The World Beneath Your Feet (Part II): A Tale of Three Soils
Emily Ellis
As we settle into the winter months, the gardens at Oak Spring take on a different kind of beauty. When the lush and vibrant plant life we enjoy the rest of the year is absent, we are able to clearly see the soil that is the backbone of the garden.
The gardeners and growers of the past were unaware that soil is, essentially, a living thing, and only recently have we begun to recognize the complex, invisible world beneath the surface and its connection to a healthy environment. Although Oak Spring’s walled garden and its surrounding areas are relatively small, the soil can vary significantly. (To read about soil management at the Biocultural Conservation Farm and other parts of the property, see our World Soil Day post from last year).
A major, ongoing project for the gardening team has been improving soil health throughout the garden, for the long-term benefit of the plants and the local ecosystem. However, their management strategies can be very different depending on where they are working - even in beds separated by a mere few feet of gravel path.
In honor of last week’s World Soil Day, we’re publishing a second blogpost about soil in the formal garden. Scroll down to read the tales of three different soils, and how they are cared for.
Walled Garden
The lime from these white-washed walls changes the soil PH in the formal garden, allowing Oak Spring’s to grow plants that typically would'n’t do well in the Virginia piedmont.
Oak Spring’s walled garden encloses only half an acre, yet its soil is very different from the rest of the property. Its beautiful white walls, decked with espaliered fruit trees and climbing roses, have been washed with lime for decades, which leeches down into the soil and significantly increases the PH levels in the beds. Many of them clock in at around an 8 or 8.5 PH level, which is quite alkaline for a part of the country that typically sees a lot of rainfall. This means that the types of plants that normally wouldn’t grow well in the Virginia piedmont, such as delphiniums, are able to thrive in the walled garden.
Identifying such unique soil characteristics is a good way to determine what plants will do best in your garden, as well as the degree of amending your soil may need. Oak Spring’s gardening team frequently tests the soil in the walled garden as part of their management strategy. As an ornamental garden that sees frequent digging and planting, its soil requires careful monitoring to ensure that it stays healthy despite disturbances.
Improving structure and the presence of beneficial micro and macro organisms is another aspect of soil management at Oak Spring. Because the walled garden, at over half a century old, had seen many years of near constant tilling and fertilization, the soil had poor water retention and an absence of organic matter until recently. Over the past two years, the team has been working hard to revitalize it through organic practices that include the application of Karbon Mulch - an attractive, high-quality ground leaf mulch that is heated to kill off bacteria or pests, such as the fungus that causes Boxwood blight - and by increasing the number of perennial plants grown in the garden, which gives the soil a chance to rest and build up its own ecology naturally. While improving soil health is an ongoing task, there has already been a marked increase in the presence of beneficial organisms such as earthworms and spiders - always a sign of happy and healthy dirt.
Potager Garden
The soil in Oak Spring’s potager garden - a space inside the walled garden designated for beautiful vegetables, herbs, and fruits - is different from the rest of the walled garden. Because it is set away from the lime-washed walls, its PH level is at 6.5 or 7, closer to the norm for native soils in this area.
Oak Spring’s potager garden from this spring. Photo by Jordan Long.
The food crops in the potager garden are planted for aesthetic purposes, and are allowed to grow longer than they would in a production garden. However, as many vegetables are annuals that need to be removed and replaced every year, the potager garden is disturbed frequently and requires thoughtful management. For instance, one practice the team has implemented is leaving the roots of the vegetables in the soil for a few months instead of digging up the entire plant, allowing them to decay and improve the soil structure. To learn more about the soil in the potager garden and how it is cared for, check out this informative essay from assistant gardener Jordan Long.
Spillway Garden
Just a short jaunt from the walled garden is the spillway that connects the Spring House Pond with the Tree Shop Pond. Last year, the gardening team planted an array of native flowers alongside it in order to beautify the space and provide a banquet for local pollinators. Although the soil required some initial rehab, it is now a largely hands-off space - a contrast to the high-maintenance dirt within the walled garden.
This soil - which began as hard-packed clay with fescue grass - required tilling and the application of compost before it was ready for flowers. The plants the gardening team chose were native species such as black-eyed Susans and asters, all of which are accustomed to with the soil and climate of the Virginia piedmont and likely to thrive in that particular spot. As these plants are never removed, the soil was allowed to rest and build a healthy structure in a natural way.
Now that the spillway garden is established, the gardening team has little to do besides cutting it back and applying mulch once a year. Leaving the plants alone through the winter allows decaying debris to break down and feed beneficial microorganisms, as well as providing shelter for overwintering native insect populations. This healthy soil will release a gorgeous flush of flowers every year with little help from humans, making it the perfect type of garden for the busy plant-lover.
Why Soil Matters
While building up healthy soil can be a long process, it’s essential to the lives of many different organisms, from unseen beneficial bacteria to the songbirds that feed on worms and spiders. Quality soil is at the core of a complex, healthy and sustainable ecosystem - and will support healthier and more beautiful plants once established.
If you’re a beginning gardener, learning about the soil you have to work with - and how you can improve it - is a great place to start. Many native plant societies have great resources and are very familiar with local soil, and books by ecological landscapers such as Larry Weaner and Doug Tallamy provide a lot of wonderful information as well. Happy gardening!
Thanks to Judy Zatsick and Jordan Long for their help with this blogpost!