I knew when I saw this plant it was in the genus Pyrola in the wintergreen family (Pyrolaceae), but my key is based on flowers and this wintergreen is in the fruiting stage. Fortunately, the wonders of the Internet made it possible to narrow it down to greenflowered wintergreen (Pyrola chlorantha). Leaves are simple and entire with white veins.
It grows through much of North America except the southeast.
For more info about greenflowered wintergreen, click here.
You probably know this flower--the common sunflower (Helianthus annuus). It's native to the Americas and widespread. Flowers can be highly variable in this annual plant.
Young sunflowers display heliotropism--that is, they turn their heads to follow the sun throughout the day.
I was delighted to see so many insects on the sunflowers, in particular this butterfly, a clouded sulphur (as best I can tell). With the yellowish tint, it's probably a male.
And the greener-tinged one is the female clouded sulphur. I saw thousands of sulphurs over an alfalfa field earlier in the summer, so it's neat to see what else they are feeding on.
I haven't seen many new plants blooming lately, so when I saw this one today, I was quite excited. It's thorn skeletonweed (Pleiacanthis spinosus, previously Stephanomeria spinosa), also called spiny skeletonweed. The plant is a wiry clump of thin stems and thorns, so the pinkish flowers are a bit of a surprise. It grows in much of the western U.S. and likes semi-arid habitats.
It's in the Sunflower Family (Asteraceae), one of the few pink flowers in the family.
This trumpet-shaped flower is Douglas's catchfly (Silene douglasii var. douglasii), part of the Pink family (Caryophyllaceae). It grows in western North America at mid to upper elevations. The name catchfly refers to the sticky stems and calyxes to which small insects may get stuck.
Not too far away I found this all white specimen, which I believe is still the same species, just with some color variation.
For more info about Douglas's catchfly, click here.
This is my least favorite weed: puncture vine (Tribulus terrestris), also known as goathead or caltrop.
The cute ferny leaves and pretty yellow flowers are deceiving, making it seem like a friendly plant. Puncture vine is in the Zygophyllaceae family, also known as the creosote bush family. My husband's favorite plant is creosote bush, so how is it possible that my least favorite plant is in the same family? 
Puncture vine is originally from the Mediterranean, but it has spread quickly. These trailing tendrils make it obvious why someone decided to call it a vine. What about the puncture part? Take a look at this next photo.
These little green fruits are fairly innocuous early in the summer, but the heat and dryness of hot days makes them get harder and harder...
...until they turn into sharp brown thorns that break apart and make even more sharp brown thorns. These thorns are so sharp that I've gotten a flat bicycle tire, a flat stroller tire, and a flat wheelbarrow tire. Needless to say, all of these tires now contain Slime.
While I was photographing the puncture vine, Desert Boy took a fall, landing right on top of a mass of it. He started crying immediately and I think he's joined me in calling this his least favorite weed.
Here are a couple of the thorns stuck in his hand. The seeds remain viable for three to seven years, so even though I have pulled every plant that I've seen in the yard, I'll probably have to keep after them for years. And unfortunately there are plenty of seeds just outside our yard.
This sub-alpine and alpine plant is elegant cinquefoil (Potentilla concinna), also called alpine cinquefoil. It grows in western and northern North America and is part of the Rose family (Rosaceae).
Leaves are very hairy with gray underneath.
This pretty alpine flower is moss campion (Silene acaulis). It flowers in July, growing in western and northern North America. It's a member of the Pink family (Caryophyllaceae), and grows in mounds, with last years growth diminished to grey areas.
For more info about moss campion, click here.
This is a thorny currant that grows at middle and upper elevations called gooseberry currant (Ribes montigeneum). It grows in western North America, and a pretty pink flower blooms in spring and early summer. Later a red berry appears that is sought after by wildlife.
For more info about gooseberry currant, click here.
This cute little yellow-flowered plant is Ross' avens (Geum rossii var. turbinatum), part of the Rose Family (Rosaceae). It looks somewhat similar to cinquefoil, but the leaves are more divided. Another distinguishing characteristic are the relatively long styles. It grows in sub-alpine and alpine areas throughout the western U.S.
Occasionally the plants grow singly, but often they grow in big groups.
For more info on Ross' avens, click here.
This prickly thistle grows from desert scrub up to the upper conifer forest. It's called Jackson Hole Thistle (Cirsium subniveum, also Greene's Thistle, Cirsium inamoenum by Flora of North America). Apparently the name confusion is partly due to some unresolved topics about this species. Sometimes plants can be funny like that. Despite botanists not being able to decide what to do with it, the Jackson Hole Thistle has decided to take up residence in many of the western states.
This is a view looking down on it.
The flowers can be white to lavender.
This pretty member of the Carrot/Parsley Family (Apicaceae) is King's angelica (Angelica kingii). It's native to the Great Basin region.
The stem is hollow, and the plant has a deep taproot.
Note the dentate leaves.
We don't see many vines out here, but here's one that grows in moister areas. It's western white clematis (Clematis ligusticifolia), part of the Buttercup family (Ranunculaceae). It's also been called virgin's bower, old-man's beard, and hierba de chivo. It grows in western North America.
For more info on western white clematis, click here.
This grass is easy to identify due to its dense cyclindrical inflorescence. It's timothy (Phleum pratense), native to Europe but frequently found in many other parts of the world due to its use in agriculture. Wildlife also find it palatable.
It grows up to three feet tall.
For more info on Timothy, click here.
Bluebunch wheatgrass (Pseudoroegneria spicata, previously Elymus spicatus and Agropyron spicatum), is an important grass in the sagebrush zone. It grows throughout western North America.
It is often bluish-gray in color and grows up to 2 1/2 feet tall.
The inflorescence is a spike about six inches long and more slender than most other wheatgrasses. The awns usually curve at right angles from the culm.
Until recently, this alpine plant was called Potentilla nivea, but it's recently been separated and now bears the name Holmgren's cinquefoil (Potentilla holmgrenii). It only occurs on three mountain ranges in Nevada and Utah: the Schell, Snake, and Deep Creek ranges. The plant is gray and grows in mats.
Flowers are yellow and look like a typical cinquefoil flower.
We found very few flowers at the beginning of August.
This flower was covered with insects (anyone know what they are?).
