Weed Seed Identification

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Check out our article on How to Identify a Female Marijuana Seed. Click for more Grow at Home information from I49 Seed Bank. Weed seeds for sale online in the USA. 1-888-441-4949 Classification of weed seeds based on visual images and deep learning Images of single weed seeds were rapidly and completely segmented, and six popular and novel deep Convolutional Neural Weed Identification Tools and Techniques Every kind of weed has an identity—its species. Following are some tools and techniques for identifying the weed species in your fields. Identifying

How to Identify a Female Marijuana Seed

Ask any experienced grower how to produce a hardy marijuana plant and they will say to start with a seed for a good strain. Lighting, soil, nutrients, and water play large roles in the final yield, but starting with a high-quality seed gives growers the best genetics with the highest potential yield possible. Most people find their first seed mixed in with marijuana, but most of these seeds are low quality and may grow to be male plants. The best way to get high-quality seeds is to purchase them from a reputable marijuana seed retailer.

Characteristics of a Quality Marijuana Seed

Quality marijuana seeds have specific characteristics that set them apart. Unfortunately, they can be difficult for consumers to find since most growers avoid seed production in their plants at all costs. Even when a rogue seed is present, it rarely grows mature enough to germinate. Though it is challenging to identify a quality seed for even the most experienced growers, it is vital to be able to do so when using seeds to grow marijuana. Below is an overview of the characteristics of a high-quality seed.

Appearance

There are several visual indicators that can give a person an idea about the quality of a marijuana seed. Some details are easy to spot while others take a higher level of scrutiny.

Color

A high-quality marijuana seed has a dark color, typically a shade of brown, grey, or black. It should have tiger-like stripes or spots on the entire surface of the seed. If the seed is green or white, it is immature and is not likely to germinate. In the rare circumstance that an immature seed germinates, it takes much longer than it would for a mature seed.

Coating

Good quality marijuana seeds have a waxy coating around the shell. This is easy to see if the seed is held up to the light because the shell will have a slight sheen.

Size & Shape

The largest seeds are the best ones to grow. It is easier to pick the largest ones if there are several to compare side by side. Growers should look for the most symmetrical seed that is round or shaped slightly like a teardrop. Underdeveloped seeds are small and have an asymmetrical shape.

A lot of information can be gleaned from the texture and hardness of a marijuana seed. After visually inspecting the seeds, growers can pick them up and feel their shell for the following:

Cracks

Poor quality seeds have weak shells that are damaged easily. These seeds will have cracks or splits on them that expose the inside. The best seeds have a smooth exterior with few anomalies.

Hard Shell

A mature, high-quality marijuana seed has a hard shell that can withstand the pressure of being squeezed between two fingers. Poor quality seeds will disintegrate when squeezed. If this happens, the seed was weak or dead and would not have grown a viable plant if it germinated at all.

How to Determine the Quality of a Marijuana Seed

While seeing and feeling a marijuana seed can give growers a lot of information, it is not always accurate. Even the best-looking seeds can be duds, especially if they have been frozen. Below are a few things growers can do to better determine the quality of their seeds.

Germinate the Seed

The most obvious thing a person can do to show seed quality is to germinate the seed. If the seed sprouts within 5 days, it is a viable seed. It will still take time to find out if the plant will be male or female and whether the strain is high quality.

How to Germinate a Marijuana Seed

The traditional way to germinate a seed is to bury it one-quarter inch deep in moist soil and watch it closely for a sprout. A freshly germinated seed has a very fragile root that is easily damaged when the seed is transplanted. This method allows the seed to germinate without root interference.

Another common way to germinate marijuana seeds is by wetting a folded paper towel or cotton pad and placing the seeds inside of it. It is important not to get the paper towel or cotton pad too wet or it could drown the seeds. Growers should check the seeds after a few days to see which have taken root.

Perform a Float Test

The float test is a more scientific approach to determining the quality of a seed. The test involves filling a drinking glass with spring or distilled water and placing the seeds inside of it. Allow the seeds to soak for one to two hours before determining quality.

