The Weekly Weeder: Whacking Weeds Can Work

          Whacking annual weeds can kill them, if you whack them low enough—right into the dirt, below the crown.  They have no means to grow without a crown, from which all their growth comes.  (Chickweed is an exception, as it does not have a crown and will keep trying to grow and set seed until it has made enough of it.)

          I saw weed whacking work several years ago, when the city or one of its maintenance contractors eliminated goat heads from the Wastewater Treatment Plant property for several years by repeatedly scalping the dirt where they grew with a string trimmer.  This year, they are blooming and seeding in their old locations near the back fence; apparently the maintenance contract has changed and the city’s institutional memory is short, but goat head seeds can sprout for at least 5 years and will come up all summer until frost.

          This year, I whacked the dense weeds along the irrigation ditch behind my mom’s house into the dirt in May, when they were still green and flowering, but hadn’t set seed yet.  A week later, I pulled a few that had been missed.  The next week, only the false dandelions had come back, and over two months later, that is still the case.

          Last week, I was pulling and cutting crab grass from the backyard below, and looking at the enormous quantity of spotted spurge growing along the same path, but not yet flowering, and asked myself why I didn’t just whack them all, as the annual weeds would be killed out, while the perennial grass and clover would come back from roots.  So I got my battery-powered trimmer out and started beating the dirt, working out which direction to work in order to throw the debris away from my legs and face.  The next week, that area was still quite barren.  This week, some were starting to grow back, and I whacked them again.

          I will have to repeat all summer and reseed clover in the fall, I am sure.  Spring weeds start in the fall and winter, flowering and setting seed around the same time in the spring, allowing one to kill them out for the season with one soil-scalping before they are ripe.  Some summer annuals, like star thistle, start together in spring and can be killed out as they start to bloom in early summer.  Most summer annuals keep sprouting through the hot weather, particularly where they are watered.  Goat heads have a final flush of sprouting as the weather cools in the fall, just as heron’s bill is starting its fall sprouting season.

What does not work to kill weeds, of any sort, is cutting two inches above the ground.  They continue to spread their flowers and ripen seed below the cutting height.  Weed control is seed control, and if the plants are still flowering, they are still violating our city code, which requires that one prevents flowering, seeding and noxious growth by cutting or killing.

                             

Rycke Brown, Natural Gardener          541-955-9040        rycke@gardener.com

Weekly Weeder: Start stopping spring weeds now

Groundsel has yellow, nodding flowers and bitter cress has tiny white, erect flowers.

          Fall has barely started, but spring weeds are already growing.  Now through spring is the best time to kill them.  Cheat, foxtail, heron’s bill, groundsel, bitter cress, cleavers and many others can most easily be killed in the months before they start blooming.  The earlier you get to them, the easier it is.

Heron's Bill, starting to bloom in the spring.  It takes a lot of mulch to smother it at this point.

          You can kill them three ways: by smothering with mulch, preferably leaves; by pulling them out; or by cutting them below the crown, the point from which roots and leaves grow.

          Smothering with mulch saves you the most work in the long run, in the places where you can mulch.  Leaves, when spread 2” or more deep, can stop weeds that haven’t even started yet and those too small or too crowded to be worth individual attention.  Tiny seedlings can grow through a few layers of light fluffy weeds, but more than that can make them run out of food before they find the light.  Blocking sunlight on soil can stop seeds that need sun on soil from sprouting at all.  And leaves make a lousy seed bed for seeds that fall on top of them because they dry out quickly.

Leaves covered with pine needles, which hold them in place.

          But not all leaves are created equal.  Some are eaten by worms before fall is even over, some by spring, some stick around until midsummer, and some have to lie around decomposing for a year before even crazy snake worms will touch them.  (If you have no soil life because fine bark has killed it all, it may take a year or more for even soft leaves to go away, but that’s a subject for another column.) 

Fallen red maple leaves stopping groundsel and other weeds 

          Hard leaves, like oak, sycamore, sweet gum and magnolia, tend to be stiff and fluffy and take a few more layers to stop weeds from growing through.  Many medium and soft leaves lie flat and can stop weeds from sprouting with only a single layer, but will be gone before summer weed seeds start flying.   A mix of hard and soft leaves 2 inches or more deep will stop most small seeds and plants from growing, and feed and soften the soil to easily pull the ones that get through.  2 inches of leaves in the fall is enough to keep flowers and shrubs fed and happy, with loose, easy-to-weed soil that is protected from rain and sun.

