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!
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.
Great Blue Lobelia (Lobelia siphilitica) is a quirky plant.
It is undeniably beautiful, with spikes of blue-violet flowers, 2 to 3 feet tall, blooming at summer’s end. It is adored by bumblebees, host to several species of butterflies and moths, and frequently visited by hummingbirds.
But you never know where it’s going to pop up!
Great Blue Lobelia in its “happy place”
Great Blue Lobelia is native to wet meadows in the Eastern half of the US from Maine to Georgia and west to Colorado and Texas. It is not truly perennial since the flowering stem and its roots die off after forming seeds. But in a favorable location, Lobelia seeds itself around — enthusiastically! — to maintain a perennial-like presence.
Lobelia seeds are tiny, like brown dust, which accounts for their easy dispersal. Whether they are carried by wind, water, animals, or even human footsteps is not entirely certain, but they seem to need open soil, moisture, and sunlight to develop into flowering plants.
Each plant begins as a semi-evergreen rosette, a circular cluster of leaves close to the ground. You may not even notice it until it begins to send up stalks in mid-summer with 2 to 3-inch-long pointed leaves. Then, in late August, the flowers begin to open sequentially from bottom to top. In a wooded area, the effect of the blue flowers is cool and soothing. In full sun, the display is a show-stopper!
Lobelia flower catches the sun
A patch of Great Blue Lobelia in full sun Photo: Cary Maish Brodie
Like its sister plant Lobelia cardinalis, Great Blue Lobelia needs moisture. In a wet summer, Lobelias can surprise gardeners by appearing in large numbers where they were not intentionally planted and never appeared before!(See “How Did That Get Here?” about the red Lobelia, Cardinal Flower). The plants do well in sun or part shade in Zones 3 to 9 in average soil. They are perfect along streams and ponds, and can even survive occasional standing water, but not drought.
Two or three Great Blue Lobelias planted from nursery containers a few years ago have filled this woodland garden with offspring
A friend in Ohio reports that Great Blue Lobelia in her sunny garden went from “oh, good!” to “oh, God!” in no time! Photo: Cary Maish Brodie
But most of us are happy to see Lobelia pop up wherever it chooses. As summer fades to fall, the flowers are more than welcome and pollinators are happy to have nourishment before the weather turns.
A bumblebee finds what it needs
The odd history of Great Blue Lobelia adds to its eccentricity. As the scientific name Lobelia siphilitica suggests, the plant was once thought to be a cure for syphilis. Native Americans used the plant’s roots and leaves to treat coughs, nosebleeds, headaches, and colds. If they used it at all to treat syphilis, it was mixed with a complex concoction of multiple herbs. Nevertheless, Europeans began using it as a syphilis remedy in the mid-1700’s when Sir William Johnson, Britain’s appointed Indian agent, bought it from enterprising local herbalists and sent it back to England as the natives’ “secret” cure. Sadly, in 1818, William Barton’ s book, Vegetable Materia Medica of the United States, concluded that despite trying the treatment in every favorable circumstance, “physicians of eminence” had found it to be ineffective against syphilis. Today, we know that Lobelia siphilitica contains a variety of toxic alkaloids similar to nicotine that can cause vomiting and other adverse reactions.
While Great Blue Lobelia may not be a cure for its Latin namesake disease, it is very effective for brightening our late summer landscapes and supporting native wildlife.
So, we still prescribe it!
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.
Have you ever seen an azalea blooming in August? It is a rare sight, indeed!
Plumleaf Azalea (Rhododendron prunifolium) is the latest-blooming of all North American azaleas. It starts blooming in late July or August, months after other azaleas have finished, and it has been reported still blooming in October!
Plumleaf Azalea on August 14
It is also the rarest of North American azaleas, native to only two states in the US. In the wild, a few small populations grow in forested sandy ravines along streams that drain into the Chattahoochee River, on the border between Georgia and Alabama. Sadly, even those few existing wild populations are threatened by development and careless logging practices, so the only native habitat of this amazing shrub is rapidly disappearing. Rhododendron prunifolium is under consideration for Endangered Species classification, but is not yet on the official list.
