You’ve seen them at every nursery and home improvement center: bales of peat moss, that fluffy brown stuff gardeners add to their clay or sandy soil to improve the flowerbed. But, what exactly is peat moss, and how does it develop? Peat moss is not soil. It is the result of the decomposition of a live colony of sphagnum moss, a wetland plant. Mosses and wetlands go together, because as primitive plants with very shallow root systems, mosses depend on a constant source of moisture to live.
However, there are some environmental drawbacks to using peat moss as a soil amendment. Although peat moss does renew eventually, a mature peat moss bog can take centuries to develop. The harvest from wetland bogs damages this delicate habitat, killing off the unique plants that live there like carnivorous sundew plants and butterwort. Peat bogs are also a natural storage place for carbon, and the harvesting process releases greenhouse gases into the air. This is surprising to many gardeners, who may rely on peat moss to lighten and acidify the soil. Flower gardeners can take steps to protect the fragile peat bog ecosystem by choosing from four soil amendment alternatives.
Compost got it’s nickname of “black gold” for a reason: This soil amendment improves the tilth of soil, adds trace nutrients, attracts earthworms, and introduces beneficial microorganisms into the garden. It's nearly impossible to overuse compost, so use it as mulch, add it to your container garden, and start healthy seedlings in screened compost. Don’t like the “ick factor” of do-it-yourself composting? Most nurseries sell compost by the bag or truckload, and many cities give residents free compost through their yard waste processing facilities.
Coconut fiber comes from the hull of coconuts, and is considered a waste byproduct of coconut processing. Like peat moss, coconut fiber helps soil absorb and retain moisture. In fact, coconut fibers retain even more water than peat moss, and unlike hydrophobic peat moss, coconut fibers are easy to re-wet. You can buy coconut fiber as dry compressed bricks, which store tidily in the garden shed until you add water to them and mix them with garden soil. The fibers are slightly acidic, ranging from a pH of 5.2 to 6.3, which is desirable for most annuals and perennials. Coco fiber bricks are pricey, so they might be a better option for the small garden or flowering container garden.
Leaf mold is like the lazy man’s compost. The product is the result of the natural decay process of leaves, without all the turning or worrying about the right ratio of greens and browns. Shredding the leaves helps them break down into humus faster, and you don’t need a fancy shredder; running over them with the lawnmower will do. In a hurry? You don't need to wait for chopped leaves to decompose into leaf mold. Chopped leaves make an attractive mulch, and unlike peat moss, they don't repel water.
Pine needle mulch is popular where pine trees are abundant, but flower gardeners can use pine needles as a soil amendment too. After all, what are pine needles but the specially shaped leaves of pine trees? The acidity of pine needles is especially beneficial to help acid loving flowers thrive, including azaleas, lilies, marigolds, and rhododendrons.
If your soil is low on organic matter, why not grow your own soil-enriching materials? Before there were garden centers hawking bagged soil amendments, gardeners improved their soil structure by planting nitrogen-rich cover crops like quick-growing legumes and grasses, which the gardener then tills into the soil. Not only does the decomposition of the plant enrich the soil, but cover crop plants themselves have the ability to absorb nitrogen from the atmosphere and add it to the soil. Factors like weather, price, and season influence which cover crop to grow. Clover, alfalfa, vetch, and rye are some popular cover crops that grow fast enough to outcompete weeds and thrive in soils of low fertility.
A one to two-inch layer of manure from plant-eating animals has a positive biological and physical effect on the soil that peat moss can't match. Well-composted manure is an earthworm magnet, which means that earthworm castings and beneficial tunneling will add to the soil health. Many trace nutrients found in manure will nourish depleted soils. The moisture-holding properties of your garden will increase, helping flowers to cope with drought conditions. Finally, the decomposition of the manure will make the soil slightly acid, which is a boon to many garden flowers.