Achilles tending the wounded Patroclus (attic red-figure kylix c. 500 BC). Photo by Bibi Saint-Pol on Wikimedia Commons, PD.

Achillea ‘Moonshine’ in the Rose Garden. Notice the lemon-yellow flowers and silvery foliage.

Achillea cultivar in the Rose Garden. Pink flowers fading to white gives a multi-toned effect. Notice the highly dissected green foliage.

Article and Morris Arboretum photos by Katherine Wagner-Reiss

Several hybrid cultivars of the flowering perennial Achillea are gracing the Morris Arboretum this summer. The genus name Achillea commemorates Achilles, a Greek mythological hero.

The genus name was authorized in 1753 by none other than Linnaeus, the Father of Taxonomy. Genus names are quite often based on the names of people who have contributed to botany, but occasionally honor mythical figures e.g. Adonis, Daphne, Hyacinthus, Iris, Narcissus and Paeonia.

Why was this particular genus named for Achilles? According to legend, Achilles was the son of a mortal man and a sea nymph. In a popular version of the story, his mother dipped baby Achilles into the River Stix to render him invulnerable, but since she was holding him by the ankle this became his weak spot: his Achilles’ heel. (This story also explains the anatomical term Achilles tendon.) Achilles is depicted in Homer’s Iliad as the greatest warrior of the Trojan War. His centaur mentor gave him knowledge of an herb that healed wounds and stopped bleeding; historians and botanists generally agree that this herb is what Linnaeus subsequently called Achillea millefolium. Nevertheless, the herb does not save Achilles who, in some tellings of the tale, dies after an arrow pierces his heel.

Achillea millefolium is the type species (the particular species for whom the entire genus is named). Achillea millefolium is a white-flowered species native to the temperate zones of Europe and Asia and introduced to North America by the Europeans; it is now naturalized across the United States, and it has also hybridized with varieties of A. millefolium that are native to North America, namely A. millefolium var. lanulosa and A. millefolium var. occidentalis. Yarrow is the common name for any member of the genus Achillea. Numerous common names, some attesting to its historic use as a healing herb, refer more or less specifically to A. millefolium:common yarrow, herba militaris, milfoilthousand-leaf, thousand-seal, allheal, soldier's woundwort, bloodwort, nosebleed plant and sanguinary.

Achillea millefolium is considered too aggressive for garden use, as it spreads by rhizomes and self-seeding; therefore, nurseries tend to sell hybrid cultivars, which may or may not include A. millefolium as one of the parent plants. For example, Achillea ‘Moonshine’ as seen in the Rose Garden is the hybrid A. clypeolata x A. aegyptiaca var. taygetea; Achillea ‘Coronation Gold’ near the Ha-Ha Wall is presumed to be the hybrid A. clypeolata x A. filipendulina.

Achillea cultivars merit a place in the garden for many reasons: their beautiful foliage and flowers, their support of pollinators, their ability to withstand poor soil and drought, their deer and rabbit resistance and their usefulness in making scented dried flower arrangements. With over one thousand named plants within this genus, gardeners have a wide range of heights, flower colors and foliage appearance from which to choose. Checking out the various Achillea cultivars in the Rose Garden, the Pennock Garden, and near the Ha-Ha Wall can help you to select your favorites and suggest complimentary companion plants.

Pronunciation note: Botanary and the Missouri Botanical Garden Plant Finder agree that the pronunciation of Achillea is ak-ih-LEE-a. Botanary also notes that uh-KILL-ee-a is an alternative.

Katherine has her Certificate in Botany from the New York Botanical Garden and is a botanical tour guide and freelance writer with a special interest in plant names.

Achillea cultivar in the Rose Garden. Achillea is in the daisy family, Asteraceae, and each individual flower has the form of a daisy.

Achillea cultivar in the Pennock Garden. Notice the LEGO® bee in the background, a reminder that bees are one of its pollinators.

Achillea ‘Coronation Gold’ by the Ha-Ha Wall. Butterflies appreciate the flat-topped landing pads from which they can probe for nectar from conveniently clustered flowers.