After the time has passed, seeds that float can be considered poor quality and discarded. Seeds that have sunk to the bottom of the glass are healthy, high-quality seeds. Once the test is complete, the seeds need to be germinated right away. Their shells will be soft from soaking in the water and will not survive storage.

Source Them Well

The simplest way for growers to ensure they have high-quality seeds is by sourcing them from a reputable seed bank. These companies specialize in breeding a variety of marijuana strains and producing seeds that, with the right care, grow into viable, high-yielding plants. Growers can choose a variety that meets their requirements for potency and desired effects and be sure they are getting seeds that produce the plant they want.

Using an Online Marijuana Seed Bank

Those who live in a state where marijuana is legal for medical or recreational use can sometimes find seeds at their local dispensary. However, online marijuana seed banks have significantly more strains available. Even individuals who live in some states where marijuana has not been made legal to use can purchase seeds online. Several states consider dormant seeds to be souvenirs, so it is legal to purchase and own the seeds as long as they don’t become high-THC plants.

Do Marijuana Seeds Expire?

Many growers who have numerous marijuana seeds need to store them long term if they want to germinate them in the future. However, seeds need to be kept in specific conditions to remain viable. They should be stored in a cool, dark, and dry room, much like the environment in which growers dry their harvested marijuana.

Germinating Old Seeds

Seeds can remain viable for three to ten years if stored properly, but more and more seeds will fail to germinate as time passes. Older seeds will take more time to germinate, so growers should use the float test before assuming the viability of their stored seeds. They can speed germination by soaking the viable seeds in water mixed with a few drops of hydrogen peroxide for 24 hours. It is important to watch them closely for signs of opening, as they will need to be removed immediately to avoid drowning.

Can You Tell if a Marijuana Seed is Female?

Cannabis enthusiasts have been trying to find out how to determine the sex of a marijuana plant by the seed for ages. Unfortunately, there is no way to tell if the seed will produce a male or female plant by just looking at the seed. Regular marijuana seeds have a 50% chance of being female, so out ten seeds, growers can expect that 5 of them will probably produce female plants.

What Does a Male Cannabis Plant Look Like?

When growing marijuana, it is important to identify male plants as early as possible. Just one male plant can pollinate an entire field, so it is critical that male plants are removed before they develop pollen sacs. There are certain signs that a young marijuana plant is male, including the following:

Preflowers

Preflowers are the earliest sign of a marijuana plant’s gender. Between four and six weeks, nodes will develop at the joint where a plant’s stem meets the stalk. Female plants develop white hairs at the internodal joints while male plants develop rounded internodal sacs that fill with pollen.

While it is best to identify male marijuana plants by their pollen sacs as soon as possible to avoid accidental pollination, there is another way to determine a plant’s sex. If male and female seeds are planted at the same time, the male plants will grow faster and taller than the female plants. Additionally, male plants have longer stems with fewer leaves, making them look spindly compared to female plants.

See also  Seeded Weed

Final Thoughts

Quality seeds are not often found in the bottom of a bag of dried marijuana, but there are ways for growers to ensure they are getting the best seeds available. With a keen eye and a reputable seed bank like i49.net, growers will have hardy, high-yield plants that make them proud of their hard work. Seed banks provide quality marijuana seeds in a variety of strains not typically available from other sources, and many of them can guarantee that the seeds will be feminized and thus produce female plants.

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    Classification of weed seeds based on visual images and deep learning

    Images of single weed seeds were rapidly and completely segmented, and six popular and novel deep Convolutional Neural Network models are compared to identify the best method for intelligently identifying 140 species of weed seeds.

    This research is beneficial for developing a detection system for weed seeds in various applications.

    When the weed seed dataset is expanded, the model can simply be retrained and the old CNN model can be replaced to complete the upgrade.

