Botany

Ian Stewart & Lori Athey

Now that spring is here many Delawareans are enjoying the colorful wildflowers blooming in their backyard, local parks and road sides. Unfortunately, the great majority of those currently flowering are alien weeds which were either deliberately or accidentally introduced by Europeans. These plants found themselves in a new environment with few or no natural enemies and spread rapidly across our area. Each weed produces hundreds if not thousands of seeds and an entire backyard can be riddled with them in just a few years.

The three most common yellow-flowered weeds have been covered in a previous blog (http://blog.delawarenaturesociety.org/2015/05/06/the-not-so-mellow-yellows/) and this follow-up blog highlights some of the other visually-appealing wildflowers that people may not realize are aggressively invasive aliens.

Three common backyard weeds stay low but spread rapidly to form sun-blocking carpets that inhibit or prevent the growth of any native seeds beneath them. Speedwell (Veronica sp.) is one of the first wildflowers to emerge and its four-petaled circular blue flower can be seen as early as March. There are several species of speedwell but most are alien. Ground ivy (Glechoma hederacea) produces dozens of tiny purple flowers and spreads by underground rhizomes which makes it especially difficult to control since pulling one part of the plant will not suffice. Clover (Trifolium sp.) is particularly common in farm fields, perhaps because it may have been introduced as livestock feed, but is now ubiquitous in urban and suburban settings. Clovers have three leaves, each with a distinctive white chevron, though finding one with four leaves may bring you luck! There are two sister species, the red and white clover, which are named after the color of their flower.

Speedwell (Left) and Clover (Right)

Ground ivy

Two striking members of the Mint family also stay quite low to the ground but are easily seen because they often grow in large patches. Purple deadnettle (Lamium purpureum) and henbit (L. amplexicaule, also known as clasping deadnettle) often grow together in fields and backyard although the former is much more common.

purple deadnettle

Henbit

Finally, three conspicuous white-flowered members of the Mustard family are widespread throughout the Piedmont. Garlic mustard (Alliaria petiolate) and roadside penny-cress (Thlaspi alliaceum) are both knee-high single-stemmed weeds which form large clumps in sunny areas, while hairy bittercress (Cardamine hirsute) is quite a bit smaller and branches into multiple small flowers.

Garlic mustard

roadside penny-cress

Penny-cress up close

Purple deadnettle (on left) and hairy bittercress (on right)

These alien wildflowers are especially problematic because they bloom in early spring and may have already produced seeds before householders begin mowing. Although it is an uphill battle, most weeds can be controlled by hand-pulling them before they go to seed, especially if the whole root system is removed.  Repeated early mowing or weed-whacking will deplete the weeds’ resources before they even flower. If you have a large yard or field an alternative option is to gradually convert it into a meadow with long grass and native wildflowers which is left standing throughout the winter and early spring. This helps to restrict early-growing weeds like ground ivy and deadnettle by reducing the amount of sunlight they receive.

Once you have removed the alien weeds you can replace them with native wildflowers which are much better for wildlife, especially our declining pollinator insects as well as the animals that feed on them. A perfect opportunity is the Delaware Nature Society’s Native Plant Sale which is held at Coverdale Farm in Greenville. It starts with a member’s-only day on Thursday May 2nd (1pm-7pm; though you are welcome to attend and join in person) and is then open to the public Friday May 3rd (3pm-7pm) and Saturday May 4th (9am – 3pm). Admission is free and there will be plenty of staff and volunteers present to answer any questions about plants and help you load them into your car!

The full catalog is online here but just to whet your appetite, here is a selection of groundcover plants which are tough and fast-growing and have a decent chance at outcompeting those pesky weeds!

Dry sunny location

Andropogon virginicus (Broom Sedge) grass

Coreopsis verticillata (Whorled Tickseed) perennial

Geum fragarioides (Barren Strawberry) evergreen perennial

Phlox subulata (Moss Phlox) evergreen perennial

 

Dry shaded location

Antennaria plantaginifolia (Woman’s Tobacco Pussytoes) semi-evergreen perennial

Chasmanthium latifolium (Wild Oats) grass

Geranium maculatum (Wild Geranium) perennial

Polystichum acrostichoides (Christmas Fern) evergreen fern

 

