Plant Invaders – Callery Pears

After an early start, then a bad freeze, this spring has settled into normalcy. In Delaware that means some glorious warm sunny days and some cold, windy, rainy days.  We’ve had an opportunity to enjoy lots of spring flowers that have been long-lasting as the weather stayed cool. One set of flowers I was not excited to see though, were the blooming Callery pears. These early flowering trees have started to clog our roadsides. They are overtaking woodland edges and many unmanaged landscapes. While you may find blooming white trees on the roadside attractive, the sad truth is they are crowding out native trees like serviceberry, dogwood and sassafras that should be blooming along in wood edges and roadsides in the spring.  How did this happen?  Bradford pears, the dominant Callery pear planted ubiquitously in the 80’s and 90’s did not produce fruit, so it didn’t spread into open landscapes.  But, it was replaced with a wide variety of cultivars bred for better branch angles to reduce the problem of splitting limbs, that plagued Bradford pears.  The wide variety of cultivars resulting in cross pollination so now Callery pears are prolific fruit and seed producers.  And that means they are everywhere!

If it bothers you that an invasive exotic species is now the dominant tree on Delaware’s roadsides, there is something you can do—remove the pears at your home and from any landscape you control.  That won’t help with those that have already escaped into unmanaged landscapes, but if everyone removed Callery pears from their property (as well as the other popular landscape plants on the Delaware Invasive Species list – burning bush, Norway maple, Japanese barberry, and privet, to name a few) we could start to make a difference in protecting our natural areas and preserving our native trees, shrubs and perennials.  It is true that what one person does won’t matter, but if everyone removes invasive plants on their property the collective effort will matter.

The good news is when you remove plants, you get to replace them with new species.  You can select native trees and shrubs that will enhance your landscape enjoyment and attract native wildlife to your garden.  For suggestions on what to buy, try consulting a Delaware Certified Nursery Professional (CNP).  The Delaware Nursery and Landscape Association, in conjunction with Delaware Cooperative Extension developed a program to certify professionals in the nursery and landscape industry.  This is a voluntary certification, but it is a good way to ensure you are hiring or buying from a professional.  Delaware CNPs purchase and study a manual and then pass a difficult exam that tests their knowledge of plants, soils, diseases, insects, weeds and many other aspects of landscape management.  If you want to find out whether a business employs CNP’s, consult the DNLA website (

Certified Nursery Professional LogoLook for this logo to identify Certified Nursery Professionals in the nursery and landscape industry.

Crazy Weather May Warrant Plant Replacements

We have had some crazy weather this spring. Warm days in January and February caused cherries and some magnolias to bloom extra early and even some trees to leaf out early.  Trees that leafed out early in most cases had tender leaves burned back when cold temperatures hit.  That should not be a problem for most trees.  Unless the tree is already under serious stress, a tree is capable of sending out a new set of leaves.  Sycamores often have to leaf out twice around here because they are so susceptible to defoliation due to anthracnose (a fungal disease) in a cool, wet spring.

Our warm winter was followed by a March snow storm with heavy rain-laden snow that wreaked a different type of havoc on trees.  Some trees were uprooted and others left leaning.  Once a tree has been uprooted it is usually a “goner.”  Even leaning trees are hard to save.  When ice and snow pull a tree over, the fine roots and root hairs are stripped away.  Root hairs and fine roots are in close contact with the soil, so when larger roots pull away from the soil, which is what happens to cause the leaning, the root hairs are left in the soil and are no longer attached to the roots.  Roots take up water and nutrient through their root hairs.  Plants can regrow root hairs, but if a large part of the root system is damaged, the tree may not be able to take up enough water and nutrients to support the growth of new roots hairs and fine feeder roots, let alone leaf out and grow normally this spring.

If a relatively small tree is leaning slightly, you may be able to use a shovel to right the tree and then stake it temporarily to keep it straight while new roots grow to re-stabilize the tree in the soil.  But, a large leaning tree or a tree that has fallen over completely should probably be removed.

