Turning Over an Old Leaf

As fall approaches, we want to remind everyone that leaf litter is critical for many pollinators and other beneficial insects. This post about fall clean-up is worth revisiting…

As we learn more about the critical relationships between plants, insects, and birds, the best advice we are getting about fall leaf clean-up is … don’t!

In the old days, suburbanites taking care of their lawns raked (yes, raked!) fall leaves into giant piles to be burned. The familiar scent of burning leaves was everywhere – and we released tons of carbon sequestered in those leaves into the atmosphere. 

Fall routine

So anti-burning ordinances were passed, and we started using gas leaf blowers to form the leaf piles, or bagging leaves for municipal workers to collect – all at taxpayer expense. Municipalities started spending millions to ship leaves out of the county. Enterprising souls then turned our leaves into compost to sell back to us. Not a good deal for us.

Bagged leaves to be collected at taxpayer expense
Leaves at the curb clog storm drains, a municipal headache

Since that routine makes neither economic nor ecological sense, we started hearing campaigns urging us to use mulching mowers. The idea was to chop leaves into tiny pieces and leave them on the lawn to enrich the soil. That method is a big improvement, and it definitely works — it’s great for lawn health and municipal budgets. 

But we have learned that chopping up leaves has an unanticipated cost. Native bees burrow into the ground under leaf litter to survive the winter. Eggs and larvae of butterflies, moths, fireflies, and many other insects hang on to leaves, or hide under them, until warm weather returns. If we chop up or remove leaves to clear the ground in our yards, we are unintentionally destroying insects that baby birds need for food in the spring, as well as insects we need and enjoy.

Many insects need fall leaf litter to survive winter 
Mourning cloak butterfly emerging in March at the Nature Center
Who is hiding in there for the winter?

The best use of fall leaves – and the best place for them – is under the trees that dropped them. Trees and all other forest plants evolved growing with a thick layer of leaves in the winter. Dead leaves nourish the soil and everything that lives in it. Leaf litter on your shrub and flower beds protects the roots of your plants and protects early buds from freezing and loss of moisture.

Leaves where they belong

Of course, you’ll want to blow (or better, rake!) leaves off of driveways and paths, and either mulch or clear leaves that fall on lawn. But the best place to put them is in your shrub and flower beds and under your trees. A loose, 6-inch deep layer of leaves will not hurt your shrubs and perennials – quite the opposite. If there are still too many leaves, create a leaf pile in an out-of-the-way area, or add leaves to a compost bin. In spring, once the weather is warm and insects have had a chance to emerge, you can mulch the remaining leaves and return them to the lawn or flower beds, or even put them out for removal with spring clean-up.

Use your leaves to protect trees, shrubs, and perennials

Pro tip: Less lawn and more garden makes leaf clean-up a cinch! If your trees are surrounded by garden beds rather than lawn, nature does the work for you!

Healthy yard maintenance is less work!

About Drought

What makes a plant, or a whole landscape, “drought tolerant”? Why do some plants need water regularly while others are fine without it for weeks or longer? Drought tolerance depends primarily on two factors:

The first is where a plant evolved. Adaptation to particular environments happened over millennia, and most plants will thrive only in conditions very similar to those where they evolved. That is why, when considering a plant for our gardens, we always want to know whether it is native to our region. Plants that evolved in tropical rainforests will never be drought tolerant. On the other hand, plants that evolved in America’s open meadows are well-adapted to life under baking sun with occasional torrential thunderstorms. Those plants can withstand weeks of heat and drought still looking great, and then stand up to the floods that so often follow.

American meadow plants can tolerate weeks of drought and heat without irrigation

The second big factor in drought tolerance is root depth. Plants that evolved in wet climates usually have shallow roots. Plants that evolved in hard-packed prairie have strong, deep roots that force their way down through poor soil to reach and hold any available water. They can withstand long periods of drought. They also can absorb flood water because their roots break up the soil, allowing water to penetrate rather than run off.

Comparative root depth of plants – note lawn grass on the far left.
Graphic used with the permission of artist

As the chart above indicates, many plants that evolved in America’s prairies like Goldenrod, Coneflower, Prairie Dropseed, Switch Grass, and Wild Indigo have very deep roots, reaching down 4 to 8 feet! As a result, they make great garden plants because they are both beautiful and very drought tolerant.

In contrast, lawn grass is not at all drought tolerant. Despite its name, Kentucky Bluegrass is not from Kentucky. It is native to mild climates in Europe and Asia. Lawn grown from typical seed mixes has very shallow roots, about 2 inches deep. Shallow roots do not retain water, so lawn needs frequent irrigation, and in heavy rain, excess water runs off rather than being absorbed and held in the soil.

An unirrigated lawn after 8 weeks of heat and drought
Heavy rainfall rushes off of lawn, dislodging pavers and overwhelming storm drains

But Americans love lawns. Perhaps perfect lawns and tightly-manicured shrubs became a status symbol in America because of our historic connection with England, where 19th Century aristocrats demonstrated their wealth by employing countless servants to hand-cut lawn and trim elaborate hedges.