A foot or more of leaves will grow big vegetables as they decompose.  For small seeds, spread an inch of compost on top and plant on it.  Large seeds and starts can be planted into the leaves without compost, allowing the leaves to stop weeds from sprouting on top. 

Cheat, blooming en masse, at the point when the roots are shrinking and it is again fairly easy to pull.

Annual grasses, large and small, are most easily pulled from 3 to 6 inches tall.  The longer they grow, the more roots they hold the soil with and the harder they are to pull.  Annuals cheat and foxtail are a lighter green and have a softer texture than perennial grasses, are often fuzzy, and grow in clumps, without runner roots.  As they send up seed stalks in the spring, they use up their roots and are more easily pulled, but time is then short to pull them all.

Most taproots are more easily pulled when the ground is wet, but some in rocky or very hard soil, or with soft stems, won’t pull and must be cut under the crowns.  This will stop most annual weeds and many perennials, but some perennial taproots, like dandelion, dock, and creeping oxalis, need the soil to be loosened with a tool and pulled eventually.  Some, like oriental poppies, can grow back from a root tip deep in the soil and take several years to get rid of completely.

                             

Rycke Brown, Natural Gardener          541-955-9040        rycke@gardener.com

The Weekly Weeder -- Wild lettuce: Ugliest Weed Ever

          Prickly lettuce is one of the ugliest weeds ever when blooming, and it has started to bloom all over town.  As it bolts, its leaves stick out at unnatural angles, edges vertical, showing off its sharp points.  It grows 3-7 feet tall and spreads out at the top into wide, branching panicle of tiny yellow flowers that soon turn to small, fluffy seeds that fly on the wind to other properties.  It grows all over town, particularly on the neglected edges outside fences, and in cracks in the pavements.  It gets its name from the prickles on the base of its stem which pierce the bare hand that tries to pull it.  It screams seediness and neglect.

Young prickly lettuce

This looks like a domestic-wild hybrid of prickly lettuce

          There are many varieties of wild lettuce.  They all have a few traits in common, starting with being a composite flower (many tiny flowers in a each bloom, often with yellow strap petal flowers around the edges of the bloom, but some have all strap petal flowers and others have no petals) with seeds that fly on the wind, much like their short perennial relative, dandelion.  Unlike dandelion, the flowers grow on branching stems that can vary from a few inches to 18” tall in the case of groundsel in the spring, to 6 feet or more in summer with prickly lettuce and cow thistle, which looks much like a thistle with lettuce flowers but is not as spiny as true thistles.  Some wild lettuce mixes with domestic lettuce, creating interesting red shades.

"Soft" wild lettuce

False dandelion, which has been blooming knee-high in yards with dandelion-size flowers, is a wild lettuce.  This year, we have a new tiny, fine variety, half the regular size with half-inch yellow flowers, which has spread widely in the area and pulls rather easily.  We also have a soft, tall-growing variety with very dandelion-like leaves, with long, vertical branches on the stems that easily bend and buckle because the stems are soft and hollow.  Look up wild lettuce varieties on the internet, and you’ll see several more that grow in our woods, at least one of which is actually pretty, but still spreads like a weed.

          Unlike dandelion, they have tap roots usually only a few inches long that do not grow if cut an inch below the top of the root crown, being mostly annual weeds, though false dandelion is perennial and still dies.  They often pull out of the ground easily, but can be cut out if they break off above the crown. 

          If you weed them out of your yard and they keep appearing, there is an infestation within a half-block.  Wind-blown seeds don’t usually fly very far in a city full of trees.

          Also unlike dandelion, these weeds need no summer water to sprout and grow and tend to invade dry lawns, vacant lots, and cracks in pavements.  But they will sprout throughout the year with water as well.  What they need is bare soil or fine-textured mulch to get a touch of sun and hold the water needed to germinate their seeds. 

Whole-leaf mulch dries out on top quickly.  It deprives lettuce seeds in the soil of that touch of sun and those that fall on top of the leaves of the fine-textured seed bed that holds the moisture needed to sprout and grow.  A few layers of soft leaves will stop spring weeds like groundsel before they are eaten by soil life.  A couple inches of harder leaves will stop most weed seeds, and soften the soil to pull the ones that grow, while encouraging big-seeded perennial grasses to take over.  Bigger-seeded annual grasses will also grow through the leaves and need to be weeded out.  They are a softer, lighter green than the perennial grasses; see “cheat” and “foxtails.”

                               

Rycke Brown, Natural Gardener          541-955-9040        rycke@gardener.com