Adapted from Seasons article by Shelley Dillard, Propagator

In July, after the flush of spring blooms are done, it is hard to ignore the holes in the garden. They can be the result of many causes. Some plants mysteriously just don’t come back. What a disappointment! After all, the term “perennial” does not translate into “forever.” Some plants, like peonies, poppies and iris DO live for many years; but others, such as columbines and geraniums, do not last as long. Shrubs die as well, leaving a big hole.

Perhaps you have taken out a plant and you haven’t decided what to replace it with. Without proper mulching, many plants heave in the winter and the roots dry out. Or, truth be told, you stepped on it this spring in your zeal to get a head start on cleaning out the beds. (I’m a professional – I’ve NEVER done that!) Now is the time to stop obsessing and perk up your garden.  

1. Plant annuals in sunny spots. Some good choices for full sun are the wonderful Profusion Zinnias— they spread nicely and do not get powdery mildew like many zinnias. They are in colors from cream to orange. I also love the small flowering tobaccos (Nicotiana). They are found in green and white, lilac and pink, and can tolerate some shade. Annual salvias such as the Lady series or Victoria are also great fillers for large spaces. Cannas, elephant ears, or bananas can add real drama.

2. Plant annuals in shady spots. Some good options are impatiens, begonias, and torenias.

3. Place pots in the garden bed. My favorite way to dramatically fill those gaping holes is to take plants I have been growing in containers and place the container right in the garden. The height of the pot really makes it stand out. Don’t forget to water! 

4. Here are some vegetables to plant in late summer for a fall harvest.

5. Note the holes in the garden and think about perennials to plant in the fall. Enjoy the rest of the summer!


Sassafras albidum. Notice the four typical leaf shapes: ovate, two-lobed right “mitten,” two-lobed left “mitten” and three-lobed “trident.” Photo by Katherine Wagner-Reiss.

Papilio troilus (spicebush swallowtail butterfly). Spicebush and common sassafras are the only two larval hosts for this butterfly; both plants are in Lauraceae (the laurel family). Photo by Katja Schulz, CC-BY-2.0.

Sassafras albidum. The epithet albidum means whitish, referring to the whitish undersides of the leaves. Photo by Katherine Wagner-Reiss.

Contributed by Katherine Wagner-Reiss

Perhaps as a child you were taught about the three leaf shapes of Sassafras albidum: ovate, two-lobed “mittens” and three-lobed “ghosts.” There are actually four different shapes, if you take into account both right-handed and left-handed “mittens”! The value of having leaves with mixed shapes on the same branch is still a mystery, but it may be related to the fact that lobes allow leaves to disperse absorbed heat more rapidly.

On the marvelous Missouri Botanical Garden Plant Finder website, which includes the etymologies and pronunciations of plant names in addition to horticultural information, the genus name Sassafras is said to probably come from an American Indian name used in Florida for this tree. I like this interpretation, over other explanations that suggest French or Spanish language origins, because it is a reminder that this is a native tree: its range is Eastern and Central United States.

The specific epithet albidum means whitish, referring to the undersides of the leaves. Botanists have at least ten nuanced terms for various shades of white, including albus (white), niveus (purest white), candidus (pure white), lacteus (milk-white) and calcareus (chalk-white).

Spotting old common sassafras trees in the forest can be difficult because they often die after losing the competition for sun to taller tree species. It can be easier to find young common sassafras along forest margins or in disturbed areas where sun is plentiful.

But, while common sassafras may be a loser in the competition for sun, it has evolved several winning adaptations for survival. The young stems are green, using twigs as sites of photosynthesis as well as for support. Sassafras is dioecious i.e. male and female trees are separate with only the females bearing fruits, thus preventing self-pollination. In addition to seeds, reproduction occurs by root suckers that create monoclonal thickets able to crowd out other species.

