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Elisabeth C. Miller Library

Keyword: Compost

composting coffee grounds

I have a composting question: I work at a large hospital and would like to collect all of the used coffee grounds/filters from the countless pots throughout the hospital and use it (tons of it!) for compost. Could you create adequate compost with just coffee and probably straw to balance it?

The information below is quoted from an article by Bob Smith, Washington State University Master Gardener Program Manager, Thurston County, in The Gardener, Vol. 6, No. 4, Winter 1995-96):

“In 1995, three local coffee houses called WSU Extension in Thurston County [Washington] for advice on composting coffee grounds. With the exception of worm bin composting, we were unable to find much information. Our Master Composter and Master Gardener volunteers decided to experiment. They composted about 270 pounds of coffee grounds donated by local espresso bars. They fed roughly 60 pounds to worms while composting the rest in regular bins.

“If coffee grounds are not worms’ food of choice, they certainly must be high on the list. In appreciation for a meal of ready-to-consume grounds, the worms produced excellent compost. Incorporate coffee grounds soon after brewing into your worm box. This reduced the possibility of the grounds souring and attracting pesky fruit flies.

“We also experimented by composting coffee grounds in three types of traditional bins:
1) an enclosed holding bin made of recycled plastic,
2) a three-level wire stacking bin, and
3) a large, round, wire holding bin. Our primary concern was whether the coffee grounds would attract pests.

“We incorporated the grounds over a four month period yet experienced only one problem: fruit flies showed up in the enclosed plastic bin almost immediately after we added coffee grounds. In open wire bins, the grounds tended to dry out quickly. Overall, though, we found coffee grounds easy to work with and satisfactory for composting.

“Coffee grounds have a carbon-to-nitrogen ratio of 20:1, roughly equivalent to that of grass clippings. After brewing, coffee grounds contain up to 2% nitrogen. For composting purposes, consider coffee grounds green material similar to grass clippings. For brown material, we used leaves and sawdust. In these trials, we used a formula of one part green material (coffee grounds alone or mixed with grass clippings) to two parts leaves, or four parts green material to one part sawdust.”

In the Winter 2009 issue of Master Gardener, WSU Extension Horticulturist Linda Chalker-Scott recommends using a thin layer (half an inch or less) of coffee grounds as mulch, topping this with a thicker layer (4 inches) of coarser organic material such as wood chips. She also says that the optimal percentage of coffee grounds in total compost volume should be 10 to 20 percent, and no more. The pH of spent coffee grounds varies, and one cannot assume they are acidic.

walnut leaves in compost

Will black walnut leaves cause compost to be allelopathic? Should they be kept out of compost? Or is this folklore? The specific compost is made with chicken manure (fresh), grass clippings and walnut leaves. Are there plants that tolerate the toxin in black walnut?

 

It seems that the main source of toxicity is the roots of the walnut
tree, rather than the leaves or shells. However, there are still those
who believe that there is enough juglone in the leaves that they should
be fully composted before use in the garden. Below are excerpts from information published online in various university extension websites, by various authors, and now unavailable:

“This toxic affect on surrounding plants appears to be related to root
contact, as walnut hulls and leaves used as mulch have not shown toxic
effects on plant growth. [Warning- Frank Robinson disagrees.] Because Walnut
roots do not occupy the surface layers in most soil, many shallow rooted
plants growing under walnut trees don’t come in contact with the roots
and are not affected by them.” [Michigan State University]

“You’ve probably always heard that you should never add black walnut
sawdust [or wood chips] to the compost pile because the juglone will kill
everything that grows in the compost. Abraham says that’s not
necessarily true; that juglone is not found in walnut saw dust or wood
chips. Nor do dead walnut trees exude juglone. Juglone is harmless to
humans so you can go right ahead and safely eat fruit and vegetables
grown near walnuts.”[Katy Abraham]

“Robinson doesn’t agree on the use of walnut residue in composting. He
has this to say about black walnut saw dust, husks and leaves affecting
plants. ‘Tomatoes growing in clean soil in pots were severely stunted
when leaves and nuts fell into the pots while we were on vacation. I know
what juglone can do. I have seen a 15-year-old rhododendron killed a few
weeks after its owner mulched it with black-walnut husks, and roses
injured by an application of compost containing black-walnut sawdust.'”
[Robinson]

“The juglone toxin occurs in the leaves, bark, and wood of the walnut but
these contain lower concentrations than the roots. Juglone is poorly
soluble in water and does not move very far in the soil. Walnut leaves
can be composted because the toxin breaks down when exposed to air, water
and bacteria. The toxic effect can be degraded in two to four weeks. In
soil, breakdown may take up to two months. Black walnut leaves may be
composted separately, and the finished compost tested for toxicity by
planting tomato seedlings in it. Sawdust mulch, fresh sawdust or chips
from street trees prunings are not suggested for plants sensitive to
juglone, such as blueberry. However, composting of bark for a minimum of
six months provides a safe mulch even for plants sensitive to juglone.”
[Ohio State University]

“To be on the safe side, composted material containing juglone should be
allowed to breakdown over a period of time before use. This composted
material can be used with plants that are not susceptible to juglone
damage. If it is important to use it for general composting purposes,
testing it first with a few tomato plants for a few weeks should reveal
its level of toxicity.” [Abraham]

This may also be of interest: The Walnut Tree: Allelopathic Effects and Tolerant Plants from the Virginia Cooperative Extension.

