Garden Q&A – Insect-Friendly Gardens

CNPS Garden Q&A with Bob Allen

Bob Allen with the book he co-authored with F.M. Roberts. Wildflowers of Orange County and the Santa Ana Mountains

I’ve been reading about the insect apocalypse and declining monarch butterfly populations. Why are native insects important, and how can I support them in my garden?

Native plants serve as food and shelter for many species of native insects. Whether in the wild or in the garden, they exhibit a variety of fascinating interactions. We can boil them down to either one- or two-sided interactions.
One-sided interactions benefit the individual insects that feed on the plant, such as on sap, leaves, buds, and/or other parts. Since most herbivorous insects are host-specific — they feed only on one or a few related plant species — just having these native plants in the garden promotes survival of their dependent native insects.


  • Larvae of the achemon sphinx moth, Eumorpha achemon, feed on leaves of native grapes, both Vitis girdiana and V. californica. Every year, the plants in my yard are inhabited by these caterpillars, which are surprisingly difficult to locate.
  • When manzanitas (Arctostaphylos sp.), bloom in winter-spring, they are host to numerous species of native butterflies, flies, and bees, such as the red admiral butterfly (Vanessa atalanta). Every garden needs at least a handful of manzanitas.Two-sided or mutually beneficial interactions are activities that provide benefit to both insect and plant.
    Red admiral butterfly on manzanita (Arctostaphylos sp.). Photo: Bob Allen

    Certainly the most widely discussed two-way interaction is pollination.
    As the insect gathers nectar and/or pollen, pollen sticks to its body, sometimes pow-dered all over like snow. Even the most careful insects inadvertently drop some of the pollen they so assiduously collect. Pollen that lands on a receptive stigma, either within the same plant/flower or between the flowers of different individual plants, successfully becomes an agent of pollination. Pollination, when successful, leads to fertilization, seed production, fruit growth, and seedling production.
    If insects were 100 percent successful at gathering and retaining the pollen they encounter, there would be no polli-nation and therefore no reproduction of insect-pollinated plants. As Charles R. Darwin said, “Natural selection will not produce absolute perfection.” (On the Origin of Species, Chapter VI.) Fortunately for plants, he was correct; pollinating insects are sloppy.

    A garden full of locally native plants provides food and shelter for native insects.

    Adult insects use the pollen and nectar they collect to feed themselves and/or feed their young. Thus, pollen-collecting and successful pollination are both mutually beneficial interactions. Insect-pollinated native plants require insects for their own reproduction.

    Bumblebee species on deerweed (Acmispon glaber). Photo: Bob Allen

    How can I support native insects in my garden?

    We can support these native insects by using locally native plants, eliminating pesticides, reducing garden disturbance, controlling our use of mulch, and changing human notions about native insects.

  • A garden full of locally native plants provides food and shelter for native insects.
  •  A hard look at pesticides reveals that nearly all are used against non-native insects that feed on non-native garden plants. A native garden, then, has no need for pesticides. The insects that show up to feed on those native plants belong there.
  •  Soil cover (mulch) is often overused. Sure, it helps keep weeds down, but it also covers the bare soil required for nesting by many species of native bees, egg-laying by grasshoppers, and soil pupation by many species of moths and beetles. Try to keep at least some areas of undisturbed bare soil to allow these insects to survive.

We must change the all-too-common human perception that having insects on our plants is a bad thing — it’s not. Enjoy the insects!

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Robert L. “Bob” or “BugBob” Allen has studied insects and plants since early childhood in San Juan Capistrano, California. He is now an adjunct professor of biology at Santiago Canyon College and Orange Coast College, a research associate in entomology at the Natural History Museum of Los Angeles County, a research associate at the Rancho Santa Ana Botanic Garden, a horticultural consultant, and author of Wildflowers of Orange County and the Santa Ana Mountains.


  1. We tore out the water wasting lawn and planted manzanita and ceanothus. The California poppies came up by the thousands and the bees really enjoy them. We trained a honeysuckle over an arbor for the hummingbirds. The back yard has dill weed and narrow-leafed milkweed. Butterflies flit through from the nearby dill patches. The tomatoes host tomato hornworms and the Monarchs like the parsley flowers.

    1. Hi there!

      I am growing A LOT of speciosa, upon which I’ve gotten monarch caterpillars before. I need to know what nectar plants they like, do you have any suggestions?

      1. Try pincushion flower (scabiosa) and cosmos. They like the parsley flowers and anything with a flat umbel. My Buddleja attracts everything!

      2. Try pincushion flower (scabiosa) and cosmos. They like the parsley flowers and anything with a flat umbel. My Buddleja attracts everything! Another good idea is Monarda.

  2. I have a blank front yard. The yard is postage stamp size. Not large. I do have fruit trees in the front. Nectrine, peach, orange trees. In the fall, I would like to plant native plants.Suggestions would greatly be appreciated. I enjoy the fruit I get from the trees. So, not sure if I want the bugs to eat them.

    1. Hi Linda. Glad to hear you are planning to plant natives in your yard! Since native plants and native insects co-evolved, native insects will most likely look for native plants for food – not non-native fruit trees! Planting natives will likely attract pollinators that may increase pollination and thus yield on your fruit trees. Check out our Native Landscape Planting Guides to get plant and landscape design ideas for your region. Also, be sure to visit to discover plants native to your location.

  3. How do we help with the cooling of our neighborhoods? Cement, housing, fake lawns? The story about the permafrost was so interesting. To bad the human race isn’t helping with our climate, except to continue to cover the earth. Suggestions!!

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