Every gardener knows that weeds are just plants in the wrong place. Webster's dictionary defines a weed as “a plant that is not valued where it is growing and is usually of vigorous growth; especially: one that tends to overgrow or choke out more desirable plants.”
Some weeds, those with large root systems or a taproot, penetrate deep into subsoil, breaking up compaction, which helps drainage and new growth. This deep penetration enables weeds to accumulate trace elements from the subsoil, and bring them to the soil's surface. The plants then die back and decompose, becoming what is called green manure.
The primary value of weeds, wrote the eminent U.S. botanist Frederick Clements in 1920, is to “reveal information about the health and pH of our soils.” For example, certain species are confined to acidic soils and others to alkaline.
The use of weeds as soil indicators is not a new idea. Many early North American immigrants to the eastern United States chose land for their farms according to the weeds, plants, and trees that it supported. Conifers were characteristic of sandy, acidic soils that had little agricultural value. Birch, beech, maple, and hemlock indicated fertile soil. They learned that the tall-grass prairies were suitable for cereals, hay, and orchards. The bunch grass regions were better suited to wheat and grass.
Another useful indicator comes from growing hydrangea, a beautiful and common flowering plant. If your soil is acidic the flowers will be blue. If your soil is more alkaline the flowers will be pink.
Ehrenfried E. Pfeiffer, a European scientist and student of Rudolf Steiner, wrote an entire book on this subject in the 1950s: “Weeds and What They Tell Us” (still in print). According to Pfeiffer, sorrel, plantain, horsetail, and knotweed are found in acidic soils. Dry soils with very little humus might support mustard, thistle, broom, and St. John's wort.
Sandy soils will have goldenrod, aster and toad flax. Alkaline soils support chicory, spotted spurge, sagebrush and woody aster. In heavy clay or compacted soil you might see morning glory, plantain, Bermuda grass, chickweed, and dandelion. Dandelions also indicate low calcium in the soil.
Identifying the weeds in your garden can be fun! In some cases knowing what their presence indicates may help you manage your soil. Controlling weeds by hand weeding or with herbicide before they seed will reduce future populations if done consistently from year to year. One year's uncontrolled weeds can produce seven years seeds! You may even develop a new appreciation for weeds.
For more information about weeds or help identifying them; see the UC Statewide Integrated Pest Management website on weeds.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at email@example.com or leave a phone message on our Hotline at (530) 538-7201. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
From the Livestock and Range blog
Did you miss the Weed Management for Small Acreage Workshop? Don't worry! Here's the link to all the presentations: https://youtube.com/playlist?list=PLLjlfxpbNglYGn38KY94aoo6z3pLjo7E4.
- Poisonous Plants
- Yellow Starthistle Control
- Herbicide Resistant Weeds
- Weed ID and Management 101
- Posted by: Gale Perez
Here's part 3 of our training videos: Weed Identification. We've broken it up into three smaller parts for easier viewing.
- Author: Lynn M. Sosnoskie
University of California Small Grains - Alfalfa/Forages Field Day
Wednesday, May 15, 2019
UC Davis Department of Plant Sciences Field Headquarters
2400 Hutchison Dr., Davis, CA 95616, Davis, CA
8:00-4:30 Includes Lunch
The annual UC Small Grains/Alfalfa-Forages Field Day will be held on May 15th at the University of California, Davis Department of Plant Sciences Field Headquarters on Hutchinson Road (west of Highway 113) from 8AM – 4:30PM.
The event showcases UC efforts in breeding and agronomic research related to small grains, alfalfa and forage crops and is one of the longest running field days in the state. The small grains portion will take place from 8 to noon and the alfalfa/forages section will take place between 12:40 and 4:30. A barbecue lunch will be provided.
7:30 Registration (no charge)
8:00 Start of Small Grains Program
8:00 Welcome and Opening Remarks
8:35 Malting Barley & Oat Breeding: Alicia del Blanco, UC Davis
8:45 Barley Breeding for Food, Feed and Forage: Allison Krill-Brown, UC Davis
9:00 New Wheat Varieties: Oswaldo Chicaiza, UC Davis
9:15 Breeding Triticales for Bread and Forage: Josh Hegarty, UC Davis
9:25 Increasing Grain Size and Number: Alejandra Alvarez, UC Davis
9:35 A New Gene Controlling Number of Grains Per Spike: Saarah Kuzay, UC Davis
9:40 Balancing Source and Sink to Increase Yield: Jorge Dubcovsky, UC Davis
10:00 Herbicide Programs for Barley and Wheat: small grain herbicides and maximizing efficacy for control: Lynn Sosnoski, UC Cooperative Extension
10:20 Italian Ryegrass: Updates on Cultivation vs Herbicide Trials: resistance and methods for control: Konrad Mathesius, UC Cooperative Extension
10:30 Warm-season legume cover crop between winter small grains: Michelle Leinfelder-Miles, UC Cooperative Extension (This project was supported by the California Climate Investments program.)
