Specimen Spotlight: Hardy Ageratum

by Melinda Heigel, EMGV

Hardy ageratum making its debut this August in Durham’s Trinity Park. (Image credit: M. Heigel)

You know it’s late summer with fall on the way when you see the delicate blue to purple flowers of hardy ageratum (Conoclinium coelestinum) begin to emerge. Hardy ageratum has more common names than you can shake a stick at: blue boneset, blue mistflower, mist flower, and wild ageratum to name a few. Beauty is in the eye of the beholder when it comes to this wildflower, as some might consider this plant to be a mere invasive weed you often see growing along roadsides. But it can be right at home in your garden, offering great fall color and texture until the first frost. This plant also provides late-season nectar for pollinators–especially butterflies, and birds enjoy the seeds, too.

Hardy ageratum is a herbaceous perennial native to the eastern US and one of three native mist flowers in the US overall.1 The flowers are tubular in nature, resemble thistles, and grow in dense clusters called corymbs. These soft, fuzzy and showy flowers offer an etherial old-fashioned look. But make no mistake about this plant– it’s tough, reliable, and get can get assertive in the cultivated landscape. It spreads by rhizomes (underground stems that creep horizontally and give off roots and shoots) and is also self-seeding. Its enthusiastic growth habit makes it a great plant for naturalized areas, cottage gardens, or urban prairies. But don’t let its vigor deter you. It is also great as a back-of-the-border plant. And while that likely means some diligent “management” on your part, it is well worth the effort. You’ll enjoy roughly 2-3 months of continuous flowers. This late-bloomer has a clumping upright habit and typically grows 1.5′-3′ tall and up to 3′ wide.

(Above) Hardy ageratum (Conoclinium coelestinum) paired with the rich autumn color of sedum (Sedum sp.), and (below) two natives make a stunning combination when you plant hardy ageratum with pink muhly grass (Muhlenbergia capillaris) (Image Credits: Eva Munday CC BY-NC 4.0 and Susan Strine CC BY 2.0)

Growing Conditions and Care

Hardy ageratum prefers full sun to part shade, but full-sun conditions ensure the most abundant blooms and compact habit. These natives grow best in average, medium to wet but well-drained soils and grow all throughout North Carolina. They prefer fertile environments. Propagating these plants is easy; clump division in early spring is best. Also consider a springtime prune as well, again, to encourage a denser plant and reduce the need to stake later in the summer. These plants can get weedy if not cut back.

Hardy ageratum isn’t a plant you easily find these days unless your local nursery places an emphasis on native plants. These fall into the “pass-along plant” category, as these might be plants you get from a neighbor or a plant swap (and there is always that roadside ditch). You can, however, find seeds for this perennial wildflower online or at your local garden center. But don’t confuse hardy ageratum with its cultivated cousin Ageratum houstonianum. You can find these tender annual varieties in abundance for sale each spring and summer. The look is quite similar, but they tend to be shorter, more compact plants (usually 6″- 8″ tall) and grow in tight mounds, though some taller varieties are available. While they share the same preferences for growing conditions as the perennial hardy ageratum and also have a long bloom time, these annuals are often best for containers and front-of-the-border spots in your beds.

Two examples of the many choices of annual non-native varieties of ageratum that bloom from spring to fall. (Image Credits: Cathy DeWitt CC BY 4.0 and Mauricio Mercadante CC BY-NC-SA 2.0 )

Despite its propensity to be overzealous, hardy ageratum can be a solid addition to your landscape. A workhorse of a plant, it supports wildlife like beneficial insects and birds while at the same time managing to be deer and rabbit-resistant. Keep an eye out for it now through November and imagine what it might lend to your garden.


1–There are 3 hardy ageratums native to the US, and Texas is the only state where you can find them all. In addition to the our specimen spotlight Conoclinium coelestinum, there are also the betony-leaf mistflower (C. bentonicifolim) native only to Texas and the palmleaf mistflower (C. dissectum, formerly known as the C. greggii) native to Texas, New Mexico and Arizona. All perform well in Zones 7-11.