Landscape fashion among English aristocracy in the 1800’s — Cliveden House, England
Landscape fashion in suburban New York, 2022

Maybe it’s time for a change of fashion? Here is a photo of that same 19th Century landscape this summer:

Cliveden House, England, August 2022 
Photo: Lawrence Siskind

Most of Europe is suffering from heat and drought this summer, and watering restrictions are now in place. Because lawn requires so much water and retains so little, lawn irrigation is usually the first target of water regulation. In the US, lawn watering (not agriculture!) uses an average of 8 billion gallons of water daily – that’s 32 gallons for every man, woman, and child in our country, every day! (Tallamy, Nature’s Best Hope) Clearly, our love for lawns is not sustainable. 

Restrictions on residential landscape watering have been a reality in California and many of our Southwestern states for years now. So, it makes sense that landscape fashion there has rejected big expanses of lawn, and turned instead to drought tolerant native plants.

Front yard in Berkeley, California
Native plant landscape in Tucson, Arizona
Lawn used only as an edger in a Mexican garden

Prolonged periods of drought and low reservoirs are becoming common in the Northeast as well. Watering restrictions were imposed this summer in much of the Hudson River valley. So, it’s time to think about changing landscape fashion here, too. We can reduce our demand for water by replacing at least some of our lawn area with native trees and drought-tolerant shrubs.

Trees, shrubs, and flowering plants replaced lawn here

By planting drought-tolerant native perennials, we can replace even small areas of lawn with color and flowers for pollinators.

A pollinator garden reduces lawn area and is a beautiful addition to this backyard
A raised flower bed full of life is so much more interesting – and drought tolerant – than lawn
 The drought-tolerant staircase garden at the Nature Center would be a stunning entry garden for any residence

Modern American landscapes need to be resilient as well as beautiful. As we rethink landscape fashion, we recognize that there is as much beauty in a vibrant drought-resistant garden as there is in a bare expanse of thirsty lawn. 

For information on drought-tolerant perennials, download the plant list we used for the Nature Center’s pollinator garden here.


Who Was Joe Pye?

Joe Pye Weed is a classic American perennial, and a garden favorite for generations. It is tall, beautiful, long-blooming, and easy to grow. It is a butterfly magnet. Whenever we are asked about the best plants for pollinators, Joe Pye Weed is at the top of the list.

Monarch butterfly on Joe Pye Weed
Painted Lady butterfly on Joe Pye Weed

Native to wet meadows in the Eastern half of the US, Joe Pye Weed nurtures butterflies, bees, and is the host plant for more than three dozen species of moth and butterfly caterpillars. It is a great alternative to non-native “Butterfly bush” (Buddleia spp.), not only because it attracts as many or more butterflies, but because it also allows them to reproduce. Caterpillars native to the US cannot eat the leaves of “Butterfly bush,” so Joe Pye Weed is the right choice if you want more butterflies.

There are five species of Joe Pye Weed, which is the common name of all five plants in the genus Eutrochium (formerly part of the genus Eupatorium), and all are North American natives. The main difference among them for gardeners is height. Hollow Joe Pye (Eupatorium fistulosum) is the tallest at around 10 feet. Spotted Joe Pye (Eupatorium maculatum) is usually about 6 feet tall, and Coastal Joe Pye (Eupatorium dubium) is the shortest at about 4 feet, with a cultivar marketed as ‘Baby Joe’ growing only 3 feet tall. They all bloom from late summer through fall, and they all have big flower clusters in shades of pink to lavender. Hardy in Zones 3 to 9 and deer resistant, Joe Pye looks great at the back of a formal flower bed or along a rustic fence.

Joe Pye in an informal garden

The flowers of Joe Pye Weed go through a fascinating progression. The initial buds are almost silver. From there, they develop into clusters, 4 to 8 inches across, composed of tubular pink blossoms. Each tube then emits a single forked pistil, the female reproductive part. The male pollen-bearing stamens remain hidden inside the tubular structure. The huge array of pistils over the top of the flower mass ultimately creates a fuzzy appearance.

Flower buds in early August
The pistils emerge, indicating available nectar
Large clusters of tubular flowers top each stem
As more flowers open, the cluster begins to look fuzzy

Joe Pye Weed does best in wet sunny areas, so it is perfect for a rain garden, or a low spot too soggy for lawn. Though it is not particularly drought tolerant, Joe Pye manages well in our Meadow at the Nature Center without irrigation.

