ENVIRONMENTAL ADVISORY COUNCIL

Planting Native Horticultural Species to Restore Healthy

Habitats by Susanne Hay, Assoc. EAC Member

After a few months of dormancy in the garden, we look forward to the first blooms that welcome spring. Unfortunately, the earliest blooming shrubs, trees, ground covers, spring bulbs are not native to our region, and many are invasive, some even considered noxious weeds (www.dcnr.pa.gov). We admire them because they are “ornamental”, putting on a show for us. However, invasive, nonnative plants originate in continents such as Asia and Europe that have ecosystems completely different from ours. They emerge earlier in the spring and remain in leaf longer in the fall, attributes that are exacerbated by a warming climate. When grown around here, they escape the boundary of cultivation and become naturalized in the wild, either through birds dispersing fruit, wind carrying seeds, or aggressive growth habits. They crowd out native plants in meadows, along stream banks and understory forests. Invasion of non-native plants will over time decimate many pollinating insects, butterflies and native birds. On the other hand, pollinators and native plants evolved together for millennia, and are dependent on one another for survival. As Doug Tallamy, Professor of Entomology at the University of Delaware points out in his book “The Nature of Oaks”, the native White Oak (Quercus alba) provides habitat to more than 550 species, whereas the Chinese Gingko tree (Gingko biloba), admired by many for its brilliant yellow autumn color and leaf shape, hosts only 5 caterpillars.

Non-native

The story of the Callery pear (Pyrus calleryana) is an example of a tree gone rogue. Introduced in the mid-1960s by the USDA, they quickly became popular among landscape designers of townships and industrial parks due to their upright, conical form, low cost, fast growth rate, and adaptability to different soil and water conditions. The initial species was diseaseresistant and unable to self-pollinate, which added to their appeal. They became the early indicator that spring was around the corner with their abundant white flowers. However, branches are brittle and break off easily in heavy winds, changing the tree forms into less compact and more unruly ones. The scent of the flowers is reminiscent of fish odor, attracting flies instead of bees. Over time, several cultivars of varied genetic backgrounds were developed and when grown in suitable proximity cross-pollinated and produced fruit that is readily eaten and dispersed by birds. The Callery pear developed into an invasive species invading not only roadsides, but also wetlands and forests, and crowding out native species. States have started to ban the sale of this tree, and it will be banned in Pennsylvania beginning in 2024 (www.agriculture.pa.gov).

Grand Parade in Valley Forge Park

Arrows toward the top of the image indicate infiltration of Callery pear in the meadow. (See photo to right.)

It is time to change our ways. The best thing we can do as individuals is to take out invasive species from our backyards and replace them with native species. Another thing to do is to volunteer with

Native Substitute organizations such as Open Land Conservancy (OLC) of Chester County and other non-profit organizations to help remove invasive species. Locally, OLC is working to remove Japanese barberry from Airdrie Forest Preserve. Callery pear and Japanese honeysuckle have infiltrated the meadows at Valley Forge Park; roadsides along routes 202 and 252 are overrun by Russian and Autumn olive and common reed; and Japanese knotweed and silvergrass are overtaking riparian buffers and wetlands. Table 1 summarizes some non-native species and potential native substitutes.

We are fortunate to have Jenkins

Arboretum and Gardens in our backyard (631 Berwyn Baptist Rd, Devon, PA 19333). You can visit to see native plants in their natural settings, study the plant tags, ask a knowledgeable horticulturist and even purchase native plants.

Shrubs

Burning bush**

Euonymus alatus

Privet (4 diff species)**

Ligustrum spp

Japanese barberry

Berberis thunbergii

Japanese flowering crabapple

Malus floribunda

Autumn and Russian olive

Non-native

Native Substitute

Grass

Japanese and Chinese silvergrass

Strawberry bush Switchgrass

Euonymus americana

Inkberry holly

Ilex glabra

Winterberry holly

Ilex verticillata

Vine

Miscanthus sacchariflorus and

M. sinensis

Japanese honeysuckle

Lonicera japonica

Autumn clematis

Panicum virgatum

Trumpet honeysuckle

Lonicera sempervirens

Native clematis

Serviceberry Clematis virginiana

Amelanchier spp

Clematis terniflora

Asian Wisteria

American Wisteria

Red twig dogwod W. frutescens

W. sinensis and W. floribunda

Cornus sericea

Groundcover

Elaeagnus umbellata and Periwinkle

E. angustifolia

Butterfly bush

Buddleia davidii

Nandina spp

Forsythia spp

Butterfly weed

Asclepias tuberosa and A. incarnata

Vinca minor

Virginia creeper

Parthenocissus quinquefolia

Trees

Norway maple

Acer platanoides

Sugar maple

Acer saccharum

Viburnum nudum Redbud

Northern spicebush

Lindera benzoin

Callery pear 'Bradford'*

Pyrus calleryana

Cercis canadensis