Protecting pollinators

There’s good and bad news about neonicotinoid pesticides during this spring’s plant shopping season. A Vanderbilt study that exposed honey bees to low doses of neonics found that after three days, the bees were sleeping half as long as normal. That’s bad news, because sleep-deprived bees have trouble finding their way back to the hive and may starve and die. 

Neonic-exposed sleep-deprived bees can't navigate

    Bees memorize visual cues for short flights, but when they’re farther from the hive, they navigate by using their circadian clock and their position in relation to the sun. Neonics disrupt bees’ circadian rhythms and throw off this navigation process.

    We seem to be accumulating more and more evidence that these pesticides harm pollinators, but the Environmental Protection Agency still hasn’t made up its mind to ban them or restrict their use, as the European Union has done. A ruling is due this year.

    As I made my plant shopping lists, I had to decide again whether to buy from my favorite garden centers. Could I trust them not to sell neonic-treated plants? I got some good news from two sources. A nearby farm stand with a large garden shop told me that most of their seedlings are started on site, and they don’t use neonics. They’ve switched to biological controls. This opens up a good source for common annuals I buy every year, such as lobelias, marigolds, alyssum, and coleus.

Pollinator-friendly marigolds and Mexican sunflowers, neonic-free

    Jack Russell, the owner of Russell’s Garden Center in nearby Wayland, called back in response to my inquiry about whether plant offerings at Russell’s are neonic-treated. I was relieved to hear his qualified no. Jack said their vegetable plants are neonic-free. For perennials and annuals, he said, they try not to sell anything treated with neonics. 

    The problem for Russell’s and other garden centers is the number of stops plants make on their way to market. Russell’s can certify that their suppliers aren’t using the insecticides, but they can’t be sure that seedlings or seeds weren’t treated before they got to those wholesale producers. Unfortunately, neonics persist for years in plant tissues.

Before planting, I want to be sure native moss phlox doesn't carry poisonous neonics

 
    Some of the suppliers whose plants I buy at places like Russell’s have made a strong commitment not to use neonics. Proven Winners, which produces many of my annuals, has vowed not to treat their plants, although they don’t quite admit that neonics harm bees. Most of the herbs offered at garden centers that I frequent are produced organically at Gilbertie’s Herb Gardens in Connecticut, so I know they’re neonic-free.

 
    In general, edible plants are less likely to be treated than ornamentals. Apparently sellers understand that consumers want pesticide-free food, but they’re slower to grasp how concerned we are about poisoning pollinators.

It's a relief to be able to source neonic-free annuals

    The good news is that the retail market is gradually catching up with ecological gardeners’ preferences regarding neonics. I’m delighted to be able to revisit my favorite plant shopping venues. Now if the EPA issues a ban, we’ll really feel sure that our gardens are safe for pollinators.

Alyssum that's safe for pollinators

 

Mulch reconsidered

 “Don’t mulch.” That was the surprising advice from native insect expert Heather Holm. What? That was a recommendation I’d never heard before. Heather’s webinar, “Attracting Bees and Beneficial Insects with Native Plants,” described the life cycles and needs of important native pollinators. Many build nests in the ground, she explained, and they need access to bare soil.

Tawny mining bee nest-photo Andrena Fulva 2d

 
    For years I’ve mulched my garden liberally. It started with an unsuccessful plan to use whole leaves to improve soil in the front yard. When they wouldn’t stay put, I invested in a leaf shredder that chopped the leaves into small pieces that didn’t blow around. Soon I was shredding all our fall leaves to spread on planting beds.

Shredded leaves make useful mulch

 
    I never had enough shredded leaves for everything I wanted to mulch, though, so I also brought in bark mulch from the garden center. In the last five years I’ve stopped using bark mulch and switched to arborist wood chips. 

     This idea came from Linda Chalker Scott, an author and urban horticulturist at the University of Washington who subjects conventional garden practices to objective scientific review. She compared different kinds of mulch head to head and found that the wood chips make superior mulch. They’re tops for holding water in the soil, modulating soil temperature, and suppressing weeds. They promote a health diverse population of soil organisms because they’re made up of a mix of different kinds of tree tissue.

 

Wood chip mulch is nice on paths and around trees and shrubs

    Wood chips fit in with my goal of reducing my garden’s carbon footprint by using locally sourced material. I get them from an arborist who works in the neighborhood.

    Now I’m re-examining my mulch approach because I want to help out native insects. What Heather advised against was bark mulch. She recommended shredded leaves, so I’m OK there. Apparently the insects don’t have a problem pushing their way through leaves to reach the soil, whereas a waxy crust of bark mulch foils them.

    Even better, Heather said, is a landscape where low-growing plants knit together on the garden floor. These plants perform the functions of mulch, and they can also provide food and shelter for native pollinators and beneficial insects (the carnivores that keep leaf-eaters in check).

 

Sweet woodruff has spread more than I'd like, but it does cover the garden floor

    Much of my garden is already provided with a groundcover layer. Two of the major players are sweet woodruff (Galium odoratum) and Canadian wild ginger (Asarum canadense). Between them they cover a lot of shady areas. There’s still not much growing under the shade of evergreens around the perimeter of the yard. This year I’m trying out native wild strawberry (Fragaria virginiana), which spreads by runners. I’m hoping it can survive and spread where other groundcovers haven’t. 

 

Wild strawberry, a native groundcover option

    Meanwhile, there are a lot more wood chips in the yard than ever before. They’ve taken the place of the lawn. Since we joined three adjoining yards to let our dogs play together, happy dogs racing around have worn away almost all the lawn grass. Instead of mud, we’re going with wood chips. I’m hoping the nesting insects will cope.

 

Lawn replaced with wood chips