Do 'nativars' count as native plants?

For the purpose of supporting biodiversity in general and native insects in particular, do we have to grow only the straight species or “wild-type” of plants that grew in our region before European settlement? What about improved versions of those plants, referred to as cultivars or “nativars”? This turns out to be a complicated question.

    Unless you’re shopping at a dedicated native plant nursery, you’re likely to find few unimproved natives at the garden center. Most plants offered as natives will be cultivars that have been selected by horticulturists for desirable traits such as bigger, brighter flowers or unusual foliage color. You can spot a cultivar by a name in single quotes: for example, Echinacea purpurea ‘Sundown’ is a purple coneflower cultivar.

'Sundown' was selected for its petals' orange tint-photo Mike Peel

    Sometimes a spontaneous mutation occurs in a plant population. An observant nursery may notice the plant’s changed appearance and decide it has market value. Other cultivars are purposely created through many generations of breeding or even through genetic modification. Some are hybrids between two species. 

     Are nativars useful in pollinator gardens? It depends. Selection for horticultural use may change flower size, color, time of bloom, or foliage color. Any of these could confuse insects seeking pollen and nectar or could mean that bloom doesn’t occur when the insects need it. 

Pollinators have evolved to synchronize their life cycle with bloom times of flowers they need

Double flowers are often sterile, because in the breeding process, pollen-carrying stamens have been replaced by extra petals. These won’t offer visiting insects any reward at all.

Echinacea 'Razzmatazz' won't help pollinators

    In general, it seems that the more closely a flower resembles the straight native’s, the more popular it will be with insects. It’s an area of active research. Doug Tallamy and Emily Baisden have found that woody plants with purple, blue or red leaves are not useful to leaf-eating insects, probably because of the anthocyanins that give leaves their pleasing colors.

Heuchera 'Amethyst Mist' is pretty, but not attractive to leaf-eaters

      Annie White intensively studied pollinator visits to test gardens of native perennials and cultivars of the same species at the University of Vermont. Delaware's Mt. Cuba Center ran another perennial trial. 

Doug Tallamy and Emily Baisden vacuum up insects for study at Mt. Cuba Center

     In general, the unimproved native flowers attracted more insects, but some cultivars were also winners. A culvers root (Veronicastrum virginicum ‘Lavendelturm’ and a garden phlox (Phlox paniculata ‘Jeana’) were visited by more insects than their straight native counterparts. Researchers speculate that this is because the culvers root bloomed for longer than the straight species and the phlox had shallower flowers that made nectar easier to reach. Hybridization made flowers less useful to insects when it radically changed flower color or reduced production of pollen and nectar.

Small, shallow flowers of Phlox 'Jeana' make nectar access easy

    For gardeners who’d like to participate, three universities are running a citizen science project called Budburst that invites us to plant some flowers from a list and contribute scheduled, structured observations of their insect visitors.

    What can we take from the preliminary research? Generally straight natives seem to do the most for insects, but many nativars are useful too. We can encourage our garden centers to stock the unimproved natives. And plant breeders can help out by selecting and marketing flowers that benefit pollinators.

Squeezing in native plants

When I read Douglas Tallamy’s book Bringing Nature Home, I was inspired to add native plants to my garden to support native insects. There was just one problem. My garden was already full.

    As a gardening beginner, I chose plants without thinking about their environmental role. By planting what I liked and could get to grow and bloom in my yard, I ended up with a mix of natives and imports. I’m fond of the nonnatives that have settled in successfully, and I had no intention of booting them out.

Doublefile viturnum isn't a native, but I love it

    Instead, I started looking for places to shoehorn in some new plants. Sometimes I could open new areas to cultivation, as by subtracting lawn or removing colonizers such as tawny daylily (Hemerocallis fulva) that didn’t appeal to me. 

Tawny daylily, native to Asia, pops up everywhere-photo A. Barra

More often, opportunities arose when something I’d planted didn’t make it. 

