Rosemary McCreary: Weed control work doesn’t end when lawn is gone

As lawns shrink in size to conserve water, patios and broad pathways are taking the place of grassy areas. These are smart solutions from an “eco” standpoint and they also take less maintenance than lawns — in most cases, that is. Depending on the type of surfaces chosen, however, upkeep can become a headache.

Concrete and pavers are widely used because they need so little attention over the long term. With special treatment, these inexpensive materials even mimic more costly stones. Wood decks are fairly easy to maintain despite the need for repeated coatings of preservatives and eventual replacement. The gardening maintenance issue arises when porous patio and path surfaces allow weed seeds to take root. Weed cloth under gravel helps if a heavy-duty material is used, and any growth there is easy to pull out.

But one of the most attractive surfaces comes with a sizeable weed-maintenance issue. Decomposed granite has been touted as eco-friendly paving that connotes a classic European look yet blends easily into high-end contemporary and casual, eclectic settings as well. There’s no doubt that it can be quite beautiful. Decomposed granite is easily installed in gradual steps to reach about a 3-inch thickness.

The pale tan or reddish brown tints — hues vary among suppliers — blend quite nicely with garden greens and flowers of every color. Because it’s so porous, this paving allows for excellent drainage and reduced runoff and thereby contributes to replenishing underground aquifers, an advantage over concrete that directs flows into gutters.

What’s not to like?

The only downside usually presented when decomposed granite is recommended is that shoes pick up grit like grains of sand and it can be tracked into the house. But this is a minor issue because most homes have a doormat that will dislodge any grit, or shoes can always be removed. Still, in some households, particularly those with wood floors, this can be a concern.

UNWANTED WEEDS

A larger problem is the outdoor maintenance. The first year after decomposed granite is laid, its smooth expanse is beautiful and inviting to walk on. But in subsequent years, seed from nearby weeds and garden plants are carried by wind, and little sprouts appear during the rainy season. And if any overhead watering of adjacent beds reaches onto decomposed granite, weedy growth progresses beyond the wet months. Depending on the extent of the decomposed granite paving, controlling weeds can become quite tedious.

All of this is not to discourage the use of decomposed granite as a lawn replacement or landscape treatment, but is a gentle reminder that it would be wise to have a maintenance plan in mind if you choose to install it.

Hand weeding works best if weeds are pulled while they’re still seedlings, but this can be a laborious task in an extensive area. Any delay simply gives weed roots time to enlarge and too much opportunity to dislodge the smooth surface when they’re pulled. But there are alternatives.

WEED CONTROL

Flaming, a non-chemical organic approach, is much faster and far easier than crawling along on hands and knees to weed. Flaming is usually only needed on winter weeds that grow during the rainy season when surroundings have a high moisture content and threat of fire is low. The apparatus is powered by propane and comes in a couple of sizes. Organic farmers use a backpack apparatus, but for most home situations, a hand-held version is adequate. Few retailers sell flamers, but Harmony Farm Supply and Nursery in Graton has always been a reliable source.

Another solution is to apply a chemical pre-emergent that prevents weed seeds from sprouting in the first place. This procedure is not organic, however, and should be used only as a last resort. Products like Weed Stopper and Amaze are best applied as the rainy season begins. They must be watered in to prevent winter weeds, the worst offenders, from germinating.

Corn gluten meal, a byproduct in food processing, is an organic pre-emergent treatment, but it is most useful in lawns. Its nitrogen content works as a fertilizer that promotes grassy growth that in turn prevents weeds from getting a solid start.

Spraying weed killers such as glyphosate — the active ingredient in Roundup but now available in generic brands — is a chemical solution when weeds appear, but afterwards you’re left with the job of clearing away a messy residue as weeds wither and die, not to mention the threat of potential side effects from a chemical spray.

Organic herbicides such as concentrated vinegar or clove oil solutions are less toxic options. These materials work best when applied to very young sprouts as opposed to mature weeds, possibly on a week-to-week schedule as seedlings appear over a period of several months in late winter through spring.

Rosemary McCreary, a Sonoma County gardener, gardening teacher and author, writes the weekly Homegrown column for The Press Democrat. Write to her at P.O. Box 910, Santa Rosa, 95402; or send fax to 664-9476.