What do the Emerald Ash Bore, Dutch Elm Disease, and the Irish Potato Famine have in common? They’re all tragedies that occurred for want of biodiversity.
“Biodiversity – the variety of life in the world or in a particular habitat or ecosystem.” – Google
What’s the 30-20-10 Rule?
Simply put, it’s a planting guideline. Over the last century, the United States has faced 2 tree diseases with serious economic impact. Ever heard of Dutch Elm Disease? My relatives have vivid memories of walking down shady city streets lined with majestic Elm trees growing up – they were everywhere! But somewhere between the 1940s-60s, the fungus Ophiostoma novo-ulmi, spread by the Elm Bark Beetle, began to move through the stands of Elms, devastating their populations across the country. By creating high density plantings of a single plant type, such as a city full of almost nothing but Elms, humans are creating ideal conditions for pest and pathogen populations to boom. Think of it like providing an all-you-can-eat buffet for your least favorite relatives… indefinitely.
The 30-20-10 Rule is a common sense planting rule that effectively limits unchecked disease outbreaks and severe economic losses to disease by recreating the biodiversity seen in Nature. Now considered an industry standard in responsible landscape planning and management, this rule recommends that:
30% of trees or less be from the same family
20% of trees or less be of the same genus
10% of trees or less be from the same species
Most pests and diseases have evolved around a few key hosts, so by planting a wider range of trees (and everything else), you can limit the amount of damage done to your property, or pocketbook, by any one alone.
To implement the rule effectively, take some time to study the growing conditions of the area you’d like to plant in. Each area of the yard will have slightly different moisture, light, and soil conditions among others. By knowing what conditions you have to work with, you can narrow your tree selections down to a less intimidating ‘short list’ with the added benefit of having confidence that your investment will grow well in your yard.
Next, compare your short list to the plants you see in your neighborhood – the 30, 20, 10 rule doesn’t just apply to your property boundaries; if all of your surrounding neighbors have ash or maple trees, it’s a good idea to consider not planting them. Or at least, planting fewer!
Finally, consider contacting your local university extension office to learn if there are any trees they don’t recommend planting. When it comes to plant problems that are in or heading towards your area, they’re the best source of information!
Regardless of your overall goals, these vendors have a variety of quality stock and extensive knowledge to back up their recommendations. Happy Plantings!