Plant Tips

Suggestions that favor native plants

Plant Tips: Invasives Out ➔ Natives In

When you’re ready to plant natives, consider these factors first:

Look carefully at your planting location; micro-climates are important. If it’s usually sunny, pick plants from a category of those that like full or partial sun. Likewise, if it’s usually a wet spot, pick those that like it damp or wet. Consider the plant’s exposure – will your plantings need to withstand salt spray or wind? Do you have loose, sandy soil, or hard clay, or thin soil over ledge? Are deer a problem for you? Do you want to attract pollinators, or provide food for birds and other wildlife?

If a few of your new plants fail, don’t get discouraged. It happens to all of us. Plant some extras, and those that survive will be your new favorites.

Here are possibilities to check out:

Click link in table for information sheet in a new tab

	Full Sun ⬤	Partial Sun ◑	Full Shade ⬤
Dryer Locations ⬤	Full Sun and Dry	Part Sun and Dry	Shade and Dry
Wetter Locations ⬤	Full Sun and Wet	Part Sun and Wet	Shade and Wet

Looking for ideas specific to Harpswell?

These Plant Tips pages will provide suggestions of native plants that you can use to replace invasive plants in your own yard. HIPP will continue to add plant ideas to address some of the most common invasive plants that we find in Harpswell. Click on the plant names listed below to expand content.

Invasive Out: Japanese Knotweed (Reynoutria japonica); Native In: Sweet Pepperbush (Clethra alnifolia)


Japanese Knotweed (Reynoutria japonica) Photo credit: Leslie J. Mehrhoff, Univ. of Connecticut, Bugwood.org	Sweet Pepperbush (Clethra alnifolia) Photo credit: Bruce Patterson, GoBotany.com
Designated by the State of Maine as “Severely Invasive”. Perennial shrub grows to 10’ in a dense stand; sometimes called “bamboo” because of its segmented stalks. Thickets release chemicals that suppress other plants, a trait referred to as “allelopathy”. Common on private properties and along Harspwell’s roadsides. Outcompetes native plants and provides limited value for native pollinators and other native wildlife.	Shrub that typically grows 3-6’ high and spreads to 4-6’ wide Produces an abundance of sweetly scented flowers during the waning days of summer, when few other shrubs are in bloom. Showy bottlebrush-like flower clusters, typically 3-5” in length, last for weeks. Attracts a variety of butterflies and bees with its attractive fragrance. Leaves turn brilliant golden-yellow in fall before dropping for the winter. Sturdy native shrub is remarkably adaptable, tolerating shade, variable soil moistures, and salty air, making it a valuable addition to woodland settings and coastal gardens.

Other native-to-Maine choices to replace knotweed:

Nannyberry (Viburnum lentago)	https://extension.umaine.edu/publications/2583e/
Red twig dogwood (Swida sericea; aka Cornus sericea)	https://extension.umaine.edu/publications/2569e/

Download this Tip Sheet:
Knotweed – Summersweet rev 1-14-25

Invasive Out: Barberry (Berberis vulgaris; Berberis thunbergia); Native In: Rosebay Rhododendron (Rhododendron maximum)

Picture of very prickly barberry stem with red berries

Photo of rhododendron plant with large pink and white flowers

Japanese Barberry (Berberis vulgaris)
Common Barberry (Berberis thunbergia)
Photo credit: Chris Evan

Rosebay Rhododendron (Rhododendron maximum)
Photo credit: Heather McCargo, Wild Seed Project

Designated by the State of Maine as “Severely Invasive” and “Very Invasive”, respectively
Perennial shrubs formerly planted as accent plants due to red fruits and adaptability to sun and shade conditions
Thorny branches make it difficult to trim/maintain; provides limited value for native pollinators and other native wildlife
Re-sprouts, even when cut severely
Dense growth form allows it out-compete native plants
Reportedly harbors more ticks than do natives. See https://today.uconn.edu/2012/02/controlling-japanese-barberry-helps-stop-spread-of-tick-borne-diseases/

Evergreen shrub that typically grows 8-10’ high and spreads laterally; produces large attractive pink flowers during spring and summer
Good to reclaim disturbed sites and provides cover and shelter for deer, bears, and bird species but does not do well in windy areas.

Sweet Fern (Comptonia peregrina)Photo credit: Becky Gallery

Preferable to Rhododendron in windy areas; smaller than Rhododendron; spreads by rhizomes
Sturdy, sweet-smelling native shrub; Remarkably adaptable. Prefers sunny areas, but tolerates shade, variable soil moistures, and salty air.

Other native-to-Maine choices to replace knotweed:

Mountain Laurel (Kalmia latifolia)	https://gobotany.nativeplanttrust.org/species/kalmia/latifolia/
Northern Bayberry (Morella [fka Myrica] pensylvanica)	https://extension.umaine.edu/publications/2572e/

Download this Tip Sheet:

Barberry – Rhododendron & Sweet Fern rev 2-10-25

Future Plant Tip

Additional Resources

These reliable websites may also help you identify native plants for your location:

The Native Plant Trust: (https://plantfinder.nativeplanttrust.org/Plant-Search) This site provides information on New England native plants and offers a search tool with numerous filters to help focus your choices.
- Note: Harpswell is in the Northeastern Coastal Zone.
- The “Cultivation Status” filter of the search tool lets you choose between original native “Species” and “Cultivars”. Species are more beneficial to the creatures who need nutrition from these plants. Cultivars are usually easier to find in nurseries. Select “Species” as a first choice.
- There are many filters to help you see the options that are important to you.
For erosion information: Maine Coastal Property Owner’s Guide to Erosion, Flooding and other Hazards:
- https://digitalmaine.com/cgi/viewcontent.cgi?article=1605&context=mgs_publications

The Wild Seed Project: (https://wildseedproject.net/blog) This site provides additional insight into the use of trees, shrubs and groundcover species native to Maine, and sample templates
The University of Maine’s Cooperative Extension Service: (https://extension.umaine.edu/) This site provides links to a variety of information on this and related topics…
- …including a link to their Cumberland County office (https://extension.umaine.edu/cumberland/)

And these books are also helpful:

Native Ground Covers for Northeast Landscapes (A Wild Seed Project Guide)
Native Shrubs for Northeast Landscapes (A Wild Seed Project Guide)
Native Trees for Northeast Landscapes (A Wild Seed Project Guide)
Landscape for Life Student Manual (United States Botanic Garden)
Maine Native Plants for Roadside Restoration (Maine DOT/Wild Seed Project/Maine Natural Areas Program)
Native Plants for Your Maine Garden (Maureen Heffernan)
The New American Front Yard (Sarah Carolyn Sutton)
Maine Invasive Plants Field Guide (Maine Department of Agriculture Conservation & Forestry)

We encourage you to contact HIPP with your questions about invasive plants and your observations of invasive plants in Harpswell. You can reach HIPP at [email protected] or by filling out the form below.