By Susanne von Rosenberg, UC Master Gardener of Napa County
Gardening myths can come from many sources. A fair number arise when information applicable to agriculture is misapplied to home gardens. Others are based on what seems like a logical extension of science.
Let's take the myth of disinfecting or sealing pruning cuts. You can still easily find wound-sealing compound in garden-supply centers and online. At first glance, it seems like a really good idea to disinfect or cover an open pruning wound. After all, we know that disinfecting and covering our own wounds to keep out germs and dirt leads to better healing.
However, in the vast majority of cases, trees and other woody perennials heal better if the wound is left untreated. They form a natural callus that repels pathogens. Disinfecting the cut damages the tissue further, and studies show it leads to greater loss of tissue than not disinfecting. Sealing the cut seals in moisture and pathogens and prevents the callus from forming.
Another logical-sounding myth is that mulching with wood chips from tree trimmings could spread disease because the chipped trees may have been diseased. A related myth is that the chips might inhibit plant growth if they came from trees that exude allelopathic chemicals, compounds that inhibit other plants.
Wood chips should only be used around perennials. They are not suitable as mulch for annual plants or vegetable gardens. In my research I was only able identify one relatively common local tree, black walnut, that might present a problem when used as wood chip mulch.
Many trees contain allelopathic compounds, but in mulch, this is actually a benefit. The chemicals are unlikely to affect established plants, but they will reduce weed-seed germination and weed growth.
Wood chip mulches may create a nitrogen deficit where the mulch meets the soil, but that also helps reduce weed growth.
There is no evidence that pathogens in wood mulch can transmit disease to established plants if you keep the mulch three inches away from the trunk or base of the plant. Applying four to six inches of wood chip mulch to your garden is an inexpensive, sustainable practice. In highly disturbed or eroding soil areas, or when working to control perennial weeds, eight to twelve inches is recommended.
Another common gardening myth that sounds logical is that you should amend the soil in a planting hole. Some sources recommend adding 25 to 50 percent organic matter or other amendments. It makes sense that improving the soil and adding nutrients would improve the growth and survival of the plant.
Initially, this may be true. But by radically changing the soil in the planting hole compared to the native soil, you are effectively creating a “pot” in the ground. When the roots encounter the harder, finer native soil, they will circle back to the material in the planting hole. With access to only the water and nutrients in the planting hole, the roots won't be able to support the canopy. Also, the planting hole will act as a reservoir for rain, depriving roots of oxygen. In the dry season, irrigation water will leach out of the planting hole into the native soil and become unavailable to the roots. Finally, most of that organic matter will eventually decompose and your plant will sink.
Sometimes a gardening myth is only partly untrue. Advice may be valid for certain climates or soil types but not for other locations. That why it's important to make sure that recommendation are appropriate for our climate.
Before I became a Master Gardener I was fascinated by the idea of “sunken beds,” a gardening technique for conserving water in dry climates. The idea seemed applicable to my area but it wasn't. Sunken beds were developed for the arid southwest. By planting seedlings in an area excavated six inches or more below ground level, they are more protected against wind, and the surrounding soil provides some cooling. In addition, the beds can capture and retain water from monsoon rains.
But the Napa Valley rainfall pattern is different. Compared to the arid Southwest we get a lot of winter rain. Unless your soil has good percolation, your plants will drown in sunken beds, and your soil will be oxygen deprived.
Successful gardeners are always learning and thinking critically. When you hear or see gardening advice, make sure that it has a basis in science and is applicable to our climate.
Napa Library Talks: First Thursday of each month. Register to get Zoom link. http://ucanr.edu/wildlifehabitat2020
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.
For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.
![Myth vs Fact (astrohub.com) Myth vs Fact (astrohub.com)](/blogs/blogcore/blogfiles/74970.jpg)
![Tree pruning wounds. The fact is the collar of the branch has healing plant hormones--no added wound seal needed. (swindon-bonsai.co.uk) Tree pruning wounds. The fact is the collar of the branch has healing plant hormones--no added wound seal needed. (swindon-bonsai.co.uk)](/blogs/blogcore/blogfiles/74971.jpg)
![Use wood chips as mulch. And keep mulch away from trunk (forethillsconnection.com) Use wood chips as mulch. And keep mulch away from trunk (forethillsconnection.com)](/blogs/blogcore/blogfiles/74972.jpg)
![Adding too much organic matter to planting hole can result in root bound trees. (arborilogical.com) Adding too much organic matter to planting hole can result in root bound trees. (arborilogical.com)](/blogs/blogcore/blogfiles/74973.jpg)
![Sunken beds are for desert gardening, not Napa County gardening (pinterest.com) Sunken beds are for desert gardening, not Napa County gardening (pinterest.com)](/blogs/blogcore/blogfiles/74974.jpg)
Help for the Home Gardener from the Contra Costa Master Gardener Help Desk
Client's Problem and Questions:
Client called (early September) and left a phone message that the her community garden colleague's tomatoes, although now 4 feet tall, set some fruit, but that the plant had suddenly started to turn yellow and appears that the plants won't surive. CCMG Help Desk responded with both a phone call and an email.
CCMG Help Desk Response:
As I mentioned in the phone message that I left for you this morning, the information in your phone message about the tomato problem your community garden colleague has experienced wasn't sufficiently detailed to allow us to diagnose the problem. You mentioned that the tomato had grown about four feet tall and had set some fruit, but that the leaves on the plant suddenly started turning yellow and it now appears that the plant won't survive.
