Even a fire escape can help bring lightning bugs back if you plant keystone species.

Dear Avant Gardener, I’ve noticed a drastic decline in insects in the city (except cockroaches) compared to when I was a kid living in the East Village. I want to join the native plant movement to help combat insect loss, but the only outdoor space I have is a small fire escape. Do you have any recommendations? I’m specifically hoping to help nurture the dwindling firefly, butterfly, dragonfly, ladybug, and/or bee populations. For my own benefit, I’d like to obscure the view of other buildings. Lastly, I should mention that I totally lack any sort of green thumb, so please suggest lower-maintenance plants. — Eva, Brooklyn

Love that insect love! My recommendation is to plant one or more keystone species to maximize your tiny garden’s benefit to insects. In fact, keystones are species everyone should have in their garden, big or small.

Doug [Tallamy]’s research at the University of Delaware has shown that a few genera of native plants, or keystone genera, form the backbone of local ecosystems, particularly in terms of producing the food that fuels insects. By planting just one of these keystone plants you can help restore native biodiversity! Landscapes that do not contain one or more species of keystone genera will have failed food webs, even if the diversity of other plants is very high. — Homegrown National Park

Keystone wildflowers for your region — and many others — include native asters, sunflowers, coneflowers, and goldenrods.

Pre-made collections for small gardens

Can you believe there isn’t a single retail nursery devoted to native plants in New York City? Well, I guess that absolves you from schlepping around to buy local! Instead, you can pre-order the Firefly Delight 12-Plant Collection now for spring delivery from the National Wildlife Foundation’s Garden for Wildlife. Its four easy-care native plant species support 38 pollinating bee species and 124 moth and butterfly species. Isn’t that an amazing ecological contribution?! Note that you won’t be able to fit 12 plants, so plan to give some to a friend. The plants arrive with instructions geared to beginners such as yourself. Here’s a preview.

Fireflies!

The two grasses in the collection attract the flashing fireflies also known as lightning bugs. (Grasses will also add winter beauty to your containers while insects may overwinter in the dead stalks.)

Fireflies love long grassses and grasslike stems. They crawl to the tops of these plants, as well as trees, to signal to prospective mates on warm, humid summer evenings. Fireflies are attracted to moist areas that also provide habitat for the insects and slugs they like to eat. — Garden for Wildlife

Ladybugs (another beetle) eat nectar as well as tiny insects and may also be attracted by the sunflowers and asters. Dragonflies, on the other hand, are least likely to find your little garden; they live near lakes, streams and ponds, where they catch insects like mosquitoes, moths and midges.

Fireflies and ladybugs, as well as dragonflies, like water. You can leave out a shallow dish of clean water — but change it weekly to avoid breeding mosquitos, which fireflies and dragonflies will love but you won’t. In any case, you’re most likely to attract fireflies and ladybugs if there is a wild space with water, soil, and rotting logs nearby.

Finding the right container

Optimally, you want containers larger than 18 inches in each direction to accommodate the deep roots of native plants and insulate them from drought and freezing. Unfortunately, leaving anything on a fire escape is illegal in New York City. You can abide by this law (and escape in case of fire) if you hang containers from the railings. Choose lightweight containers (plastic or metal) and potting mixture and strong brackets. Unfortunately, most railing planters and window boxes are uselessly shallow — usually less than eight inches deep, so they dry out quickly in summer and freeze deeply in summer. The only railing planter I found that comes close to meeting these constraints, below, is expensive; it happens to be on sale now if you act quickly.

Wishing fireflies to light up your summer nights,

— The Avant Gardener

Why, How, Wow!

Why?

There are at least 165 species of firefly in the United States and Canada, with most flashing species found east of the Mississippi. Firefly populations are indeed declining amid the general decline in insect population — 41 percent in 10 years.

[B]ased on assessments published on the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species, one in three assessed North American fireflies may be at risk of extinction. — Xerces.org

The main threats to firefly populations are pesticide use, loss of habitat, climate change, and light pollution.

More than three-quarters of firefly species in the United States and Canada are nocturnal or crepuscular (active at dusk), and these species use light of their own making to communicate. Growing evidence shows that artificial light from street lamps, residences, and other sources may obscure natural firefly bioluminescence, with potentially catastrophic outcomes for species that depend on these signals to find mates or ward off predators. — Xerces.org

How

You can help fireflies find mates by turning off outdoor lights and closing blinds when lights are on indoors at night. Planting the natives described here, eschewing pesticides, and keeping dead material (leaves, sticks) in your planters or garden beds will also support firefly populations.

Readers with balconies, patios, or yards have lots of options for arranging Garden for Wildlife’s four firefly plants. Allotting each plant about a square foot, all four species could fit together in a container 24 inches or more in diameter and 18 inches deep, for example. 

Those with shallow balconies or fire escapes, like my subscriber, can create linear arrangements in trough planters on the ground or a railing. In 30- to 36-inch containers, plant two species in each planter — one wildflower and one grass. Giving each plant equal space, arrange them symmetrically with two of the shorter species on either side of one of the taller one, as follows:

• Shorter plants: Smooth blue aster — side oats grama grass — smooth blue aster

• Taller plants: Little bluestem grass — oxeye sunflower — little bluestem grass

Examples of deep linear planters for fire escapes and shallow balconies that won’t break the bank, from left to right below: West Elm 36-inch railing planter; Earth Box 30-inch self-watering planter; Veradek 32-inch metal outdoor planter.

Wow!

Here are the four species in the Garden for Wildlife firefly collection.

Related Resources

• Interested in keystone species for containers? See Homegrown National Park’s keystone plants by ecoregion.

• Ready to order a collection of natives to support wildlife? Search by zip code at Garden for Wildlife.

• Nostalgic for summer nights lit by fireflies? Relive them this summer at a firefly tourism site. Yes, it’s a thing. Find one near you on the Xerces firefly tourism map.

• Want to contribute to firefly research? Check out firefly citizen science projects.