This is a post about my philosophy of landscaping. In the last few years, I’ve worked with a few groups of folks on choosing plants for the gardens around our building. Everyone has different tastes, and different ideas about what our landscape should look like. I’ve heard both praise and criticisms of decisions that were made, and questions about why certain plants were chosen, so I thought I would tell you the ideas behind my choices.
Summary: My goal is to get more native plants into urban gardens. Native plants provide habitat for native insects. Native insects are important to us because they provide food for songbirds, and pollination for our crops and gardens. As wild land disappears, the habitat for native insects disappears. We’re starting to see fewer pollinators, and declining populations of songbirds. As urban gardeners, we can help stop this decline by planting native plants in our gardens.
First – some definitions:
Native plants are plants that were here before the European settlers came. They’ve been here for thousands of years, and have been evolving with each other and with the insects and other animals that have been living here with them.
Exotic plants have been here only a few hundred years or less. European settlers brought plants with them – some on purpose for crops or gardens, and some unintentionally. Some have escaped and have become ‘naturalized’ – they grow in the wild. We may think of these as natives because they’re so common in our landscape, but they actually haven’t been here very long. We continue to bring plants here from other places, and some still escape into the wild.
Exotic plants have been very useful to us. Most of the plants we eat have come here from somewhere else, or have been greatly modified from the original plants they came from. They have been modified to produce larger fruits, or keep longer in storage, or bruise less when being shipped. Most flower gardeners grow exotic, or genetically modified flowers because of their long bloom times, interesting colors, or extra large blossoms.
But there are problems with growing only exotics. Or only genetically altered plants.
Native insects mostly need to eat native plants. Plants and insects evolved together. Plants don’t like to be eaten, so they evolve ways of discouraging insects – often producing chemicals that insects can’t eat. Some insects figure out ways around those defenses – ways of neutralizing or avoiding them. To make this a bit easier, insects often specialize in one kind of plant.
One familiar example is Monarch Butterflies. Monarch caterpillars eat only milkweed plants. Milkweed gets its name from the milky juice that is in the stems and leaves. The juice contains several toxic compounds. Monarch caterpillars have specialized to feed on the leaves in spite of their toxicity – in fact, monarch caterpillars use the toxic compounds to make themselves toxic to predators.
Exotic plants have these evolutionary relationships with insects in their home countries, but not with our insects. So native insects can’t eat most of our garden plants.
This may sound like a good thing. Who wants insects eating their flowers? But native insects seldom cause permanent damage to native plants. It’s an evolutionary relationship – the insects benefit from having the plants around, so they usually don’t do a lot of damage – only enough to keep themselves alive.
Insects that eat nectar – bees, and adult butterflies, among others – are a bit less particular about where they get it. Nectar is pretty similar from one flower to the next. Nectar eating insects care more about the shape of the flower and the accessibility of the nectar. Insects with long tongues can drink from flowers with nectar at the bottom of long tubes. Insects with short tongues prefer flowers with more accessible nectar. But studies have shown that native insects still prefer getting their nectar from native flowers.
Genetically altered plants are another issue. The alterations are usually made to make the plants work better for people. We seldom pay attention to whether the flowers will still have nectar, or whether the nectar will still be accessible to insects. Often the modified plants are not as easy for the insects to use as the original ones. Double flowers, for example, make the nectar much harder to get to.
The BIG Problem:
As our population grows, we expand our use of land for agriculture, roads, houses and industry, and for endless acres of mowed, chemically treated lawns and non-native landscape plantings. Every year there is less wild land, and even the small ‘wild’ areas we see are usually overrun with non-native, invasive plant species that don’t provide much habitat for native insects, birds and animals. This habitat loss is especially important when it comes to native insects.
Why should we care about native insects?
Besides being beautiful and interesting, native insects have several important ecological roles. Many are important pollinators – both of wild plants and crop plants. And they are a very important food for songbirds.
Almost all of the vegetables and fruits we eat come from plants that must be pollinated by insects – among them tomatoes, apples, beans, blueberries, almonds, and pumpkins. Much of this pollination is done by non-native honeybees, but scientists estimate that about 15 percent of the pollination of crops in the U.S. is by native insects. And honeybees are in trouble – colony collapse disorder and other diseases are killing honeybees at higher rates than in the past. We really need to protect native pollinator populations to be sure we can grow the crops we depend on for food.
Food for birds
Nearly all songbirds eat insects. Even birds that we think of as seed eaters, like sparrows, eat insects when they’re feeding their babies. Insects are high in protein, which is what growing fledglings need.
So – if we don’t have insects, we won’t have songbirds, and we may not have some of our favorite foods.
What can we do?
One thing city dwellers can do to help is to grow diverse plantings of native plants – plants that pollinators and other native insects can use – in our gardens.
Now that I’ve been growing native plants for many years – both in my gardens and at our farm – gardens with only non-native plants in them seem ‘dead’ to me. There’s very little movement – the flowers are beautiful but they’re like a painting. Very few insects buzz around them; there are few butterflies or dragonflies. So those gardens are not very interesting to look at.
Native gardens are full of life. A few days ago Mike and I walked through Saint Anthony Park and noticed that every native garden had several Monarch Butterflies nectaring on the flowers or chasing each other across the tops of the plants. The butterflies were only in the native gardens – there were none in the non-native gardens. If you visit our prairie and wetland gardens you’ll see butterflies, dragonflies, bees, moths, beetles, and lots of birds.
I would like all our 1666 gardens to be full of life. Growing natives helps the environment – it would provide more habitat for the insects we need to nourish. But I’d also like to grow natives for selfish reasons – I love to see butterflies and dragonflies in the gardens. I love watching and listening to songbirds in the mornings outside our windows.
Many of the older parts of our landscaping are non-native flowers or shrubs. It’s my hope that we can gradually replace the older, non-native plantings with native species that will make our environment more beautiful and more interesting for all of us.
Most of the insects we consider pests are not native. Like non-native plants, they were brought here from other countries – sometimes intentionally; sometimes by mistake. Japanese Beetles, Emerald Ash Borers, and Gypsy Moths are all non-native pests. Some are ‘weedy’ species and will eat almost anything – like Japanese Beetles and Gypsy Moths. Some eat native plants that have developed no defenses against them (they didn’t evolve together) – Emerald Ash Borers eat our native Ash trees. The best thing we can do to avoid problems with these pests is to grow lots of different kinds of plants. Even pest insects usually have preferences, so in a diverse planting, some plants will get eaten more but some will be fine.
To learn more about native landscaping:
Bringing Nature Home by Douglas Tallamy. This book was reviewed at 1666 by Dottie Waltz a few years ago. Doug Tallamy is the chair of the Department of Entomology and Wildlife Ecology at the University of Delaware. Click HERE for a link to an article with a summary of his ideas about natives and insects in gardens. There’s a copy of the book in the 1666 library if you’d like to read the real thing.
Attracting Native Pollinators Published by the Xerces Society, this is a guide to identifying and attracting native pollinators. It discusses the importance of pollinators in our world, and suggests ways we can help protect them. A new copy of this book has just been donated to the 1666 library.