10:45 Using Nitrogen Rich Reference Zones to Guide Wheat Topdress Decisions in the Sacramento Valley: Sarah Light, UC Cooperative Extension
10:55 Yield and Protein Stability for Wheat and Triticale Varieties Grown under N and Terminal Drought Stress: Mark Lundy, UC Cooperative Extension
11:05 Updates on UC Statewide Small Grain Trials: Seasonal conditions, pests and diseases, nitrogen management, and extension efforts: Mark Lundy, UC Cooperative Extension
11:15 Comments from breeders with entries in UC Statewide Small Grain Trials
11:30 UC Statewide Small Grain Trial Observations
11:50 Return for lunch
12:00 BARBEQUE LUNCH – Sponsored by CCIA – Many thanks to the staff at CCIA!
12:40 Start of Alfalfa and Forage Portion
12:40 Welcome and Introductions—Dan Putnam, UCCE/UCD Alfalfa Specialist
12:50 Managing Alfalfa in a Wet Year- What are the Diseases?-How to Help your Fields Recover? Rachael Long, UCCE Farm Advisor, Yolo County, Woodland, CA
1:05 IPM and Managing for Weevil Resistance in Alfalfa – Ian Grettenberger, Entomology Specialist, UC Davis, CA
1:20 Evaluation of N Stabilizers in Corn –Michelle Leinfelder Miles, UCCE Farm Advisor, Delta Region.
1:35 Forage Sorghum as a Summer Option: Controlling Sugarcane Aphid in Sorghum/ Sudangrass—Nick Clark, UCCE Farm Advisor, Kings/Fresno/Tulare Counties
1:50 Innovations in Overhead Irrigation – How that might improve Water Use Efficiency—Isaya Kisseka, UC Davis Professor, Irrigation Technology
2:10 Fun with Drones –Detecting Pest and Diagnosing Problems with Aerial Photography—Umair Gull, UC Davis Graduate Student, Plant Sciences.
2:25 Controlling Difficult Weeds in Alfalfa—Lynn Sosnoskie, UCCE Farm Advisor, Merced County.
2:50 Alternative Crops Research—Kura Clover, Switchgrass, Hemp—Dan Putnam, UC Davis
3:05 Reduced Lignin Alfalfa Varieties and Interactions with Harvest Scheduling—Brenda Perez, Graduate Student UC Davis
3:20 Analyzing Alfalfa Varieties for Pest Resistance (Nematodes, Insects, Diseases) and other characteristics—Dan Putnam, UC Davis
3:35 Alfalfa and Tall Fescue Breeding Programs at UC Davis –Charlie Brummer and students, UC Davis.
3:50 Test your Weed ID IQ: Weed Identification—Brad Hanson, UC Davis
4:15 Return to Headquarters
- Author: Lynn M. Sosnoskie
The importance of proper weed identification
Weeds are a problem in a variety of systems, from agronomic and horticultural crops, to orchards and vineyards, to turf and ornamentals, to rangelands, and to natural areas. The first step in developing a successful weed management program is to ensure that the unwanted vegetation has been identified correctly. Not all weeds respond equally well to all treatment measures. For example, broadleaf weeds will be managed by the auxinic herbicides (WSSA Group 4) whereas grasses will not. Mowing may be more effective at suppressing upright growing species as opposed to those that are more prostrate. Shallow cultivation may control annual weed species while missing deep-rooted perennials.
- A successful identification provides you with the knowledge that you need to develop a successful management plan
- Your strategy should based on the sensitivity of a target species to control measures
Weed identification books, phone applications and submitting samples
There are numerous tools available to help you identify weedy species, including guidebooks (Weeds of the West, ISBN-13:0-941570-13-4; Weeds of California and Other Western States, ISBN-13:978-1-879906-69-3) and phone applications (Pl@ntNet https://plantnet.org/en/; iNaturalist https://www.inaturalist.org/).
Local extension advisors can also help with the identification of troublesome species. Identifications can be made either from live specimens or from digital images. If submitting a fresh sample, collect several plants that are representative of the infestation. Collect as much of each individual plant as possible (including roots, flowers and seed pods). Place the samples in a sealed ziploc bag with a few damp paper towels and deliver (or ship) your specimens to your county office (the faster, the better, as fresh samples are easier to identify). Be sure to include your name and contact information, the location of where the weeds were collected (GPS coordinates, address, and description of the habitat (i.e. roadside, orchard, alfalfa field, etc)), as well as any other relevant information.
If emailing digital images, be sure to capture pictures of the plant's leaves, stems, flowers, roots, and seedpods, as well as a photo of the specimen in its environment. Try to remove excess vegetation from around the sample so that its growth habit is apparent. Take photos of any unique structures (such as spines) that could be a diagnostic tool. Include the same contact information (name, address, etc) as listed above in your message.
Remember, it can take several days to determine an ID and some specimens may require confirmation from additional sources, such as the staff at the UC Davis Herbarium.
Figure 1. Strategies to improve weed ID success using digital images.