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MONOCULTURE PLANTING SURE SETUP FOR DISAPPOINTMENT
We set ourselves up for disappointment when we fill our spaces with just one species or variety of plant.
I got to thinking about this the other day as I read a newspaper article about a re-forestation program in China that involved planting 43 billion (that's billion with a B) poplar trees since 1982.
On a trip to China in 2000 I remember seeing poplars growing everywhere in cities and rural areas but I had no idea of the scale of the project. 43 billion!
Over the years, I have received numerous phone calls from frantic landowners who had planted dozens or hundreds of just Colorado blue spruce and now these non-native evergreens were suffering from common fungal diseases.
I wrote recently about the sad plight of Minnesota's once-majestic monoculture of American elms as they succumbed to Dutch elm disease.
Recent headlines have warned of Sudden Oak Death, a severe fungal disease that is devastating California oak trees. Experts say it is a matter of when, not if, SOD will arrive in Minnesota. At this juncture, it appears that SOD primarily affects red oaks and is not a significant threat to bur and white oaks.
Another pest working its way towards Minnesota is the emerald ash borer, a nasty wood-boring beetle that attacks and kills all species of ash. Emerald ash borers arrived from Southeast Asia and are ravaging ash trees in southern Michigan and Ohio.
It's the old "putting all your eggs in one basket" risk metaphor -- gamble on just one species of plant and sooner or later a disease or insect will discover your susceptible or scrumptious crop and wipe it out.
A monoculture led to one of the most infamous famines in history, the Irish Potato Famine of the 1840s. For 200 years, millions of low-income Irish people grew only potatoes because potatoes required only minimal labor to grow and produced more calories per acre than any other crop. By relying on a single crop, they left themselves open to crop failure caused by pests, disease or adverse climate conditions.
In 1845, a fungus that arrived accidentally from North America caused potatoes to rot in the fields. With no surplus and no income, the people had no money to buy seed to start new crops.
From 1845 to 1847, the Irish potato crop dwindled from two million acres to 300,000; half a million people were evicted from their homes; and one and a half million people emigrated to America. Ireland's population dropped from eight million to five million due to famine, disease and emigration. If the Irish had included squash and sweet potatoes in a crop rotation, a famine would most likely have been avoided.
In U.S. agriculture, monocultures had a high price tag during the 20th century. The Southern Corn Leaf Blight epidemic in the early 1970s was a strong signal of how a monoculture can jeopardize the stability of our food system. Decades earlier, monoculture cotton hopelessly depleted the fertility of millions of acres across the Delta and Southeast. In the Red River Valley, sunflowers suffered from diseases and insects that wouldn't have gained a foothold if farmers had practiced more crop rotation. And of course, the current dominance of corn and soybeans makes these crops extremely vulnerable to weeds, diseases and insects.
Failed gardens and woodlots don't have the economic consequences of failed farm crops. Don't expect, however, that this argument will make a gardener feel better when his or her trees have all died or when dozens of a single variety of tomato drop all their leaves from blight.
The alternative to monoculture planting is diversity and crop rotation.
In a new-home landscape, instead of planting six green-ash trees, choose one ash and an assortment of other hardwood trees. Instead of planting a row of disease-prone spruce, choose conifers that are less susceptible to fungal diseases.
Monocultures in the vegetable garden should also be avoided. Jackie Smith, a veteran Master Gardener, recommends practicing inter-cropping -- the process of mixing plants of complementing needs (radish with carrot, lettuce with tomatoes, melons and potatoes, etc.). "This often works to confuse pest insects," she says, adding that it also makes it difficult for insects to simply move straight down a row of plants laying eggs on each one!
Smith suggests several clever ways to thwart plant diseases in the vegetable garden. Instead of planting a 30-foot row of a single variety of bush beans, divide the row into segments with five feet each of six varieties. Or, instead of 12 plants of the same variety of tomato, try two each of six varieties or, better yet, 12 completely different varieties. "Not only will disease resistance vary, you will have a much more varied and pleasing harvest with lots of new flavors and colors to sample," she says.
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PUTTING DOWN ROOTS:
A Delightful Blend of
Gardening Wisdom, Wit
and Whimsy
$10 + $2 for shipping
by Cliff Johnson |
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