The good news is this gives you the chance to plant something new.  A great opportunity to find new and interesting plants is the University of Delaware Botanic Gardens plant sale.  The sale is held over the weekend of Ag Day every spring.  This year that will be Thursday, April 27, 3-6 PM (UDBG members only; to become a member go to, Friday, April 28, 3-6 PM and Saturday, April 29, 9:30 AM – 4 PM (Ag Day).  This year the sale is celebrating 25 years of bringing interesting and hard to find plants to the gardening community. The plant sale catalog is available online (  If you want to learn about some of the plants at the sale, come to the Spring Plant Sale Preview Lecture on April 5 from 7-9 PM in The Commons in Townsend Hall on UD’s campus.  The lecture is $5 for UDBG Friends and $10 for nonmembers.  On Wednesday, April 12 from 4:30-6:30 PM, Dr. John Frett will lead a guided walk of the 2017 Plant Sale Highlights.  The guided walk is also $5 for UDBG Friends and $10 for nonmembers. Register for either event by emailing or calling 302-831-2531.  Proceeds from the sale support internships for students to work in the gardens and learn about public garden management.

UDBG Plant Sale Catalog cover celebrating 25 years of featured plants!

Harbingers of spring

Little did I know when I planned to write this article, we would have a week with temperatures in the sixties and even reach the seventies for a few days in February.  It does feel as though spring is arriving early this year.  However, leaves are not out yet and you can still walk through the woods and find some of the early harbingers of spring.  One of my favorites is the skunk cabbage (Symplocarpus foetidus). Much maligned for its smelly foliage, inconsequential flowers and leaves that start to melt down in late spring; it has wonderful qualities as well.  When the forest floor is still completely brown with old leaf litter, you can find the unusual flower buds peeking up through the leaves.  Look in wet woods where skunk cabbage is plentiful and you will find four-to six-inch high hood-like leaves that enclose the flowers.  Some leaves are deep wine or red and others have mottling with patches or stripes of yellow or yellow green.  The leaves usually twist and eventually open to reveal a round flower head peering out. The flower is a cluster of petal less flowers with stamens that protrude, giving it an interesting texture.  Skunk cabbage is one of the first flowers available for our pollinator insects.  Bees are already out visiting flowers this spring, and they are finding skunk cabbage pollen to bring back to their hives.

The large, wide leaves emerge after the flowers.  Their chartreuse green color is stunning in the otherwise barren woods.  Skunk cabbage grow in moist conditions and only last a few months.  The leaves start to die back at the end of spring/early summer.  However, their early flowers are a fun find and their colorful leaves brighten up the bleak woods at the end of winter.

Another early spring ephemeral (plant that comes up in spring and dies back to the ground before summer) is Virginia bluebells (Mertensia virginica).  Virginia bluebells have bell-shaped (duh!) blue flowers borne on spiral shaped cymes at the end of arched stems.  Some flowers are pink, especially in bud.  This flower is another bee and butterfly favorite.  Its bright green leaves also brighten the forest floor in early spring.

Bloodroot (Sanguinaria canadensis) is another early bloomer with white flowers that come out before the leaves in early March.  Delicate white petals and yellow stamens are quite showy.  Leaves emerge after the flowers, are a fleshy consistency, and spread out to a wide toothed platter shape. Bees and flies pollinate bloodroot, but ants spread their seeds.

If you are tired of looking down at the forest floor for spring interest, look up.  Red maple is blooming now!  The flowers have very small petals, but the bright red stamens are showy enough that trees look red when viewed from a distance.

We will probably still have some cold weather to endure at the end of winter and beginning of spring, but seeking out the early blossoms and bright, cheerful leaves of these native woodland species can provide some diversion before the weather warms up completely.  Enjoy!

Mottled twisted leaves are covering early flowers and a few bright green leaves are starting to open on this skunk cabbage growing at the edge of a stream.

Delaware Plants of 2017

Every year the Delaware Nursery and Landscape Association selects an herbaceous plant (usually a perennial that dies back to the ground each winter) and a woody plant (usually a tree or a shrub) to designate as Plants of the Year.  Plants are selected that will thrive in Delaware’s conditions and that have few disease and insect problems.  If sited properly, these plants are guaranteed to succeed.  These plants are often underused in the Delaware landscape.  So, if you purchase one of these plants, you will be a trendsetter in your neighborhood.  The 2017 selections were just announced at the Delaware Horticulture Industry Expo in Dover.

