Weed Identification Guide for Schools
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This document provides guidance for identifying common weeds found in school gardens. It introduces the topic by defining weeds as unintended plants and outlines a three-step process for weed identification and management: 1) identify the plants, 2) assess their impact, and 3) decide what action to take. The bulk of the document consists of descriptions and photos of the 30 most common weeds arranged by the time of year they are noticed, along with suggested student activities for teaching weed identification.
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Weed Identification Guide for Schools
- 1. WEED IDENTIFICATION for SCHOOLS Wonderful Weeds: What’s Growing in the Garden and When? By Mary Van Dyke Green STEM Learning – January 2015
- 2. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 1 -‐ Wonderful Weeds: What’s Growing in the Garden and When? By Mary Van Dyke Green STEM Learning Introduction What is a weed? It is simply a plant growing where you had not intended. Usually a “weed” only becomes problem from an aesthetic viewpoint or once it grows or reproduces rapidly and reduces the available resources for other plants that you are cultivating. There are three steps in weeding: 1. Identify which plants are growing in your schoolyard 2. Assess the plants’ impact and contribution to the ecosystem 3. Decide what action to take How to treat weeds is a complex topic. In schoolyards synthetic or “toxic chemical” treatments are not permitted. So weeding by hand or other mechanical systems are encouraged. If you have a large area of weeds you might simply smother them by putting down layers of newspaper and mulch or solarize the area under black plastic for a few months. Other ways to reduce weeds are to actively use no-‐till crop methods and to plant cover crops or other plants. Or you might redefine your appreciation and judgment of what is a “plant in the wrong place” or a “weed”. Sometimes you will choose to leave plants that “volunteer” as weeds in your schoolyard, sometimes you will want to take them out, but the first step is to identify these plants and their characteristics. Guide arrangement and selection The photos and text describe a selection of the “top 30” most frequently found “weeds” that may grow in your schoolyard, or garden. The plants are arranged by the time of year when you are likely to first notice the plants, with an index of common and Latin names. Many other plants could be
- 3. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 2 -‐ included such as: Japanese Stiltgrass and Bush Honeysuckle, or recent vigorous growing arrivals such as Wavyleaf Basket Grass. I also chose to exclude several “ornamentals” (other than English Ivy) that are still sold in the nursery trade, and yet are now being termed “invasive”. This ambiguous category of plants includes non-‐sterile Buddleia cultivars, Nandina, Common Daylilies and several others. To remove these “invasive ornamental” plants from a schoolyard or community garden often requires negotiation with your garden’s stakeholders and education on the aesthetic value versus the ecological value. You might try to suggest replanting with alternative native plants or less ecologically-‐harmful plants. Metric units are used in the guide to complement science curricula. One inch is approx. 2.5 centimeters, cm. To use this photo guide Weed Identification for Schools while outdoors with students and teachers, first: • Print off the photo pages in color, and one sided • Make several copies of the photo pages • Laminate the photo pages • Bind the photo pages with a ring Activities with students • Discuss and demonstrate: What is a weed? • How do plants grow and reproduce? • What do we mean when we call plants: native, invasive, naturalized, cultivated or wild…? • Discuss cultivation practices and ways to reduce or eliminate “weeds”. What are sustainable management practices? • To teach “weed” identification over a few weeks you might consider growing and labeling weeds in a “weed patch” • Try a “speed weed”: Identify weeds with students, then track how many weeds you can pull in your session. What types of weeds and how many of each did you pull this time in your garden? Chart and do statistics. Repeat other times of year. What do you notice? • Notice variations in patterns in your weeds. For example, what is the range of leaf characteristics: color, shape and size?
- 4. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 3 -‐ January and February Common Groundsel Senecio vulgaris Groundsel has deeply lobed leaves, yellow flowers and a small white ‘puff-‐ball’ seed head like a Dandelion. It can grow 10 to 50 cm tall. White Clover Trifolium repens ! Note the trefoil, three leaves to a stem. Clover has a low creeping habit and spreads with ‘above ground stems’, stolons. The sweet white flowers in the summer attract bees. Annual Bluegrass Poa annua There are many different kinds of grasses. This is Annual Bluegrass, an upright clump forming grass. It has white flowers in April.
- 5. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 4 -‐ January and February Persian Speedwell Veronica persica Speedwell is a winter annual with small blue and white flowers and round hairy leaves with rounded toothed edges. English Ivy Hedera helix English Ivy has become invasive in this area. Ivy can choke trees. We try to take it out, although it is pretty! The glossy leaves are evergreen. Henbit Lamium amplexicaule ! Henbit is a winter annual with square stems. The flowers are pink-‐purple and the plant can grow 40 cm tall. The heart-‐shaped leaves have rounded toothed edges. Henbit looks very like the Purple Deadnettle, but the upper leaves of a Purple Deadnettle are more triangular and purple-‐tinted.
