Gardening season is underway, or at least it should be, and you may have questions as you prepare for spring. To ask one, simply go to the OSU Extension website, type it in and include the county where you live. A photo is very helpful.
Q: I have been researching organic fertilizer for my native and other plants. I’ve always heard animal fertilizer and fish fertilizer can really be useful for plant health.
Recently, I have read that animal manure can be dangerous to people and animals. I read that the manure can carry E. coli and other germs, etc. Which makes total sense scientifically and medically. I’ve read fish fertilizer can be dangerous to the earth because of the processes used for catching and processing and because of the type of fish used.
What are your thoughts? If I can’t use animal or fish, what would you suggest to fertilizer my plants organically?
Also, I am looking for a natural weed killer. Most people in my native flower group say they do not use as vinegar as it is harmful to the earth. Is the only safe way to get rid of the weeds to dig them up? – Washington County
A: First, while you’re researching, research the nitrogen requirements of native plants. They are long adapted to the local conditions, and many do well without additional fertilization.
Manure: Yes, E. coli is an important member of the gut microbiome. Bacteria tend to create a self-protective coating (cyst) around themselves when conditions aren’t to their benefit. E. coli is especially sensitive to gut temperatures. In the soil, they are not active, but if they were to be ingested in garden produce they would find themselves back at those gut temperatures they love.
Be thoughtful about the part of the plant you eat if you side-dress garden vegetable plants with manures. Lettuce, which grows close to the soil surface and is generally eaten raw, would be a risky candidate for side dressing. Trellised tomatoes, whose fruit are well above the soil surface would not be a risk.
Fresh produce from any source should be washed before consumption, and hands should always be thoroughly washed after handling soil, soil amendments, compost or manure.
Fishing by dredging is an all-too-common practice that is ecologically disruptive whether the use of the fish is for consumption or fertilization. Still, fish emulsion is a good source of nitrogen. It would be worth communicating with the manufacturer of the product(s) available to you to determine the source of the offal that they emulsify.
Now, about the weeds: I work closely with the horticultural weed specialist at Oregon State University, and he has assured me that herbicides approved for organic production are so harsh as to rival conventional herbicides in their hazards to people handling them.
Cleaning vinegar is likely not strong enough to make much of a difference to established perennial weeds.
I have three go-to strategies for weed management. Sometimes digging is the only solution. I once eradicated comfrey from my yard by digging out every piece of tissue visible every week for two years. That was my Saturday-morning after coffee task. I prevailed.
For dandelions emerging from the cracks in the sidewalk, I use boiling water. I just take the kettle out in the yard and pour it on. This is not a single application solution. This is the second spring I’ve been working on a dandelion at the back patio. But each appearance is smaller than the last. I scalded that weed this past Saturday and nothing is visible above the pavement right now (Tuesday). I think persistence is key here, too.
My third, and newest, choice is a propane flame thrower designed for weeds. This is excellent for newly emerging annual weeds. It’s only necessary to expose the growth point to the flame. You don’t need to set it on fire. Do be cautious about using a tool like this during dry weather or around flammable mulches. A fourth favorite stratagem is mulching. The seeds of many annual weeds require exposure to sunlight to germinate. Covering the soil reduces germination. Note that if you are encouraging freely self-seeding annuals, they will be set back by mulching as well. Some important points I’ve learned by working with the weed specialist:
Younger weeds are always easier to kill then well-established ones.It’s essential that you manage weeds before they set seed.
Right now, bittercress is No. 1 on my hit list. It’s a fine edible before it blossoms, but it can really take over. – Linda Brewer, OSU Extension soil scientist
Q: We purchased a 2-year-old home with immature landscaping including daphne in August 2022. Much of the new landscape looked rather sickly then and now. I am not sure if any of the sickly-looking plants are worth keeping or if we should replace them. – Yamhill County
A: Daphne live only about 10-15 years. Yours don’t look that big so let’s assume old age is not the issue for them.
You might prune them back lightly after they have finished blooming. It is safer to take two or three springs to rejuvenate the daphnes, and it’s best to err on the side of conservatism. Daphnes can be temperamental.
Be careful when pruning as the bark is susceptible to tearing; use well sharpened tools. Remove any dead or obviously dying branches and cut back to a healthy bud or side branch. – Susan Burdell, OSU Extension Master Gardener
PrivetOSU Extension Service
Q: We planted a wax leaf privet hedge two years ago. Now we find brown spots over all the leaves. Can you confirm this diagnosis and suggest how we can save our plants? – Multnomah County
A: Your privet appears to be showing signs of one of two fungal diseases called Cercospora, described here. The guide says to provide more airflow around your plants and rake up fallen leaves. You can apply one of three listed fungicides (chemicals that kill fungi), which are marked “H” (available to homeowners) during wet weather. Be sure to read and follow label instructions. – Kris LaMar, OSU Extension Master Gardener
Q: Should I be concerned that my asparagus has not begun to sprout? — Marion County
A: The weather in western Oregon has been unusually cold this spring. Those of us who plant spring vegetables are seeing a substantial delay in seed sprouting. Many plants, including trees and shrubs, are behind schedule this year, so I would not worry about your asparagus showing up late. – Lynne Marie Sullivan, OSU Extension Master Gardener
Black walnut trees contain a toxic chemical called juglone. Oregonian file photo. Sami Edge/The Oregonian
Q: I wish to plant a Cornus contraversa ‘Varigata’ in my yard about at the drip line of a black walnut that I just removed. I know a black walnut is allelopathic. An old Oregon grape has long thrived nearby the black walnut. Now I need to know if the cornus will be adversely affected by the decaying roots, nuts and leaves of the black walnut. – Lane County
A: Black walnuts (Juglans nigra) contain a toxic chemical called juglone that can inhibit the growth and can even kill some plants growing nearby. This phenomenon is called allelopathy and black walnuts are one of best known allelopathic plants. Juglone is released from the roots but is also found in lower concentrations in the leaves, nut hulls, bark and wood of black walnut trees. Even though you have removed the black walnut tree in your yard, the toxicity from juglone can persist for five or more years until the roots have completely decomposed.
A plant that is affected by juglone will begin to wilt soon after it comes in contact with the roots of a black walnut tree. As the wilting becomes more severe, the leaves will begin to brown, and the plant begins to die. Juglone is not water soluble, but the highest concentration of juglone is at the dripline of the tree and can stretch as much as 50 to 60 feet from the trunk.
Some plants are tolerant to juglone and Cornus species, or dogwoods, are listed as one of them in the article, What plants are sensitive to the juglone produced by black walnuts?. Be sure to note that it does state “that there are no definitive lists and very few official studies on the impact of juglone on different plant species”. – Jan Gano, OSU Extension Master Gardener
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