Signs of Summer 14: Our Yard (Two Years On) (Part 4) Unintended Plants!

Photo by D. Sillman

(Click on the following link to listen to an audio version of this blog … Our Yard part 4

When we moved into our Greeley house in late July, 2020 there were several tiny flowering plants primarily growing out from the thin spaces in between the sidewalk and driveway concrete pieces on the southwest corner of the front yard. The flowers were small (about a half an inch in diameter) but stunningly beautiful. Their delicate beauty seemed to contradict their apparent “weed-like” locations and growth habits!

The flowers each had five petals (two purple, two white and one yellow) that sat atop six-inch-tall stalks that were loaded with dark green, lanceolate leaves. We had seen these flowers before in our front yard back in Pennsylvania. In fact, we had watched them, over the years, steadily spread across our yard and on out into the neighboring  field. They were “Johnny Jump Ups,” or “wild pansies” (Scientific name: Viola tricolor).

Wild pansies are native to Europe but have been in North America ever since European colonization. Some, undoubtedly, were imported purposefully to plant in flower gardens for their beauty or in herb gardens for their use in a variety of folk-medicine cures (they were traditionally used to treat a wide range of maladies including eczema, bronchitis and asthma). Thomas Jefferson grew wild pansies in his garden at Monticello and wrote about them in his notebooks. Today, most major seed companies sell wild pansy seeds, and many garden websites extoll their beauty and vigor. However, many states have listed V. tricolor as an invasive species whose rapid rate of reproduction and extremely robust rate of proliferation and spread can negatively impact a long list of native species.

Photo by D.Sillman

In short, these wild pansies are exotic, invasive weeds, but to their credit they are beautiful! Their presence gave our sunbaked, flower-starved yard of summer 2020 a very nice splash of color! We decided, in spite of their aggressive nature, to let them grow!

Wild pansies bloom from late spring to the end of summer with a significant burst of mass flowering in the month of June. Their name “Johnny Jump Up” refers to their remarkable ability to send their seeds across broad areas of lawn or field where they germinate and “jump up” in the next growing season. This “jumping” potential is due to two factors: 1. The oval seed pods of the plants, as they dry, become tense, tightly coiled, spring-like structures. When these pods are excessively heated (as on a very hot,

Johnny Jump Up seed pods. Photo by D. Sillman

sunny day) or if they are mechanically disturbed (as by a passing animal or even a strong wind gust or a striking raindrop), they burst open and fling their seeds out into the air. Some viola species, using these “ballistic dispersal” mechanisms, can send their seeds up to 16 feet away from the parent plant! And, 2. Once the seeds hit the ground, they attract the attention of ants! The ants pick up the seeds and carry them off to their underground nests. Although the ants undoubtedly consume some of the seeds, more than a few survive and, after being transported significant distances from their parental sources, germinate and then “jump up” the next spring!

Here in Greeley, we have watched our wild pansies march across the front yard. At first (summer 2020) they were confined to the southwest edge of our property, but by 2021 they had reached halfway across the mulched section of the yard. By this spring (2022) they had reached all the way to the sidewalk at the edge of the mulched areas. They lined the edges of the gravel walkways and rock “dry creek beds” and grew straight up out of the shredded cedar mulch. They were beautiful but were beginning to make us a bit uneasy!

We have decided that they have spread far enough and have started to collect the drying plants. Hopefully, we’ll be able to gather them with their as yet unexploded seed pods (although this seems unlikely based on our most recent examination of the plants). We would like to keep them from entering the north part of the front yard where the buffalo grass is growing. We’ll see if we can control the spread of this feral flower or if we have to add them to our “bad weed list” next spring!

Photo by D. Sillman

Our second, “unintended” yard component came in from nearby roadsides and field edges: wild, common sunflowers (Helianthus annuus).  In summer 2021, we had four, robust patches of these volunteer sunflowers out in our front yard. They self-seeded (probably via bird transport in the previous summer or fall). Seeds from these 2021 sunflowers, then germinated all across the yard in spring 2022 and we then had hundreds of wild sunflowers growing all across the front of our house.

