Gardening for good bugs part I: nectar and pollen sources
Given the bomb cyclone, I'm glad that I had previously decided to spend the month of January discussing topics other than my vegetable garden. My winter protection of straw and floating row cover works great for typical January weather (and even a few inches of snow), y'know, when it barely reaches freezing temperatures just before sunrise and warms to the 40s in the afternoon. We've now had more than a week of continuous below-freezing temperatures and I am losing confidence that I can expect any of my veggies to survive. Clearly I have some thinking to do about how to be more prepared for next winter, to employ more of the strategies used by Northern gardeners.
Now on to our scheduled programming: this will be a four-part series about gardening for good bugs. In this post, I will discuss nectar and pollen as food sources for good bugs. In future posts, I will discuss specific larval food sources for butterflies, bug-protective gardening practices, and how to support soil-dwelling bugs.
To begin, when I say "bugs," I mean all of those tiny invertebrate animals that crawl, hop, and/or fly, whether they have six legs (insects), eight legs (spiders), a whole lot of legs (centipedes and millipedes), or no legs at all (worms). Most of the time when gardeners talk about bugs, they talk about how to kill garden pests. However, fewer than 1% of bugs cause harm to people or plants! So the entire point of this series is to urge you to shift your focus away from the harmful minority of bad bugs and towards the overwhelming majority of bugs that are beneficial. When we reach for pesticides to stamp out a handful of bad guys, we're robbing the legion of good guys of their chance to "take out the trash" for us. Many pesticides (including natural and organic ones) don't discriminate between unwanted pests and desirable beneficials, so pesticide use leads to the unintended negative consequence of killing off the good guys.
While doing my research, the singularly most fascinating fact I read came from Attracting Beneficial Bugs to Your Garden by Jessica Walliser: plants and bugs communicate through smell. If a plant is being chomped on, that plant is capable of emitting herbivore-induced plant volatiles (HIPVs) to alert nearby predators of the situation. Essentially, the plant screams for help. And these HIPVs can be pest-specific. A cabbage under attack by caterpillars will emit a different HIPV than one being chewed by slugs. Different predators recognize these different signals. Parasitic wasps respond to the caterpillar signal while ground beetles respond to the slug signal. Of course, for predators to be able to come to the rescue, they have to be near enough to notice that something is going down.
What keeps good bugs in the garden? An abundance of pollen and nectar. Lots of bugs make meals of pollen and nectar besides the bees and butterflies we commonly think of as pollinators. Predators such as beetles, flies, and ants rely on protein-rich pollen and the sugar rush of nectar when their preferred buggy prey isn't present. Since all flowering plants produce pollen and nectar, albeit in differing amounts and chemical compositions, planting a diversity of flowers with different bloom times throughout the year will ensure that predators linger in the garden.
The pollen and nectar contained in different flowers are accessible to different bugs due to natural differences in bug anatomy and flower architecture. Flat and open flowers put out the welcome mat for the widest variety of bugs, which is why plants in the Asteraceae family dominate North American pollinator plant lists. Larger bees and beetles are big and burly enough to push their way past the petals of lipped flowers, such as those in the Lamiaceae family. Tubular flowers require specialized equipment to sip its nectar; butterflies (and hummingbirds) possess long straw-like tongues that enable them to get a drink.
I believe that encouraging Americans to plant a diversity of flowers for good bugs was the honest, well-meaning intent of the controversial "Bring Back the Bees" campaign. The seeds that Cheerios gave away were a mixture of flowering annuals and perennials, natives and non-natives, which is not a bad idea unto itself. However, the problem arose from the fact that Cheerios used only one mix for all of the United States, as if the landmass of our country has only one climate. "Right plant, right place" is the motto of gardeners everywhere, meaning that plants are most successful when they are matched to their preferred growing conditions. And not all of the plants in the Cheerios mix were right for all places in the US; some plants would struggle to survive in local conditions while other plants could grow so successfully as to become invasive, with the potential to displace sensitive native populations. By contrast, the Xerces Society has taken a scientifically-informed approach, tailoring their lists of recommended native flowering plants by regional climate.
In my garden, I welcome well-behaved (non-invasive) non-native annual flowers. Besides, all of my favorite vegetables to grow are non-native. The tomatoes, peppers, and beans enjoyed in the summer have origins in South and Central America, okra originates from Africa, and cucumbers originate from Southeast Asia. All of these crops require pollination (and protection from pests as offered by predators), so plant more flowers to bring on the good bugs! Since I don't have a lot of space, I prefer plants that are multi-taskers. Basil, dill, cilantro, johnny jump-ups, borage, nasturtiums, and marigolds all fit the bill because they attract good bugs with their flowers and I can eat them! (Eat the plants, I mean, not the bugs...I'm not *that* hungry, thanks.)
For perennial multi-taskers, I go with natives. In addition to providing pollen and nectar, many native perennials serve as larval food sources for butterflies and they provide habitat for native bugs and wildlife. Some native perennials produce berries that may be eaten by birds (but not all berries are safe for human consumption, so make sure to properly identify any berries you intend to eat). Again, the Xerces Society's Mid-Atlantic list is my go-to because it was designed with small gardens in mind. If I had more space for larger trees and shrubs, I would refer to Plants of the Chesapeake Bay. For further discussion of native perennials, stay tuned for Part II of this series.
A partial bibliography