Today’s objective was to collect ferns from the rock outcrops along 110 Street. This is a beautiful area, part of what was a late add-on to the original park design. Originally, the Park only went up to 106 Street. Olmsted and Vaux wanted the rugged wild-looking area from 106th to 110th Streets and eventually made it part of the Park. We are lucky they did or we would not have the Great Hill, North Woods and Meer!
Historic records show at least 18 species of ferns grew in Central Park. Most have been extirpated (gone locally extinct). A few lingered on through the years and some are making a comeback due to restoration efforts. As you walk along the drive, you see many nooks and crannies out of which are growing all sorts of plants. Fern spores easily fall into these crevices and since there is often shade and moisture, they grow quite well. We found several species growing in this area.
Some ferns, such as sensitive fern (Onoclea sensibilis), are easy to identify. The large, coarse fronds (leaves) are bright yellow-green and somewhat triangular in shape. This fern grows in moist soil in part to full shade. Control of invasive species and restoration of compacted soil has helped this species spread throughout the Park, especially in the woodlands.
For ferns that are not so easy to identify, you have to look to the spores. Spores are how ferns reproduce and disperse. They are tiny, dust-like particles that can survive harsh conditions and germinate when conditions are favorable. They occur in two different ways on ferns – on the back of a frond, or on a separate, highly-modified frond, called a sporangiophore. When spores are present, we call it a fertile frond.
The Sensitive fern has its spores on separate fertile fronds. These fertile fronds give the plant its other common name, bead fern. Ok, some more fun botany terminology: spores are formed in structures called sporangia and sporangia are clustered into structures called sori. For this species, the sori are the bead-like structures we are seeing on the fertile frond. Patterns of sori are a main character we use to identify species of ferns.
Next we found ebony spleenwort (Asplenium platynueron). It is also a very recognizable fern, but if you are not sure, turn the frond over and if it is fertile, you will see the sori. Check your fern field guide and match the pattern. In this case, the sori form two lines that resemble a row of chevrons along the back of the frond. This fern can be found growing on the rock outcrops as well as the perimeter and Blockhouse walls.
Blunt-lobed cliff fern (Woodsia obtusa) is a small fern species that has survived through the years of the Park’s history. It can be found growing on rock outcrops as well as on the Blockhouse and perimeter walls.
We also found hayscented fern (Dennstaedtia punctilubula) in this area. This is a species that the Conservancy has been using in restoration projects and it has begun to spread nicely. The common name of this fern comes from the scent given off when you crush a frond. Hayscented ferns have very small round sori on the backs of the leaves (not shown). The photo below shows a lovely bed of this fern in the Shakespeare Garden.
We came across a couple of species of other plants common in the park, but with structures that are often overlooked. The very abundant field garlic (Allium vineale) was in flower. This plant, however, has tiny aerial bulbils and very few flowers. Like onions, field garlic grows from an underground bulb. Bulbils are just what they sound like – small bulbs – and in this case they occur above-ground. These bulbils are how the plant reproduces, the structure breaks apart dispersing the bulbils. Sometimes these bulbils sprout and begin to grow before falling off the parent plant (second photo).
The other somewhat common plant with an interesting structure was the Osage-orange (Maclura pomifera) we came across at the northeast corner of the North woods. If you do not know the Osage-orange, you should look for it this fall. It has a very interesting fruit. The tree is in the Mulberry family, but the fruit looks nothing like the mulberries we like to eat. It is a large sphere, around 3-6 inches in diameter and bright yellow-green. The tree itself is easily confused with a mulberry, both having orange inner bark and glossy green leaves. However, the Osage-orange has thorns and mulberries do not.
The structure shown below is a fruit fallen from the tree prematurely. It is much smaller than it would have become at maturity, and the “hairs” you see are the stigma and styles of the many flowers that made up the female inflorescence (cluster of flowers).
Each day we see so many good species, it is hard to include them all here. I will share more on our next day of collection. For now I will leave you with a non-plant organism that has made a nice comeback in Central Park, the Eastern chipmunk (Tamias striatus). He was busy stuffing his little cheeks with food and he didn’t seem to mind us working near him.