Why Native Plants? The Advantages To An All Locally-Native Garden

A species, like a plant or animal, is said to be native if it occurred naturally in that area, before human intervention.  Because plant distribution can be very localized, there is a distinction between the idea of being locally native, and being native to a continent or broader region.

A plant is usually said to be locally native if it naturally occurs or occurred in or near a small region, like the typical size of a county.  So, for example, a plant native to the Lake Erie seashore in Pennsylvania, would not be locally native to Philadelphia or central PA, even though it would be native to the state of PA.

Because governmental or political boundaries do not always correspond to natural geographic boundaries, it is more important to consider whether a plant is local to your particular ecoregion, rather than your state.  For example, if you live in southeastern PA, it would be better to plant something native to northern Delaware but not native to PA, than it would be to plant a "PA native" plant only found in far western Pennsylvania and not found anywhere in NJ, DE, or MD.

Humans have altered the natural environment extensively, changing habitat, introducing new species, and removing or eliminating others.  Plants not native to an area, but growing in wild populations are said to be introduced or naturalized.

Some introduced plants become invasive, meaning that they grow aggressively and cause problems for the ecosystem.  Not all introduced or naturalized plants are invasive.

It can be subjective what is classified as invasive.  For example, Canada thistle (Cirsium arvense) is widely considered invasive, but it is eaten by a wide variety of native insects, so it is not as ecologically damaging as a number of other plants.

The classification of plants as invasive can be politically or economically motivated; Canada thistle is classified as invasive as large part due to being an agricultural pest.  Similarly, Marijuana (Cannabis sp.) is classified as invasive due to being a controlled substance, even though it tends to have no negative ecological impact in North America: its status as a controlled substance ensures that any populations of it in the wild are quickly eliminated (either by law enforcement or people who transplant it to grow for sale or for their own use).

There are many different ways to find out if a plant is native.  I recommend:

• USDA Plants Database - The range map above is from this database.  You can search the database from this link, or just by typing the scientific name or even sometimes common name of a plant into a search engine, followed by "USDA plants profile".  Look at the range map for the species, and then check to see if it is labelled "N" for native or "I" for invasive or introduced.  This site is not perfect, it tends to classify some plants as "native" which are native to North America but have expanded their range due to human influence, and it does not usually distinguish native vs. introduced range for these plants.

If you are going to use a published, print resource, I recommend one that is up-to-date, ideally the newest edition from the past 10-15 years or so.  This is because new information comes out about plants distribution, so old books, particularly very old ones published before genetic studies had been carried out, are likely to have misinformation about what is native.

Native plants are the ultimate in tried-and-true plants to grow in a particular region, because they've been living there for years--in most parts of the U.S., thousands of years, since the most recent glacial period.  They are thus well-adapted to the local conditions, including soil.

Especially in regions like the continental U.S., there can be unpredictable climate conditions from year to year, with some years bringing severe cold in winter, other years a mild winter, some years severe drought, other years exceptionally wet conditions.  But native plants are usually able to handle whatever the climate throws at them, especially if they're grown in their preferred habitat.

When gardening in arid areas, locally native plants can also handle the normal lack of rainfall, making them excellent for xeriscaping (landscaping with drought-tolerant plants to avoid the need for irrigation or watering).

If you garden with native plants, you will need to do less work to make your garden look lush and healthy.

Plants are the primary producers in an ecosystem, and thus the cornerstone of the food web.  They capture light from the sun and are the starting point through which energy enters ecosystems.

In a healthy, natural ecosystem, plants are eaten by a wide range of insects and other invertebrates, as well as by larger animals.  Mammals eat the leaves of plants, and birds and other animals eat fruits, seeds, nuts, and other parts of plants.  But birds and insect predators also prey on the small insects and insect larvae that eat the leaves, stems, roots, and juices of plants.

Plants and insects co-evolve, and insects are often very specialized in what they eat.  When people introduce plants to a new area, they typically don't bring any or all of the insects and other animals that eat the plant to this area, and often, the plant won't be eaten by as many native insects.

With fewer or no local insects or other herbivores eating the plant, the plant creates a "dead zone" in the food web, reducing insect biodiversity and indirectly reducing the diversity of birds and other larger animals as they have less insect food to eat.

By planting native plants, you help protect and restore this biodiversity by supporting the whole food web!

I often hear people argue or express reservation about the insistence by ecologists and activists that all-native gardens are the best approach ecologically.  Is it ever okay to plant non-native plants? I say only if they are food plants.  Are non-native plants doing harm?  The short answer is yes, nearly always, and it is nearly always better to garden with all natives.

But the amount of harm caused by using non-native plants is hugely variable from one plant to the next.  The main concerns are:

