Monday, May 20, 2024

Pollinators - new paper and tips for your garden

Bumblebee on blueberry flowers

I wanted to announce a new paper I've been kindly included as an author on (despite minimal contributions) - Li et al. 2024. It's a methods paper about using land cover data to predict floral resource availability for pollinators. There are a few potentially interesting things in here. 1) Most pollinators don't make much honey, so their populations are limited by the time of year w/ the least food available (pollen and nectar). The methods here help you figure out those bottlenecks if you want to target habitat restoration to boost pollinator populations. 2) Plants vary a lot in how much nectar pollen they make. Not every crop makes flowers that feed pollinators (likely obvious, but some crops and cover crops are harvested or terminated before flowering, and wind-pollinated plants don't have nectar). Trees produce a ton of nectar and pollen. 3) The paper looked at two different ways to map land cover, and surprisingly the simpler approach worked as well (similar error levels)! It's a good reminder to always question whether you need more complexity and accuracy.

I was asked "How can we use these insights in NYC if at all for urban pollinator husbandry?" which made me realize I should have been more clear about tips for people who want their gardens to better support pollinators.

The actual results are specific to upstate New York and wouldn't apply elsewhere. To make this work one of the authors had to visit many places to see what plants were blooming in what kinds of habitat at different times, then use remote sensing to make a land cover map, then do the math to see when floral resources are scarce.BUT here's how I have been using the very rough concept it in my own garden!

1. Take notes and photos throughout the year as you walk around your neighborhood. When do you first see bees (and/or other pollinators like flies and beetles), and what flowers are they visiting? If you're not seeing bees in your garden - try planting those early bloomers in your own yard.

2. What weeks do you notice the most and least flowers? This isn't a perfect proxy since some flowers have big petals but don't provide much food (like marigolds, geraniums, lilies, and tulips). But it's a start. Write down the weeks where you see the fewest flowers in the neighborhood. That tells you where your garden can have the most added value.

3. Are there certain plants absolutely mobbed with pollinators certain weeks (bees, flies, moths, etc.)? That's a good clue they may be offering food when it's scarce, and/or it's high quality, and you could plant more of them. If you want diverse pollinators, include some plants with small composite flowers (I find those are the most popular overall, especially for sweat bees and bomber flies, something like anise hyssop / Agastache or goldenrod) and some with bigger flowers larger bees like (Penstemon is a favorite of my bees, although the bees also love basil flowers).

4. Based on your notes, add perennial plants that flower when there are the fewest available flowers in the neighborhood. For me that was early spring, late fall, and mid to late summer. Consider also adding some plants that flower intermittently year round like rosemary - it's consistently a star performer in late winter / early spring for me, but also gets some love in the summer. For folks in the DC area my top performers are probably penstemon, anise hyssop, goldenrod, swamp milkweed, and obedient plant (for late fall / early winter)

5. Take notes and/or photos of what you see in your garden. It's fun to see how specific flowers will attract species that won't come otherwise. Use Google Lens or iNaturalist to identify at least the rough kinds of bees. Look for the metallic green or orange Agopostemon bees, get close photos of sweat bees, and whatever other ones surprise you. Here are my pics of pollinators in my garden.

6. Experiment! One year I planted sunflower and it was the only time I saw a long-horned bee in my garden (check out the pics: it's a pretty cool bee). I used to have some lambs ear which I got rid of b/c it wasn't native, but then I stopped seeing carder bees (which collected its fuzz).

7. Leave the dead flower stems through the winter; when new shoots and leaves form on the plant, break off the stems at different heights and toss them elsewhere in your garden (not compost). Many bees and other pollinators lay their eggs in the stems and you don't want to get rid of them before they hatch. See this guide from Xerces for more.

8. Have fun. It's really cool to see how much impact you can have on your garden and neighborhood.

9. Don't forget about habitat for other wildlife! My favorites: 

a) add a birdbath if you're able to commit to dumping and replacing the water daily (you can use rain barrel water like I do). Scrub it with a brush weekly. Get one w/ rough iron sides or leave in a stick so bugs can drink but escape if they fall in.

b) make sure you have some bushes for birds to hang out in. Mine love the swamp dogwood and viburnum more than the inkberries I planted specifically for birds.

c) if you're in the Mid-Atlantic, plant cut-leaf coneflowers. You get 7-8' tall plants that attract so many goldfinches that eat the seeds!

d) let some of your herbs flower. In addition to bees loving basil, cardinals love coriander seeds from cilantro!

e) pokeweed is a native aggressive perennial that provides so much free bird food, especially to catbirds but also robins and mockingbirds and sometimes other species. Cut it back or dig it up when it spreads too much.

e) if you have room, make a brush pile from any pokeweed stems and woody stems and bush trimmings. Several species appreciate them.

f) I used to think "certified wildlife friendly" signs were silly and bragging, but then I heard some neighbors walk by complaining about how unruly my garden was (they didn't see me on the porch). I ordered a sign, and a week or so after I put it up, I heard the same neighbors walk by, see the sign, and say "oh that's cool! it's a wildlife-friendly garden!" So it's worth looking into and the process has a few more tips.

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