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GARDEN TIPS – Written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Published July 31, 2016

While both new and experienced gardeners know that garden soil may benefit from the addition of compost, they do not know about the problems that can arise when from adding too much or using poor quality compost. Let’s take a little time to chat a bit about the pitfalls of adding compost to garden soil.

While good quality compost is considered the holy grail of garden organic matter, there are no set standards for compost. The quality of compost varies with the types of materials composted and the composting processes used. Mature compost is one where the organic materials are fully broken down into stable organic matter. Quality compost is mature compost that is not high in salts, contains no contaminants from industrial waste, has few weed seeds, and can provide plant nutrients.

You can not discern quality compost by looks. If purchasing commercially made compost, ask the seller for a copy of the laboratory analysis provided by the compost producer. Look for the carbon to nitrogen ratio (C:N) that indicates the stability of the organic matter (OM). A ratio between 12:1 to 15:1 is an indication that the OM is stable. If the ratio is less than 10:1, it is an indication that it contains organic materials that are still in the process of decomposing. A ratio above 25:1 indicates that the compost contains high carbon materials that break down very slowly and will tie-up available nitrogen as it decomposes, depriving garden plants of nitrogen and hampering plant growth.

On the analysis look for the EC or electrical conductivity of the compost. This is a measure of the soluble salts in the soil. High soluble salt levels are harmful to plant roots. Compost with an EC above 8mmho/cm are high in salts and should be avoided. It is better to purchase compost with an EC that is between 0 and 4 mmhos/cm.

Also, pay attention to the percent (by dry weight) of organic matter in the compost. If the percentage is lower than 30 per cent, it means that soil or sand have been added to the mix. If higher than 60 percent, it is unfinished or immature compost containing undecomposed organic materials.

Be aware that each batch of compost that a producer makes varies in its analysis. One time the salt levels may be acceptable and the next time they may be too high, so check the analysis each time you purchase compost even if it comes from the same supplier or producer.

While local soils often benefit from the addition of quality compost, it is possible to over do it. Too much compost can cause problems including excess nutrient levels, especially nitrogen and phosphorous, high soluble salts, and excessive levels of organic matter. (Levels of organic matter above 5% to 8% by weight are too high.)

The general rule of thumb when adding compost to the soil in vegetable gardens or annual flower beds is to add no more than 2 to 3 inches of quality, low-in-salt compost to garden. The compost should be thoroughly incorporated into the top 6 to 8 inches of soil before planting. Done annually, the level of organic matter in your soil will increase. To avoid excessive levels of organic matter, reduce the amount of compost you are adding to only 1 inch after three years or get a soil test to determine the level of organic matter in your soil. As with so many things in life, too much of a good thing can be bad. The same goes for compost.

Garden Hint: How much compost do you need to apply one inch to the garden? Three cubic yards will cover 1,000 square feet to a depth of one inch.


GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written October 18, 2015

I will be teaching a composting workshop at the end of this month. To be a successful backyard composter, I think it is important to learn a little of the science behind composting, not just the basics of “how to” make a compost pile.

Decomposition is Mother Nature’s way of recycling. Without decomposition we would all be buried in dead plant and animal matter. Technically, decomposition is the process by which organic materials, both plant and animal, are broken down into simpler compounds. A variety of “decomposer” organisms carry out the process by feeding on dead organic matter.

The most important primary decomposers of organic matter are bacteria. They are the “workhorses” of a compost pile. They predominate in the compost pile early in the process. Their feeding helps break organic matter down into compounds that other organisms can feed on. As the bacteria feed and multiply, they utilize the carbon in the organic matter for creating new cells. With their feeding and multiplication, energy is released in the form of heat. This results in the compost pile heating up.

There are millions of bacteria in the world so it is no surprise that there are a variety of different bacteria at work in a compost pile. The bacteria that get to work first are referred to psychrophilic bacteria, working best at temperatures of approximately 55 degrees. As these bacteria do their beginning work, the pile starts to heat up. When the temperature gets to about 70 degrees, mesophilic bacteria take over. The pile temperature continues to increase and thermophilic bacteria start to dominate once the pile temperature goes above 90 degrees. At temperatures above 160 degrees, all the bacteria start to die off because it becomes too hot.
Other primary decomposers are invertebrate organisms, like millepedes, sow bugs, and millepedes. They help speed the decay process along by tearing the materials into smaller and smaller pieces with their feeding. This exposes more surface area for the bacteria and other decay microorganisms, such as fungi and actinomycetes, to do their work.

As part of the cycle of life that happens in a compost pile or naturally on a forest floor, the primary decomposers are eaten by other organisms, such as springtails, mites, and beetles. These secondary organisms are in turn eaten by a third level of larger “consumers,” including ground beetles, centipedes, and ants.

