July Silphium

July Silphium

Few grieved when the last buffalo left Wisconsin, and few will grieve when the last Silphium follows him to the lush prairies of the never-never land.

  Aldo Leopold

A Sand County Almanac

Silphium stand out in the prairie, not only because of their enormous size, but because of their interesting attributes.

Cup Plant on corner

I didn’t plant Cup Plant in my garden–a seed of it must have been inadvertently buried in a pot of something else that I purchased.  Cup Plant (Silphium perfoliatum) is the first silphium to bloom this summer in my garden.  A single, large 3 “, lemon yellow daisy opens first, followed a few days later by side clusters of blossoms that bloom in the upper part of 3-8’ tall stems from early-July through August.  Like all silphium, there is a charming story to tell about it.  Its huge triangular opposite leaves encircle the thick square stem to form a cup that holds rainwater.  These little reservoirs provide water for birds, butterflies, dragonflies, and other insects.

cup plant with water

Reservoir of rain water in its cup.

 Cup Plant is a majestic plant, but I can’t recommend it for small home gardens–not because it is unattractive, but because it is extremely aggressive.  I’ve never planted it–but it still appears spontaneously.  And it keeps on appearing spontaneously–everywhere.  It is a wetland plant, but it grows anywhere in the sun–at least it does in my yard.


I planted 3 Rosin Weed in my new side yard garden many, many years ago.  Unbelievably, a few weeks later, one night a car pulled into my driveway, then turned and drove down my sidewalk and ran over my entire side yard garden.  Prairie plants, fortunately, are tough. and while they were all broken, none were killed–they were just shorter that year.   The Rosin Weed, since then, has increased exponentially–I now have dozens and dozens in every sunny garden in my yard.

Rosin Weed on parkway  Clusters of large, canary yellow daisies bloom at the top of the stems in July and August.  The rough, sandpapery, stalkless leaves are arranged in pairs along the length of the stiff stems.    In the prairie, Rosin Weed grows 2-4’ tall; in my garden, it is over my head.  (If you want a shorter plant, cut the stems back hard at the end of May.–or run them down with your car.)  It’s called Rosin Weed because it produces resin along the stems and on the flower stalks that Indian and pioneer children used to chew like gum.

compass plant in full bloom

Like many other sunflowers, the blossoms of Compass Plant (Silphium laciniatum) turn toward the sun, from east to west.  The 3-4” golden blossoms bloom alternately along the top half of the 3-9’ tall stems from early July through mid-to late August. The most striking feature of this plant, however, is its magnificent, oversize oak leaf-shaped leaves.  They orient themselves in a north-south position, thus providing a compass in the prairie for native tribes and early settlers.

compass plant foliage

While Compass Plant has a deep taproot, small rhizomes extend from the taproot to create colonies. Within the last few years, my Compass Plants have formed a huge colony–much too large for the space it’s in.  While these leaves are upright, most of them have splayed out awkwardly–a most unnatural position.compass plant in schulenberg prairie

In nature, in the prairie, Compass Plant is scattered here and there,  This is at Schulenberg Prairie at Morton Arboretum.

compass plant in fall CTL prairie

Compass Plant also grows in scattered locations in Christ the Lord Lutheran Church  prairie just west of Elgin.

prairie dock leaves

The enormous, rough, spade-shaped basal leaves of Prairie Dock (Silphium terebinthinaceum) are a spectacular presence in the garden and in the prairie.  Its smooth leafless stalks rise up to 10’ or more; a cluster of yellow daisies begins to bloom at the top of each stalk the 3rd or 4th week in July.

Prairie Dock is also remarkable for its large, deep taproot, says Suzanne Masi, in her comprehensive book, The Sunflower Family in the Upper Midwest.  She goes on to quote Russell Kirt by telling us that its roots can penetrate to the water table, reaching depths of 14 1/2 feet or more and enable the plant to survive during periods or extrme drought.

prairie dock shap

Arrange it at the front of a garden as an accent; one can easily see  through the tall stems.

prairie dock fall leaves

It  makes a striking focal point in the prairie garden from early spring through late fall and into the winter, as the leaves turn from green to gold to a gorgeous red-mahogany.   Hold your hands on both sides of the leaf–it will feel cold no matter how hot the day.   It’s not nearly as aggressive as the other members of its genus–I planted three of them 15 or so years ago, and I now have five.

prairie docl ;eaves in schulenberg prairie

Its leaves are stunning in the prairie, as well.  This is next to the path at Schulenberg Prairie at Morton Arboretum.

In a prairie garden, Silphium are at their best when planted singly, here and there,  in dry-mesic to mesic soil.  It’s important  to give them lots of competition, such as Aster ericoides and Aster laevis,  Eryngium yuccifolium, Euphorbia corollata, Liatris spicata, Dalea purpurea, Monarda fistulosa, Parthenium integrifolium, Ratibida pinnata, Solidago rigida, Sporobolus heterolepis, and maybe a few Coreopsis palmata, Coreopsis tripteris, and a couple of Sorghastrum nutans–beware though–these last three are aggressive species.








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6 Responses to July Silphium

  1. sue July 10, 2014 at 3:18 pm #

    I love silphium leaves. They are so cool and lush.

  2. Ginger Duncan July 11, 2014 at 5:00 am #

    Hi Pat, love these pretty lemon yellow flowers! I think I have some olong my fence by the sidewalk that you gave me years ago? Thankyou! I can’t believe someone would drive their car over you plants! Enjoy the rest of your summer! Ginger

  3. Suzanne Massion July 11, 2014 at 7:32 pm #

    I have the Compass Plant and Prairie Dock Silphiums. I don’t know who told me this, but they said Prairie Dock, with it’s deep tap root, is like an oak tree in the prairie. When it finally produces flowers on those long stalks, it’s very permanent and that tap root has gone very deep. I hope a wayward Cup Plant seed finds it way here. Currently we have none.

  4. June July 11, 2014 at 9:59 pm #

    I have often wanted to cut cup plant to the ground because there is so much of it, but just as I’m ready to do so, a sweet little goldfinch drops in for a drink from the “cup”.

  5. Pat July 14, 2014 at 4:59 pm #

    Such a wonderful plant Prairie Dock is! Despite the height I prefer it at the edge of the border or prairie. It has not seeded or moved around – just stays put!

    Cup Plant has been most aggressive here. I now cut the flowers off before they go to seed. Yes, I’ve heard Indian Grass (Sorghastrum) is aggressive from many folks, but here so far, no. Coreopsis tripteris is quite the seeder but I really don’t mind it. It fills in gaps and is really quite lovely.

    I have only one Compass Plant and no Rosin Weed. I’ve seen Rosin Weed dominate a planting so I would prefer to add it once other plants are well established.

    I just love your choice of quotes. They really draw me into your posts!

  6. Jason July 15, 2014 at 2:35 pm #

    I have two clumps of cup plant, one in the front yard and one along the alley. It is one of my favorite plants and great for attracting goldfinches – but not a plant for the faint at heart.

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