Gardening for habitat
CONTENT BY Aaron Parker, Edgewood Nursery
Ecological context
We live in a place that was recently glaciated and even more recently colonized. In the past 200 years, many new species have been introduced and various human activities have caused very rapid climate change. All this has brought us to a situation where many habitats are at risk of being lost or seriously degraded. “Hands off” type management turns out to not be a feasible option for many areas. Whether you are managing 10 sq ft or 10 sq miles your choices have an impact on habitat quality. Luckily, with a little thought and care, having a positive impact on the habitat you live in can be pretty easy, not to mention fun!
The importance of native plants
Because plants are the base of terrestrial habitats having suitable plants around is necessary for most other species to survive. While non-native plants often provide some level of habitat for generalist pollinators, this doesn’t account for specialist pollinators and when we start to examine plants that support caterpillars (an important food source for birds and other animals) the numbers skew even further towards native plants being very important. Seed-grown “straight species” as opposed to clonal cultivar / “nativar” plants generally offer better habitats and protect the gene pool of the plants themselves. While they are currently a bit hard to find in the marketplace, local ecotype plants are probably the very best choice possible for habitat gardens. With the climate shifting rapidly, it is also worth considering near-native plants, especially those whose historic ranges are to our south and west.
What to leave, what to plant
Before considering what to plant, it’s generally a good idea to figure out what you already have! Identifying every plant in your landscape is an admirable goal, but not strictly necessary. A general understanding of what is growing and where is all that’s required. Books like Wildflowers of New England by Ted Elliman, websites like Go Botany, and apps like Inaturalist are all very helpful. You might want to consider removing plants considered invasive, non-native trees, lawns, or any non-native plants without known human or ecological benefit. No need to do it all at once or remove all plants that don’t particularly serve the ecology. Aiming for 75% native plants is a good goal. This 75% should be calculated by leaf area, so those native trees matter quite a bit.
When it comes to what to plant, trees are a good place to start. Do you have at least a couple of native trees in your landscape? If not, planting one or two might be a high priority for creating habitat. My top picks would be Oaks, Willows, Maples, and native Cherries/Plums. Many landscapes already have lots of native trees or lack suitable space for more trees, so don’t worry if you don’t have a spot for a new tree.
Sunny areas can provide a space for many native species of perennials to thrive, some of these species are experiencing significant loss of habitat as most
non-forest areas of the state are either cultivated with non-native species or have significant pressure from invasive species.Native shrubs provide many important habitat niches as well as food for many insects, birds… and humans too!
Styles of garden
An ecological garden can be arranged in many different ways and can have many different aesthetic qualities. That said, some of the landscape styles and practices that we have become accustomed to create inherently poor habitats and should probably be abandoned.
Lawns catch a lot of flak for being ecological disasters, and a lot of that is probably deserved. That said, lawns do often serve important functions (like outdoor play), no other planted landscape feature can take sustained foot traffic like turf grass. I advise replacing lawns/mown grass areas where they do not serve a function and diversifying areas that make sense to keep.
“Traditional” beds can be excellent habitat spaces when planted with suitable species. However, the aesthetic and management practices commonly associated with this style of landscaping are not conducive to high-quality habitat.
Meadows are open sunny or part shade areas with minimal or no woody species and complete coverage of grasses and other herbaceous plants. They nearly always require some sort of maintenance to keep them from growing into woodlands. Careful annual or bi-annual mowing or burning plus occasional hand weeding of woody plants is usually good. Meadows can be established relatively cheaply by direct seeding, typically in the fall.
Management
Even with a wonderful slate of plants, a suburban landscape isn’t always a good habitat for many species. Some landscape management strategies are very detrimental to wildlife, lucky for us, they are pretty easy to avoid. Good ecological management could fill lifetimes of study, but the basics can be boiled down to “don’t screw up natural processes”. Here are some rules of thumb, exceptions exist to all of them.
Avoid using poisons of all kinds. Herbicides, pesticides, fungicides, etc. are bad for habitat quality…but sometimes as a last resort, they can be an important tool. Avoiding pesticides includes plants grown with systematic pesticides, avoiding big box stores, and supporting small local nurseries.
