Right Place, Right Plant: What’s Your Ecoregion?

Step 1 in How to find the best native plants for your garden

If you are interested in adding native plants to your landscape but feel unsure about exactly which plants to choose, read on. This is the first article in a series on how to determine the best native plants for your garden.

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I remember the moment I learned about ecoregions. It suddenly brought home to me the fundamental links between soil types, topography, and plants. The soils in a place dictate what plants can grow there. Some plants can thrive in rocky soils while others do better in rich floodplain soil. Of course! The slopes and aspects (direction the spot is facing) and drainage patterns further narrow the conditions and influence the character of the landscape. Finally, the climate and weather patterns dictate seasonality, precipitation, and annual highs and lows that various plants can withstand. When you put this together, you get an ecoregion: a geographic area defined by climate, geology, soils, and native plant communities. This is why the landscape looks a lot different in the spruce forests of northern Maine than the palmetto scrub in Florida. Different soils and conditions —> different plants and animals.

An ecoregion is a geographic area where the ecosystems are similar, based on the geology, soils, climate, plant communities, and wildlife found there.

Why should you care about ecoregions?

As humans living in a place we call a country with state and county lines dividing us up, we have organized a lot of information based on our imaginary political borders. There are many databases we can consult that list the plants native to a particular state or county or even ZIP code. But of course plants and animals do not have any concept of those lines on a map. Rather, the landforms of the Earth dictate what grows where. And that is where ecoregions come in.

If you want to add plants native to your area into your landscape, then you will need to understand the landforms and environmental conditions that exist where you live. To best support the ecosystems and wildlife that naturally occur in your area, it helps to know how your property fits into the wider environmental context.

What are ecoregions?

The US Environmental Protection Agency (EPA) has mapped ecoregions for North America at four levels, from Level I (broadest) to Level IV (most specific). There are 15 Level I ecoregions, which describe rather generally the different kinds of landscapes found across the continent (such as Tundra, Great Plains, Eastern Temperate Forests). The 50 Level II ecoregions provide a bit more specificity within the larger Level I areas, like Mixed Wood Plains vs. Southeastern USA Plains.

Level III, an example of which is shown above, includes 182 designations across North America and divides the more general ecoregions into descriptive classifications to help with ecological monitoring and management. This is probably the most relevant level of interest to wildlife gardeners. (Level IV gets even more specific, but there is less available information or even descriptive text at this granularity.)

So, as an example, the part of Northern Virginia where I currently live can be described as being within the Level I ecoregion 8.0, “Eastern Temperate Forests”; Level II ecoregion 8.3 “Southeastern USA Plains”, and Level III, 8.3.1 “Northern Piedmont.”

How do I find my own ecoregion?

There are several places to look for your ecoregion, including the EPA website. There, you can open up maps by level and see how the landscape fits together. However, you will have to do a lot of zooming and panning to identify your area and may not be able to pinpoint your exact location. The Wild Ones website has a very handy search page where you can simply enter your street address and it will bring up a description of your Level I, II, and III ecoregion

The “What’s My Ecoregion?” page on the Wild Ones website lets you enter your address to find your own ecoregion. Easy!

Why not just use USDA Hardiness Zones?

Many gardeners are familiar with USDA Hardiness Zones, which divide the country into numbered zones from 1 to 13. You might already know that you garden in a Zone 6 or a Zone 7b. The hardiness zone system is purely based on the lowest average winter temperature measured each year in a given area. In other words, how cold does a place get on the coldest winter day? From this, we are supposed to guess how hardy a plant is and whether it can withstand a low temperature of, say, 0°-10°F, but not -10°-0°F.

This tells us nothing about a plant’s nativity or natural habitat requirements or ecosystem niche; only about how much cold it can withstand. While it might be quite useful when planting overwintering food crops or fruit trees, it is not very helpful for designing appropriate ecological gardens!

Ecoregion equivalents outside the US

If you are located outside the US, there are global and regional resources for determining your ecoregion, such as:

• WWF Global Ecoregions – WWF Ecoregions (no longer updated but still useful)

• One Earth Bioregions – Bioregions: Nature’s Map of the Earth (updated WWF data)

• Europe: EUNIS Habitat Classification – European Nature Information System

• Australia: IBRA Bioregions – Australian Government Bioregional Framework

• Canada: Ecological Framework – Canada’s Ecoregions

• UK National Vegetation Classification (NVC) – JNCC NVC Database

If you know of any other good sites, please share in the comments below!

Next Steps

Once you know your ecoregion, you begin to have an appreciation for the natural landscape type and a description of the general ecological community. This provides an immediate insight at a basic level: if you live in the Northern Piedmont ecoregion, you will have a clue that a plant called a tropical night-blooming water lily or a barrel cactus is probably not going to do well in your area. The ecoregion essentially gives you a broader context for your gardening/planting efforts.

Stay tuned for my next article in the series, where I’ll dive into plant communities and lists to begin forming a reference based on your geographic location.

A wetland opening in a temperate floodplain forest within the Northern Piedmont ecoregion.