Friday, August 21, 2015

Where Trees and Summer Wildflowers Cohabit

Since I gave such short notice about the canal walk tomorrow, I'll offer this virtual tour. Along the DR Canal towpath, just west of Harrison Street in Princeton, there's a nature trail loop. Most people head to the canal with a bike or running shoes to clock some miles, but for those who want to take in their surroundings, the winding, mowed trail offers a lot of wildflower interest this time of year.

While most habitats hereabouts are either dense forest or open field, the trail loop is more of a glade or savanna, with scattered trees offering many gradations of shade and sun to please the eye and meet the varied needs of diverse wildflowers.

Most of the trees along the winding trail are oaks--some planted long ago by the university when this strip of land was tended as an attractive entryway into campus. Oaks tend to have thick, fire resistant bark that can survive the sorts of periodic fires that once would have sustained open woodlands such as this. One of the oaks is a bur oak, uncommon in NJ but famed in the midwest for the bur oak savannas it lords over with its dark spreading limbs contrasting with the deep green obovate leaves that remind me of bison. Many of these savannas have been restored using prescribed burns.

Here's the wildflower that led to the creation of this mini-preserve and nature trail. The cutleaf coneflower has a rosette of leaves at its base. At some point around 2006 I was walking along the towpath and noticed these basal rosettes, which were surviving what were almost weekly mowings at the time. There were many of these clumps scattered throughout the broad area between Carnegie Lake and the towpath, all of which were getting mowed down before they could bloom. It seemed a waste of natural "talent", so I contacted the DR Canal State Park staff, and they agreed to reduce mowing to once a year in that area. There was a bit of a complication because the land is owned by the university, but they were amenable as well. The show of cutleaf coneflower that first year was spectacular.

Seeing the attractive result, the park staff later added a trail and a sign. My role is to send a reminder in late winter to make sure they mow before spring growth begins. Less mowing, more wildflowers--all in a day's rest.

To the right of the sign is a patch of native switchgrass--a tallgrass prairie species that propers in the east as well and is sometimes planted for ornamental purposes.

There's also a patch of knapweed, a nonnative which appears to be Tyrol's rather than the highly invasive spotted knapweed that's moving east from the midwest.

There's a plausible cause and effect here, given that the larvae of ladybugs are voracious consumers of aphids, numerous on the underside of this common milkweed leaf.

Deertongue grass, another native grass that is sometimes used as an ornamental, for instance in the raingarden in front of the Whole Earth Center, prospers along the trail.

The various species of goldenrods are just coming on. Goldenrods get wrongly blamed for being allergenic, because they bloom at the same time as the inconspicuous ragweed.

Some benches were donated to provide restful views of the rowers laboring away on Carnegie Lake.

If you take a closer look at the shore, you'll see yellow pond lilies, lizard's tail and rose mallow hibiscus.

It's really gratifying to see that wildflowers are growing more numerous under the state park's annual mowing regime, with lots of ironweed elevating above the other vegetation,

and expanding patches of Joe-Pye-Weed. This species has hollow stems that provide homes for the local insects.

At one point on a bright morning walk last weekend, I had to stop for a moment, take in the majestic oaks, the bountiful wildflowers extending down the long corridor of the winding trail, a downy woodpecker busy on a limb overhead, insects feasting on the nectar--and realize that we actually did accomplish something here that is lasting, and without spending a nickel. A change in management released the native growth force that had been there all along. Managing with nature rather than against it brought better results with less work.

One fun aspect noticed this year is that the mowing crews appear to be getting creative with the trail mowing, adding attractive lookouts,

and a new circular clearing. Not sure what the purpose of this one is, but it could well serve as habitat for low-growing species that can't compete where there's only one mowing per year.

A favorite sedge, fringed sedge, grows along the trail edge here and there.

Another favorite: wild senna, which in this photo looks a bit like a beehive hairdoo wig that's been in the attic too long. The seedpods are forming below the last few blooms at the top.