The rate of growth of these plants was astonishing! I have photographs of the front yard in mid-June 2022 in which there are no sunflowers in sight and then, three weeks later, the same view was dominated by a dense, three-foot tall, sunflower jungle! We were forced to thin the sunflower plants very aggressively in order to have room for our other front yard plants to grow!

Photo by D. Sillman

When these sunflowers were young and growing so rapidly, we watched them exhibit the property of “heliotropism.” At dawn, the entire yard of sunflowers were positioned so that their developing flower heads faced the east and the rising sun. They then, through the day, slowly turned their flower heads to follow the sun across the sky until at sunset, they were all facing to the west and the setting sun. Only the young sunflowers exhibited this behavior, though. The older, mature sunflowers positioned their flower heads toward the east and kept them there.

One explanation of this interesting behavior is based on the previously mentioned rapid growth rate of the sunflower stems. Apparently, during the day, the cells and tissues on the east side of the stem grow more rapidly than those on the west side, thus turning the sunflower head to the west. At night, the cells and tissues on the west side of the side of the stem grow more rapidly, thus turning the sunflower head back to face the east. By the time the sunflower is fully grown, though, these stem cells and tissues have stopped growing and the heliotropic behavior ceases to occur!

Photo by D. Sillman

The pollinators love the sunflowers! There have been clouds of buzzing insects around the flower heads from the end of June well into August! The sunflowers are an important source of nectar and pollen for these insects and help to sustain these vital organisms through the summer season.  Deborah did a visual census of these sunflower pollinators and observed honeybees, bumblebees, several species of solitary ground bees,  vespid wasps (yellowjackets, paper wasps and pollen wasps), several species of mud daubers (including the black and yellow mud dauber (who were there hunting spiders to provision their nests!)), several kinds of beetles and homopterans, damselflies and more! Talk about a keystone species!!

Common sunflowers are one of five native, sunflower species found here in Colorado. The other four native species include the Maximillian sunflower (H. maximilanii) which grows all over the Americas in dense clumps of ten foot-tall stalks (we planted Maximillian sunflowers in one of our “intended” garden planting rings, and I wrote about them last week!), the Nuttalls sunflower (H. nuttalii) which grows primarily in the damper regions of the nearby foothills of the Rocky Mountains, prairie sunflowers (H. petiolaris) which make relatively low, branching sunflower-bushes especially along roadsides that cut through the Colorado plains, and bush sunflowers (H. pumilus) which primary grow on dry hillsides.

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The common sunflowers (H. annuus) are the wild stock from which Native Americans some 3000 years ago derived the larger seeded common sunflower which they then grew extensively across North America as a food plant. Some scientists think that these cultivated sunflowers were actually developed for human food even before corn! These native American sunflower varieties were exported to Europe in the 1500’s (in that great, post-Columbian shift of plant species back and forth across the Atlantic Ocean!) and then were further developed into the very large flower/very large seed varieties that are currently grown around the world for human consumption, oil, and livestock and wild bird feed.

Last year, starting in late September, birds (house finches, chickadees and house sparrows) swarmed the flower heads and gobbled down the tiny seeds. Several fox squirrels also climbed up the two and a half inch thick sunflower stems and pulled whole flowers off of the plant to eat the seeds. Then one day in early October, a flock of goldfinches (a bird I had not seen all summer) descended on one of the sunflower patches. The adult finches pulled seeds out of the dry flower heads while a large number of their recent fledglings peeped and fluttered at them demanding to be fed. One reference that I consulted stated that the late summer reproduction timing of goldfinches is primarily driven by the late summer abundance of wild sunflower seeds!

This year, the goldfinches showed up in our sunflower jungle in July! They have been feasting on the maturing seeds along with flocks of house finches for the past month!

In 2021, the plants quickly lost their summer luster and turned brown with the coming fall. They were not very attractive out in the front yard but were feeding so many animals in the yard that we decided to leave them in place until they have been stripped bare of seeds. A prodigious number of seeds fell off of these 2021 plants and caused the sunflower explosion of 2022! Left alone, it seems that the whole world would soon be completely covered with sunflowers! I hope that we have room for a few other, “non-sunflower” plants next summer!