Sunday, July 31, 2016

Spreading Dogbane: Weed or Wildflower? By Vicki Barney

I inherited an interesting garden with a house purchased a few years ago.  It was a cottage style garden planted with an abundance of bearded iris, hostas, and vinca, along with specimen perennials and flowering trees.   In an effort to encourage new growth between the existing plants, I removed weed barrier fabric from beneath a heavy layer of mulch, and then waited to see what plants would emerge from the bare soil.  Would seeds sprout from native wildflowers growing close by? Would weeds take over? More importantly, would I be able to distinguish between weeds and wildflowers?

In David Whiting’s The Science of Gardening, landscape weeds have many definitions, including: plants growing where they are unwanted, visually unattractive plants, plants that pose a health or safety hazard, and plants that displace more desirable plants in the garden.  The following spring, a variety of plants emerged, as well as numerous weeds.  I identified the first two types of weeds and sought professional help with the other types from botanist Karen Vail.  She identified my plants, pointing out native versus nonnative plants.  Then, except for one truly invasive cultivar, she left it to me to conclude whether I wanted to consider the remaining plants weeds or wildflowers. I chose the prettiest and hardiest looking native plant to investigate first: spreading dogbane.

Spreading dogbane (Apocynum androsaemifolium) is a bushy perennial that grows up to 2 feet tall and has opposite, oval leaves on reddish stems.  It produces small bell-shaped slightly pink flowers that flower for several weeks in the summer and is native to most of the US.   It exudes a slight lilac scent and produces a milky sap when a stem is broken.  This sap and the root contain toxic substances that Native Americans used for medicinal purposes.  Related to milkweeds, dogbane was once thought to be a host plant to monarch butterflies.  It supports bees and other beneficial insects and attracts a variety of butterflies to the garden.

Although pretty and growing in the right places in my garden, spreading dogbane’s toxicity might be a health hazard, and therefore might classify it as a weed.   Its common name means “poisonous to dogs” and the translation of its genus Apocynum is “Away dog!”   The milky sap contains a chemical that is toxic to dogs as well as to livestock and other humans, and it can cause blisters on the skin.  Its roots are also toxic.  Fortunately, I am not sensitive to the sap, and my dog (who does not dig but loves to eat grass) has no interest in eating the plant.  “Health hazard” can be ruled out.

Spreading dogbane might also be labeled a weed if it spreads too aggressively from its underground rhizomes. It is considered a nuisance weed in some parts of the US, where it successfully outcompetes with other plants.   It will thrive in both sun and shade and will grow in a variety of habitats.  I may find it grows too aggressively in my garden, but so far, it is nicely filling in the empty spaces.

Weed or wildflower?  For now, I am classifying spreading dogbane a wildflower. I like that it is a pretty native that attracts pollinators, and it is easy to pull when I see it crowding another plant.  And because it is a native plant and not a noxious weed, I get to choose on the matter. As a bonus, its leaves turn a bright yellow in the fall, providing visual interest in my garden for several months.
A long time Steamboat resident and casual gardener, Vicky Barney is a member of the Master Gardener Class of 2011.

Thursday, July 28, 2016

Monsoons by Irene Shonle

If you haven’t lived in Colorado or the Southwest for very long, you may think that monsoons only occur in India or tropical areas.  And even through the late 1970s, there was serious debate about whether a monsoon truly existed in North America. But we do have actual monsoons here -- they are defined as large-scale wind and rainfall shifts in the summer.

The monsoons bring beneficial summer moisture to the Southwestern states. We count on the monsoons to arrive sometime in early-mid July here in the mountains, relying on the cooling clouds building in the afternoons, and the brief or torrential rains to water our gardens and wildflowers.  But, the monsoons have a dark side to them as well, bringing dangerous lightning and the potential for flash floods.  And this year, the monsoons have been late to the table, and have not brought that much rain (at least so far to Gilpin County).

How do monsoons work? As the summer heats up, the land warms faster than the Pacific Ocean. This temperature imbalance becomes large enough that a change in the high and low altitude atmospheric movement occurs.  The warm land creates low-pressure zones as hot air rises. Once this pattern establishes across the region, the winds shift to fill in the vacuum,  carrying with them moisture from the Gulf of Mexico.