Showy tick trefoil is another legume that forms pods quickly beneath blooms higher up. Anyone heading off trail may find these on pantlegs after the walk.

Sticking with the theme, pokeweed berries form lower on the stalk, with flowers higher up.

Pokeweed is usually considered too rambunctious for a garden, but is very attractive and at home in this floodplain.

The long pods of Indian hemp, which is related to milkweed, not that miracle plant hemp, which still remains tragically illegal to grow in the U.S.

This native Clematis virginiana has toothed leaves, while the non-native Clematis autumnalis sometimes found in gardens has smooth-edged leaves. Both can be highly invasive in a garden, popping up in new, undesired spots in the yard.

A really bad actor is this non-native porcelainberry, with leaves and viney growth habit reminiscent of wild grape. Its berries turn white, blue or pink--very attractive but avoid the temptation of picking them and transporting them elsewhere. You can see this kudzu wannabe's over-the-top aggressive growth behind the Clark House at the Princeton Battlefield, and it's been colonizing new areas of Princeton. In past years, it looked like it was going to overwhelm all the wildflowers along this trail, but this year the balance is better for some reason.

The elderberry bushes were getting mowed down each year, which kept them from blooming and making berries, so I've started tagging them to alert the mowing crew in late winter to mow around them. Little interventions like that can make a big difference, simply by making it a little easier for the native growth force to do its thing.

The trail got windier, and actually more interesting, after the stiff winds of Hurricane Sandy, when many trees fell and the trail was mowed to circumvent them.  

Jewelweed is a common annual whose tubular flowers attract hummingbirds. Try touching the swollen seedpods to see what happens.

The trail loops back to the towpath. Walking back towards Harrison Street, you'll see the elephant-ear sized leaves of a Princess tree (Paulownia) that gets cut down each year or two by a different crew that's responsible for keeping vegetation controlled along the canal itself.

Climbing hempweed--that's not related to hemp either--is a native vine common along the edge of the canal.

Sometimes it has parasitic dodder mixed in.

That's the hike. Oh, I forgot the figwort--a tall wildflower that only a botanist could love. It's not blooming in the photo, but the flowers are so small that you're not missing anything. I've only seen maybe five plants of this species in all of Princeton, so it's special to see it has survived another year on this island where land and lake, tree and wildflower, native growth force and human tending, all cohabit so pleasingly.


  1. had to miss your hike this a.m., but I did do a and walk from the Canal House to Turning Basin and your pictures were helpful- saw lots of climbing hemp weed and the bees and butterflies like it a lot. Each clump has a hundred little mini-florets ....also lots of cardinal flower everywhere but by the golf course and it is eye-bendingly bright. Thanks for the plant IDs and the suggestion to get out by the canal.

  2. Just found out there's a group that walks every Saturday morning at 10am from Turning Basin Park to the viaduct and back. Princeton Canal Walkers, they're called. Mostly for exercise, but a good chance to get down along the canal. They give notice in the local newspaper calendars. Can't find the phone number right now.

  3. Cindy Carlin8/28/2015 4:35 PM

    Thank you so much---We walked the trail today. I never would have realized that it was there without your blog. And because of your virtual tour, we were able to spot most of what you mentioned. (but not all--we'll just have to make a second trip.)

  4. I was hoping that would happen, that the virtual would lead readers out to witness the actual. One of these days, I'll actually stuff some informative flyers in that box at the trailhead.

  5. Thanks for the information--I had been wondering about the identity of both the clematis and the jewelweed recently. There's been a nice showing of jewelweed at Barbara Smoyer Park this summer.

  6. Thanks for the reminder to stop by Smoyer Park. I planted a few wildflowers in the old tree nursery over there earlier in the year, but haven't looked recently. If they haven't mowed too close, there may be some swamp milkweed growing along the pond's fringe that would be a good place to look for monarchs.