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Wildflowers and Weeds of the Boise Foothills

By: Daniel Murphy, Collections Curator and Anna Lindquist, Garden Lead | 06/18/2019

This time of year the Idaho Botanical Garden serves as a welcoming oasis as temperatures climb and we all seek the shade of the Meditation Garden or the bounty of the Vegetable Garden. However, being nestled against the Boise Foothills allows us the unique opportunity to observe not only our cultivated spaces, but also the wild spaces that exist just outside (and inside) our deer fence.  While inside the grounds we are able to keep weeds at bay, our local ecosystem is a complex dance between native and non-native plant species. Last Wednesday, at the Jim Hall Foothills Learning Center, Collections Curator, Daniel and Garden Lead, Anna led a walk exploring the foothills ecosystem. If you couldn’t make it to the event, here is a brief look at a few of the plants that were mentioned.

A great strategy employed by many of our native wildflowers this time of year is dormancy! Blooming in the spring means that they’ve already gotten down to business and now their seed is set, waiting for the next cycle of moisture in the fall or spring to germinate. So while the Arrowleaf Balsamroot #superbloom has passed, there are still many other great late season wildflowers to enjoy; especially with all the extra precipitation we’ve had in May.

1. Munro’s Globemallow (Sphaeralcea munroana) is hard to miss with its bright orange flowers and contrasting with grey leaves. Keep watch as the flowers go to seed—the genus name is derived from the Greek word for sphere, referencing its interesting circular fruits.

2. Fiddleneck (Amsinckia tesseallata) is beautiful too look at with its inflorescence that resembles the head of a fiddle, but fickle to the touch; another common name of this plant is Devil’s Lettuce, presumably because of the bristles that cover the plant and can cause skin irritations.

3. Bottlebrush squirreltail (Elymus elymoides) is one of our native bunch grasses, but can be easy to mistake for the non-native Medusahead grass. But the purple awns of squirreltail make this grass a lovely ornamental addition to your garden.

Weeds are an enterprising group of plants that have joined humans in their journeys around the globe. Some of these plants were invited along and later escaped cultivation, establishing themselves in nearby natural areas. Others hitchhiked, then made themselves at home before we could stop them. Once established, most weeds rely on regular disturbance to continue their reign and expansion, and humans consistently assist with this.

Sadly this story has played out in our Boise Foothills. Among the native wildflowers is a whole suite of uninvited characters. Weeds in the Foothills are problematic because they compete with native plants for space and resources like pollinators, nutrients, and water. In a climate where water is particularly limited, competition is fierce. When weeds win, native plants suffer.

Some weeds commit acts that are even more nefarious. Introduced, annual grasses like cheatgrass, medusahead, and feral rye have become widespread in our region. By early summer their life cycle is complete, and their dead, dried up bones become fuel for wildfires. The dry grass ignites quickly and readily, unlike the native plants they have replaced. This results in an increased occurrence of fires – a devastating shift in a region unaccustomed to frequent fire.

1. Medusahead (Taeniatherum caput-medusae) is an annual grass introduced from Eurasia. It decomposes slowly, creating a thick layer of dried thatch that is highly flammable.

2. Whitetop (Lepidium draba) is a plant in the mustard family native to western Asia and southeastern Europe. It spreads rampantly via underground stems, forming extensive clonal colonies.

3. Rush skeletonweed (Chondrilla juncea) is a summer flowering perennial with a deep taproot. Its wiry, practically leafless stems make it easily recognizable. Like dandelion, it readily grows back from root fragments left in the ground when the plant is pulled up and has parachute-like tufts of hair attached to its seeds allowing for long distance dispersal via win

4. Redstem filaree (Erodium cicutarium) is a low-growing annual native to the Mediterranean with attractive fern-like foliage and little pink flowers. Long awns attached to the seeds coil and straighten with changes in humidity, drilling the seeds into the soil.

5. Bachelor’s button (Centaurea cyanus) is a popular ornamental flower from Europe that has escaped our gardens and become commonplace in the Foothills. It is a close relative to several noxious weeds like spotted knapweed and yellow starthistle. Despite being an abundant weed in various parts of the world, its population has declined dramatically in its native range.