Monday, February 23, 2009

Benefits of Indoor Plants

The benefits of gardening are not limited to the beauty and productivity of an outdoor garden. Indoor garden plants have long been known to have positive effects on the mental and physical health of office workers. Specifically, a 1998 study by researchers in Norway revealed that workers in offices complained less about fatigue (reduced by 30%) and cough (reduced by 37%), and reported lower levels of throat and skin discomfort (reduced by 23%) relative to workers in offices without plants.

Now, a group of Korean researchers may have identified a mechanism for these positive benefits of indoor plants. (Kwang et al. 2008. Efficiency of Volatile Formaldehyde Removal by Indoor Plants: Contribution of Aerial Plant Parts versus the Root Zone. Horticultural Science 133: 479-627.)

Researchers from Korea's National Horticultural Research Institute examined the ability of Ficus benjamina and Fatsia japonica to absorb formaldehyde from the air. To study this, the researchers pumped formaldehyde into a container that held one of the two plants, or into a container that was empty. On average, containers with plants removed 80% of the formaldehyde from the air in only 4 hours. Containers without plants lost only 7% of the formaldehyde in 5 hours. Plant leaves reduced more formaldehyde during the day, while roots of reduced more formaldehyde at night. This suggests that formaldehyde is taken in through plant stomates during the day, when rates of photosynthesis are highest. The night removal of formaldehyde by the root zone suggests that soil microbes play an important role in formaldehyde removal.

Formaldehyde is a common household VOC (volatile organic compound) that is known to have negative effects on human health. In fact, VOC's, including formaldehyde, have been linked to 'sick building syndrome'.

What is the bottom line for the home gardener, or the party guest who is looking for a suitable hostess gift? Indoor plants will reap multiple benefits, not the least of which is better air quality, for the gardener or the gift recipient.

Wednesday, February 18, 2009

Landscaping with Native Plants

If you attended the 2008 Master Gardener Mini-College, perhaps you heard Doug Tallamy speak about the importance of native plants to the conservation of bird and insect species. A seminal paper, which provides data in support of Tallamy's arguments, was recently published in Conservation Biology (Burghardt, Tallamy and Shriver. 2009. Impact of native plants on bird and butterfly biodiversity in suburban landscapes. Conserv Biol. 1:219-24).

Burghardt and colleagues measured the diversity of birds and caterpillars (which are, of course, the larval or juvenille form of butterflies) in 12 suburban yards in Pennsylvania. Six yards were landscaped almost exclusively with native plants (43% native and 6% exotic plant cover), and the other six were landscaped with exotic shrubs and groundcovers (although, native trees were present on these properties; 18% native and 26% exotic plant cover).

The abundance of caterpillars (the larvae of butterflies and moths) was 4 times greater on the 'native sites', relative to the 'exotic' sites. In addition, the number of different species represented by these caterpillars was 3 times greater on the 'native' sites, relative to the 'exotic' sites. Approximately 19 species of bird were found at the native sites, compared to 11 species at the 'exotic' sites. Mean abundance of birds at the 'native' sites was 17, compared to 11 birds at the 'exotic' sites.

Why do yards landscaped with native plants contain a greater abundance and diversity of birds and butterfly larvae? Burghardt and colleagues hypothesize that greater food availability for caterpillars at 'native' sites creates greater food availability for birds at such sites. Because many plant feeding insects can not feed exotic plants, and because many birds rely upon insect protein (rather than seed protein) to rear their young, planting native plants seems to cascade up the food chain - fostering an increase in abundance and diversity of plant feeding insects, which in turn fosters an increase in abundance and diversity of insect-feeding birds.

What does this mean for the home gardener? A yard landscaped with native plants can be beautiful, may reduce your fertilizer and water use (if you zone your plants accordingly, and if the natives are adapted to your soils), and can help to conserve biodiversity in your area.

For more on native plant gardening, please visit the Eco-Gardening website created by OSU Extension's Linda McMahan.

Monday, February 16, 2009

Happy President's Day

In honor of President's Day, I thought I would take a few moments to honor some of our past presidents, who were also prolific gardeners.

Topping this last has to be the first President of the United States of America (one of my personal heros, for the way that he so selflessly stepped away from power, despite the protests of many compatriots). George Washington farmed at his Mount Vernon estate, where he overcame the poor soils by practicing a relatively novel plan of crop rotations. When he abandoned tobacco farming in about 1765, he switched to wheat and at least 60 other field crops.

Of course, we can not forget Thomas Jefferson, who grew more than 170 varieties of fruit and 330 varieties of vegetables in the gardens at his Monticello estate, and had a special interest in the pea plant. In fact, Jefferson cultivated over 22 varieties of pea. Following the expedition of Lewis and Clark, Jefferson developed a curiosity about the plants of North America, and how they could be used for practical purposes.

In 1825 John Quincy Adams developed the first flower garden at the White House. Adams also planted herbs and vegetables at the White House, as well as ornamental trees.

In 1835, Andrew Jackson established a White House orangery (a type of greenhouse) where tropical trees and flowers could be grown. Jackson also added the Jackson magnolia to the White House grounds. The orangery was demolished in 1857. In 1878, Rutherford B. Hayes started the tradition of planting commemorative trees for Presidential Inaugurations - a tradition that persists today.

As for First Ladies - Eleanor Roosevelt famously began the Victory Garden movement in 1943, when she planted a vegetable garden on the lawn of the White House and Lady Bird Johnson has long been associated with efforts to conserve native plants.

Today, Roger Doiron of Kitchen Gardeners International is helping to lead a campaign to re-establish a Victory Garden on the lawn of the White House.

Happy President's Day!