    Abstract

    Weeds are mainly spread by weed seeds being mixed with agricultural and forestry crop seeds, grain, animal hair, and other plant products, and disturb the growing environment of target plants such as crops and wild native plants. The accurate and efficient classification of weed seeds is important for the effective management and control of weeds. However, classification remains mainly dependent on destructive sampling-based manual inspection, which has a high cost and rather low flux. We considered that this problem could be solved using a nondestructive intelligent image recognition method. First, on the basis of the establishment of the image acquisition system for weed seeds, images of single weed seeds were rapidly and completely segmented, and a total of 47 696 samples of 140 species of weed seeds and foreign materials remained. Then, six popular and novel deep Convolutional Neural Network (CNN) models are compared to identify the best method for intelligently identifying 140 species of weed seeds. Of these samples, 33 600 samples are randomly selected as the training dataset for model training, and the remaining 14 096 samples are used as the testing dataset for model testing. AlexNet and GoogLeNet emerged from the quantitative evaluation as the best methods. AlexNet has strong classification accuracy and efficiency (low time consumption), and GoogLeNet has the best classification accuracy. A suitable CNN model for weed seed classification could be selected according to specific identification accuracy requirements and time costs of applications. This research is beneficial for developing a detection system for weed seeds in various applications. The resolution of taxonomic issues and problems associated with the identification of these weed seeds may allow for more effective management and control.

    Weed Identification Tools and Techniques

    Every kind of weed has an identity—its species. Following are some tools and techniques for identifying the weed species in your fields.

    Identifying all the weeds on a farm is not easy, and it is usually not necessary. However, correctly identifying major weeds can be an important first step toward effective control. Two weed species can look very similar at certain growth stages, yet differ greatly in life cycle, modes of reproduction, effects on crops, and responses to control tactics.

    What’s in a Name?

    A plant’s species name can be spelled out in Latin (its scientific name, e.g., Amaranthus retroflexus) or in plain English (its common name, e.g., redroot pigweed). Scientific names are more precise, as each species has just one valid scientific name at any one time. They are also less descriptive and a little harder to pronounce, especially for those of us who did not take Latin in school.

    Common names are more user-friendly but less precise. A given weed might have two or more common names. For example, common lambsquarters is also called fat-hen or white goosefoot. Some common names have been attached to two different weeds; for example, lambsquarters has also been called pigweed in some regions, and the term witchgrass has been applied both to the perennial quack grass and to an annual weed closely related to fall panicum. In order to minimize such confusion, weed scientists have adopted official common names, such as common lambsquarters for the species Chenopodium album, and redroot pigweed for Amaranthus retroflexus.

    Botanists position each plant species in the enormous family tree of the plant kingdom, which illustrates current best estimates of each species’ genetic and evolutionary relationships with other plant species. A genus (plural genera) is a group of closely related species that share many characteristics of appearance, growth habit, and genetic makeup. Latin names are usually in two words, denoting the genus (e.g., Amaranthus) and the species (e.g., retroflexus).

    Some plant species have distinct variants called subspecies, for which the Latin name has three words. Subspecies may evolve naturally as a species adapts to different environments (as many weeds do), or may be developed through plant breeding (e.g., cabbage, broccoli, kohlrabi, cauliflower, collards, and kale are all subspecies of Brassica oleracea). Subspecies can cross-breed, a fact that is important to understand. For example, Japanese millet (Echinocloa crus-galli ssp. frumentacea), a useful grain and cover crop, is a subspecies of barnyard grass (Echinocloa crus-galli), the world’s third worst weed!

    Plant Families

    The next larger grouping above genus is family. Some of the better-known plant families in agriculture include the grass family (including cereal grains, corn, sorghum, millets, and pasture grasses); the legume family (including peas, beans, clovers, and alfalfa); the brassica family (including cabbage, broccoli, cauliflower, radishes, and mustards); and the nightshade family (including tomato, potato, pepper, and eggplant).

    Knowing a weed’s plant family is important, as many economically important crops have weedy relatives in the same family, which may harbor insect pests or pathogens of the crop, or in some cases cross-breed with the crop itself. Occasionally, the weedy relative can play a beneficial role, acting as a trap crop to divert pests from the cash crop, or supporting important natural enemies of the pests as well as the pests themselves.

    Identifying Characteristics of Weeds

    Identify weeds with the help of a good field guide, manual, or taxonomic key to the agricultural weeds in your region. Collect a representative specimen or several specimens (recommended), and examine them closely, including foliage, stem, flowers, roots, and other belowground parts. Familiarize yourself with some of the jargon used in your field guide or key (most references have a glossary of terms).