Resources and Additional Information


Visit North Carolina State University’s plant toolbox website for more details on hardy and annual ageratum

Native perennial: https://plants.ces.ncsu.edu/plants/conoclinium-coelestinum/

Non-native annual: https://plants.ces.ncsu.edu/plants/ageratum-houstonianum/

Missouri Botanical Garden’s website offers a through profile of hardy ageratum


For a finer look at the taxonomy changes for hardy ageratum formerly known as Eupatorium coelestinum, the University of Arkansas extension site outlines the journey of scientific classification


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August To Do in the Garden

by Gary Crispell, with Melinda Heigel, EMGVs

Zinnias are easy seeds to direct sow in the garden. And they encourage some pretty cool visitors.

Your beloved monthly to-do writer, Gary, is taking a little time away this week. With some of the showers we’ve been having, maybe you had the chance to kick back a little bit this week too–at least with the watering. According to CoCoRaHS (Community Collaborative Rain, Hail & Snow Network),1 some spots in Durham have enjoyed anywhere from a trace amount up to well over 2+” of rain this last week. Did I see you out there dancing, arms stretched to the skies? Remember, a good rule of thumb for things planted in the ground is 1″ of water per week.

I know you will be anxiously awaiting news in September on the progress of the Accidental Cottage Garden (ACG). There is always something blooming up a storm in the ACG. Nod to Gary on that one. Despite all the hot and incredibly dry weather this summer has brought, he has planted the right plants in the right place–another important well-worn trope master gardeners chirp all the time. That means if you are planting in a hot, sunny and dry place make sure you choose plants that like those conditions. Be like Gary.

Below is a “repeat performance” of Gary’s August To Do in the Garden from last summer, and the advice still rings true. He’ll be back in September, and while he is away, I will take a minute to shamelessly plug my own cottage-style garden in the photos below. Here it is in all its wild and wooly summer glory! –M. Heigel

The side garden is a riot of color and texture in August. Some might call it a mess; I prefer to call it delightful. Some of the featured plants (left to right, top to bottom) are autumn sage (Salvia greggii), pincushion flower (Sacbiosa columbaria ‘Butterfly Blue’), purple coneflower (Echinacea purpurea), black-eyed Susan (Rudbeckia fulgida), Zinnia (Zinnia spp.), white garden phlox (Phlox paniculata ‘David’), spider flower (Cleome houtteana ‘Rose Queen’), dwarf goldenrod (Solodago rugosa ‘Fireworks’), and branching and single-stem sunflowers (Helianthus spp.).

Check out this video to get a real sense of the true pollinator magnet the cutleaf coneflower (Rudbeckia laciniata) really is. It’s usually the busiest plant my garden. Plus, it is hardy, disease resistant, and can grow anywhere from 3′ to 10′ inches tall. If you have full sun to part shade, I recommend this heat-loving plant. (Volume on for the full effect.)2



Scope out the lawn for grubs. Treat ‘em if you find ‘em. Otherwise, leave the sprayer hanging in the shed. Late in the month you can prepare areas the need to be seeded with cool season grass (fescue, Kentucky bluegrass—not the kind with banjos and fiddles. Save them for the IBMA in September.)


If you have strawberries hit them with a little nitrogen. DO NOT fertilize trees or shrubbery again until December.


If you are a start-them-from-seed kind of person then by all means get to it. Sow pansy seeds in flats to be set out in September. Perennials like hollyhock (Alcea rosea), larkspur (Delphinium elatum and a host of other specific names), and Stokes’ aster (Stoksia laveis) seeds can be sown now to get a jump on healthy plants in the spring. Plant a fall garden. Root crops E.g., beets, turnips, rutabagas and radishes are good to plant now as are many salad greens E.g., Chinese cabbage, kale, lettuce, arugula, and mustard. Other fast-growing veggies that are fine to plant now are squash and cucumbers. That should keep you in fresh produce until after Thanksgiving.


Fuhgeddaboudit. No more pruning until the end of November. You get a pass if a hurricane not associated with PNC Arena should pay a visit.


Same stuff as last month. Look for spider mites on coniferous evergreens (juniper, arborvitae, Leyland cypress, etc.), lace bugs on azaleas and pyracantha and aphids on anything green. Maintain your spray programs for roses, fruit trees and bunch grapes. Look for worms on cruciferous vegetables (cabbages, broccoli, cauliflower, etc.) and borers on squash. Only spray when necessary and
follow the directions on the label.


It is still okay to take cuttings of shrubbery.