Common sassafras is in the laurel family, Lauraceae, which is typically aromatic, e.g. the scented laurel leaf wreaths crowning Greek heroes, or the bay laurel leaves and cinnamon bark used in cooking; so, we anticipate the spicy leaves of sassafras. Sassafras root oil gave traditional root beer its distinctive flavor, but in 1960 one of its components, safrole, was labeled as a carcinogen by the FDA. Current iterations of commercial root beer rely on either artificial root beer flavoring or safrole-free sassafras root oil. Fortunately, the leaves do not contain a detectable dose of safrole, so that Louisiana Creole cuisine continues to use filé, powdered sassafras leaves, to thicken and flavor gumbo. Of course, the aromatic oils of Lauraceae evolved, not to gratify humans, but to deter pests and attract pollinators.

Sassafras albidum. Notice the characteristic green photosynthetic stem of a sapling— a good ID trait in winter after the leaves have fallen. Photo by Katherine Wagner-Reiss.

Only two plants can serve as larval/caterpillar hosts for the spicebush swallowtail butterfly: common sassafras and the spicebush, Lindera benzoin, which is also in Lauraceae. Common sassafras leaves, twigs, roots, and berry-like drupes also serve as sustenance for other animals, although common sassafras is not considered a major food source for wildlife.

The Morris Arboretum has three Sassafras albidum trees and exact locations can be found on Collection Connection. You will also find them growing in the wild. Experience the surprising shapes, colors and smell of the leaves and twigs. Complete the experience with a frosty glass of root beer!

Nomenclature Nerd Note: In Botanical Latin, trees are generally considered feminine. Sassafras is one of the rare exceptions, treated as neuter; thus, the specific epithet is albidum with the neuter ending “um,” rather than albida with the feminine ending “a.”

Sassafras albidum. When ovate unlobed leaves predominate, the stout red petioles, distinctly sunken leaf veins and spicy scent of crushed leaves aid with identification. Photo by Katherine Wagner-Reiss.

Sassafras albidum. Notice the fall leaf colors, which can include red, yellow, purple, pink, and orange. Photo by Katherine Wagner-Reiss.


Thanks so much for staying connected with us this spring via #MorrisFromHome. It means so much to us to know you’re out there connecting with the Morris Arboretum even if you couldn’t be in the garden. While we have been closed, our staff has been busy preparing to welcome visitors back to enjoy our open spaces and beautiful gardens. We are delighted to announce that as part of our phased reopening plan, we will be opening on Thursday, June 18!⁣

Advance tickets are required for all visitors and may be purchased at ⁣
Members may reserve their tickets today, Tuesday, June 16, and non-members can purchase tickets tomorrow on Wednesday, June 17. ⁣
Memberships have been extended for the amount of time the Arboretum was closed.⁣

In conformance with CDC, state, local, and University of Pennsylvania guidelines, the following changes have been made to our visitor experience in order to provide a safe, fun, and relaxing experience for all visitors during this first phase of opening:⁣

  • Advance tickets are required for all visitors in order to restrict the number of people visiting at one time. Members visit free but must reserve a time. Collectors Circle Members will receive 4 "Anytime" tickets via USPS this week. Keep them in your car or some other handy place. ⁣
  • If you feel sick, stay home.⁣
  • The City of Philadelphia mandates that all visitors age 2 and older wear face coverings.⁣
  • One-way circulation will direct visitors on paths to facilitate social distancing.⁣
  • The Visitor Center, the Shop, and Compton Cafe are temporarily closed, but picnicking will be permitted in certain areas.⁣
  • The Garden Railway, Out on a Limb, the Fernery, and the Log Cabin are temporarily closed.⁣
  • Restrooms are open and sanitized regularly.⁣
  • Hand-sanitizing stations are located throughout the Arboretum.⁣
  • Bring your own water and snacks.⁣
  • Guest passes will not be accepted at this time.⁣

Head to to reserve your tickets now. Call 215-247-5777 ext. 333 Monday through Sunday, 9:30am - 4:30pm to reserve your tickets over the phone and have your tickets emailed to you.⁣

We can't wait to see you!