    Plants are identified by visible characteristics that remain roughly constant among all individuals within a species. These can include:

    • Leaf shape, leaf margins, and venation (branching pattern of leaf veins)
    • Leaf structure (simple or compound)
    • Arrangement of leaves on the stem
    • Presence or absence of hairs on leaves or other parts of the plant
    • Flower structure, color, size
    • Inflorescence (arrangement of flowers or flower clusters on plant)
    • Size, shape, structure, color, and arrangement of fruits and seeds
    • Roots, rhizomes, and other underground structures
    • Life cycle (annual, biennial, perennial)
    • Habit of growth (erect, prostrate, climbing, etc.)

    Characteristics that are more variable within a species, yet can help identify the weed include:

    • Plant height and lateral spread
    • Degree of branching, arrangement of branches on main stem
    • Leaf size
    • Leaf and stem coloration; stem hollowness

    Other distinctive characteristics that help identify some weeds include:

    • Presence of spines, thorns, prickles, or stinging hairs
    • Milky juice or sap when stem or leaves are cut
    • Presence of a leaf sheath surrounding the stem at each node
    • Stems square in cross section

    For more on how to recognize identifying characteristics of weeds, see A Basic Illustrated Glossary of Plant Identification Jargon below.

    The more defining characteristics you can observe, the faster and easier it is to get a positive ID on the weed. Useful tools for identifying weeds include a ruler or folding rule to measure plants and plant parts; a hand lens or magnifying glass for examining small plant parts or features; a trowel, spade, or digging fork for exhuming intact root systems and other underground structures; and a weed identification guide or manual (Fig. 1).

    Figure 1. Some basic weed identification tools. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Noting when and how a weed emerges and grows can aid in identification. Summer annuals are mostly frost-tender, usually emerge between the spring frost-free date and late summer, and die at the first fall frost. Winter annuals emerge any time between the end of summer and early the following spring, flower and set seed in spring or early summer, and usually dry up with the onset of hot weather. Thus a weed that is still thriving after a fall frost is almost certainly not a summer annual such as pigweed, purslane, or galinsoga, and a weed that is succulent and vegetative in July is probably not a winter annual like henbit or yellow rocket.

    How a weed first emerges from the soil can give clues to whether it is coming up from a seed or from a rhizome or other perennial underground structure (Fig. 2). Dig up the emerging weed to see if it is a true seedling (easy to dig up, few fine roots, remains of seed or seed coat may or may not still be visible), or sprouting from a perennial root or other structure (harder to dig up, attached to a larger root, rhizome, tuber, or fragment thereof).

    Figure 2. The small weeds in this photo are true seedlings, having germinated over the past two weeks. The larger weeds with somewhat arrow-shaped leaves are shoots of hedge bindweed that have emerged from rhizome or rhizome fragments within the top foot or so of soil. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Identifying Weeds at an Early Age

    Flowering specimens are easiest to identify to species, because they display the greatest number of defining traits. In fact, plant families are delineated to a large degree by flower structure. However, growers often want to identify major weeds in earlier growth stages, even as emerging seedlings, in order to determine best management strategies while the weeds are small and relatively easy to control. This can be challenging to say the least. If a particular species has you stumped, let a few individuals develop into mature, flowering plants, then identify them.

    Some weed manuals include good photographs and descriptions of seedling characteristics that allow identification of the weed’s plant family or genus, if not species. Seedling characteristics include:

    • Presence or absence, number, size, and shape of the seed leaves (cotyledons) on the aboveground part of the emerged seedling
    • Shape, arrangement, and size of the first true leaves emerging above the cotyledons
    • Stem and leaf coloration
    • Presence or absence of hairs on leaves or stem

    Finding the Weed’s “Photo ID”

    Once you have a weed specimen in hand, use one of these methods to identify its species:

    • Compare the weed with photographs and written descriptions of similar-looking weeds in a field guide or manual.
    • Use a dichotomous key, which consists of a series of “either–or” pairs of categories of plant characteristics, through which you gradually narrows possibilities down to one or a few species. At this point, the key provides detailed descriptions, usually with photos to verify the ID.
    • Use an interactive key, usually available on line or on a computer CD-ROM, which allows you to start with the most readily observable characteristics of the specimen at hand to identify the species or arrive at a short list of possible species IDs. The interactive key is usually better than the dichotomous key for identifying a weed in a vegetative (non-flowering) stage of development.