Plumleaf Azalea is strikingly beautiful. Its flowers are a deep red-orange with extra-long stamens that curl outward like exaggerated false eyelashes. The flowers are not particularly fragrant, but bees do visit them.
Long red pistil and stamens protrude from the blossom
Shiny, dark green leaves show off each cluster of flowers
Despite its very limited native range, the shrub does very well in gardens throughout the Eastern US in Zones 5 to 7. It prefers rich, acidic soil, even moisture, and dappled sun. It has a rounded, fairly compact shape, and will reach 5 to 8 feet tall and 3 to 4 feet wide. It is an absolute show-stopper in a shady garden when nothing else is in flower.
Plumleaf Azalea in a woodland garden
A plant as rare as Plumleaf Azalea poses a challenging question for ecology-minded gardeners. If it is native only to a limited area in Alabama and Georgia, should we be planting it in Northeastern gardens? There are several considerations:
We know that plants introduced into areas where they are not native can become invasive and cause ecological harm. (See our blog posts on very aggressive invasive plants introduced from other continents: Nip ‘Em in the Bud!, Evil Ivy Over Everything, and Boo!) While there are some native US plants that have become a nuisance when introduced outside their native range to other parts of the US, the danger is far less than with plants introduced from other continents. Plumleaf Azalea does not spread itself by the roots, and is not easily spread by seed, so it is not likely to move into areas where it is not intentionally planted.
But we also know that the value of any given plant to an ecosystem is greatest within its native range because it will have co-evolved with the other plants and animals in that ecosystem. A Colorado Blue Spruce, for example, supports insects native to the Rocky Mountains, but is of little use to most insects in the Mid-Atlantic region. Similarly, we can imagine that insects native to the Northeast may have no use for a plant from Alabama, though insects that evolved along the Chattahoochee River may depend upon that plant for survival. It is not known whether Plumleaf Azalea is a host plant for insects outside its native range, or whether it is useful to pollinators in the Northeast, but we do know that plants native to the Northeast are more valuable to local insects.
For these reasons, the best ecological choice is to plant species native to your specific region. But what if a plant is endangered in its own native region?
Michael S. Dosmann, writing for the Arnold Arboretum at Harvard University in 2022, noted that shortly after the founding of the Center for Plant Conservation in 1984, the Arnold Arboretum began collecting seed from disappearing populations of Plumleaf Azaleain three counties in Georgia. The goal was to prevent the extinction of the species. As of last year, the Arboretum was growing 34 Plumleaf Azalea shrubs – in Massachusetts. He said “preserving wild populations remains the highest priority, but it is important to have a back-up…”. He also observed that Plumleaf Azalea looks great in the garden, and for endangered species, “being charismatic and attracting attention is a gateway to its security (just look at the giant panda)!” Does planting Plumleaf Azalea in our gardens provide additional “back-up” for conservation of an endangered species? Maybe…
A rare flower
With that justification, anyway, growing a beautiful rare azalea that flowers in August (!) is practically a public service!!
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.
The intoxicating perfume of Summersweet (Clethra alnifolia) is made for the sultry days and balmy evenings of late summer.
A native shrub that blooms from mid-July through August, Summersweet has a scent like honey and cloves — not as heavy as gardenia, but spicier than lilac. Another common name for the shrub is Sweet Pepperbush, which hints at the spicy notes in its heady fragrance.
Summersweet (Clethra alnifolia) in bloom
Summersweet blooms in large fluffy panicles of white flowers that open gradually from bottom to top. The blossoms are carried upright over shiny dark green leaves. Each stalk has dozens of individual flowers with protruding stamens offering pollen, and tubular petals surrounding a supply of nectar. Summersweet is a buffet for butterflies and bumblebees.
