Winning the battle of the weeds
Surely weeds are some of nature’s greatest opportunists.
They appear spontaneously in places where other plants would not stand a chance, such as in disturbed soil or along the dry salty edges of Vermont’s beloved dirt roads.
And in our gardens? Within weeks of making our beds all tidy and seemingly weed-free, new weeds just pop up uninvited!
How does this happen?
First, it is helpful to understand that many weed SEEDS can lie dormant in the dark earth for a long time — 10 years or longer in some cases. As soon as we dig in the soil, some of those seeds are exposed to light — a condition all young plants need to grow — which causes those cunning seeds to germinate.
Secondly, when the conditions are favorable, the ROOTS of many perennial weeds are able to spontaneously regrow from a joint or node. And additional light favors this process also.
THE CYCLE OF WEEDS
The sad fact is that many aspects of normal gardening inevitably perpetuate the cycle of weeds.
For instance, as we fluff up the soil in preparation for a new row of vegetable seeds or we break up clods of earth before planting a new perennial bed, we unavoidably churn up the soil. And thus some of those dormant weed seeds and weed root fragments finish up near the surface of the soil, where they promptly respond to the added light by cheerily sprouting.
And, as we cultivate around established flowers and vegetables, it will not take long for persistent weeds with filamentous roots — like sorrel and bishop’s weed — to begin to regrow. Also, as everyone knows, when you break off the tap root of a dandelion in the middle, rather than getting the whole thing out, it too will grow back into a new dandelion plant.
So before planting it is really important to manually remove as many perennial weed roots as possible. I am always on the lookout for telltale problem roots — especially those filamentous roots that run horizontally through the soil — and try to follow them back to their origin.
But to prevent surface weed seeds from germinating and the remaining weed roots from re-sprouting, we need to cover the ground and shade the soil from light.
Let’s take a look at three easy ways to cover the ground and deter those weeds.
Tarps are inexpensive and durable, and I use them to cover any section of my vegetable garden that is temporarily empty.
My vegetable garden consists of four 12-foot square beds and every year I rotate the crops around the squares. Each year, one square will be devoted to sprawling winter squash while in the remaining three squares I use three-foot wide rows separated by narrow paths for individual crops.
During the summer, after I harvest an early crop like garlic, I cover the empty row with a 12-foot by 4-foot tarp (sold to cover wood piles) until I get around to planting some late season peas or greens.
And every fall, after the harvest is complete, I cover each square with a pair of overlapping 12-foot by 8-foot tarps. These remain in place until next season when I am ready to plant that particular square. This strategy prevents those opportunistic weeds from getting a head start in spring and it also warms the soil ahead of planting.
Everybody knows about mulch, and indeed sometimes we see way too much of it.
A sea of mulch separating a few paltry perennials looks anything but natural. And those “mulch volcanoes” that get heaped up around the base of trees are positively harmful. They provide a winter haven for rodents who enjoy nibbling the bark. And if they are mounded up over the root flare, it stimulates the tree to produce girdling roots at the surface. These eventually encircle the entire trunk which strangles the tree.
But, if used in moderation, mulch has a role in every garden. For instance in a new flower bed it is critical to shade the soil to prevent those weed seeds from germinating. I like to start by covering the soil with about six layers of overlapping newspaper to keep out the light. In my flower gardens I will top off the newspaper with a thin layer of finely ground bark mulch (one to two inches is plenty), whereas in my vegetable garden I cover the newspaper with fluffed up hay.
You need less mulch as the garden matures, but a small amount is often a great way to show off special plants or garden features.
GROUND COVERING PLANTS
The final way to deter the weeds is to use the plants themselves to shade your soil.
A carpet of groundcover around the trees and shrubs is an attractive addition (and is less work than replenishing the mulch annually). Barren Strawberry (Waldsteinia ternata), Barrenwort (Epimedium), Deadnettle (Lamium maculatum) and various types of Hardy Geranium including Geranium “Biokova” and Geranium macrorrhizum are all well-behaved ground covers.
Also I like to position my perennials so that, as they mature, their leaves overlap to naturally shade the soil. For instance, the leaves of a single daylily plant can easily grow into a three foot circle and very little light reaches the soil beneath it. So, in a sunny border, a group of three or five daylilies becomes completely self mulching. Similarly in a shady bed, large leaved hostas and dense ferns perform the same function.
PUTTING IT ALL TOGETHER
This picture of the bed that surrounds our gazebo illustrates these ideas.
A narrow ribbon of mulch not only deters the weeds but also draws attention to the stepping stone path that meanders through the bed. The remainder of the soil is naturally shaded by groups of taller plants including daylilies and azaleas and some low-growing geranium and sedum. And finally, a small amount of mulch serves to visually separate the main plant groups from their neighbors.
Judith Irven and Dick Conrad live in Goshen where together they nurture a large garden. Judith is a Vermont Certified Horticulturist and teaches Sustainable Home Landscaping for the Vermont Master Gardener program. You can subscribe to her blog about her Vermont gardening life at www.northcountryreflections.com. Dick is a landscape and garden photographer; you can see more of his photographs at northcountryimpressions.
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