    The direct comparison method is especially useful when you want to verify the ID of a weed with which you are familiar, or for which you have narrowed it down to a short list of possibilities. A strong likeness of the specimen to a photo or diagram, and a close match with the manual’s written description suggests a correct ID. A clear discrepancy in one or more defining characteristics indicates an incorrect ID—try again. This method can be quick and efficient when the list of possible species is reasonably short—if the manual is well organized, is written for your region, and includes the weed in question! Time-consuming pitfalls include random guessing, and trying to verify ID of a weed that the manual does not include.

    The dichotomous key is the time-honored method by which botanists and agricultural scientists have identified weeds, native vegetation, or cultivated plants for the past century or more. The dichotomous key can provide a definitive ID when skillfully used. Starting at the beginning of the key, read each pair of characteristic descriptions or categories, and choose the one that best matches the specimen at hand. Each choice gives a reference number directing you to the next pair of characteristics to examine. It works much like a treasure hunt.

    Dichotomous keys often use a lot of botanical jargon, so make sure the key has a good glossary of terms before buying the book. One disadvantage is that some of the dichotomies may refer to characteristics not shown by the specimen (e.g., flower color when the specimen is vegetative), or may be difficult to see. In this case, you will need to explore both sides of the dichotomy. Errors early in the process can send you on a lengthy “wild goose chase” until the error is discovered.

    Several land grant universities and the Weed Science Society of America have developed interactive keys, based on computer databases that catalogue all of a region’s or the continent’s main agricultural weeds. The interactive key allows you to begin with the most readily visible or measurable traits of the specimen at hand. There is no set order in which to answer questions about the weed; instead, you can click on leaf shape, life cycle, flower color, root structure, or other characteristics, choosing the best match from a list of several alternatives. The key maintains a list of weeds that match the description being developed, narrowing the list down with each choice until the weed is identified or a short list of possible species remains. The database includes verbal descriptions and photos of each weed to assist with positive ID.

    Weed Identification Challenges

    Any of these methods is only as good as the weed manual, key, or database used, the quality of the specimens available, and the observation skills of the user. If the weed in question is not included in the key or guide being used, you can waste a lot of time searching for it in vain! It is important to choose a manual or database that is written for your region and includes all of the region’s major agricultural weeds. If a particular weed cannot be found in the reference you are using, it could mean any of the following:

    • The manual is not sufficiently comprehensive.
    • The plant was not recognized as an economically important agricultural weed in the region when the manual was written.
    • The weed is a new invader from another region, country or continent.

    If you cannot identify an important or abundant weed species present on the farm:

    • Try to narrow it down to plant family or genus.
    • Watch it closely to determine life cycle and habit of growth.
    • Collect and try to identify additional specimens at different seasons and growth stages.
    • Bring fresh specimens to the county Extension office or a nearby university weed science department for help with identification.

    Farmers who bring fresh specimens of new or unfamiliar weeds in to Extension or university departments for positive ID can help with early detection of a new exotic invader or changes in weed geographic ranges related to climate changes or other factors.

    A basic illustrated glossary of plant identification jargon

    Figure 3. Structures on a broadleaf weed or crop. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 4. Structures on a grass weed or crop. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 5. Broadleaf seedlings. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 6. Roots and other underground structures. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 7. Leaf shapes. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 8. (a) Leaf margins. (b) Leaf venation. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 9. Leaf structures. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 10. Arrangement of leaves on stem. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 11. Flower structures. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 12. Types of flowers. Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    Figure 13. Inflorescences (arrangement of flowers in clusters). Figure credit: Mark Schonbeck, Virginia Association for Biological Farming.