Schizachyrium scoparium ‘Standing Ovation’

‘Standing Ovation’ little bluestem is a warm season grass with blue-green spikey stems and leaves. Leaves have a purplish caste at the base.   Fluffy, light-catching seed clusters appear in late summer/fall.  In fall, little bluestem turns an apricot color that brightens the winter landscape.  ‘Standing Ovation’ has sturdy blades that are thicker than most bluestems, remaining sturdy even in richer garden soils.  ‘Standing Ovation’ with its sturdy habit and excellent fall color makes a good accent or mass planting in a perennial or shrub border.  Cut back in early spring to make room for new emerging leaves.   Little bluestem is a great addition to a meadow.  If you are managing a meadow and want to add some interest, buy a few ‘Standing Ovation’ little bluestems to spark up your meadow.  They can also be planted in a garden bed, but be careful about rick soil.  While ‘Standing Ovation’ can tolerate garden soils, most little bluestems do best in sterile, non-organic soils (i.e. the kind we have throughout Delaware if we aren’t working hard to improve the soil).

‘Standing Ovation’ little bluestem looks fantastic throughout the year. Photo credit: North Creek Nurseries

Taxodium distichum

Bald cypress is a pyramidal, deciduous conifer that grows 50-70 feet tall.  It thrives in average to wet soils, preferring sandy soils, but tolerating anything from dry conditions to standing water. Trunks are buttressed at the base, often developing knobby root growths, called knees, when grown in water. Soft, yellow-green needles turn an attractive orange/cinnamon-brown in fall. Purplish green cones mature to brown.  Bald cypress is a striking specimen tree for a variety of large areas since it tolerates a wide range of conditions.  You can see lots of bald cypress in Trap Pond State Park in Laurel, Delaware.  You can canoe or take a pontoon boat out into the water to see the most northern natural collection of bald cypress trees.  Remember, these trees are deciduous, meaning they lose their leaves in the fall.  So, don’t get out the chain saw when the needles begin to drop.  They are conifers and most conifers are evergreen so you would not be the first person to think the tree had died.


Bald cypress turning coppery in the fall. Photo credit: Rick Darke

Bald cypress needles and interesting cone. Photo credit: John Frett

Visit a garden center in Delaware this spring and pick up one or more of these great plants for your garden!

Fall Leaves – Asset or Annoyance

Of course they are an asset.  Just consider the rich soil of a forest.  Leaves fall naturally and decompose on the forest floor, where they return nutrients for plant uptake and provide organic matter to improve soil structure.  But, when leaves coat the lawn or, in my case, the patio, they can be an annoyance.  A few weeks ago after I had carefully swept and raked both patios on a Saturday, the weather turned cold and windy.  My husband looked out on the patio on Sunday morning and decried “You didn’t do a very good job raking the patio yesterday!”  There were about 4 inches of leaves covering the entire surface.  Haha – grit teeth.  He was kidding, of course, but the chore still required repeating, so — annoyance!

Leaves can’t be allowed to cover the lawn for too long, because they exclude light and prevent the lawn from thriving.  But they can easily be raked into nearby landscape beds and gardens.  If you don’t have enough garden space to accommodate all your leaves, you have two choices.  Either plant more beds (much more attractive and better for the environment than lawn anyway) or compost your leaves.  If you are lucky enough to live within the city of Newark, the city will compost your leaves for you.  Just rake them out to the road and a truck will come and suck them up!  You can pick up composted leaf mulch from the pile on 896.  For those of us outside city limits, we can chop leaves up with a lawn mower or leaf vacuum. They will shrink dramatically in size, making them easier to store.  When they decompose, they provide rich mulch for next year’s beds and gardens.

Leaves can also be used to protect tender plants.  I have been using a wire cage filled with leaves to protect a fig plant that is marginally hardy here for several years now.

Cutting back perennials is another fall garden task.  The more you cut back in the fall, the less you need to do next spring.  But, be sure to leave some perennials with attractive structure to make the winter landscape interesting.  Echinacea seed heads with caps of snow are beautiful and contain seeds to feed birds.  There are many perennials that get beaten down by the winter weather and won’t require much, if any, clean up next spring.  It is important to remove weeds before they go to seed or seed heads from aggressive plants you want to control in your garden.  I have a nice patch of cup plant (Silphiumn perfoliatum), which I love to see bloom in the back of my perennial border, but if I don’t remove the spent flowers, I will have a border that is nothing but cup plant.  In other areas, I want the aggressive plants to spread.  A patch of sea oats (Chasmanthium latifolium) has been spreading in a section of the garden where I want it to take over, so I don’t cut them back until spring, after they’ve dropped their seeds.

