Thursday, July 28, 2011

Spectacular wildflower blooms this summer in the Rocky Mountains

This time of year foothill areas from Colorado north to Montana are usually brown and fire prone. This year, by contrast,
the hills are still lush and green with many wildflowers

It has truly been an odd year for weather in the Rockies, but the net result has been perfect conditions for intense displays of wildflower blooms in July through even August. In dry regions like this, spectacular blooms can occur every 10 years or so when the combination of large winter snowpack, warm sunny summer weather and summer showers converge. These events are of great scientific interest since this is when most of the fruits and seeds are produced for these plants, providing great opportunities for the establishment of new plants or even changes to the species mix on transitional habitats next year. This also the time to see unusual phenological events, such as long periods of floral blooms.

The reasons for these spectacular floral displays are many. In general when you have a cool spring, less energy is available for plants to flower, so flowering is delayed for many species. If the cool spring is followed by some warm summer weather then you may have both the late flowers from the spring as well as summer flowers in bloom all at once. A cool spring may also have, as in this year, above average precipitation. This then provides more resources for plants to produce more and larger flowers. In Montana for example flowers have been observed with many more leaves and much larger sizes even in low elevation prairies. In alpine or subalpine areas at high elevations these patterns can be even more dramatic. The growing season is normally quite short, but still you normally observe a regular pattern of different species coming into bloom at regular intervals over the season. In a cool spring by contrast you often observe many of these species flowering all at one time.

For example, when working in Alaska I observed several species of huckleberries (Vaccinium spp.) which flowered about 2 weeks apart. Early huckleberry was always first, then usually Alaska blueberry, then finally red huckleberry (V. ovalifolium, V. alaskaense, and V. parvifolium). In the alpine in a cool year all of them could be seen in flower at the same time. One intriguing but as far as I know unanswered question is what the implications of these changes in phenology are for pollination. It is generally assumed that plants that are closely related tend to flower at different times so that they minimize hybridization between species. So are there more hybrids after years like this?

The other ecological factor that goes along with moist cool summer and spring weather is long periods of floral bloom. As most gardeners have observed if your bulbs come out in cool moist weather flowers can be in full bloom many more weeks than when it is hot. The same pattern applies to wildflowers. Besides providing a beautiful display for us, these long displays can be very beneficial to wildflowers as well. In general the longer the flowers are in bloom the more likely they will be pollinated and produce large amounts of fruit. This is why it is always important to note when flowering ends for species that you observe for Budburst. Flowering time is a critical factor in helping scientists better understand how plants are adapting to climate change and environmental change in general.

This summer monsoonal rains have been so intense and frequent in Colorado that in some towns local residents are using 30% less water than in a normal year. This is also the first major break from a 10 or 11 year drought cycle in many parts of the region. So the summer rains are another key explanation for the spectacular wildflowers we are seeing, especially at lower elevations.

Of course the other general consequence of cool wet weather in a climate that is normally dry, is large amounts of lush vegetation. Grasslands that normally would be brown and dormant are now alive with many wildflowers and tall lush green grasses. So it should not be any surprise that this is also an epic year for grasshoppers. Just today walking through a local prairie, there was a constant noise of grasshoppers landing on grasses all along my hike.

So if you have a chance to get up to these mountains, this is the year to see them. You might as well bring your camera and contribute occasional observer observations on them for Budburst too!

Photos: Paul Alaback.

Top: lush low elevation meadow near Rocky Mountain National Park a few weeks ago.

Middle: mid afternoon monsoonal* storm in low elevation grassland near Berthoud, Colorado

Bottom: grasshopper nymph on old sunflower seedhead in a prairie open space preserve near Loveland, Colorado.

*These storms are called monsoonal since they occur in the middle of the summer and are connected with patterns of flow of humid tropical air from the Gulf of Mexico. This is a key factor of the climate of the southern Rockies.


  1. Paul: Thanks for the excellent ecological background on what so many of us are observing this year--from the hillsides covered in arrowleaf balsamroots on Mt Jumbo in late May---more blooms than we can ever remember--to the higher elevation bonanza of wildflowers now. interesting questions about pollinators (seeing so many butterflies and bees this year too!).

    In some places, it seems like there are wildflowers blooming where we haven't noticed them in the past--anecdotal for my part but I'm sure the good journal keepers could comment on this. I'm wondering if seeds have remained underground for several years just waiting for this right combination of moisture, cool spring and warm summer--then they germinate and grow and flower? What have you noticed, Paul?

    In Death Valley, I know this applies for annuals--see this link:

  2. Great point about flowers coming up only when conditions are perfect like this year. It is well established that some plants in the Rockies (usually with very tough seed coats) can survive for decades in the soil, then they emerge when there is an intense wildfire. The other possibility is that seeds may be short-lived but are well dispersed and only emerge when conditions are right. Sounds like this could be an interesting new study to work on!

  3. Great blog post Paul! So interesting to think about whether or not hybridizing increases in years where Vaccinium bloom together in the Alaska alpine...