) and other herbs in the Bartram’s garden plot (sans, sadly, Sweet Annie), and what perfect time to have received my order of bee-friendly seeds from Cheerios, which recently promoted a “Bring Back the Bees” campaign. It seems most of the mix really does contain native, bee-friendly species such as purple cone flower, bergamot, sweet alyssum, New England aster, and corn poppy.

I’ll be putting down my own roots – knees with a contractual year-long signed lease promising ruthless financial ruin for premature leave of premises – in South Philly in May and which includes what metropolis folk call a “yard”. For my rural family, consult Craigslist’s apartment ad section and type this in the search function. Then laugh, while imagining how much I’m shelling out for rent.

Still, the bees will be happy in my small patio garden, and I’ll hopefully see you at Bartram’s Garden*, where I’ll be leading tours of this ever-fascinating historical, botanical site. And bygod, there’ll be Sweet Annie if I have anything to do with it.

*Or at the opening of Bartram’s Mile, a greenway running along the west bank of the Schuylkill River between Grays Ferry Avenue and 56th Street), on Saturday, April 22nd, at 11 a.m.

A pesky intruder that’s prolific in more than just Bartram’s gardens, Lesser Celandine (Ficaria verna). NPS recommends planting other ephemeral plants, such as bloodroot!

Written by Robin Lee Dunlap

April 20, 2017 at 6:25 pm