    This article is part of a series on Twelve Steps Toward Ecological Weed Management in Organic Vegetables. For more on weed monitoring and identification, see:

    Weed Identification Resources

    Books

    • Baldwin, F. L., L. R. Oliver, and C.M. Bonner. 1982. Identifying seedling and mature weeds of Arkansas field crops. University of Arkansas, Fayetteville, AR.
    • Chomas, A. J., J. J. Kells, and J. B. Carey. 2001. Common weed seedlings of the north central states. North Central Regional Extension Publication No. NCR 607. Available online at: https://cdn.shopify.com/s/files/1/0145/8808/4272/files/NCR607.pdf (verified 23 Jan 2020).
    • Fishel, F., B. Johnson, D. Peterson, Mark Loux, and C. Sprague. 2000. Early spring weeds of no-till crop production. North Central Regional Extension Publication No. NCR 614. MU Extension, University of Missouri-Columbia. Available online at:http://weeds.cropsci.illinois.edu/extension/Other/NCR614.pdf (verified 23 Jan 2020).
    • Miller, J. F., A. D. Worsham, L. L. McCormick, D. E. Davis R. Cofer, and J. A. Smith. 1975. Weeds of the southern United States. Circular 599. North Carolina Agricultural Extension Service.
      This field guide covers 120 major weeds of the southern region (AL, AR, FL, GA, KY, LA, MS, NC, OK, SC, TN, TX, VA). The weeds covered were culled from a larger list of 300 weeds based on a survey conducted throughout the region, and thus does not cover all the significant weeds present. Weeds are arranged by family, and entries for each weed include a photograph, common and scientific name, and a one-paragraph description of life cycle, vegetative and flower characteristics.
    • Holm L. G., D. L. Plucknett, J. V. Pancho, and J. P. Herberger, 1991. The world’s worst weeds. Kriegar Publishing Company, Malabar, FL.
      Lists the world’s 18 most damaging weed species (17 of which occur in the United States!) in descending order of global economic impact, followed by another 58 major weeds in alphabetical order. Chapters on each weed give thorough descriptions, black-and-white drawings, world distribution maps, and information on habitat, propagation, biology, effects on different crops, and environmental conditions that favor, suppress, or kill the weed. This can be a particularly valuable resource for evaluating the potential impact of certain serious weed species on the organic farm, as well as learning the weed’s weak points that can be exploited for control.
    • Isely, D. 1960. Weed identification and control in the north central states. Iowa State University Press, Ames, IA.
      Includes a key to plant families, and to weed species. Chapters are organized by plant family. Some of the Latin and common names are out of date, but high quality illustrations of plant, leaf, and flower structure, and a thorough glossary make this a potentially valuable plant identification resource.
    • Pratt, D. B., M. D. Owen , L. G. Clark. 1999. Identification of the weedy pigweeds and waterhemps of Iowa. Iowa State University Cooperative Extension, Ames, IA. Available online at: https://store.extension.iastate.edu/product/Identification-of-the-Weedy-Pigweeds-and-Waterhemps-of-Iowa (verified 23 Jan 2020).
    • Radford, A. E., H. E. Ahles, and C. R. Bell. 1968. Manual of the vascular flora of the Carolinas. University of North Carolina Press, Chapel Hill.
      Most common weeds of the southeastern US will be included in this flora.
    • Stubbendieck, J., M. J. Coffin, and L. M. Landholt. 2003. Weeds of the Great Plains. Nebraska Department of Agriculture, Lincoln, Nebraska. Order form: http://www.agr.ne.gov/forms/nw11.pdf (verified 16 Dec 2010).
      Standard ID reference for most people in the western Corn Belt. Excellent color photos and black-and-white line drawings of 265 species, descriptions of an additional 125 species. Almost 600 pages in a hardbound book.
    • Stucky, J. M., T. J. Monaco, and A. D. Worsham. 1994. Identifying seedling and mature weeds common in the southeastern United States. North Carolina Agricultural Research Service and North Carolina Cooperative Extension Service, Raleigh, NC.
    • United States Department of Agriculture, Agricultural Research Service. 1971. Common weeds of the United States. Dover Publishing, New York.
      Lists significant weeds of the US by plant family. Each entry includes a distribution map for the continental US, drawings of the whole plant, flowers, leaves and seeds, and a thorough description of the plant and its habitat(s). Some names and distribution ranges may be out of date, but this classic still has a lot to offer.
    • Uva, R. H., J. C. Neal, and J. M. DiTomaso. 1997. Weeds of the northeast. Cornell University Press, Ithaca, NY.
      This reference covers 299 common weed species, arranged by plant family, with excellent photographs, detailed verbal descriptions, and comparisons to help the user distinguish between similar species. A dichotomous key, based on vegetative characteristics and supported by an excellent illustrated glossary of terms, allows the user to narrow a weed down to a short list of possible species whether or not the specimen at hand is in flower. Identification is then completed by comparison with photos and descriptions.
    • Zomlefer, W. B. 1994. Guide to flowering plant families. University of North Carolina Press, Chapel Hill.
      Although not focused on weeds per se, this volume gives excellent descriptions and anatomical diagrams of the defining characteristics of plant families, including all the major weed families. Excellent and comprehensive illustrated glossary of terms in botany and plant anatomy.