When finished, a properly managed compost pile yields a dark, fairly stable mix of complex organic compounds. Quality finished compost is a dark uniform crumbly material with no sticks, twigs, or other distinguishable materials. When added to your garden soil, quality compost makes the soil more productive by improving soil structure, adding nutrients, and increasing nutrient retention. Some refer to it as “black gold” because it is a valuable component of healthy soil.


written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA

Autumn has arrived! What are we going to do with all the falling leaves? How about composting them? Composting is a great way to recycle leaves and other garden waste, but both beginning and experienced composters may have some questions about which leaves can and can’t be composted. Here are some of the frequently asked questions that come across my desk.

Question: Can I compost pine needles? Will it make my soil too acid like my gardening books indicate?

Answer: This is a persistent myth. Pine and other conifer needles won’t make your soil too acid. Pine needles are very acidic before they start to break down, but once composted they become slightly acid to neutral along with the rest of the composted materials. University research reveals that most compost has a pH of 6.8 (slightly acid) to 7.0 (neutral).

One concern with composting pine needles is that they’re high in plant waxes and lignin, making them slow to decompose. If you want to use pine needles or other conifer foliage in a compost pile, chop them up well before adding them to the pile. Don’t add more than 10% by volume because they’re so slow to break down.

Question: I heard that you shouldn’t compost oak leaves. Is this true?

Answer: No, this isn’t true either. I’m not sure how this myth originated, but oak leaves cause no problems in a compost pile. However, they are high in lignin (a complex organic compound that binds wood fibers together) and slower decomposing than most other tree leaves. Again, chop them up well and don’t overload the compost with them.

Question: Someone warned me against composting sycamore leaves. Why shouldn’t I compost them?

Answer: One problem with composting sycamore leaves is that there tends to be lots of big leaves, sometimes too many for a simple backyard compost. I recommend chopping up sycamore leaves first using a shredder or by mowing over them with a mulching mower. By chopping them up you create more surface area where the decay organisms can work, plus it reduces the volume you have for adding to a compost pile. When working with sycamore leaves, your nose and throat may become irritated from the pubescence or fuzz on the undersides of the leaves so you may want to wear a dust mask.

Question: Is it true that walnut leaves are toxic and shouldn’t be used in compost?

Answer: It is true that black walnut roots produce a plant chemical called juglone that is toxic to certain plants, such as tomatoes and rhododendrons, when they’re growing in proximity to the tree roots. Black walnut sawdust, wood chips, nut hulls, bark, and leaves all contain juglone. However, the leaves can be safely used in compost piles because the juglone breaks down during the decay process. Persian (English) walnuts also produce juglone but in much smaller quantities and aren’t considered ‘toxic’ unless they’re grafted plants with black walnut rootstocks.

Published: 10/5/2012 11:52 AM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Not everything offered for sale in a seed catalog is a seed or a plant. Many seed companies also offer a variety of nifty garden gadgets, equipment, and supplies. Here are some that I found while thumbing through the seed catalogs in my mailbox.

Compost Thermometer: Twice a year I teach a composting class where I talk about the composting process. When built correctly, a compost pile quickly heats up due to the activity of aerobic bacteria working at breaking down the organic matter. The temperature of the pile can go above 150 degrees in just a few days. If the pile gets too hot, above 170 degrees, it will kill off these valuable bacteria. A compost thermometer allows a gardener to take the internal temperature of the pile and decide when to turn it. Made out of stainless steel, the compost thermometer has a long (18-20″) stem and a dial with a range of 0 to 200-220 degrees. These typically cost about $30 to $80. You can find one for $32.50 from Territorial Seed Company (

Soil Thermometer: Also available from Territorial Seed Company is a soil thermometer, a diminutive device compared to a compost thermometer, with a 6.5 inch stem . It comes in handy when you’re starting seeds indoors or directly into the soil outdoors, since soil temperature is critical for good seed germination. Warm season vegetables tend to germinate best if the soil is 65 to 70 degrees. Gardeners are often tempted into thinking things have warmed up enough for planting because of balmy weather. Using a soil thermometer tells you if the soil is warm enough for sowing seed.

You might also want to know that you shouldn’t plant spring flowering bulbs in the fall until the soil temperature drops below 60 degrees; the roots of trees and shrubs will continue to grow until soil temperatures drop below 40 degrees in the fall; crabgrass will start to germinate when the soil temperature reaches 55 degrees for four or more days in a row; cool-season grass seed can be planted when the soil temperatures are in the 60 degree range; and seed potatoes tend to rot in cold, wet soils below 50 degrees, sprouting best in soils of 55 to 70 degrees.