Check over your landscape plan (I just know you have one) so you will be ready for the fall planting season. If (when?) the August thunderstorms skip your yard try not to run the well dry nor to seriously deplete Lake Michie or Little River Reservoir. You could build a compost bin. Dig Irish potatoes. (I dig ‘em roasted with olive oil and tarragon.) Stay cool and hydrated. I had hoped not to be repeating this by now, but wear your mask and wash your hands. The fat lady has not sung yet. If we all quit worrying about our rights and do the right thing it will make life easier sooner.


1–Begun at Colorado State University’s Climate Center in 1998, CoCoRaHS is a non-profit community-based network of volunteers who use low-cost but precise measuring tools and the internet to report precipitation. Anyone can become a reporter. It’s a resource to track precipitation in your area on a daily, weekly, monthly, or annual basis. Check out their website for more information to get involved and to track precipitation. https://www.cocorahs.org/Content.aspx?page=aboutus

2–Image credits: M. Heigel.


Additional Resources and Information

Central North Carolina Planting Calendar for Annual Fruits, Vegetables, and Herbs

Organic Lawn Care Guide

North Carolina Extension Gardener Handbook – Starting Plants from Seed (Sexual Propagation)

Learn more about insects and how to control them from the North Carolina Extension Gardener Handbook

NC Extension Gardener Plant Toolbox (find your perfect plant or figure out what that unknown weed is!)

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Honeybees, the Summer Dearth, and How Gardeners Can Help

by Karen Lauterbach, EMGV

I have gardened for most of my life, but it wasn’t until I became a beekeeper that I learned about the “summer dearth.”  That’s the term beekeepers use to describe a shortage of nectar-producing flowers.  Nectar, the sugary liquid produced by flowers, entices bees to flowers to help with pollination, while at the same time providing food for the bees.

In North Carolina, the summer dearth follows the spring abundance. The majority of nectar that bees collect in the spring comes from trees.  Beekeepers talk about the nectar flow, which in the Piedmont region of North Carolina usually begins in late March and ends in June.  Local beekeeper listservs are full of reports of the first tulip poplar (Liriodendron tulipifera) blooms, which provide the bulk of the nectar that bees in North Carolina’s Piedmont turn into honey each spring. 

The stunning and fragrant flower of the tulip poplar tree (Liriodendron tulipifera) can grow 1.5 – 2 inches in diameter. (Image Credit: Karen Lauterbach)

“The tremendous amount of flowering plants we have in spring, mostly tree flowers that are unnoticed by normal people, make the pretty little garden flowers we have in summer look like nothing at all,” explains Randall Austin, a North Carolina Master Beekeeper.

By mid-June, he said, the tree flowers have stopped blooming, and that’s when the abundance of nectar subsides. Beekeepers generally harvest honey in June.  They leave the honey the bees produce during the summer and early fall for the bees. 

Just as the nectar flow is declining, honey bee populations are exploding.  Hives generally have the most bees in mid-summer. “It is a double-whammy of high demand and low supply,” notes Austin.

Beekeepers often feed their bees a sugar-water solution during the summer dearth.  But gardeners can help by making sure they have plenty of plants in their gardens that bloom in July and August and into the fall.

“Things in the aster family are typically excellent, as are most flowers that have an “open” flower (coneflowers, for example) versus a “closed” flower (tubular flowers such as Japanese honeysuckle and tomatoes). For fans of natives, Joe-Pye weed (Eutrochium spp.) and sumac are good summer bee plants,” Austin says. There are 15 species of sumac in the United States and they all are good bee plants. Staghorn sumac (Rhus typhina) is very common in our area (and everywhere) and is a great example of a bee-friendly variety of sumac that provides a lot of both nectar and pollen.

(Left to right) Plants that can help fill the void in the summer and fall for honeybee nutrition include Joe-Pye weed (Eutrochium spp.), climbing aster Ampelaster carolinianus), sumac, such as this staghorn sumac (Rhus typhina), and purple coneflower (Echinacea purpurea).

Besides planting things that flower in the summer, Randall Austin notes there is another way to help:  buy local honey so that your local beekeepers can continue providing free pollination services.