    One chance to add sun-loving natives came when we took down a white-flowered redbud (Cercis canadensis f. alba) that had become ungainly. Daylilies I’d planted nearby when the tree was small had stopped blooming as it cast more shade. Without the tree, they took heart and sent out flowers the next summer. Around them there was space for threadleaf coreopsis, or tickseed (Coreopsis verticillata), which has gradually spread along 10 feet of border, weaving around the perennials and low shrubs in the bed. 

Native threadleaf coreopsis coexists happily with daylilies

The tickseed is a native that draws insects to the area. Behind it, I scattered seeds of common milkweed (Asclepias syriaca). My reason for introducing this possibly aggressive spreader was to attract monarch butterflies, which need milkweed leaves to feed their caterpillars.

I hope monarchs will lay eggs on this common milkweed

    When I planted some dwarf trees around a garden pond, I chose Colorado blue spruces (Picea pungens) for two of the corners. Native to Massachusetts? Well, no, but they’re native to North America, and they provide shelter for moths and butterflies during the summer. I’ve since learned to check a plant’s native range more carefully.

Blue spruce fits in nicely around the pond

    Several native flowers moved in when I converted half of the vegetable garden that was too shady to produce food into an insectary bed, a pollinator garden that also offers benefits for beneficial insects and native leaf-eaters. There I can grow native perennials that are comfortable with part shade. Two kinds of milkweed (Asclepias incarnata and A. tuberosa), oxeye sunflower (Heliopsis helianthoides), garden phlox (Phlox paniculata), black-eyed Susan (Rudbeckia hirta), and purple coneflower (Echinacea purpurea) mix with pollinator-friendly annuals not native to New England, such as zinnias (Zinnia elegans), sweet alyssum (Lobularia maritima) and cosmos (Cosmos bipinnatus).

Insectary plants offer food and shelter for native insects

    A new perennial bed off the back deck offered lots of space for sun-loving natives. That’s a story for another day. Meanwhile, the sad decision to cut down our hemlocks (Tsuga canadensis), native evergreens that were under attack from a nonnative insect, opened up a back corner of the yard. I’m adding native shrubs and perennials there, seeing which ones will take hold with a minimum of watering. That may develop into the garden’s most authentic New England thicket.

Allegheny spurge, a native pachysandra, getting a foothold at the back of the yard

 

Woman versus squirrel

Wildlife—can’t live with ‘em, can’t live without ‘em. This month it’s squirrels. I’ve been driven to elaborate measures to keep them from digging up my young seedlings.

Squirrel at work--photo by pelican

     A fair percentage of the seeds I planted indoors this spring succeeded in growing into little plants around four inches tall. I hardened them off, moving them outdoors for lengthening periods over a couple of weeks to make sure they were ready for this season’s wildly oscillating temperatures. 

Toughening up to live outdoors

Then there were delays during days of heavy rain that kept me out of the garden for fear of trampling the soil into concrete.

    In the last three weeks I used whatever dry days there were for planting the seedlings out. Most were headed for the fenced, rabbit-proof vegetable plot.

The vegetable garden fence reaches 12 inches underground to keep rabbits out

Basil and dill seedlings landed in a corner dedicated to herbs. Nearby I also planted seeds of peas, cucumbers, and beans directly in the ground.

     Opposite the herbs is a section that stays dry and partially shaded because of a neighbor’s tall red oak. The tree’s branches extend above the vegetable plot, and its roots efficiently draw up whatever irrigation I provide. This area can’t sustain vegetables, so it has become an insectary garden offering food and shelter for native insects.

      This month I added some seedlings of common milkweed (Asclepias syriaca) and cockscomb (Celosia species) to it and edged the path that bisects the vegetable bed with sweet alyssum (Lobularia maritima).

Sweet alyssum attracts pollinators and has a honey scent

     Near the insectary bed, I’m hoping to produce flowers for cutting. In that section I planted the zinnias, bachelor’s buttons, and cosmos I started indoors with hopes of enjoying summer bouquets. Some spider flower (Cleome hassleriana) that had popped up in the homemade potting mix came along too. The flowers of these easy annuals are popular with pollinators.

