Blog

Much Ado About Mulch

We are re-thinking mulch.

Gardeners are routinely advised to apply a 2 to 3-inch layer of wood chips or bark mulch around new plantings, and to mulch regularly thereafter. We are told that mulching maintains soil moisture, suppresses weeds, improves soil, and looks tidy. This advice has been given and followed for years without regard to plant type, soil conditions, or location.

Typical planting with bark mulch around widely-spaced plants

There is plenty of expert advice available about types of mulch and how to use them. For example, there is general agreement that color-enhanced mulch is not beneficial. And tree experts routinely warn against “mulch volcanos,” which can “girdle” a tree and kill it by holding excessive moisture around the trunk.

Color-treated mulch does not benefit plants, soil, or wildlife
Incorrect mulching actually damages trees and shrubs

Until recently, however, there has been little discussion about whether it is necessary, or wise, to mulch at all. Our reconsideration of mulching began with a startling statement by noted horticulturist (and garden philosopher), Roy Diblik:

“There is not a plant on earth that has evolved living in a pile of wood chips.”

Roy Diblik

In his excellent book, The Know Maintenance Perennial Garden, Roy Diblik observes that plants have widely differing needs. When we buy a new plant, at a minimum we want to know whether it prefers sun or shade, dry or wet soil. The answer depends upon the habitat where that plant evolved. Did it originate in shady moist forests with soil enriched by fallen leaves, or did it evolve surviving in hard-packed clay in open prairies? The one thing we know for sure, is that it did not evolve in a habitat with a 2 to 3-inch layer of man-made wood mulch.

So, a wiser practice may be to consider whether mulching is appropriate in a given situation. Mulching vegetable gardens with compost or light organic matter that can be tilled into beds makes sense. Mulching formal beds of annuals for aesthetic and maintenance reasons is understandable. Trees and shrubs planted in full sun in lawn may very well benefit from a proper application mulch, if only to protect them from lawnmowers.

On the other hand, trees and shrubs in a moist wooded area may suffer from mildew and pest damage with a similar application of man-made mulch. They are better off as they evolved – with groundcovers and woodland perennials. As seasons change and leaves fall and decay, these plants become natural mulch and enrich the soil.

Correct mulching can benefit trees and shrubs surrounded by lawn
Under-planting trees acts as natural mulch, contributing to soil health and wildlife

Contrary to traditional advice, applying a layer of wood mulch when planting perennials (the flowering plants we hope will return every year) may be counter-productive. First, mulch can hold excess moisture, and actually reflect heat, causing plants to die.

Second, heavy mulch prevents perennials from growing naturally. Perennials grow by expanding from the base of the plant, or by sending out shoots that run below or on top of the soil and then reach up for light. Many perennials form seeds after flowering and drop their seeds on open soil to begin new plants. A thick layer of wood mulch defeats both processes. If plants can’t grow and reproduce, they eventually fade away.

Mulching perennials prevents natural growth

But if we don’t mulch, what about weeds? A good strategy is to plant perennials densely enough that within a season or two the desired plants occupy all the available space, making it difficult for weeds to establish. That is the approach we used in the Pollinator Garden at the Nature Center. (For a description of that process, click here)

New Pollinator Garden densely planted, without mulch
Pollinator Garden in its second season, not much room for weeds

Weeding and watering are important in the first season or two until the perennials begin to fill in. As plants expand naturally, and even seed themselves into open areas, weeds become less problematic. If it is available, leaf mulch is a good alternative to wood chips or shredded bark. Leaves break down much more quickly, and do not inhibit the natural growth habits of perennials.

Open soil in new plantings may be covered with leaf mulch, chopped leaves, or even whole leaves until new plants fill in

In the absence of man-made mulch, nature may offer some wonderful surprises. Not all of the plants that appear on open soil are “weeds.” We have seen “volunteer” native perennials return to areas that were previously mulched. Self-seeding perennials, like the wandering pink coneflower in the opening photo, surprise us by popping up in new spots. And native bees find open soil for their seasonal nests where we stopped mulching.

Native trout lily appeared under trees when we stopped mulching!
Native columbine surprises us in new spots every year
Ground nesting bees found this open spot!

The important thing is to recognize that plants are not all the same, and the best approach to gardening is to be thoughtful about their differences. By understanding what they need, and allowing them to live as they were meant to, we open our minds – and our gardens – to nature and its surprises.

THIS BLOG IS AUTHORED WEEKLY BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, GREENBURGH NATURE CENTER. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.