Additional Resources and Information

For more ideas about what to plant to help the bees, visit Chatham County Extension Agent Debbie Roos’s excellent website, check out her list of her top 25 native plants for pollinators, and visit her Pollinator Paradise Demonstration Garden in Chatham County.




The North Carolina State Beekeepers Association’s website provides information about bloom times for flowering plants that honey bees frequent for nectar and pollen.


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The Budding Orchardist: To Everything there is a Season

By Jeff Kanters, EMGV

I am the wisest man alive,
For I know one thing,
And that is that I know nothing


Ever think about planting a fruit tree in your yard or helping in an orchard? I did. As a new Extension Master Gardener, I joined Durham’s Briggs Avenue Community Garden teaching orchard as a volunteer and co-leader in February 2022. Initially, my knowledge specific to orchard management was limited. But soon, I found myself catapulted into acquiring and applying a vast new knowledge base. One great truth for me is that the more I learned, the more I realized how much more there is to learn. I am excited about this new series of articles on fruit-tree management where I can share what I learn with you. Maybe you, too, will be ready to dive head-first into growing fruit trees.

Conditions for Planting and Growing Fruit Trees

I was first introduced to the orchard in mid-February 2022 with other prospective team members to get instruction and hands-on practice at the winter pruning of newly planted orchard trees. I learned the history and organization of the orchard: how, what, and where new trees were planted. Given the heavy compacted clay soil of the orchard area, in 2020 elevated rows or berms were created from quality soil consisting of a mix of topsoil, compost, and soil amendment that was brought in.

My takeaway: Some fruit trees, like peaches, need well-draining soil.

The long berm rows were constructed 7-feet wide and elevated 2-feet from the ground and oriented in a north-south direction. Dormant small new fruit trees were planted on top of the respective berm rows in December 2021.

My takeaway: Best to plant or transplant new fruit trees when dormant, usually winter to very early

To stabilize the new berms from erosion, reduce weeds, hold moisture, and buffer the tree roots from the summer heat, the orchard team settled on covering the berms with shredded pine mulch. We preserved a 2-foot diameter well around each tree topped with Permatil® to deter voles from chewing at the base roots and trunks of the new trees.

Getting to Know the Orchard

After understanding the core berm construct, I familiarized myself with the planted orchard trees. The orchard is currently divided into two sections, the larger south orchard and the smaller north orchard. The large south orchard trees are planted along 6 specific rows based on the type of fruit tree and their root stock:

  • Row 1 consists of plums (Prunus domestica) and peaches (Prunus persica), both members of the Rosaceae or Rose family.
  • Row 2 are apples (Malus domestica) of the Rosaceae or Rose family
  • Row 3 are pears (Pyrus communis) of the Rosaceae or Rose family
  • Row 4 are persimmons (Diospyros virginiana) of the Ebenaceae family
  • Row 5 are elderberries (Sambucus sp.) of the Adoxaceae family
  • Row 6 are paw paws (Asimina triloba) of the Annonaceae family

My takeaway: Fruit trees need to be spaced far enough apart to maximize sunlight penetration into each tree at its mature size and so that the tree canopies do not grow into each other.

The newly-established Briggs Avenue Community Garden teaching orchard. (Image credit: Jeff Kanters)

The north “mini” or small orchard consists of two curved berms shaped like parentheses and oriented north to south. Each row holds an assortment of plum, peach, apple, pear, and persimmon trees. At the far north end of the small orchard flanking the small shed are planted a regent serviceberry (Amelanchier alnifolia ‘Regent’) of the Rosaceae or Rose family and a pineapple guava (Acca sellowiana) of the Myrtaceae family. Between the north and south orchard, near the entrance of the beehive area are planted two cultivars of pomegranates (Punica granatum) of the Lythraceae family. And planted across from the pomegranates between the north and south orchards is a weeping mulberry (Morus alba) of the Moraceae family.