Moist shaded location

Asarum canadense (Wild Ginger) perennial

Osmundastrum cinnamomeum (Cinnamon Fern) fern

Phlox stolonifera (Creeping Phlox) perennial

Zizia aurea (Golden Alexanders) perennial

 

Moist to wet sunny location

Carex cherokeensis (Cherokee Sedge) grass

Eupatorium perfoliatum (Boneset) perennial

Iris versicolor (Blue Flag) perennial

Panicum virgatum (Switchgrass) grass

 

By Jim White: Senior Fellow for Land and Biodiversity

It’s not every day that a new species of animal is found in Delaware. In fact, it is very rare indeed. However, in the summer or 2015 Adam Mitchel, a PhD candidate at the University of Delaware did just that. While collecting insects in a meadow at the Ashland Nature Center for his PhD research project on the effects of invasive alien plants on native insects, Adam found several insect specimens that he could not identify.  After examining them under a microscope in his lab he could only identify them as insects belonging to the Insect Order Thysanoptera commonly called Thrips (both the singular and plural of the noun has an (s). The Order Thysanoptera are minute insects with reduced wings, most species being around 1mm long. All but a few use sucking mouth parts to feed on the stems of plants. Several species are considered pest as they can damage crops and other plants. However, the vast majority of the 6,000 or so species are not pests to humans and are valuable members of the food chain.

This species of Thrips, new to science, was discovered at the Ashland Nature Center by entomologist Adam Mitchel. It has no English common name, but scientifically it is called Konothrips polychaeta.  Photo courtesy of Dr. Mitchel, from Goldarazena et al. (2017).

These tiny insects are not often studied unless they are considered pests and information on the many non-pest species is limited. Lucky for Adam, a professor from Belgium, Dr. Arturo Goldarazena…an authority on Thrips, was visiting the University of Delaware. Adam approached Dr. Goldarazena and asked if he would look at some of the Thrips specimens that he collected.  It did not take long for the professor to realize that he had never seen some of the specimens and declared that Adam might have discovered a new species. Adam agreed to give Dr. Goldarazena the specimens to study back in Belgium.  After an exhausting investigation the new species was described and published in Goldarazena et al. (2017). Its official scientific name is Konothrips polychaeta which loosely translates to “hairy tenacious woodworms”.  At this time, there is no common English name for this new species of Thrips. However, I propose to call it Mitchell’s Thrips.

Andropogon virginicus is the host plant for the newly discovered Thrips. Is the new species found wherever this plant exists??? Photo courtesy of Dr. Mitchel, from Goldarazena et al. (2017).

Finding a new species of animal or plant is a dream for biologists – finding them right under our noses in places like Ashland is even more exciting. Adam found the new species inside the flowers of the broom-sedge, Andropogon virginicus but he believes that Konothrips polychaeta probably feeds and breeds on other grasses and sedges that are abundant in the meadows and marshes at the Ashland Nature Center and beyond. These meadow and marsh habitats have been restored and maintained at several of Delaware Nature Society sites as part of the land and biodiversity management program. The program is dedicated to the conservation and preservation of native species and their habitats.

Dr. Adam Mitchel is a native Delawarean and discovered the new species of Thrips while he was a PhD candidate at the University of Delaware. Photo courtesy of Dr. Mitchel.

Dr. Adam Mitchel is a native Delawarean. He attended St. Marks High School and received his undergraduate degrees at the University of Delaware in Wildlife Conservation, Entomology, Plant Protection, Agriculture and Natural Resources (quad majored), and earned his master’s degree in Fish and Wildlife Management at Montana State University. Adam returned home to University of Delaware to obtain a PHD in Entomology and Wildlife Ecology (concentration: Entomology) at the time of the discovery of the Thrips. Adam is now employed as an Assistant Professor of Entomology at Tarleton State University in Texas.

Reference:

Goldarazena A, Mitchell AB and T. Hance (2017) Konothrips polychaeta sp.n. from Delaware, North America, with a key to the three species of this genus. Zootaxa 4341: 445-450.

Ian Stewart

Happy New Year everyone! If you’re looking for an interesting New Year’s Resolution to get you outdoors, why not seek out and learn about a different tree every month? This is exactly the time of year to spot one of Delaware’s most distinctive trees – the Osage orange.

The Osage orange (Maclura pomifera) is a small to medium-sized deciduous tree native to the Midwest that was originally restricted to a relatively small stretch of Arkansas, Oklahoma and Texas. It is not related to oranges but is in the Mulberry family. The name refers to the bright orange color of its wood and the Osage Nation, a midwestern Native American tribe who used the wood for making bows and apparently supplied early settlers with young plants.

