However, we prefer to use as little as possible, and in place of mulch we use plants when we can. There is not always a plant for some spots, and there are places we like to keep a little tidier, so we turn to wood mulches.
In Parts One and Two of this series, we discussed the benefits of living or green mulch, in place of traditional wood mulch. This may seem like an easy process, but a living landscape takes time, care, and patience. In many cases, a green mulch will not fill in for 3 to 5 years (depending on species and plant spacing). Wood mulch is very useful during this transition time.
What does mulch do?
Wood mulches, if used properly, provide nutrients, moisture conservation, and weed suppression. The mulch you choose should be of high quality. Low quality mulches often have weed seeds and artillery fungus spores, which can leave black spots on building siding and sidewalks. By applying a light layer (2-3 inches) of high-quality mulch between newly planted trees, shrubs, and perennials, you can reduce the amount of watering necessary to sustain the fresh planting. It also helps with weed suppression.
In our display gardens, we often mulch around edges to give the garden a distinguished look. Mulches are also useful for maintaining walking paths, covering soil in bare-spots, or around garden décor and accents that may be lost among taller plants.
What kind of mulch to use?
We carry three varieties of high-quality mulch: bagged & shredded pine bark, bulk cedar chips, and bulk hardwood mulch. Avoid dyed mulches and mulch from shredded pallets, as these do not offer the same moisture retentive properties as shredded wood.
Be careful not to use TOO MUCH mulch!
Even if your mulch is high quality, too much is still not good! Beneficial bacteria and fungi utilize nitrogen to break down mulch. If you apply too much mulch, the population of these microorganisms soars, robbing nitrogen from the soil, and making it unavailable to your plants.
With a light layer of mulch, nitrogen leaching is a temporary concern and often not a concern at all. With a thick layer of mulch and sparsely spaced plants, you almost always will have a nitrogen issue. Plants “stuck” in these mulch deserts often show signs of nitrogen deficiency by turning yellow or having stunted growth. In addition, roots in search of oxygen and water sometimes grow into excess mulch. During dry periods the mulch will dry out and the roots will have no moisture. Another danger of a lot of mulch is that a light watering may only wet the mulch and the soil will remain dry.
Some other side effects of too much mulch include:
• Mulch piled up against the trunks of trees and shrubs creates decay and an entry point for diseases and insects. Pull back the mulch about 3 inches so it does not touch the bark.
• Too much mulch may delay the onset of dormancy in the fall by keeping root zone temperatures warm. It also can delay the breaking of dormancy in the spring due to cooler root zone temperatures.
The Process of Establishing a New “Mulch-less” Garden
Step One – Choose Your Plants
Perennials have limited bloom times, so pay attention to foliage, texture, and the plant’s appearance during its entire life cycle. For example, Virginia bluebells can create a lovely, colorful groundcover. But by early summer, the foliage begins to yellow, and by mid-summer they are completely dormant underground.
Choose plants with different bloom times, and intermix with foliage plants, such as sedges. Any plant with persistent foliage all season could be considered a foliage plant, it does not have to be something with particularly “interesting” foliage. With a variety of plants, the contrasting leaf shapes, textures, and tones will provide plenty of interest, as well as build a nice habitat for beneficial insects and other desirable garden critters.
Step Two – Place Your Specimen Plants
Specimen plants are those plants you wish to stand out and make a statement; they are often larger, colorful perennials, shrubs, or small trees. Place them in a way that is pleasing to you. There is no magic right or wrong. Put them where you can see them from a window, or where you will see them as you drive in the driveway at the end of the day, or where you can enjoy them from your porch. The choice is up to you and your preferences and what delights you in the landscape.
Step Three – Place Your Non-Living Things
Once your garden space is full of shrubs, trees, and or larger perennials, determine what non-plant things you may want to add to your garden, such as decorative rocks or logs. Place these items in their desired locations; consider partially burying some large rocks to create variability and depth in your space.
Step Four – tuck in your green mulch plants!
Green mulch plants are often lower, ground-hugging plants that will compliment your specimens, but will not take away from their appearance or compete with them. Sedges, wild ginger, pussytoes, moss phlox, violets, creeping juniper, ‘Snowflurry’ heath aster, and green-and-gold are all green mulch suitable plants that come to mind (though, there are MANY others).
Allow individual plants the space they need to reach full size. It is important to follow spacing recommendations, which for most lower ground-covers tend to be 8 to 18 inches apart on center. Plants will grow larger and faster if they are not initially crowded. At first your planting may look sparse and there will be a need to cover the bare ground in between your plants.
After your green mulches are placed, mulch with wood mulch between everything to prevent weeds and conserve soil moisture. Since you want your green mulches to spread, and specimen plants to remain healthy, mulch lightly, using only an inch or two of mulch. Keep mulch away from plant crowns to promote spreading and growth; pushing it up against plants will hinder their growth and spread.
Step 5 – Observe and Tweak
As your plants begin to spread over time, you will notice that you need less mulch because they are covering more ground. You might also notice areas where you need more plants, where the plants are not filling in enough to reduce your mulch needs.
It may take 3 to 5 years for plants to fill in as desired. As the years progress, you will see what plants are working well, and what is dependably spreading to create a groundcover, or green mulch. During this time, it is important to keep beds weeded to reduce competition to your plants. Traditional wood mulch can help alleviate some of this, but there will always be some weeds.
In time, from a combination of not allowing a weed seed bank to form through manual control, light mulching, and use of groundcover plants, you will find that there are far fewer weeds to worry about and your garden will require less maintenance.
In the next of this series we will outline how to transition an existing garden with wood mulch to a garden with green mulch. Stay Tuned for Part 4.
Part One Living Mulch, an Ecological Alternative to Wood Mulch
Part Two Living Mulch: Species Suggestions