Joe Pye in a rain garden with White Turtlehead and Swamp Milkweed
Joe Pye Weed in the Meadow at the Nature Center

So, who was Joe Pye and why was this wonderful plant named for him? There was a story, repeated in various forms over the past 100 years or so, that Joe Pye was “an Indian medicine man” who saved an entire colony of English settlers in the 1600’s from typhus fever using a tea made from the plant. As with many such stories, the details often changed in the telling, and the only cited source was “legend has it.” Recently, however, curiosity prompted the first scholarly research on the question, and in 2017, Richard B. Pearce and James S. Pringle published their findings in The Great Lakes Botanist journal. They concluded that the plant was likely named for Joseph Shauquethqueat, a highly-respected Mohican sachem or paramount chief, also known to white neighbors as Joe Pye, who lived in the Mohican community in Stockbridge, Massachusetts in the late 1700’s to early 1800’s. Although there is no evidence that he was an herbalist or ever used or recommended the plant medicinally, many members of the First Nations did know of the medicinal properties of the plant. Pearce and Pringle speculate that since Joseph Shauquethqueat was also a selectman in Stockbridge, well-known and respected by his white neighbors, “it would not have taken many observations of his collecting the plants now called Joe-Pye-weed for medicinal use, or suggestions from him that they use those plants for the treatment of fevers…before someone, when referring to those plants, associated them with the man they knew as Joe Pye.”

Joseph Shauquethqueat was a remarkable man. Remembering him with a plant as remarkable as Joe Pye Weed is a worthy honor, indeed.


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.


What’s the Buzz?

This week on around the grounds, we learn about the ecological advantages of pollinator pathways. Additionally, get some useful home gardening tips that help our pollinator pals! 

Have you heard all the “buzz” about pollinator gardens? It seems that community groups everywhere are planning, planting, or maintaining pollinator gardens. Schools, parks, churches, and homeowners are adding pollinator-friendly native plants to landscapes all around us. Are you involved?

Pollinator Pathway garden sign

The original “Pollinator Pathway” idea was to create linked gardens through urban and suburban areas so that pollinators could travel, finding what they need to survive along the way.

The concept has grown wildly and Pollinator Pathway organizations are popping up everywhere, including locally in Irvington, Hastings-on-Hudson, Dobbs Ferry, Bedford, Elmsford, and many others.

Physically connecting pollinator gardens into an actual pathway is less important than having lots of them everywhere. From big meadows to front lawn patches to container gardens on balconies, every blooming native plant helps pollinators.

August Brosnahan and friends started a pollinator garden along the Old Croton Aqueduct
Friends of Dobbs Ferry Waterfront Park planted native plants for pollinators
Photo: Don Vitagliano

Driving this movement is recent documentation of a stunning decline in insect populations, especially pollinators. Since many of our food crops depend on insect pollination, this is a huge wake-up call for all of us. Insecticides, agricultural techniques, and loss of habitat all contribute to crashing insect populations. And since most birds depend upon insects to feed their young, bird populations also are declining rapidly.

The New York Times reports on the “Insect Apocalypse”

Unlike many other global problems, we can actually do something about this crisis — right in our own yards. Pollinator gardens are a powerful force for good. And the bonus? They are gorgeous! Every time we convert a patch of lawn, or bare dirt, or a weed-infested spot to a pollinator garden, we not only provide survival essentials for birds, bees, and butterflies, we brighten our neighborhoods with color and life.

The pollinator garden at Dobbs Ferry Waterfront Park
Photo: Nancy Delmerico
This pollinator garden replaced a lawn in Hastings
Photo: Myriam Beck

So, what makes a garden a pollinator garden? Short answer: native flowering plants. The two main classes of pollinators we are trying to save are butterflies and bees, especially native bees. Bees need flower nectar and pollen. Butterflies need nectar and host plants for their caterpillars to eat. Pollinator gardens should provide all 3 essentials: nectar, pollen, and host plants.

Native bumblebees need pollen from native plants
Photo: Travis Brady

The reason we keep emphasizing native plants is because most of these insects are specialists — they depend upon one or two specific species of plants for survival. For example, there are over 20 species of native bees that can only eat the pollen of Goldenrod! And just as Monarch caterpillars can only eat the leaves of Milkweed, other butterflies’ caterpillars are also completely dependent upon specific plant species – their “host”plants.

Swallowtail butterfly caterpillar on its host plant, Zizia
Adult Black Swallowtail on Zizia at the Nature Center

Pollinator gardens do best in sunny spots. Butterflies and bees prefer sunshine and are more active in sunny areas. Any place that lawn grass grows is a good spot for a pollinator garden.

The best plants for pollinator gardens are native meadow or prairie plants. Adapted to harsh environments, they don’t need rich soil and never need fertilizer. Most of these plants are drought-tolerant, so they don’t need irrigation once they are established, and many are deer-resistant. And we recommend perennials rather than annuals, so the plants come back every year. It is easier, and definitely cheaper in the long run, to plant a perennial pollinator garden than it is to buy, plant, water, and fertilize annual bedding plants every year.

Pollinator Garden at the Nature Center

Spring is almost here! If you are thinking about planting or expanding a pollinator garden, there are loads of great resources to get you started. The Pollinator Pathway website linked above has how-to’s and plant lists. Watch for local native plant sales. The Native Plant Center will hold its annual plant sale this year at Westchester Community College on April 30. And the Garden Club of Irvington will have native plants for sale at the Greenburgh Nature Center on May 7, plus lots of knowledgeable help on hand.

And watch this space! Over the next several months, this blog will highlight many of our favorite pollinator plants. Come see them in action at the Greenburgh Nature Center all season long!

Come visit our Pollinator Garden!