Exuberant zinnias at Locust Grove in Poughkeepsie, NY

     So far the sustainable-enough approach was working. I’d managed to procure most of the annuals I wanted without resorting to seeds or plants treated with neonicotinoid insecticides. I’d gotten the young plants safely into the garden. That’s when squirrels became a menace. 

     When I dig, squirrels follow after me, digging in the same spot and throwing the young seedlings I’ve planted out of the ground. If I don’t notice and replant them, the exposed roots dry up and the little plants die. Squirrels don’t seem to want to eat the seedlings (except sunflowers, which must have delicious sprouts). Maybe they suspect I’ve buried nuts. Whatever the reason for this behavior, it’s very frustrating.

     To foil this sabotage, wherever I dug in the vegetable garden, I had to cover the loosened soil with wire fencing and then anchor row cover fabric on top of it. 

Row cover fabric lets water and light through and keeps squirrels out

That gave the vegetable seeds and the young seedlings a chance to take root. Yesterday, after the row cover had been in place for two weeks, I lifted it off. I left the fencing in place.

Lettuce and greens growing through the wire fencing

 I covered the bare soil with leaf mulch. Here’s hoping I’ve outsmarted the squirrels, and they’ll dig somewhere else.

 Are these pea plants old enough to be squirrel-proof?

A reprieve for bees?

The clouds may be parting for gardeners who have been unknowingly poisoning bees and other insects. The bad news is that many of the flowers we buy to help pollinators may be treated with pesticides that poison them. The good news is that a campaign to stop this practice is bearing fruit.

This cosmos attracted a bee to my garden

     In 2014, Gardeners Beware, a report from Friends of the Earth, showed well-documented proof that insecticides called neonicotinoids (“neonics”) were present in more than half of bee-attracting commercial nursery plants bought at a broad sample of garden centers and big box stores in the United States and Canada.

     At commonly used concentrations, neonics kill bees. At lower levels, they cause neurotoxicity. Picture a bee that can’t remember how to get back to her hive. Friends of the Earth concluded, “. . . the chance of purchasing a plant contaminated with neonicotinoids is high. Therefore, many home gardens have likely become a source of exposure for bees.” 

Poisonous for bees?

     Growers treat annuals and perennials with the neonics in order to display plants unmarked by insects. The chemicals persist for years in plant tissues, including flowers, pollen, and nectar that bees touch. 

    I take this very personally. I don’t buy pesticides or spray them on my annuals or perennials. It’s upsetting that plants I used to create my insectary bed could have been killing insects rather than providing them with safe food as I intended.

I planted black-eyed Susans to feed insects, not poison them

    The good news is that thanks to pressure from activists, some major retailers have agreed to phase out neonics and plants treated with them. BJ’s Wholesale Clubs was the first major United States outlet to respond, requiring that its suppliers label plants treated with neonics and stop using them by the end of 2014. Home Depot has committed to stop selling treated plants by 2018 and Lowe’s by spring 2019. These retailers are way ahead of the Environmental Protection Agency, which still hasn’t put a moratorium on use of neonics while it reconsiders their registration for use in the US.

    Predictably, the chemical companies that make these pesticides, including Bayer and Ortho, blame the drastic bee population decline on diseases and non-native pests. The burden of scientific evidence now indicates these are less serious problems for bees than neonic toxicity. Restrictions on neonic use in France, Germany and Italy have sharply curtailed bee colony losses.

    I don’t know whether I’ve been buying neonic-treated plants at my favorite garden center. That will be my first question the next time I’m there.

     Marigolds, which I buy every year, tested positive at three quarters of the Massachusetts sites in the Friends of the Earth study. 

Marigold seedlings are fun and easy--but are they safe for bees?

Young annuals change hands several times from germination to sale. If any one of those handlers treats them with neonics, my bees are in trouble. 

    If I can’t get full assurances that plants I buy are safe for pollinators, I’ll have to go to Plan B (so to speak). That will be to buy only organically grown plants or seeds until this issue is fully resolved.