• Invasive species - Many plants, including ones that are widely planted, are invasive and can cause severe problems to the local ecosystem.  Where I live, some widely-grown plants that are invasive and harmful to the ecosystem, include privet (used as hedges), English ivy, and bush honeysuckle.  All these plants can and do escape into wild ecosystems, where they compete with native plants and also cause other problems (Bush honeysuckle can increase the risk of Lyme disease, for instance).
• Not supporting the food web - Even if a plant doesn't spread from your property, it's taking up space that would otherwise be occupied by a native plant, and it's not supporting the food web through supporting insect herbivores, pollinators, and all the other animals that depend, directly or indirectly, on native plants.
• Not spreading seed of native plants - Because harmful invasive plants are so widespread, and because so many people still garden with these invasives, our ecosystems can use all the help they can get.  Any space taken up by non-native plants in your yard is space that is not occupied by native plants that could be producing seed and spreading off your property, and into surrounding wild areas, helping to preserve and protect the ecosystem in these areas.
• Requiring more resources - This is more an issue for some plants than others, but many non-native plants require a lot of care.  For example, growing a plant in an arid region that is native to a wetter climate, requires extensive watering, and growing a plant in a region colder than its native range requires you to wrap or protect it in cold winters. Growing plants native to an area with richer soil will require fertilizer or amending the soil. These resources are all resources that you could instead be putting towards other uses, or just conserving outright.
• Other interactions that harm native species - Plants interact with their environment in many different ways, such as releasing chemicals into the environment, and cycling water and nutrients. Native and non-native plants can cycle water and nutrients differently, and planting non-native plants can harm communities of native plants that would grow together with or underneath native plants. Plants can also produce allelopathic chemicals, chemicals that inhibit the growth of other plants.  Allelopathy is selective, and non-native plants tend to inhibit the growth of more native plants, because they are poorly adapted to it, whereas native plant communities evolved to grow together and can thus tolerate each other's allelopathy.

I tend to make a few exceptions for my rule about non-native plants, for food plants.  Growing food plants in your garden is a great way to save money, promote better health and nutrition, and also lessen your environmental impact, as you save the cost of producing and transporting these foods in society.

Besides food plants, however, I think it harmful to the environment to plant non-native plants.  Take all your money, time, work, and other resources, and direct them towards growing locally native plants.  That's the way to use your resources to have the most positive impact on the environment possible!

When you buy native plants for your garden, you want to check for the following things:

• Check that the species you are buying is native to your local region, not just your continent, state, or broader region.
• Buy pure species, not a cultivar.  Cultivars are typically cloned, and lack genetic diversity. They also often have attributes that make them less beneficial to the insects. For example, cultivars selected for their flower shape may not be as beneficial to pollinators like bees or butterflies, and cultivars selected for insect resistance will not support the food web as much.
• Buy plants grown from seed from a local population.  Some plants, like trumpetweed pictured above, have a large range.  If your garden is in Maine, it would probably be okay to grow a plant grown from a Vermont population, but you don't want to buy a plant taken from a Florida population. 

Most large garden centers, and even some smaller nurseries, can be poor places to find locally native plants.  Many of these nurseries only stock mass-produced plants, cultivars, and non-native species.  If the nursery staff can't verify all three points for any plant you buy, you're probably not shopping at a nursery that is committed to ecological principles.

The Mt. Cuba Nature Center maintains a list of nurseries that will be useful to people near DE, MD, and Southeast PA.  For a national directory, check out PlantNative's directory.

In some regions, it may be hard to find a local plant nursery committed to ecological principles.  Search online for nurseries specifically oriented towards native plants.  You may also have luck buying plants from the nurseries associated with non-profit wildflower preserves or other non-profit organizations.  Some of these nurseries are only open by appointment or for special events, but it can be worth going out of your way to get your hands on these locally-native plants grown in ecologically-mindful ways.

First: do not dig up, transplant, or remove native plants from intact ecosystems.  This can harm the wild population.

Learning how to identify plants can be a lot of work, and can be a unique intellectual challenge.  But if you learn how to identify plants, you'll often be able to find lots of free plants.

Some great ways to obtain free native plants include:

• Utilize plants that come up from seed in your garder or on your property.  This is especially effective if there are populations of native plants with wind or bird distributed seeds, near your property.  Sometimes, you can encourage germination of plants you want by creating the right conditions or substrates for germination in your garden.
• Transplant plants from land right before it is cleared or developed.  If a parcel of forest, wetland, or meadow is about to be developed, you have a unique chance to harvest plants from there, since they will be destroyed anyway.  I've also removed native plants from vacant lots in cities, prior to development, or from gardens adjacent to sidewalk prior to the sidewalk being torn up.
• Transplant plants that come up where they will be removed or killed.  Examples include in gardens or flower beds of peoples' homes, on college or university campuses, office parks, maintained beds in municipal parks, right-of-ways along roads, paths, or railroad tracks, or anywhere where plants are pulled, pruned, sprayed, or mowed.
• Gather seeds from populations in the wild where the plant is abundant, and grow the plants from seed.  Take only a small portion of seed, and make sure you know how to germinate the seeds, and the right habitat and conditions to grow the plant in, so it does not go to waste.
• Gather seeds from gardens and grow the plants from seed.  This is a good method, if and only if the plant population is one that is grown from seed from a locally-native population.  Do not propagate cultivars like this.
• Grow plants from cuttings.  Some species are easy to grow from cuttings, producing a clone of the original plant.  If you use this method to grow multiple plants, make sure to take each cutting from a genetically unique individual, so that your established population has genetic diversity.  If you take cuttings of a wild plant, make sure to only take small cuttings from a healthy, vigorous plant.

Make sure to get permission from property owners before doing anything potentially controversial on someone else's land.  I've found it very easy to get permission for these sorts of things--most property owners love to have someone remove things they see as weeds, for free, from their property.  Make sure to leave the property looking nicer than when you found it!

Most of the plants I garden with, I obtain these ways.

Here are some resources to help learn more about plants:

• Why Native Plants - Lady Bird Johnson Wildflower Center - Start with this little article on native plants, but this site has a huge database of native plants, with info about growing conditions and ecological relationships.
• What's This Plant? Subreddit - If you're active on reddit, this can be one of the best place to get quick (and often expert-level) feedback on plant ID, especially when you're stumped.  Primarily a Q&A community based on posting photos and having people respond with ID guesses, the subreddit also has some good guides on the most commonly requested plants, which can be super useful to look through for learning to ID common weeds, which can include both native and non-native plants.