The Trouble With Double

One beautiful spring morning, we stood under our Kwanzan cherry tree and noticed that something was missing: pollinators! Not one bee or butterfly was visiting the tree, even though it was loaded with flowers. Not far away, a blooming crabapple tree was literally humming with pollinators!  What accounted for the difference?

We realized that the cherry tree has “double blossoms.” Its flowers have been modified by humans to replace all of its pollen-bearing stamens with flower petals. The flowers are beautiful – but only to people. There is no pollen or nectar for bees or butterflies. The flowers of the crabapple, on the other hand, were loaded with pollen and nectar. And the pollinators were all there for breakfast!

The stamens are missing completely in these sterile double blossoms
The stamens in these flowers are ready for pollinators

Flowers are the reproductive organs of plants. Pollen contains the genetic material that must be transferred from the (male) stamens to the (female) pistil for pollination (fertilization) to occur. In most flowers, the petals form an outer ring and the stamens are just inside, forming a second ring around the pistil. The flower’s colorful petals, its fragrance, and the sweet juice called nectar all are designed to attract pollinators. As pollinators sip the nectar located at the base of stamens, and collect pollen to feed their offspring, they “accidentally” transfer pollen from flower to flower and deposit it on the pistil where pollination happens. Successful pollination results in seeds, which then grow to produce more plants.

But sometimes nature makes little mistakes. Sometimes a plant will develop extra flower petals where the stamens should be. This is not a good thing for the flower, because with fewer stamens there is less pollen, which reduces the chances of pollination and, therefore, reproduction. In nature, plants that continue to develop too many petals instead of stamens eventually would fail to reproduce.

For hundreds of years, however, horticulturists have been fascinated by this “mistake” of nature. Humans enjoy flowers, and we tend to think bigger and fuller flowers are better. So, when horticulturists discover a flower that has extra petals where stamens should be, they can select that plant for special treatment. They can propagate the plants with extra petals and, eventually, even develop plants with so many extra petals they have no stamens (or pollen) at all! Without stamens, of course, those plants are sterile. They cannot develop fruit or seeds or reproduce themselves.

Roses are a good example. Natural roses have 5 petals surrounding a circle of many stamens carrying pollen.

A simple rose with 5 petals, stamens with pollen, and pistil in the center

Roses frequently make the “mistake” of trading stamens for extra petals.

Note the under-developed petals in the ring of stamens

Over centuries, horticulturists have selected these “mistakes” for intentional manipulation to create roses that are more interesting to people.

In fully double roses, extra petals replace virtually all of the flower’s stamens and pollen is scarce or non-existant

Today we have thousands of flowering trees, shrubs, perennials, and annuals that are popular specifically because they have double blossoms. But this comes with a cost to pollinators. Butterflies need nectar. Bees need nectar and pollen to feed their offspring. Butterfly and bee populations are declining under pressure from loss of habitat, pesticide, and limited food sources. We can help with our garden choices.

Double peony with no stamens, pollen, or nectar
Double trillium with no stamens or available pollen
Double sunflower – native, but not useful for pollinators
Single peony with stamens and pollinator
Single trillium open for breakfast
Single sunflower and happy bumbles

We humans love our double blossoms, but if you’re making a choice, think about providing a big variety of native single-blossom flowers for our pollinator friends!

A buffet for pollinators in the Nature Center’s meadow

Let’s “Switch Grass”

On this week of Around the Grounds we learn about Switch Grass, a native plant that can replace invasive ornamental grasses.

Do you have this ornamental grass in your yard? If so, it may be time to switch grass!

Miscanthus sinensis, or Chinese silver grass, is a too-popular ornamental grass so problematic that New York State has regulated it as an invasive species. Switch Grass (Panicum virgatum), on the other hand, is a native ornamental grass that is a perfect substitute. Maybe it’s time to switch?

Ornamental grasses have become increasingly popular as modern tastes have shifted to more naturalistic garden designs. Grasses bring year-round interest, movement, structure, and seasonal changes of palette that enhance every garden. Unfortunately, at least this one non-native grass has created an ecological problem.

Invasive Miscanthus sinensis offered for sale on line
Miscanthus sinensis “zebra grass”

Sold under the names Chinese silver grass, zebra grass, maiden grass, and porcupine grass, Miscanthus also has many cultivars, including “Morning Light,” “Flamingo,” “Ghana,” “Adagio,” and over 100 others. Despite being identified as invasive by New York and other states, it is still being sold, and is still spreading itself everywhere. It is invading natural areas because it has no biological controls on this continent.

Switch Grass is just as attractive as Miscanthus, just as easy to grow, and just as diverse. An original denizen of America’s prairies and meadows, it has deep roots and is both drought tolerant and deer resistant. It is increasingly available in a huge variety of sizes, shapes, and colors. And Switch Grass is the host plant for very cute native butterflies called, “skippers.”

Skipper butterflies lay their eggs on Switch Grass
Photo: Pixabay
Switch Grass is a beautiful native plant 

Switch Grass is gorgeous through all four seasons, and its versatility is on full display at the Greenburgh Nature Center. The cultivar “Heavy Metal” is steel blue in summer and grows up to 5 feet tall. It is equally impressive in winter when it provides texture, movement, and contrast to evergreen shrubs.

Panicum virgatum ‘Heavy Metal’ frames our patio in summer
The golden tones of ‘Heavy Metal’ contrast with Inkberry and Red Twig Dogwood in winter

Another Switch Grass cultivar, ‘Shenandoah,’ is 3 to 4 feet tall and has a graceful vase shape that complements both shrubs and perennials. Because it hosts skipper butterflies, it is a great addition to pollinator gardens. Like all Switch Grasses, it enjoys full sun and tolerates poor soil. No supplemental water, no fertilizer, no worries.

 Panicum virgatum ‘Shenandoah’ in the Pollinator Garden at the Nature Center

When we planted the Gerrie Shapiro Memorial Pollinator Garden at the Nature Center last June, we started with tall Switch Grasses as the center “spine” of the garden. Along with ‘Heavy Metal,’ we planted ‘Northwind,’ a Switch Grass cultivar that stays tall, narrow, and straight all season long. These two native grasses support tall flowers that would otherwise flop over when in full bloom. Switch Grass evolved supporting tall wildflower companions in American meadows and prairies, so it’s perfect for that job.

Tall Switch Grasses define the structure of the new garden
A month later, ‘Northwind’ Switch Grass supports tall flowers

One of our favorite smaller Switch Grasses is ‘Ruby Ribbons.’ At only 3 feet tall, it’s a good choice for smaller gardens. It has multi-colored leaves in shades of red and purple all summer long, and just gets prettier in the fall. Even smaller is ‘Cape Breeze.’ At less than 2 feet, it makes a great edger along the garden path.

Panicum virgatum ‘Ruby Ribbons’
‘Ruby Ribbons’ in October

And if you want to see what Switch Grass looks like in its natural habitat (almost) come visit our Meadow! After spring mowing, Switch Grasses start showing new growth. By late June, they fill out the Meadow terrain. And in the fall, clouds of tiny seeds hover above the Switch Grass stalks, feeding flocks of birds then and all winter long.

 Switch Grass in the Meadow in the fall

So, are you ready to switch grass?