Understanding Scions and Root Stocks

If that’s not enough, I needed to acquaint myself on the specific root stocks grafted onto the applicable scions of peaches, plums, apples, pears, and persimmons, and what they contribute to a fruit tree’s growth. I was shown how to identify the graft union between the rootstock and scion, and the optimal planting position of the tree so that the graft union was only 2-3 inches from the ground level. That meant educating myself on a few key terms that would be helpful for you to know as well:

  • Scion pertains to the visible top growth, above-ground trunk, and canopy. The scion determines the fruit variety, characteristics, flavor, aroma, texture, ability to stay viable on and off the tree, uses (fresh picked, for juicing, or cooking), season of ripening, and disease and pest resistance or susceptibility.
  • The root stock is selected for interaction with soil, providing the roots or supporting underground structure. It obtains the necessary water and minerals, drought tolerance, and resists the relevant pests and diseases. These are factors to consider whether a tree is planted in the heavy clay soils of Durham County or the sandier soils of Franklin County. Moreover, the root stock may also have a dwarfing effect on the scion and result in a smaller than expected tree if it were growing from its native root. This can be desirable for a number of reasons, including planting in small spaces and having fruit produced lower so that it’s easier to pick.

Pruning 101

Another layer of knowledge I had to grasp and apply is the training of fruit trees via pruning and spreaders. I came to understand that while the root stock may influence the vigor and size of the scion grafted to it, tree pruning was the greatest driver in managing the size and shape of the tree. Below are some important factors to keep in mind.

  • Pruning needs to start as soon or soon after the sapling is planted, preferably in winter or very early spring while still dormant. Pruning is an active process and continues every season during the life of the tree. There are 2 key times of year fruit trees are pruned. Winter-prune when the tree is dormant for shape and vigor. This includes removal of diseased, dead, or damaged wood as well as crossing branches. Summer-prune around the time of the summer solstice for size, shape, removing upright and vigorous current season’s growth. This helps to maintain and open tree shape for maximum photosynthesis and fruit development.
  • Pruning shears must be sharp and as free from contamination as possible between cuts and trees. I clean-sterilized tools with 70% alcohol or Lysol® to prevent the introduction of any cross contamination between cuts and trees.

(Left to right) Before pruning and after summer-pruning of a young peach tree.

(Image Credit: Jeff Kanters)


In addition to proper pruning, I needed to learn and apply the ‘training’ part of the equation. This entails the use of limb spreaders to train new pliable growth at a crotch angle of 45-60% from center or leader of the tree, like a wide vase or bowl shape. Why? To keep the center of the tree as open as possible to maximize fruit production. They say practice makes perfect, so after a few failed attempts I began to analyze a particular tree and see where a spreader could be set to widen a branch angle. Nice thing, the spreaders do not stay in place forever, as typically after 1 to 2 years of growth the branch being trained has stiffened to its angle of growth and the spreader may be removed.

My takeaway: The objectives of pruning and training are to achieve maximum tree life and productivity.

(Left) Spreaders applied to an apple tree to widen branch angle and maximize sun penetration and fruit yield. (Right) Regular scouting for pests like Japanese beetles on this apple tree is an important task. (Image Credit: Jeff Kanters)

Pest and Pathogen Management

And last but certainly not least, I am only beginning to touch on the vast knowledge needed for orchard management regarding pests and diseases. This came to light especially with our recent horrific Japanese beetle (Popilla japonica) infestation of all the orchard trees that began this May. I can attest that all of the team members became adept at manually popping beetles off tree leaves into soapy water. In general, mechanical methods like handpicking destructive insects such as Japanese beetles have proven both a sustainable and effective way to control pests.

And with this, my saga is just beginning. Looking forward to taking you on my journey of challenges, knowledge gained, and lessons learned in orchard management. We will dig deeper into all facets of orchard management and growing fruit trees. Fasten your seat belts and stay tuned.


Additional Resources and Information

“Grow a Little Fruit Tree: Simple Pruning Techniques for Small Space, Easy Harvest Fruit Trees,”
by Ann Ralph. December 30, 2014.

Check out North Carolina State University’s Production Guide for Smaller Orchard Plantings.

North Carolina Extension Gardner Handbook, Chapter 15 Tree Fruits and Nuts is an excellent resource on fruit growing for the home gardener.

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Interested in Becoming a Master Gardener?

Durham County Master Gardener Volunteer training is back!

If you are looking for a way to up your gardening game and give back to the Durham community, consider becoming a Durham County Master Gardener.  All applicants must attend one of the Information Sessions being offered in late August through September of 2022. 

Classes begin in January 2023 and run for 16 weeks. For more information about the Master Gardener Program and the date and times for each of the Information Sessions, visit https://go.ncsu.edu/durhammg2023.