Flowers open from the bottom to top
A red-banded hairstreak butterfly sips nectar
Summersweet is native to the East Coast of the US from Maine to Florida. Although its native habitat is swamps and moist forests, it is adaptable, and does well in average garden conditions in Zones 4 to 9. It will grow in sun or part shade and average soil, though it prefers consistent moisture. It requires no special care, and is deer and rabbit resistant. It’s an excellent choice for low wet areas and rain gardens.
A bumblebee gathering pollen on Clethra
Two butterflies share the bounty with a bumblebee
Clethra is a suckering shrub, which means that it grows outward from its base, sending new branches along the ground where they will root and begin producing flowers within a season or two. The shrub can easily be pruned to confine it to its original spot by trimming off the suckers as they appear, or it can be allowed to gradually form a colony or thicket. In most conditions, the shrub will grow to 5 or 6 feet in height and about as wide, though it can reach 8 or 9 feet. Tall stems can be cut back in the fall without risk of losing spring flowers.
At the Greenburgh Nature Center, a 15-year old Clethra has reached the eaves of the Manor House at about 9 feet, while 4-year old shrubs are still only 3 or 4 feet tall.
The nursery trade has been busy developing cultivars of Clethra alnifolia over the past few decades, so there are good choices for every home garden, and all of them are fragrant. The dwarf cultivar ‘Hummingbird’ only grows to about 3 feet tall and wide, while ‘16 Candles’ tops out between 3 and 5 feet and produces abundant flowers. Another cultivar called ‘Ruby Spice’ produces lovely pink flowers, though it is unknown whether the change in flower color adversely affects its value to pollinators.
The leaves of Summersweet are hosts for at least 11 species of moths and butterflies, which is just one reason this plant is a much better choice than so-called “butterfly bush” (Buddleia sp.). Butterfly bush is not native to North America, and has become invasive in many areas because it produces vast amounts of seed while providing very little other value to native insects and birds. Butterflies will drink its nectar, but their larvae cannot survive on butterfly bush. Summersweet is the perfect native alternative, and you will find it widely available at nurseries.
A silver-spotted skipper nectars on Summersweet
Summersweet leafs out very late in spring, so don’t worry if you still see bare branches well into April. On the other hand, its fall color is an attractive bright yellow, and when the leaves finally drop, interesting seed clusters remaining from spent flowers provide winter interest.
It’s not too late to add Summersweet to your fall planting list! It would be a perfect choice near a deck or patio where you can enjoy its heady aroma while watching butterflies sip its nectar. You can be sure you won’t be the only one in the neighborhood to appreciate summer’s sweetest scent!
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.
It’s weed season. Mid-summer heat and rain cause weeds to come up everywhere. Uggh!
But weeds are not all equal. Some of them can be ignored for a bit while you enjoy a little summer relaxation. But others are so aggressive and so destructive they should be eradicated on sight. Can you recognize the worst culprits as soon as they emerge?
There are over 1000 invasive plant species in the US. These are non-native plants that have spread themselves widely because they have no natural controls on this continent. They cause enormous harm when they take over natural areas, displacing native plants, and often ruining ecosystems.
Each region in North America has its own “worst enemies” among invasive plants, so any short list will be too limited. But learning to identify the worst plant villains in your local area is worthwhile, especially so you can take action when they first appear.
So, here are “baby pictures” of a few of the worst culprits to watch out for in our area (Southern Westchester County, New York) and in much of the Northeast and Mid-Atlantic regions:
Mugwort (Artemisia vulgaris)
Mugwort is a perennial herb introduced to North America long ago, probably by settlers who valued its medicinal properties. It spreads very aggressively, mostly by underground runners. Bits of Mugwort root can be transported in soil in nursery pots, transplanted trees and shrubs, sod, purchased topsoil or fill, on lawnmowers, and even in compost. Any root fragment in the ground will sprout new plants, so when you are weeding, roots must be dug out completely and repeatedly. Left alone for even a season, Mugwort will invade large areas. If (when!) you see little sprouts that look like chrysanthemum leaves, dig them out as soon as possible. They can pop up anywhere, so monitor your gardens, lawn, and even tiny cracks in pavement. The goal is to prevent them from forming new communities like this:
A Mugwort patch will become very difficult to control
Porcelain Berry (Ampelopsis glandulosa var. brevipedunculata) is a terribly destructive vine that overgrows trees, shrubs, and groundcovers, eventually killing them. It was introduced intentionally by the nursery trade as an ornamental garden plant and, shockingly, is still offered for sale. Millions of dollars have been spent trying to control this invasive weed since it has escaped gardens and now covers trees, roadsides, and open areas throughout the Eastern US.