Our warm weather has made fall garden tasks a pleasure.  You still have time to rake those leaves into your beds, prune back aggressive perennials, pull a few weeds, pick up sticks and branches the wind brings down and then enjoy a warm fire with the kindling you gathered.


Fig with wire basket of leaves for winter protection.

Fall in Delaware

Cooler temperatures and lower humidity and (thank goodness) some rain have come along with the start of fall this year.  On a recent trip downstate, I saw sweeps of yellow from sweet goldenrod (Solidago odora)—our state herb.  Goldenrod often gets a bad rap as the cause of fall allergies.  In fact, goldenrod pollen is extremely heavy.  It is pollinated by bees, butterflies, moths etc., but not by wind.  It blooms at the same time as the inconspicuously green-flowered ragweed.  Ragweed has light pollen, is wind-pollinated and is the most likely cause of many fall allergies. Contributing to the roadside yellow were also tickseed sunflower (Polylepis bidens) and swamp sunflower (Helianthus angustifolius).  Warm season grasses, switchgrass (Panicum virgatum), Indiangrass (Sorghastrum nutans) and little bluestem (Schizycharium scoparium) are also blooming in great sweeps along our roadways.  Fall is the season in which Delaware’s native vegetation shines.  Along Route 1, groundsel bush (Baccharis halmifolia) is poised to burst into bloom with white fleecy flowers.  Soon our native sumacs (Rhus typhina, Rhus copallina, Rhus glabra and Rhus aromatica) will turn bright red and make a great combination with groundsel bush.  The first fall color we see in Delaware is the crimson color of black gum (Nyssa sylvatica).  At the northern end of Route 1, the black gums are just starting to show hints of red.

Goldenrod, Delaware’s state herb, blooming in community common land in Northern Delaware.

Goldenrod, Delaware’s state herb, blooming in community common land in Northern Delaware.

If you want to do more than view our beautiful fall landscape, there are plenty gardening activities best accomplished in the fall.  Fall, once we get some consistent rainfall, is a great time to plant most trees and shrubs.  Trees and shrubs put energy into root growth in fall, so plants quickly become established in their new sites.  One exception is with evergreens, which do not grow many roots as the weather gets cooler and the day length shorter, so avoid planting evergreens in the fall.  Perennials can be planted in fall, but if you are planting very small plants or plugs, it is best to wait until spring.  Alternate freezing and thawing during winter, pushes small plants out of the ground.

Fall is the best time to renovate your lawn.  Start by evaluating how you use your lawn.  Where do you need circulation? Play areas? Gathering spaces? Or green carpet to unify the scene?  If lawn is not serving a purpose, get rid of it.  Allow it to become a meadow or forest; or plant landscape beds or vegetable gardens in place of unused lawn.  For those areas you do use, a thick, dense lawn will keep the weeds out and serve the intended purpose fully.  Grass seed requires good contact with the soil to germinate.  If you are over-seeding a relatively weed-free lawn, use a hard rake or core cultivator to expose soil before spreading the new seed.  If you are renovating a poor quality lawn, it is best to kill the existing vegetation before seeding.  You can smother the existing grass and weeds with black plastic, but if the area is large and full of perennial weeds, it will be more effective to use an herbicide, such as glyphosate. Take a soil sample to determine pH and nutrient deficiencies.  Correct pH with lime and add nutrients following the recommendations of the soil test.  Next core aerate or till to expose soil.  Then spread grass seed.  Turf type tall fescue is the preferred grass for all of Delaware.  It is drought tolerant and tough enough to withstand modest play and traffic.  Cover your newly seeded lawn area with a light layer of straw or salt hay to help keep the soil moist.  Water frequently (daily at first) until the grass becomes established.  Cut when the grass reaches 3-4 inches with a sharp mower blade.  Dull mower blades may pull the seedling out of the soil instead of making a clean cut.  Fertilize again once grass is established, usually by mid-fall.