Mineral-based herbicide was applied to suppress some aggressive patches of white clover. photo credit: R. Robert

It was applied to suppress some aggressive patches of white clover. Prior to this treatment young turfgrass seedlings were planted among the white clover. This herbicide application allows the turfgrass seedlings to develop the size and maturity needed to compete on their own.

As a general rule, I address perennial weeds by hand digging, then dropping grass seed in the hole. photo credit: R. Robert

Anyone who has worked with me should have been indoctrinated to the fact that grass seed is the best weed control. Any product– organic or not– has risks and drawbacks. As a general rule, I address perennial weeds by hand digging, then dropping grass seed in the hole. And I expect routine overseeding by tractor to steadily crowd out annual weeds, while their seeds are prevented from germinating by landing in a dense stand of grass. Products are several rungs down in my line of weed defense.

I utilized a product called Fiesta, whose active ingredient is chelated iron and is generally considered to be “low-risk,” although it is not OMRI approved. photo credit: R. Robert

In this case, however, I utilized a product called Fiesta, whose active ingredient is chelated iron and is generally considered to be “low-risk,” although it is not OMRI approved. The organic lawn team sprayed the dense clover patches with this product, then seeded the area.

Temporary signage helps teach visitors about the organic practices we employee to maintain the lawn. photo credit: R. Robert

Where clover re-grew alongside the delicate grass seedlings, we re-sprayed about a week later. We also followed up with more “scratch and seed” by hand anywhere that didn’t have a strong new crop of grass.

The blue dye allows the applicator to see where they have sprayed already. photo credit: R. Robert

But why the blue dye? Imagine zig-zagging across a lawn with your head down, concentrating on spritzing clover with the mosaic of species. When you lift your gaze, you’ll be grateful to have that indicator of where you have been and where you have yet to treat.

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This patch of lawn has been taken over by wiregrass. photo credit: R. Robert

It is one tough plant: some improved hybrids of the species can be maintained at a height of ¼”! It tolerates heat, drought, salt, and heavy wear. It spreads by stolons, rhizomes, seed (non-hybrids only), and even mowed clippings. Why not embrace such a durable species? Because in our region, which is the cold edge of its range, it spends about five months of the year brown and dormant.

Wiregrass spreads by stolons, rhizomes, seed, and even mowed clippings. photo credit: R. Robert

In 2012, we attempted to organically kill a section of wiregrass along the northern edge of Mertz Lawn. We first used a tractor-pulled york rake to comb through the upper few inches of the soil, removing the bulk of its rhizomes and stolons. We followed up with FIVE applications of a concentrated citric acid herbicide. Each application caused the grass to drop its leaf blades, but they regrew from the unfazed stolons over and over again.

Reseeded tall fescue happily growing in the organic lawn. photo credit: R. Robert

The past two summers, we opted to eradicate patches of wiregrass with glyphosate (trade name Roundup). It required one overall spraying and a few touch ups to create the thoroughly-dead brown spots you see today, which will be re-seeded with a tall fescue blend this September. Although glyphosate is a synthetic herbicide, and debates about its health and environmental safety rage on, arboretum staff weighed its risks against the urgency of the rapidly-spreading weed patches and the need to keep the lawn’s utility for college students’ and summer campers’ recreation.

The patches will be reseeded this fall. photo credit: R. Robert

In 2015, we will utilize the organic control method that I often recommend as a non-toxic alternative– solarization. When implemented optimally, 8 weeks under clear plastic can sustain soil temperatures up to 130 degrees, killing not only many weeds and seeds, but also fungal diseases and insect pests. While beneficial microorganism populations will also be reduced, they tend to recolonize quickly, or can be reintroduced through compost or compost tea applications. See UC Davis’s outstanding publication on solarization and try it on your own problem areas.

The organic lawn is a great place to play freeze tag. photo credit: R. Robert

Check out all our past commentary on our organic lawn initiative.