Yellow leaves on tomatoes is associated with many different problems, including lack of nutrients, excess salts in the soil or in irrigation water, toxicity in the soil from nearby walnut trees, and many different plant diseases. You report that the plant had been growing well and producing fruit and declined very rapidly leads me to suspect that the cause may have been a vascular wilt disease.
There is nothing that can be done for plants that have Verticillium or Fusarium wilts. Plants that die should be removed and destroyed. Put the diseased plant refuse in the garbage. Don't compost it since doing so could contaminate the compost with the fungal spores. Crop rotation is of limited value as the vascular wilt fungi may survive in the soil for several years.
You can learn more about Verticillium and Fusarium wilts at these websites: http://www.ipm.ucdavis.edu/PMG/r783100911.html and http://www.ipm.ucdavis.edu/PMG/r783101011.html.
One other word of caution about something you mentioned in your phone message. You indicated that you are using free wood chip mulch from a tree service company in your community garden plot. You said that your plants are growing well and look beautiful, but you didn't mention whether you are growing vegetables or ornamental plants. We don't recommend the use of wood chip mulch in vegetable gardens. Using such mulches for vegetables leads to two different problems. One is that wood chips, if dug in, and as they haven't been fully decomposed, will rob much of the nitrogen from the soils. This depletion of a critical nutrient can affect some ornamentals. It is particularly a challenge for heavy feeders such as tomatoes. If your colleague was using wood chips as compost for her tomatoes, it's possible that one of the problems for her tomatoes was a lack of nitrogen which would also lead to yellowing of the leaves.
The other problem with using wood chip mulch in vegetable gardens is that such gardens need to be replanted after each growing season. The wood chips really get in the way when you're trying to prepare the planting beds, add compost, etc. It is not a good idea to simply work them into the soil since they will continue to decompose, using up the available nitrogen in the process.
A better mulch to use for vegetable gardens would be weed free straw or dried leaves.
Hope that this information is helpful to you and your colleague.
Contra Costa Master Gardeners Help Desk
Editor's Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523.
We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, and we are on the web at http://ccmg.ucanr.edu/
- Author: Betty Homer
Last month, I blogged about cultivating oyster mushrooms in the backyard by inoculating a cylindrical plastic bag containing straw, with mushroom spawn. I am happy to report that my mushroom log project was a success and have enjoyed literally, the fruits of my labor.
This month, I will be discussing another simple method of cultivating culinary mushrooms in your backyard. The variety that I am currently experimenting with is Stropharia rugosoannulata, commonly known as the wine cap mushroom. Although creating the substrate and environment to grow wine cap mushrooms is fairly simple and straight-forward, it may not be until a year or more before you know whether you are successful (contrast this with cultivating oyster mushrooms discussed last month, which will mature fully in a month or less from the time you assemble the mushroom log).
Below are instructions on how to cultivate wine cap mushrooms at home.
Materials List:
1. Large piece of corrugated cardboard (e.g. from a shipping box or grab several boxes from a warehouse store);
2. A large basin, clean garbage can, or plastic tote with which to hold water to soak the cardboard;
3. Wood chips (can be obtained from local arborist looking to dispose of his/her tree waste);
4. Wine cap mushroom spawn (can be purchased on-line); and
5. 1 to 2 plastic kitchen trash bags.
Directions:
Creating Cardboard Spawn
Step 1: Soak cardboard for 30 minutes until the cardboard layers separate easily to reveal the corrugated layer.
Step 2: Shake off excess water from cardboard. Cardboard should be damp, but not dripping wet. Separate cardboard by tearing back top layer to reveal the corrugated layer.
Step 3: Sprinkle and distribute the spawn all over the cardboard until a uniform, thin layer forms.
Step 4: Roll up the cardboard at the short-end so that it resembles a scroll. Note that the moisture level in the cardboard is similar to a wrung-out sponge or something close to it. Place the rolled-up inoculated cardboard into a kitchen trash bag, keeping the bag open so that the inoculated cardboard can breathe.
Step 5: Leave the plastic bag containing the rolled-up cardboard in a warm place (i.e., room temperature), out of direct light. Check every couple of days to see whether your cardboard is still sufficiently moist (moisture will evaporate over time). If the cardboard has dried out some, just spray some water on it, enough to keep it moist.
Step 6: After 2 weeks, the cardboard should be fully colonized. You can tell by unrolling the “scroll” and examining the cardboard for white mycelium threads, which form various spider web-like patterns. When it is fully colonized, transplant it outdoors in a shady spot by layering it between woodchip layers (directions to follow).
Creating a Woodchip Bed Using Cardboard Spawn
Step 1: Soak wood chips in clean water until thoroughly saturated.
Step 2: Choose a shady place in your garden and rake aside the topsoil in that spot.
Step 3: Set down one layer of your inoculated wet cardboard.
Step 4: Shovel a layer of wood chips 1-2 inches deep on top of the inoculated wet cardboard.
Step 5: Set down another layer of your inoculated wet cardboard on top of the wood chip bed (think of creating lasagna layers, alternating between your inoculated wet cardboard and wood chip layers).
Step 6: Finish the bed by shoveling another layer of wood chips on top of your inoculated wet cardboard.
Step 7: During the course of the year, keep your wood chip bed moist but not overly saturated. Avoid having water pool or puddle in or around the wood chips.
Step 8: Wait the year for results.
![Finished product after assembling Finished product after assembling](/blogs/blogcore/blogfiles/19167.jpg)