Interspecies collaboration among trees to share carbon? Pretty cool! New research shows that trees that have an environment with heathy mycorrhizae in their ecosystem not only share water and nutrients with each other, but also carbon. It was also found that trees shared these resources with trees of a variety of species, not just their own. It is thought that this type of sharing could help trees support other trees that are experiencing stresses associated with climate change, helping make the whole forest a healthier place and giving more trees a chance for successful growth. What if our understanding of mycorrhizal activity and interspecies tree collaboration could help support urban forests and streets trees too? What practices could be implemented to support healthy and abundant mycorrhizal activity in tree pits and parks?
As pollinator habitat disappears, through development of native habitats, pesticide use, and other stresses, there has been a large body of research and instruction on how to support pollinators (and other beneficial insects) with native plants and overwintering techniques. Many sites recommend leaving dead plant material through the winter to help pollinators and other insects overwinter, and removing it in spring. Yet, spring happens over an extended period of time, weather warms and cools repeatedly, plants bloom early one year and other years, so I find the term “spring” to be rather vague.
Are there indicators we can use as guidelines for ecological garden maintenance? I found it difficult to find practical information about when it is relatively safe to remove overwintered debris in spring, but these sources about native bees that I’m sharing here provide a lot of information that can guide our recommendations and practice.
Bulletin #715 from the University of Maine Understanding Native Bees states, “The most likely place to find bees is in the flowers of native plants, when the day is sunny, relatively calm, and the temperature is above 70°F. To be active, fly and feed, bees need to be warm. A few species are active below 60°, but most prefer temperatures above 72°.” And, “Although some species may be active by late February if temperatures are unusually warm, the vernal bee species (those present in the spring) generally become active by mid-April. You may observe them on early blooming flowers, such as willow catkins and dandelions. Some native bee species continue their activities into the autumn until the last asters, dandelions and autumn dandelions die.”
“A suitable habitat for any bee species must contain a minimum of productive floral resources and patches, as well as nesting sites, and each of these must be within flight range of each other. While bees can often exploit many different floral resources, solitary bees often have specific species that they utilize for their pollen sources. If these bees require specific pollen sources, their life cycle will often revolve around the blooming period of the specific plants. The adult bees will emerge when the plants are in bloom, so that they are able to maximize pollen collection (Cane, 2001) UVic Restoration Project. For instance, the blue orchard Mason bee nests in stems or manmade nesting tubes and their emergence coincides with the blossoming of most fruit trees, including apples, pears, and stone fruits (Home Orchard Society).
Despite being from California, the general guidelines from entomologist Robbin Thorp should be applicable elsewhere: “It’s probably best to frame the bee calendar in context of the bloom of various plants,” Thorp points out. “Manzanita (a CA native) is one of the first flowering shrubs and when they come in to bloom that is the time to look for queens of our two early bumble bee species, Bombus melanopygus and B. vosnesenskii. Some of our large digger bees like Habropoda and some Anthophora come on during that bloom. In the vernal pools, early flowering starts in late February and some of our solitary ground nesting mining bees, Andrena start about then. When the red bud comes into bloom about mid-March the Blue Orchard Bee (BOB), some other species of bumble bees, and some sweat bees come out. Leafcutting bees (Megachile) and some long-horned digger bees (Melissodes and Svastra) start their activity about mid-May. ”
And another great resource is Heather Holme’s website Restoring the Landscape with Native Plants. The website provides very
accessible information on a wide variety of plants and insects native to the Midwest (many that the Northeast has in common) and discusses how the plants and insects interact with each other. The website for her book Pollinators of Native Plants includes links to downloadable full-color pdfs of native plants for specific site conditions, the nesting habits of native bees, and common host plants of butterflies, skippers, and moths.
And for those on the West coast:
Organic garden products such as pesticides (insecticides, herbicides, fungicides, etc.) and fertilizers are usually marketed as a more natural and safer approach to garden maintenance. People interpret this to mean that products derived from natural sources won’t harm the user or the environment. It is important to realize that both organic and synthetic products are chemical compounds. Any chemical compound, both organic and synthetic, has the potential to cause harmful physical side effects. Any chemical compound, both organic and synthetic, also has the potential to cause harmful environmental side effects.
When garden products are sprayed or dusted on plants, or incorporated into the soil, those products leach into the soil or runoff into lakes and rivers when it rains causing chemical contamination and algae overgrowth. People pass by plants and gather the chemicals on skin and clothes, or inhale particles and dust. Children are more likely to have hand to mouth exposure and their small bodies put them at higher risk to smaller and less frequent exposure. Pets frolic in the lawn and gardens, inhaling the dust and ingesting lawn chemicals during their grooming, and are also at higher risk of exposure because of their small size.
Use of pesticides and fertilizers is often considered essential for successful ornamental and edible gardening, but there are healthier and safer alternatives. Supporting soil health and using a greater variety of plants will give you a more beautiful garden and encourage beneficial insects and birds to control pests while also decreasing your cost, work, and exposure to harmful substances.
Sustainable gardens first start with creating healthy soils that support an abundance of microorganisms which symbiotically support plant health. Some of these organisms break down nutrients, some attach themselves to plant roots to help plants use the nutrients, and some help create better soil texture so oxygen and water can move through the soil. Using chemical products disrupts the lifecycle of soil organisms, which will then disrupt the natural nutrient cycling of microorganisms and plants.
Sustainable gardens also include a diversity of plants which attract a variety of insects. You actually want to host a large number of insects in your garden for two reasons. First, to help keep pests under control. Beneficial insects are natural predators of garden pests. Insecticides will kill a broad spectrum of insects, both beneficial and pests (even if the product is labeled for only one type of insect). Because beneficial insects are also killed, this often leads to more insect pests in the garden, rather than less. Second, insects attract and support birds and other wildlife. If you kill the insects, you remove a lot of important food sources for local and migratory birds, and small amphibians and mammals.
Organic garden products will carry the same warning labels as synthetic products and are regulated the same way. Labeling includes both mandatory and precautionary statements and will include warnings of “Danger”, “Warning”, or “Caution”, based on whether the product meets the criteria for Toxicity Category I-IV (Category I and Danger being most toxic), and even inert ingredients are not necessarily non-toxic. For more detailed information, please refer to EPA information for Active and Inert Ingredients, Types of Pesticide Ingredients, and Label Requirements.
Below are some helpful online resources showing what native plant species benefit what birds, mostly as food sources, but some as cover or nesting material. Adding a variety of these plants to your landscape can support bird ecology with cover protection, nesting material, fruit and seeds for multiple seasons, and increasing the insect population that many birds feed upon. These plants also support pollinators, such as bees and butterflies, and other beneficial insects. Native plants can easily fit into a traditional landscape while adding beauty, drought resistance, and increased biodiversity for a variety of ecological benefits.
Native Plants for Breeding Birds by Credit Valley Conservation is a beautiful visual reference that includes foraging guilds and nesting.
Gardening for Wildlife Plant List.pdf by Loudoun Wildlife Conservancy. This list includes wildflowers, shrubs, and trees. The document also provides a great list of books used to develop their plant list and which provide even more detailed information.
Audubon now has a Native Plant Database that allows you to enter your zip code to search the native plants in your area and includes information about which bird species those plants support – this one is pictorial and lists plants alphabetically. Or you can use the Full Results page that provides the information as text. Both tabs allow you to search and filter by plant type, plant resources (think fruit, butterflies, seed) and attractors of specific bird families (hummingbirds, finches, warblers, etc.).