Porcelain Berry looks innocent emerging through hosta
Porcelain Berry seedlings can be tricky to identify since the leaves actually change shape as they mature. Young leaves look like grape leaves, but as they mature, they become more deeply divided, with 3 long-pointed fingers and 2 shorter ones. The leaves branch from a thin stem that quickly threads itself through taller plants.
Changing leaf forms on Porcelain Berry
Porcelain Berry seeds are widely distributed by birds who eat the berries, so you will see seedlings sprout under trees, shrubs, fences, and power lines wherever birds perch. It is important to catch the seedlings early before the vines cover everything within reach, stealing sunlight and choking trees and shrubs. Learn to identify Porcelain Berry’s young leaves, and pull seedlings out by the roots as soon as you see them.
Porcelain Berry destroying trees and shrubs
Oriental Bittersweet (Celastrus orbiculatus)is another destructive vine that also was introduced as an ornamental garden plant. Although it can look innocent as a seedling, mature vines can grow 80 to 100 feet tall, becoming incredibly thick and heavy, and often pulling down even large trees.
Oriental Bittersweet seedling
Like Porcelain Berry, Bittersweet spreads primarily by seeds carried by birds. When the seeds germinate, the young leaves have pointed tips that become more rounded as they age. Young stems immediately begin reaching upward, making their identity as vines clear.
Pull young vines out by the roots as soon as they appear, and cut down any vines that have reached your trees and shrubs before berries can develop. Preventing seed distribution is critical to controlling this invasive plant.
Mature Bittersweet vines loaded with berries are very heavy and threaten trees
Remove vines before berries can develop
Japanese Knotweed (Polygonum cuspidatum or Fallopia japonica) has invaded 42 states in the US, including large areas of open meadows and wetlands, overwhelming native plants and destroying essential habitat for birds and other animals. It, too, was introduced intentionally as an ornamental plant and for erosion control on highways. It spreads both by seed and by underground roots and should be destroyed the minute it appears in your garden.
Japanese Knotweed must be dug out by the roots or cut constantly until it dies from lack of photosynthesis
Its large, heart-shaped leaves are easy to spot, and its stems form a characteristic zig-zag shape. In late summer, large fluffy white flowers appear on top of stems that can reach 5 to 7 feet tall. But you really don’t want to let it get anywhere near that size. If you are unlucky enough to have a large stand of Japanese Knotweed on your property, you may have to call in professional help to eradicate it.
Japanese Knotweed grows very tall and very fast, overcoming any other plants
If you find any of these plants on your property, zero tolerance is the best policy. Pull them out with the roots while they are small and monitor for re-growth. Be sure to dispose of the weeded plants in the trash, not in compost or weed piles where they may survive to germinate again. Avoid sharing garden plants from areas where you know these weeds have been present.
Though use of chemical herbicides is usually a bad idea for human and environmental health, for big infestations of these particular weeds, you may have to resort to targeted professional applications of specific herbicides. Consult experienced tree care and landscape maintenance professionals and your local agricultural extension service for recommendations. Routine seasonal applications of herbicides on lawns and ornamental shrubs cause far more harm than good, and are not particularly effective against these most difficult invasive plants.
Weeds are a fact of life in even the best-kept landscapes. Knowing which ones can be tolerated and which cannot is important. Be vigilant, and nip ‘em in the bud!
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.
