Compost tea, you say? As a Baby Boomer from the 60's and 70's, I clearly remember being fascinated by organic gardening wanting a victory garden of my own. The idea of brewing compost teas was pretty cool back then, but I did not have the means to make my own. Today as an arborist and horticulturist, I am delighted to share that organic methods are entering the limelight in the world of tree and shrub care. And that includes compost teas…for the trees.

We now know that soils consist of an important organic layer located in the top few inches of the soil. Most tree roots can be found in the top 6-10 inches of the soil and will extend two or three times beyond the drip line (or tree canopy) than ever thought. Our urban soils are void of this organic layer especially in areas where top soils are removed in order to have a firm foundation on which to build a house. Landscape plants that include trees, shrubs, and groundcovers need this organic layer to be present in order to sustain healthy root systems. We can import compost and top soil to the landscape but still have to build a layer that will support an incredible biological network of microbes, fungi, protozoa and earthworms. Without this living soil web, our plants simply cannot flourish. So why not just add compost to the soil?

Not just any old compost will do. Compost that favors a fungal environment is preferred by trees; a bacterial compost will be preferred more by growing turf grasses. The brewing process extracts beneficial fungi & bacteria, nutrients, and microbes that can be used more readily.

Turf grass benefits from this organic layer by manufacturing an environment in the roots that is bacterial in nature. In contrast, trees growing in healthy forest soils produce a root environment that is fungal in nature. There is a balance that must be present for either turf or tree ecosystems to thrive. By introducing a living brew either fungal or bacterial in nature and applying it in soils void of these components, we begin to create the soil environment that can sustain itself.

These living brews can also be prescriptive by the addition of beneficial nematodes to target certain problems. Benefits of using compost teas in your landscape include disease suppression, healthier soils that sustain your plants' growth, thereby reducing the need for regular pesticides. Landscapes that have a history of no pesticide use and organic methods have higher soil fertility and healthier plant growth.

Organic programs are labor intensive at first, but as soil fertility is brought to a healthy balance of fungi to bacteria present in soil, the frequency of applications is often reduced. A biological soil test is used to provide a baseline measurement of the soils' fertility. This test is different from standard soil tests in that they measure living organisms such as bacteria, fungi, protozoa, nematodes, earthworms and other similar organisms. The perishable brews must be applied 24-48 hours from when they are brewed.

Local trees that have benefited from local tree tea parties hosted by The Care of Trees, include a large 3 trunk hemlock located near the corner of Madison and Federal streets in Middleburg at the former location of the Black Coffee Bistro. This hemlock, once plagued by insect problems, construction impacts and drought, was pale green about 2 years ago. After two years of tea applications, the tree has a lush green color. Hemlocks require the highest fungal to bacterial ratio of any tree species. The trees at the Leesburg Courthouse are also recipients of this tea program. The next time you drive through Middleburg or Leesburg, have a look at these lovely native trees.

The latest active research on this subject has been done by Dr. Elaine Ingram, founder of Soilfoodweb, Inc. in Corvallis, Oregon. More information on the use of compost teas and soil biology can be found on her website: www.soilfoodweb.com

When combined with cultural practices such as proper tree selection, planting, correct mulch practices (remember, no "mulch volcanos"), compost teas can give your trees the party they deserve. We must be responsible stewards of the land and that includes the care of our urban landscapes. Further information on accepted gardening practices can be found at your local Cooperative Extension office.

Bonnie Deahl is a Certified Arborist for The Care of Trees. For more information on SoilCare contact The Care of Trees: 703.661.1700 or 540.687.6800. Website: www.thecareoftrees.com