How Sweet It Is!

Itea virginica is one of our most beautiful and versatile native shrubs. Its romantic common name, “Virginia Sweetspire,” is a good one, because this shrub is a sweet addition to the landscape year-round.

Itea virginica or “Virginia Sweetspire” shrub 

Itea (pronounced eye-tee-uh) grows in a loose mounding form, reaching 4-5 feet tall and wide in a few years, with gently arching branches. In mid-June, after most trees and shrubs have finished blooming, Itea is just starting its summer show. Spikes of white flowers 4 to 6 inches long cover the shrub, arching away from the deep-green leaves on long stems. 

Itea starts blooming in mid-June
The flowers open gradually

The star-shaped flowers begin opening from the stem to the tip, and last several weeks. And they are sweet! The elegant fragrance is not over-powering, but definitely carries in sultry June air. The flowers are loaded with nectar and butterflies flock to them. When the flowers fade, birds will feast on the seeds that remain all winter.

Itea’s fragrant flowers justify the name “Sweetspire”

Itea is native to swampy meadows and wet woodlands from New Jersey to Florida, and west as far as southern Illinois, but it does very well in more northern gardens. It can thrive in full sun or part shade, and is surprisingly drought tolerant given its swampy origins. It is winter hardy in Zones 5-9, and is not attractive to deer or rabbits. 

Throughout the summer, the foliage remains fresh and glossy, so Itea looks great in full sun as a hedge or foundation plant. But because of its shade tolerance, it can even replace pachysandra, vinca, or ivy under trees.

Itea is part of our full-sun foundation planting at the Nature Center’s Manor House
Itea in part shade under a Redbud tree at the Nature Center

And have we mentioned fall color? Itea is known for its gorgeous fall foliage, turning various shades of red, orange, and purple while holding onto its leaves until snowfall. Cultivars called “Henry’s Garnet” and “Merlot” are specifically marketed for their brilliance in the fall landscape. Fall color is best in full sun, but it’s still impressive in part shade. We frequently recommend Itea as a native alternative to invasive burning bush.

The same Itea planting in mid-November
All the fall colors

So, Itea is carefree, a hedge or foundation plant, an under-tree plant, has showy and fragrant flowers, offers nectar for butterflies and seeds for birds, grows in sun or shade, and has fabulous fall color – we think that’s pretty sweet!

THIS BLOG IS AUTHORED WEEKLY BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, GREENBURGH NATURE CENTER. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.

Billy Goat or Nanny Goat?

“Goat’s Beard” is the common name of Aruncus dioicus, a gorgeous native plant that is perfect for shade gardens. It is spectacular toward the back of a mixed border, along a fence, or at the edge of a woods. Blooming from late spring through mid-summer, Aruncus (pronounced “ah-runk-us”) grows 4 to 6 feet tall with very large, fluffy white flowers. Many different pollinators are attracted to its flowers, which makes Aruncus especially valuable in shade where great pollinator plants are more difficult to find.

Aruncus dioicus lights up the woods
Bumblebee collecting pollen on Aruncus

Sometimes confused with Asian astilbe, Aruncus blooms only in white, is much taller, and has bigger flowers. Common names can add to the confusion – we have seen Asian astilbe sold in nurseries as “false Goat’s Beard,” and we’ve seen Aruncus labelled as “false astilbe” or “false spirea,” so it’s always important to check the Latin or scientific name on plant labels.

Asian astilbe is shorter and has smaller flowers

And, as is often the case, the scientific name is very interesting! Aruncus dioicus refers to the fact that Aruncus is “dioecious,” meaning the plants are either male or female. The word “dioicus” in its name comes from Greek meaning “two households.” While dioecious plants are fairly common among trees and shrubs, they are rather unusual in garden perennials.

The flowers on male Aruncus plants have many pollen-bearing stamens, while the flowers on the female plants have only 3 pistils and, of course, no pollen. Bees are drawn to both types of flowers by nectar, and transfer pollen from the male to the female flowers.

Male flowers have many stamens loaded with pollen
Female flowers have 3 pistils and nectar to attract bees

The male flowers are somewhat showier because the stamens give them a fluffy appearance, but the plants are not typically labelled separately for sale. You’ll have to look closely to see whether your Goat’s Beard is a Billy goat or a Nanny goat! Both make excellent garden plants, and look fabulous massed in the shade.

