Growing Concerns 370: Ponder peat, design a landscape, fatten the hedge, sharpen the mower


Bales of peat become weighty issue for the Under-gardener


What is the purpose of peat moss? My wife adds it to everything driving the non-gardener laborer (me) nuts. My inquiry, "Why do we do this?" results in the definitive, "Because it's good for the soil." - S -

Soil does support plants but plants also support soil. The answer to your question is a lesson in soil science.

Step one in soil formation is weathering of rock. We name the fragmented minerals by their size -- from largest to smallest they're sand, silt or clay. Still, you wouldn't recognize them as soil, yet.

Few plants can grow in thin, raw mineral matter. Some alpine species do grow in "scree", a mix of these shifting particles plus loose rock. The plants use solar power to combine water-soluble minerals at their roots, carbon from air and hydrogen, oxygen and nitrogen from rain to make complex carbon compounds -- organic matter. When the plants die or shed parts, the captured minerals return to the soil along with "new" carbon, hydrogen and nitrogen.

Fungi, insects and other soil-dwellers move in now. They feed on carbon and nitrogen, converting dead plant matter to humus and then adding to the stew their excrement and a humus residue called microbial glue. These are sticky in both atomically electric and Elmer's glue fashion, pasting mineral particles together in crumbs. Soil crumbs provide places for water to linger where it could not before. A wider range of plant species grows in this richer, moister mix.

Succeeding plants use fresh ions from the mineral part of soil but also reuse nitrogen and other elements from decomposing organic matter. Over eons, continually crumbling base rock and new organic matter make the soil deeper but the organic matter in it never stops breaking down and being reused. If plants continue to grow there but something blocks the return of organic matter, carbon and nitrogen levels decline and the soil's crumby structure breaks down.

When we prepare to plant we remove weeds, roots, turf and other organic matter. As we garden we block our plants' complete return to the soil by weeding, deadheading, harvesting, mowing, and pruning. Your wife chooses to replace this lost organic matter in the form of peat -- plant parts that have been partially decayed and then preserved in bogs.

So keep adding peat if you want that healthy loam to stay healthy. Or if you wonder about the wisdom and sustainability of importing organic matter when there is plenty right here being carted away to landfills and compost sites, you can compost your yard waste and replenish the soil with that form of humus. Composted animal manures, raw fall leaves, shredded paper and grass clippings work, too -- anything with carbon compounds in it.

(More discussion developing right now about using peat, at our Forum. Go see.)


I just bought a house with a small yard and want to have a really nice landscape. I've been shocked by the landscaping estimates and think I'll do the work myself. Any suggestions where to start or how to proceed? - T. G. -

Don't rush -- landscapes last a long time when they're well planned and planted. Loosen the soil and add organic matter. Talk to gardeners in the area about what works and what doesn't. Look at mature landscapes in yards similar to yours and learn the names of plants you like.

Then sit down with paper, pencil and a book (that's the purpose Janet had in mind when she wrote Designing Your Gardens and Landscapes), or take a class where you can develop the design as assignments that other students and the instructor can comment on.


Timely Tip

Hedge getting thin at the bottom? The underlying cause is not lack of fertilizer or disease but shade. If upper limbs overhang by even an inch, that's less light for the base. To keep lower foliage on evergreen shrubs or restore it on deciduous plants, cut the hedge so it's narrower at the top than the bottom. Thin upper branches to open tiny windows that can be lifesavers for leaves below.


Green thumbs up

To late season garden walks. We learn from May, June and July tours but also need late summer and fall examples as we pursue continuous color and interest in our gardens and landscapes.


Green thumbs down

To those who whine about badly mowed lawn yet do nothing more productive than pester the family mowing crew about dull mower blades. Why not surprise them by taking the blade to be sharpened or buying and learning to install a replacement blade?