The monsoon is variable – in timing, the amount of rain, and the amount of lightning.  Long-term monsoon researchers have found, though, that the overall character of the monsoon has not changed in the past 100 years, according to Eric Pytlak, Science and Operations Manager at the National Weather Service in Tucson.

Some things that can cause a stronger monsoon season include a La Niña event (it brings increases in easterly air flow which tends to bring more moisture from the Gulf of Mexico). An active Madden-Julian Oscillation (MJO) in the tropical Pacific Ocean can also increase the strength of the monsoons.
Two factors causing a weakened monsoon include cooler temperatures in the Midwest and an above-average snowpack in the Rocky Mountains.  This year (2016), we are in an El Niño cycle, and had an above-average snowpack, so perhaps these have contributed to our lack of rains (so far).

The role of climate change on the strength of the future monsoons is unclear. The best educated guesses come from 19 general circulation models, or GCMs, used in the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. Only two of the models simulate monsoon precipitation, and one predicts an increase in future rains while the other predicts a decrease. The model that shows an increase in activity factors heavily on the likely increase in the temperature differential between the land and the Pacific ocean. For the model with suppressed monsoon activity, the higher air temperature is thought to increase the dew point, causing less likelihood of rain. Joellen Russell, assistant professor of biochemical dynamics at The University of Arizona says that she bets that the monsoon will strengthen (in other words, she believes the first model more).  But, it may take years to understand the links between increasing global temperatures and the monsoon activity.

Monday, July 18, 2016

Spirea in the Garden by Vicki Barney

I have several plants hiding in plain sight.  Landscaped by the previous owner, my yard has a variety of cultivars tucked into inconspicuous places: hugging a wall, behind a showy perennial, hiding under bushes, and the like.  A white flowering spirea bush is one of them.

Spirea plants (genus Spiraea), part of the Rosaceae family, are deciduous shrubs of various sizes.  They are low maintenance, hardy, prolific bloomers and are a great addition to any garden.  Some species bloom in the spring, others in summer, and the showy tiny flowers grow in clusters along woody stems.  Flower colors may be pink, red, yellow, or white, depending on the variety.  Most varieties tolerate poor soil, need a lot of sun, like to have room to spread out, and do not like wet feet. While they are not classified as xeric, they can manage with little water once established.  Their flowers are more prolific, however, with regular summer watering, and mulch around the plants help retain moisture.

As for plant selection, cultivated varieties are numerous, the species being a horticultural favorite for generations.  The small (2-3 ft) pink flowering varieties of s. japonica are popular, as is the large bridal wreath species (s. prunifolia) which may grow up to 10 feet tall (take note that these two species may not be hardy above 7,500’).   The native spirea (holodiscus dumosus), called rock-spirea or mountainspray, has white flowers and is a good choice for a natural landscape.  The Blue Mist Spirea is another popular plant but, do not be confused, it is a spirea in name only and is a cultivar in the genus caryopteris, part of the Lamiaceae family.

While spirea is low maintenance, it benefits from annual pruning.  Spring bloomers like s. prunifolia should be pruned after flowering as they bloom on old wood.  Pruning helps them keep their shape and size, and cutting out the oldest stems prevents them from becoming woody and unproductive.  For summer bloomers (like varieties of s. japonica), recommended pruning time is early spring, after allowing the larger plant to have a mound of protection through the winter. Pruning a plant in half in early spring will result in a more compact shrub with abundant flowers on new wood.
Best of all, spirea appears to be unappetizing to wildlife.  My garden is visited by both deer and moose and, while they nibble on the red osier dogwood, the pansies, and the daylilies, they leave the spirea alone.   It must not taste very good.

My white flowering spirea is a mystery variety that blooms in the spring.   Parts of the bush look quite healthy but other parts are woody and produce no flowers.  As a spring bloomer, it will benefit from pruning after it finishes flowering, to improve its shape and to remove old woody stems.  It may also benefit from a bit more water in the driest part of the summer, but I will be careful with the water to be sure it does not get too wet or grow too large in its location next to the wall.  Now that I have noticed it, I like how it hides in plain sight.

A long time Steamboat resident and casual gardener, Vicky Barney is a member of the Master Gardener Class of 2011.