Seed Starting Supplies: It’s logical that many seed catalogs also offer all sorts of seed starting equipment from flats, to seed starting potting mix, mini-greenhouses, bottom heat mats, plant labels, hand seeders and more. Rootrainers caught my eye. Thirty-two Rootrainer cells come with a tray. Each of the cells is 1.5 inches square and 5 inches deep, deeper than many other seed starter cells. These deep cells encourage a longer root system and help improve transplant survival. Each set of four cells can be opened up so you can check the progress of the roots and so you can easily remove the seedling for transplanting. These can be found in Park Seed Company’s catalog (

Park Seed Company also has a complete special mini-greenhouse for starting seeds on your windowsill called a “Bio-Dome”. This is a seed flat with 60 individual cells and a plastic dome cover with vents. Each is about 15 inches long and 9.5 inches wide and comes with 60 cells that are 2.25 inches deep. The $25 cost per dome is a bit pricey, but it’s reusable from year to year.

Yes, there are plenty of wonderful seeds for sale in seed catalogs, but there’s also a wealth of other handy gardening treasures to be found.

Published: 1/29/2011 3:42 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Hopefully, all the Thanksgiving dinner leftovers have been used up. I still have some “leftovers” from other columns earlier in the fall. They didn’t get used up when I wrote those columns, but they’re too good not to share with you.


Ever wonder why flower bulbs planted in the ground don’t freeze over the winter? As you might guess, nature provides a way for bulbs to avoid cold temperature damage. The first is the insulation that soil provides. Even if the soil freezes, the soil temperatures where the bulbs are planted, typically don’t fall much below freezing, staying in the 29 to 30 degree Fahrenheit range.

Of course, there are also biochemical changes that occur within the bulb, according to the Netherlands Flower Bulb Information Center. With the onset of fall and cooler temperatures, starches stored in the bulb start to break down into glucose and other molecules. The glucose acts much like salt would by lowering the temperature at which water freezes. Also, layers of mulch and snow provide extra insulation during severely cold weather.

Have you ever noticed that the bulbs you planted two years ago or more come up much later than the first year they bloomed? For some reason, established bulbs tend to bloom about two weeks later than they do after their first year. For some, this is simply an interesting bit of trivia. For others, it’s important to know for when you’re adding bulbs to an existing planting and trying to coordinate bloom times for specific color combinations.


Where do gourds fit into the scheme of things when we’re talking about pumpkins and winter squash? Are they just dried out squash? The title of “gourd” is not an official botanical term. Instead, it generally refers to any member of the squash family that isn’t good to eat, dries well, and may be useful in some manner. As with any rule, there are exceptions. The Turk’s turban squash is considered by some to be a gourd, but it actually is a winter squash that’s both decorative and good to eat.

The bumpy, warty, colorful gourds that are so familiar to many are all in the group of Cucurbita pepo, along with some pumpkins, acorn squash, and all kinds of summer squash. The gourds are a subgroup or a “botanical variety” of this squash species. This subgroup includes pear, apple, orange, flat fancy, and the ugly warty-skinned fancy gourds.

In recent years, the lagenaria (Lagenaria spp.) or utilitarian gourds have become quite popular for use as birdhouses, crafting decorative items, and creating utilitarian items, such as ladles or bowls. Prized for their thick, hard shells when dry, this group includes bottle, siphon, calabash pipe, dolphin, club, and birdhouse gourds.

The third group of gourds are the luffas or vegetable sponges. The luffa gourds have elongated fruit with an outer shell that’s easily removed. Beneath the outer shell, the pulp is a tough and fibrous. When dried it can be used as sponges for scrubbing or made into ornamental items.


Is it safe to compost black walnut leaves, oak leaves, and pine needles in a compost pile? While you may have heard that one or all of these are bad to use in compost piles, don’t believe it.

Black walnut leaves do contain small amounts of the toxic plant chemical juglone. Juglone can cause the wilt and death of sensitive plants that come in contact with low concentrations of juglone. However, the juglone in black walnut leaves can be degraded in two to four weeks, according to Ohio State University Extension. That’s because this plant toxin degrades when exposed to air, water and bacteria. It breaks down completely within two months in a compost pile.

If one has volumes of black walnut leaves and wants to make sure there is no problem, the leaves can be composted separately and then tested for juglone toxicity by planting tomato seedlings in the compost. Tomatoes are very sensitive to juglone and will wilt and die if there are toxic levels of juglone present in the compost. Sawdust mulch, fresh sawdust or wood chips made from black walnut are a different story. They should not be used as a mulch around plants sensitive to juglone, such as blueberries, peppers, or tomatoes.