    Computer Disk

    • Old, R. 2008. 1,200 weeds of the 48 states & adjacent Canada: An interactive identification guide [DVD]. XID Services, Inc., Pullman, WA. Available from: http://xidservices.com/ (verified 16 Dec 2010).
      This is a computer CD that includes a database and an interactive key to 1,200 agricultural weeds throughout the continent. Instead of moving through dichotomous categories in a set sequence, the user can select from a wide range of vegetative and reproductive characteristics, using the most obvious traits of the specimen at hand to narrow down the list of possibilities.

    Online Weed Identification Resources

    • New Jersey Weed Gallery [Online]. Rutgers New Jersey Agricultural Experiment Station. Rutgers, the State University of New Jersey. Available at: http://njaes.rutgers.edu/weeds/ (verified 16 Dec 2010).
      Alphabetical listing by common name or scientific name. Excellent photographs and very brief descriptions of 135 of the most common weeds in the mid-Atlantic region, including may major weeds of the South.
    • Hall, D. W., V. V. Vandiver, and J. A. Ferrell. 2006. Weeds in Florida (SP 37). EDIS – Electronic Data Information Source – UF/IFAS Extension. University of Florida, Institute of Food and Agricultural Sciences. Available at: http://edis.ifas.ufl.edu/topic_book_florida_weeds (verified 16 Dec 2010).
      Photos and brief descriptions of 37 common weeds in Florida.
    • Weed Identification [Online]. Board of Trustees, University of Illinois. Available at: http://web.aces.uiuc.edu/weedid/ (verified 16 Dec 2010).
      This easy-to-use interactive key covers 172 species. The user enters known characteristics including life cycle, growth habit, leaf and flower characteristics to narrow down the list. Brief description and one or more photos for each weed. A few errors were discovered on the site, such as classifying the perennial weeds field horsetail and tall fescue as annuals.
    • Hagood, S. 2008. Virginia Tech Weed Identification Guide [Online]. Department of Plant Pathology, Physiology and Weed Science. Virginia Polytechnic Institute and State University. Available at: http://oak.ppws.vt.edu/weedindex.htm (verified 16 Dec 2010).
      This resource covers 324 weeds of the southeastern United States, arranged alphabetically by common name and by scientific name. Each entry includes photos of seedling and mature phases, close-ups of leaves and flowers, and verbal descriptions of life cycle, growth habit, leaves, flowers, and specific identifying characteristics. An interactive key to grass weeds is included to assist the user with this large family of hard-to-identify species.
    • Photo Gallery [Online]. Weed Science Society of America. Available at: http://www.wssa.net/Weeds/ID/PhotoGallery.htm (verified 16 Dec 2010).
      Has photographs of many weeds, including close-ups of leaves and flowers that can aid in identification, but no written descriptions.
    • PLANTS Database [Online]. United States Department of Agriculture, Natural Resources Conservation Service. Available at: http://plants.usda.gov/ (verified 16 Dec 2010).

    Published January 23, 2020

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