The exposed orange roots of a fallen Osage

Although their original range was small, Osage oranges are now found throughout the lower 48 states after lines of them were planted to provide windbreaks in flat open landscapes such as farmland and isolated homesteads. Lines of Osages were also planted throughout the rest of the country to act as natural thorny fencerows for housing livestock and to delineate driveways and land borders, which is why you most often find Delaware Osages arranged in rows on either side of old country roads. Coverdale Farm Preserve’s famous ‘Avenue of the Osages’ contains no fewer than 72 of these striking trees which were probably planted over a hundred years ago.

Coverdale Farm’s famous ‘Avenue of the Osages’, with fallen fruit in foreground

Gnarly, orange-tinged bark of an Osage

The easiest time of year to identify Osage oranges is in the middle of winter as the bare trees now reveal their distinctive gnarled orange-tinged bark made up of many twisted strips. Some trees still bear their large green fruit, commonly known as ‘monkey brains’, although most of these have now fallen to the ground. Be careful – if they fall on a sidewalk or road they become a slippery hazard to pedestrians and motorists alike!

Osage orange fruit with knobbled surface

Interior of an Osage fruit with some seeds

Osages occur as either male or female trees but only the female trees produce the softball-sized fruit which contains several small seeds within its gooey white flesh. Although the fruit is edible almost all animals ignore it as it is tough, unpalatable and exudes latex, so the clusters of monkey brains simply remain where they fall until they decay. Squirrels do eat the seeds however, which may be why you see so few young trees mixed in with the old ones.

Interestingly, almost every Osage I see has a poison ivy vine growing up its trunk, perhaps because the vine finds it easy to grip onto the furrowed bark. Next time you are a passenger in a car being driven along a country lane, try to spot some rows of Osage oranges. If you spot some it might make you resolve to learn about our local trees in 2019!

This Osage was cut down at Coverdale and has about 90 growth rings, suggesting it was at least 90 years old. The poison ivy vine seen in cross-section on the left of the trunk had 19 growth rings so it had been attached for many years.

Ian Stewart

Jewelweed is a colorful native annual wildflower that is common in damp marshy areas where it grows as a thin bush about 4 feet high. It is also known as ‘touch-me-not’ because of its curious habit of expelling its projectile seeds when the flowers are handled or brushed against. Jewelweed is a classic folk remedy because the juice of its leaves and stems is a well-known antidote to stings and rashes from stinging nettle, which it often grows close to.

Jewelweed growing along the boardwalk at Ashland

Many Delawareans are familiar with jewelweed as it is often found in shaded suburban gardens and parks, but few people realize that there are two species and they usually grow right next to each other! The most common is spotted jewelweed (Impatiens capensis), which is also known as orange jewelweed. This has bright orange petals densely covered with red spots and a long ‘nectar spur’ which curls along the bottom of the flower. The second, less-common species is yellow jewelweed (Impatiens pallida), which is also known as pale jewelweed. This has larger, yellow flowers with only a smattering of red spots and a shorter nectar spur which dangles downward. The leaves of yellow jewelweed have more veins and are more deeply toothed than those of the orange jewelweed. In my experience, spotted jewelweed outnumbers yellow by about 5 to 1.

Side by side views of spotted (left) and yellow (right) jewelweed showing the differences in petal pattern, the length and angle of the nectar spur, and leaf venation

Jewelweed is pollinated by both hummingbirds and bees and watching these insects crawl into the depths of the flower to access the nectar pooled up in the spur is a fun way to spend a sunny afternoon! If you’re very lucky you may get to see a hummingbird feeding from the nectar spur.

A bee burrows into a jewelweed flower in search of nectar

The bee’s back is now coated in pollen from the pollen stalk dangling above it. The bee may now pollinate the next jewelweed it enters!

Both jewelweeds have a long blooming season from late spring through the early fall and are an attractive native wildflower to plant in a damp, shaded corner of your yard to attract pollinator insects and hummingbirds.

Learn more about how you can garden for native plants and wildlife by certifying your yard as a wildlife habitat through the Delaware Nature Society

https://www.delawarenaturesociety.org/what-we-do/protecting-habitats-wildlife/garden-for-wildlife/