There is absolutely no reason why you shouldn’t use oak leaves or pine needles in a compost pile. The concern that they’re too acidic for adding to the soil is false. They should have no greater affect on soil acidity than other types of organic matter used in your compost pile. If they perchance do acidify the soil, that would be highly beneficial because most of our area garden soils are quite alkaline and the majority of garden plants prefer a slightly acid soil.

One drawback with oak leaves and pine needles is that they’re quite tough and break down slowly in the compost pile. If using them in a compost, be sure to chop up leaves first by shredding them in a shredder or running over them several times with your lawn mower. Smaller pieces of leaves and needles will decay more rapidly.

Also, take note that pine needles make great mulches for your garden. One reader let me know that she used pine needles as a mulch in her rose garden… based on my recommendation. It may have been circumstantial, but she notes that her roses are healthier than they have been in years and she has had much less of a problem with powdery mildew. It’s nice to hear from readers who have used my advice… successfully.

Well, I hope you enjoyed your leftovers.

Published: 12/4/2004 2:12 PM


written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

No place for a compost pile in your yard? Gardeners don’t have to build a classic ” pile” to recycle yard and kitchen waste via the natural process of decay. There are other ways to compost that don’t involve constructing a pile and building or buying something to contain it. Alternatives include sheet or layered composting, trench, and pit composting.

Sheet composting is an easy method that works well if you have a veggie garden that’s not permanently mulched. All you need to do is chop up your plant waste and spread it out in your garden as a layer of mulch. If you collect your grass clippings, it’s a great way to get rid of them and use them to help build your soil. One word of caution, a heavy layer of fresh grass clippings tends to form a mat and impede water and air movement into the soil. Try to vary the texture of your layers or allow the grass clippings to dry out before placing them in the garden.

You can also use this method with other types of yard and garden waste, but it’s important to chop it up before applying it to the garden. If you don’t have a chipper, you can chop up non-woody plant waste using your mower. This works best if you place the plant waste on your lawn and run the mower over it a couple of times. Then rake up the chopped waste and spread it out in the garden.

Our fall and winter weather tends to be quite breezy, so sheet composting in the fall is not practical in wind exposed situations. However, you might find that trench composting would work for you. This is pretty simple. Just dig a trench in your garden and fill it up with your garden waste. More waste will fit into the trench and it will all rot more quickly if you chop it up first. Cover the trench with soil and water it all in. Over the late fall and winter months these materials will decay and then can be tilled into the soil next spring. If we have dry and mild late fall and winter weather, consider watering the trench area of the garden several times to help aid with decay. The microbes and little critters that are the “workhorses” of the decomposition process require moisture to live and do their job.

Yet another way to compost is in a pit. Pit composting isn’t a practical way to get rid of volumes of yard waste, but you can use it for plant-based kitchen waste. Just dig a little pit in your garden and fashion a board to cover the hole so no person or creature accidentally falls into it.

As you accumulate fruit and vegetable waste in the kitchen, take it out and put it in the pit. Some gardeners have a covered container that they keep near the sink to collect the waste to minimize the number of trips. Definitely do not put meat, dairy, or foods containing fats or oils in your pit compost. These are very smelly as they rot and can attract both flies and animals. However, it’s okay to put coffee filters, tea bags, and egg shells in a pit compost.

You can add new waste to the pit compost at any time. The waste will decrease in volume as it decays from the bottom up. Once the hole is completely filled up and doesn’t significantly decrease in volume with time, cover the pit with soil and dig a new pit nearby. It’s a simple way of composting and enriching the soil at the same time.

If you have lots of yard, garden, and kitchen waste, you can always build a compost pile and contain it in some way, such as a bin. However, now you know some other ways to get rid of your yard waste. If you have humongous volumes of waste, you may want to try all of these methods. Whatever way you chose, you’ll be recycling your waste into the soil and helping build up the organic content of your soil. This will mean a healthier garden and less solid waste going into the landfill.

Caution! There are some wastes that shouldn’t be put in compost piles, trenches, or pits:

Onion and Garlic Peelings: Uncooked garlic and onion waste can spread disease to the garden.

Potato Peelings: Uncooked potatoes and their skins can introduce harmful nematodes to your soil.

Pet Manure: Dog, cat, and pig manures may contain diseases and parasites that can potentially infect humans. Rabbit manure is considered safe.

Perennial Weeds or Weeds with Seeds: Perennial weeds, such as Bermuda grass and bind weed, should not be composted in anyway. Even the “hot” composting process of a pile may not kill perennial weeds or weed seeds. Annual weeds without seeds may be composted. Also avoid composting diseased plants, such as flowers with mildew.

Published: 10/18/2008 1:37 PM



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