Female Goat’s Beard blooming in the shade
Tiny pollinator on male Goat’s Beard

Aruncus is native to the US from Pennsylvania to North Carolina and west from Indiana to Arkansas. Although it is not native to New York, it does very well in northern gardens and is hardy through Zone 4 in rich, moist soil, and part sun to full shade. It is not generally attractive to deer or rabbits, and it is the larval host plant for the Dusky Azure butterfly.

As pollinators face increasing stress, providing native plant sources of nectar and pollen is more critical than ever. Goat’s Beard does that while adding light and beauty to your shade garden.

Bumblebee with a paste of pollen and nectar packed into her pollen basket (corbicula) for transport
THIS BLOG IS AUTHORED WEEKLY BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, GREENBURGH NATURE CENTER. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.

Happy Pollinator Month!

June is here — the bees are buzzing, the butterflies are fluttering, and everybody is excited about summer flowers. It’s National Pollinator Month!

At the Nature Center, we are also celebrating the first anniversary of our newest Pollinator Garden. It is astonishing to see how lush, diverse, and colorful our garden has grown in just one year!

Want to know how we did it?

The “Before” photo

Right next to our big open lawn, in a very visible spot near the beehives, there was a messy patch of weeds. The soil was poor and dry, and there was very little shade. So…the perfect spot for a pollinator garden! The first task, done by Guy Pardee of Suburban Natives LLC, was to clear the area, getting rid of all the weedy invasive plants. Then, the ground was covered with leaves and left for the winter.

After the first clearing

The following spring, we cleared it again and prepared to plant.

Ready for planting, May 2021

A good friend to the Nature Center, Bill Boyce of Biosphere Landscape Architects, came up with a great idea for the garden. We would make a literal “pollinator pathway” wandering through the blooming flowers, with signs along the way identifying pollinators. Bill did a “back-of-the-envelope” concept sketch for us on site.

The idea in formation

We roughed out the lines in the dirt, and then defined the path with mulch.

The idea emerges
Pathway lined with mulch

Then it was time to plant. We chose tough native plants — species that evolved in our region growing in open dry meadows, able to survive without fertilizer, pesticide, or supplemental water. And though we planned to water and weed the garden for a season or two until the plants were established, we wanted a garden that eventually would need little maintenance. We also needed plants that would not be attractive to deer, rabbits, or woodchucks. We made a plant list, scoured the nurseries, and bought about 450 plants in containers (with funds contributed by multiple donors).

If you would like to know which plants we selected, click on the link below.


We started in the middle, planting the “spine” of the garden with tall, deep-rooted Switch Grasses that would support the tallest flowers in the center of the garden.

The center “spine” of the Pollinator Garden

We then worked outward, planting clusters of flowering species arranged in descending height. Shorter native grasses and ground covers were added along the edges to fill in and provide texture. We planted densely, aiming to have the plants grow together to occupy all soil areas within 2 seasons, thereby reducing available space for weeds.

Plants are spaced 12 – 18 inches apart

We decided not to mulch after planting, for a few reasons. Some of the invasive plants removed from the area were deep-rooted and would re-appear soon, with or without mulch. Weeds would be easier to see and remove promptly if we did not mulch. We also hoped our new plants would quickly grow together, expanding to occupy the entire ground space, and reseed themselves freely in the garden. Mulch would inhibit those natural growth processes. Finally, mulch would prevent the pollinators we are trying to attract from nesting in the ground, as many of them want to do. We want to support pollinators through their entire life-cycles.

We finished planting the Pollinator Garden on June 2, 2021. By August 2, it was in full bloom and alive with pollinators.

Two months after planting, August 2021

As we had hoped, this spring the garden came back full and lush. Weeding is ongoing, but not as difficult as we had anticipated.

The Pollinator Garden this week, June 2022
Photo: Nick Macaluso

So, please come celebrate Pollinator Month with a walk on our new pathway, and let the pollinators give you a tour!

THIS BLOG IS AUTHORED WEEKLY BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, GREENBURGH NATURE CENTER. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.

Click the picture below to get more ideas on how to plan and plant your very own pollinator garden.

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
THIS BLOG IS AUTHORED WEEKLY BY CATHY LUDDEN, CONSERVATIONIST AND NATIVE PLANT EDUCATOR; AND BOARD MEMBER, GREENBURGH NATURE CENTER. FOLLOW CATHY ON INSTAGRAM FOR MORE PHOTOS AND GARDENING TIPS @CATHYLUDDEN.