Frank Robinson’s article “Under the Black Walnut Tree,” Horticulture magazine, October 1986, pp. 30-33 concludes that many plants are indeed able to tolerate juglone’s toxicity. Some of the juglone-tolerant plants listed in the article and in other sources are included on Morton Arboretum website.

applying compost versus adding fertilizers to gardens

I have a large and never-fed garden. I wish to start feeding these plants. I’m composting now, but when and how often do I fertilize?

 

Has your garden been thriving in years past? If so, I don’t think you need to add fertilizers. There’s no single packaged fertilizer that will be universally beneficial to every plant in your garden. Different plants have different needs, and it’s never wise to add fertilizer without doing a soil test.

On the other hand, you mention you are tending a compost pile. You can apply compost once or twice a year and it will be helpful to all your plants.

Here is information from The Ann Lovejoy Handbook of Northwest Gardening (Sasquatch Press, 2007):
“When do we need to feed? For ornamental plants, including trees and shrubs, spring and fall are the traditional feeding times. Spring feeds are generally fast-acting, offering rapidly growing plants the nutrients they need for a strong summer performance. A feeding mulch of compost can be fortified with fast-acting alfalfa, which will release more nitrogen if combined with composted manures. Alfalfa comes in meal or pellets. I like the big pellets used to feed goats, which are easy to spread and are available without added medication [my note: some alfalfa is treated, for use as animal feed].

“In fall, most plants stop producing fresh top growth, even though our Northwest winters are generally mild. Fall is a good time to feed roots, which continue to stretch and grow underground despite low temperatures. Adding whole fish meal to your compost feeding mulch will fortify roots with phosphorus.”

Professor Sarah Reichard, director of UW Botanic Gardens, discusses fertilizers as sources of pollution in our water supply. In her book The Conscientious Gardener: Cultivating a Garden Ethic (University of California Press, 2011), she states:
“If water inevitably drains downhill, how do we stop fertilizers and pesticides from moving with it? The easiest way is not to use them. This needn’t come at the cost of your plants. Most woody plants and herbaceous perennials do not require much fertilizer. Mulching with well-aged manure, compost, or other easily broken-down organic materials will supply all the necessary nutrients.”

removing sod and preparing soil for vegetable gardening

We plan to put in a vegetable garden next spring where we now have grass. It is a great sunny spot that we think would work well for this. The question is, after we cut out the sod this fall, someone has suggested we plant rye grass for the winter, is this a good solution? If not, what do we do to the soil this winter? (We plan to bring in some top soil after we take out the sod).

 

There are several approaches that you can use to get your new garden ready. One is from Growing Vegetables West of the Cascades by Steve Solomon. He
recommends removing the grass, covering it with no more than 1/2 inch of
completely rotted compost or 1 inch of raw ruminant manure, and spread
agricultural lime at 50 pounds per 1,000 square foot. Do this in early
October. Then scatter small-seeded fava bean seed at 6 to 8 pounds per
1,000 square feet. Rototill no more than 2 inches deep and relax until May.
In late May you rototill deeply and or spade in the overwintered garden
area. Then you can plant.

Another information source, Seattle Tilth’s Maritime Northwest Garden Guide,
recommends using an annual winter cover crop to improve the soil. It
suggests using 85% legume and 15% grain for maximum nitrogen fixation. For
the legume, you can use Field peas, Crimson clover, Fava beans or vetch. For
the grain you can use cereal rye, winter wheat, spelt or barley. Most of
these are applied at about 2 pounds per 1,000 square feet. Again you would
rototill or turn under the cover crop in late April or May.

Solomon’s method will provide a better total approach. You also should
consider having your soil tested to find out what is missing and what your
pH level is.

conditioning clay and heavy soils

Help! My clay soil is stunting the growth of my plants. I’ve amended the soil with compost and manure. Is there a another method of conditioning the soil that you can recommend?

 

First and most important, it appears mulching is the best organic solution for conditioning clay and heavy soils. Organic soil conditioners include compost, well-rotted animal manures, and natural fertilizers. Planting green manures such as clover, rye grass, or vetch are also effective for breaking up large clods in clay soil over time.

Sheet composting – laying compost over the entire area to be worked and using a fork (or rototiller) to work it into the soil to a depth of 2-4 inches – is cited by the resources listed below as an efficient method of soil conditioning. Both books listed below recommend repeating this process at least twice a year, in early spring and in late fall.

Secrets to Great Soil [by Elizabeth P. Stell, 1998, (pbk)] and

The Gardener’s Guide to Better Soil [by Gene Logsdon, 1975, (pbk)]

The Saving Water Partnership (the City of Seattle and other government entities) has a website full of information about improving soil.

The site includes Growing Healthy Soil.

Current thinking contradicts the notion of working compost or other amendments into the soil, as explained in a March 31, 2010 Garden Professors blog post by Professor Linda Chalker-Scott of Washington State University Extension Horticulture. She specifically takes issue with the “Growing Healthy Soil” information linked above. Here is an excerpt:
“Not only will extensive digging or rototilling destroy any soil structure you might have, it will also take out the roots of any desirable plants in the vicinity). […] improper soil amendment can cause serious problems such as soil subsidence, perched water tables, and nutrient overloads. This last point is especially important to anyone living near aquatic ecosystems, since excess nutrients always end up in the water.
Before you plant this year, find out what your soil needs before amending it. And remember that mulching is the natural (and sustainable) way to add organic matter to the soil.”