Avoid jumping the gun on “cleaning up”, while cutting back herbaceous plants and removing fallen leaves in autumn is a common aesthetic practice, it destroys important overwintering habitat for many species. Once spring temps are consistently over 50º F you can tidy up a bit as needed. Even then, I tend to cut material down and let it sit on the ground and decay in place. Some exceptions include pruning woody plants and disease or pest issues in cultivated plants. Most of the time insects eating the plants in your garden is what you want, not a pest issue, Cabbage moths on your Broccoli is a pest issue.
Many species use standing dead wood. If managing woodlands, leaving some standing dead wood is a good idea. In an urban/suburban environment, you can create a habitat for these species by simply leaving large chunks of wood around to rot. Holes can be drilled in these pieces of wood to provide nesting habitat.
Deer can be an issue in habitat gardening. Like anything munching in your garden, deer are part of the ecosystem and need to eat something. However, without their natural predators, their populations and behavior can get out of wack and have detrimental effects on their habitat. Hunting and installing deer fences can have large impacts, but often if something is needed, a short-term fence around a specific planting is enough.
Disturbance and succession
Succession is an ecological process where habitats change over time. Around here most areas will become old-growth forests, given several hundred years. Disturbance is a force that moves succession in the opposite direction, disturbances include cutting trees, bulldozing, tilling, extreme weather, and fire. Once established, a habitat garden may experience succession or you can create disturbances to keep succession from happening. Common small disturbances would be mowing, prescribed fire, pulling weeds/tree seedlings, etc. Too much disturbance can damage habitat quality and animal populations, so use these tools with care.
Adding habitat features
Across a broader landscape, many features exist that might not be in your current garden, if you want to provide habitat for the maximum amount of species you can consider adding one or more of these.
Water features can range from a 1 sq foot mud puddle (which provides habitat and nesting material for insects) to a 1’ deep mini pond (which provides reproductive habitat for amphibians + insects) to a 4+ ‘ deep pond (which would provide overwintering habitat for amphibians, turtles, fish, etc).
While covering soil with plants and/or leaf mulch is generally desirable, having a little bare ground for ground-nesting insects is nice. This area should not be
in a path or other area with foot/vehicle traffic. If your soil is heavy/clay digging a hole and filling it with sandy soil adds another type of ground-nesting habitat.If standing dead/fallen trees are not present, you can add large chunks of untreated wood. Laying on the ground or standing upright. Woodpecker holes are
an important habitat feature of woodlands, if not present, you can add bird boxes to fill that niche.
Establishing new plantings
My preferred method for starting a new bed is sheet mulching, which involves mowing the area and then laying a layer of cardboard or several layers of newspaper over existing vegetation. This smothers it out and creates a blank slate to put in new plants. Compost and other amendments can be placed under the sheet layer, but are often not needed for native plants. Leaves, wood chips, hay, or other mulch layers are placed on top of the sheet layer. You can plant into a fresh sheet mulch by cutting holes in the sheet layer, or let it sit for a season. The sheet layer will completely biodegrade in 1 year. Be careful to remove plastic tape and labels from cardboard before using. Where sheet mulching is not practical (steep slopes, high density of woody plants, Japanese Knotweed) some other options are occlusion (covering the area with a silage tarp for a season), prescribed fire, tillage, and in some circumstances careful use of herbicide. Most people are familiar with planting in spring (late April to mid-June), but fall planting (Early September to early October) is also a good time. Summer planting is possible, but more difficult.
Additional resources
Wild Seed Project (wildseedproject.net) has a huge amount of great info on habitat gardening. Consider joining the organization to receive their annual publications. They are also a great source for native plant seeds.
Bringing Nature Home by Douglas W. Tallamy has inspired a huge number of people to garden for habitat, it is available at many local libraries and through MaineCat/ILL
The Xerces Society for Invertebrate Conservation (xerces.org) has a huge amount of info on insect habitat and conservation.
Maine Audubon (maineaudubon.org) has several types of information available, from native plant gardening to woodland management and many others.
Edgewood Nursery has a selection of native plants. Learn more at edgewood-nursery.com
Plant Lists: These plant lists are extremely helpful when thinking about what to plant in a habitat garden.
Wild Seed Project has several great plant lists at wildseedproject.net/plant-lists. They also have listings for other local and regional nurseries on their website at wildseedproject.net/buy-native-plants.
Plants for Pollinators, xerces.org/pollinator-resource-center/northeast