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Although scoliid wasps may look intimidating when they congregate, they will only sting humans if severely harassed. Green June beetle and Japanese beetle grubs, on the other hand, have plenty to fear. A scoliid wasp stings a grub to paralyze it, lays an egg on its surface, and provisions an underground cell with additional paralyzed grubs for its larva to eat as it matures. She then repeats this process, dooming additional grubs as live feed for her offspring in other chambers.

Your best chance to examine these attractive wasps is while they feed on nectar. They enjoy a wide variety of flowers, including white clover and mountain mint. They have lovely metallic blue wings and a pattern of yellow spots on the abdomen that varies with the species and gender. Their distinctively curved back is the origin of their scientific name– think “scoliosis.”

Scoliid wasps’ many common names, including flower wasps, scarab hunters, and scarab hawks, remind us of their multiple functions in our ecosystem and their extraordinary value for gardeners.

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by Marc Remillard

Get inspired and empowered to use compost tea with confidence. Compost Tea Making is a short book covering all you need to know to start using compost tea on vegetables, flowers, orchards, vineyards, and lawns. It addresses when, why, and how to use it for fertility as well as disease suppression. It offers recipes tailored to different situations, and explains how to produce suitable compost or worm castings to use in the brewing process.

The text works hand-in-hand with some fabulous photos of magnified microorganisms to render the mysterious, microscopic life that powers compost tea comprehensible at last! Aerobicity, protozoa, biofilm, and more, become fascinating and useful terms in this manual. The author cites both modern science and “wisdom accumulated through the ages” (ancient Romans used compost tea), to encourage more people to try using this organic fertilizing method.

Compost Tea Making is not only a practical guide, but a personally and passionately written book, drawing connections between the way we garden and the well-being of our environment and society.

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The Scott Arboretum has published a brochure detailing the concept, practices and research behind the Organic Lawn Initiative. You can view it online at http://www.scottarboretum.org/publications/OrganicLawnBrochure2-11.pdf or pick up a copy from the brochure box at the organic lawn, installed just below the stairs of Magill Walk.

Four Swarthmore College biology majors are studying the biological diversity in our soil and the effects of our organic and conventional landscape maintenance practices on soil organisms. Such knowledge will improve our ability to maximize soil fertility and plant health by harnessing natural ecological processes. Organisms including fungi, bacteria, protozoa, nematodes, and earthworms are the key to organically improving the structure and chemistry of the soil– the life support system for plants. On April 6th, Elaine Ingham, Ph. D., — internationally respected soil microbiologist, Chief Scientist for the Rodale Institute, and President and Director of Research at Soil Foodweb Inc.– will spend the day at Swarthmore training students, as well as several of the College’s science faculty and horticultural staff, in the use of a light microscope to identify microbes and analyze the quality of soil, compost and other biological materials. We are thrilled to bring together such a diverse group of constituents to learn with and from one another.

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The saddleback caterpillar is stunningly beautiful, but it is most likely to impress its presence upon you with a devilish sting. If you innocently brush against one where it hangs on the underside of a leaf, you will be punished with an intensely burning welt for several minutes at least. Perhaps you can forgive its cruelty as you marvel at its vivid color and otherworldly form.

The caterpillar’s common name refers to the brown, saddle-like blotch in the center of its rich kelly green back. Each end is capped with reddish-brown and bears a pair of imposing bristly “horns.” The head is moustachioed with additional spines and the tail end bears large white eye spots reminiscent of spiderman’s. Both sides of the abdomen are lined with yet more spines.

Saddleback capterpillar photo credit: N. Lewis

The saddleback caterpillar is the larva of a fairly inconspicuous brown moth. The species, Acharia stimulea (formerly Sibine stimulea), is native to the eastern United States. You are most likely to encounter the caterpillar in August and September. I have found them on roses, Itea, shrub dogwoods, and Carex, but they are documented to feed on dozens of common garden plants.

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