Gardening and landscaping with native plants is different and sometimes more restrictive than a purely ornamental approach – so having a good reason WHY can be helpful inspiration. For me, the most convincing WHY ever is the way that native plants sustain other organisms around them.

The familiar narrative that says native plants are easier to grow and better adapted than non-native plants is only true sometimes, as it depends on what non-native plants you are comparing them to.  For example, a parking lot in Portland Oregon may be easily filled with beautiful plants that are easy to grow, require no water, and originate in Italy, Spain, Mexico, California, and Australia. These plants will actually do better than a native plant that originates in a forest, because the forest plant won’t be able to handle the sun and heat of a city environment.

Plants as Citizens

To me, the REAL reason why we should plant natives is the functional role they play in the greater ecosystem: how they contribute as citizens of a biological community.

Plants from all over the world can be beautiful and low maintenance, but cannot support the rich web of life that a native plant community does. If we want songbirds, salamanders, bumblebees, and red-tailed hawks to be part of our world, we need native plants. And if we want these creatures to exist in our cities and towns and farmlands, then we need native plants in these areas too.

Wasp gall on Oregon White oak
Wasp gall on Oregon White oak

Insects eat native plants, animals eat insects

The reason comes down to leaf chemistry, as is wonderfully explained in Doug Tallamy’s book Bringing Nature Home. Insects (mainly larvae) that eat plant leaves are an extremely important element of the food web, because so many other organisms eat them. As just one example, the vast majority of songbirds feed their young exclusively on insect protein. And those insects can only eat the leaves of plants that have compatible chemistry. If we want birds, we NEED insects, and if we want insects, we NEED native plants.

Every plant species has its own distinct brand of chemical compounds in its leaf tissue, and over millennia of co-evolution, certain species of insects have been adapted to be able to digest those chemicals. This process of adaptation literally does take millennia – mere hundreds of years are not nearly enough. The Norway Maple, originally from Europe, has been separated genetically from North American maples for over 80 million years. Even though it was first introduced to North America more than 250 years ago, and has naturalized throughout the Northeastern United States, 250 years is such a minuscule amount of time in evolutionary terms that no North American organisms have yet adapted to its chemistry. (Tallamy, 66-67)

Eew, bugs?

Even if you like the idea of attracting songbirds to your yard, an understandable reaction might be, ‘does that mean the bugs going to eat up ALL my plants?’ Luckily, no.  The actual aesthetic effect on the plants is so minor you would probably be challenged to find them. I bet you walk by native plants every day, and never even notice all of the insect larva they are supporting.

Just any native plant?

So now you are convinced, but you only have room in your yard for a few plants. Are there some that are better than others?

Although it’s a safe rule of thumb that by planting native plants you are providing food for somebody, some plants and plant families are especially generous. Plant genera that support a very high number of wildlife include Oak (Quercus), Willow (Salix), Cherry/Plum (Prunus), and Birch (Betula). (Tallamy, 147)

What counts as native?

Some plant reference guides call a plant Native if it is from the same continent, or the same state, where you reside. However, for the sake of supporting local wildlife you need plants that the locally occurring insects will actually recognize. Therefore, it’s best to stick to plants that occurred in your specific bioregion pre-European settlement, as these are the ones that have been around long enough to have co-evolved with your wildlife.

When you are shopping for native plants you have the choice between the ‘straight species’ (i.e. Philadelphus lewisii) as it comes from the wild, or you can buy named selections, such as Philadelphus lewisii ’Blizzard.’ The named selections have been chosen for specifically desirable characteristics such as mature size or bloom color, but each plant will be a clone of the others of the same name and there is much less genetic diversity in the population. You should make the choice of what is best for your yard, and be aware of the context for your choice. Portland’s Backyard Habitat program does not count named selections as native, because the research has not been done on their benefit. Doug Tallamy states that these named selections are most likely still beneficial.


Want to learn more?

Online resources for learning about Willamette Valley and Pacific Northwest native plants:

Books about planting for biodiversity:

  • Bringing Nature Home, Doug Tallamy
  • The Living Landscape, Rick Darke & Doug Tallamy
  • The Xerces Society Guide to Attracting Native Pollinators

 

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