- 6. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 5 -‐ January and February Wild Garlic Allium vineale Wild Garlic looks like a grass, but the leaves are hollow and round like chives. Can you smell the oniony smell? If you dig up the plant you see the little white bulbs. Dig up all the Wild Garlic bulblets and put in the trash, or they will keep growing. Mugwort Artemisia vulgaris ! Mugwort spreads quickly by ‘underground stems’ called rhizomes. You need to dig out all of these white underground stems to get rid of the Mugwort weeds. The leaves are deeply notched, green on top and soft gray underneath. They have a smell. A Mugwort leaf might remind you of a chrysanthemum leaf. Garlic Mustard Alliaria petiolata All parts of Garlic Mustard give off a garlic-‐like odor. Garlic Mustard is native to Europe and Asia, and a biennial. It winters the first year as a rosette of crinkled leaves. The second year it flowers and seeds. The plant is edible, used as salad or vegetable in many cuisines. Here in the US outside of its native range, Garlic Mustard has become highly invasive. The flowers can be self-‐fertilized or pollinated by insects, and Garlic Mustard also produces chemicals that outside of its native range inhibit the growth of mycorrhizal fungi that support trees and other forest plants. Weed out by hand, before plants go to seed.
- 7. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 6 -‐ March Dandelion Taraxacum officinale The Dandelion leaf is edged like a lion’s tooth, “Dent de lion” in French. Dandelions grow everywhere in the US, so they are a good indicator plant for tracking climate change. When did you notice the first Dandelion this year? Pollinators appreciate Dandelion nectar. You can eat Dandelion leaves for a nutritious salad. The seed head is the familiar puffball with ‘parachutes’ to help seed dispersal by wind. Dandelions have a long taproot like a carrot. Dig the whole root out or the plant will resprout. English or Buckhorn Plantain Plantago lanceolata ! English Plantain has narrow, parallel-‐ veined leaves arranged in a rosette. The flower is cone-‐like and cream-‐colored on a 10-‐20 cm stalk. Plantain likes dry grassy sites. Plantain leaves are good food for caterpillars of the Buckeye butterfly and several kinds of moth. Rabbits, chipmunks and squirrels eat the flowers. Look out too for Broad-‐leaved or Common Plantain with a similar rosette of parallel-‐ veined leaves and cream cone flowers. Hairy Bittercress Cardamine hirsuta Bittercress is an annual, and can reproduce with several generations in a year. Bittercress likes moist soils. The leaves are arranged in a rosette. The flower stalk can be 30 cm high with white flowers and 25 mm long seedpods. The seedpods explode propelling the seed up to 3 meters from the parent plant!
- 8. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 7 -‐ March Shepherd’s Purse Capsella bursa-‐pastoris A winter annual with leaves in rosette and white flowers on a stalk, 10 – 60 cm tall. The plant is easily identified by its heart-‐shaped seedpods. The seedpods look like a shepherd’s purse. Annual Sowthistle Sonchus oleraceus ! The leaves are in a rosette and are slightly prickly at the edges. The stem exudes a milky sap when cut. The Annual Sowthistle has a short taproot. Sowthistles have yellow flowers and have white feathery ‘parachutes’ to help seed dispersal by wind. Other kinds of Sowthistle, Spiny Sowthistle and Perennial Sowthistle have very prickly leaf edges. Perennial Sowthistle spreads by rhizomes, while the Spiny Sowthistle has a long taproot.
- 9. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 8 -‐ April and May Violet Viola species Low-‐growing perennial with smooth heart-‐shaped leaves, and violet or whitish flowers. Plants spread by short stout rhizomes (underground stems). So, if you choose to remove Violets you need to dig them out. 30 species of Violets are native to our area and you might decide to keep them: both for wildlife benefit and beauty. The flowers are decorative and edible. Yellow Woodsorrel ! Oxalis stricta Clover-‐ like perennial, that grows low to the ground and higher (3-‐50 cm). Oxalis spreads through reseeding. Try to weed it out while it is still flowering. It has long pink underground rhizomes and fibrous secondary roots. Creeping Woodsorrel, Oxalis corniculata, is the purplish-‐leaved or green-‐leaved, low-‐ growing species. It spreads by aboveground stolons. Vetch Vicia species Vetches are vining plants that trail over other plants. Notice the feather-‐like compound leaves and twining tendrils. Flowers are purplish. Seedpods and flowers are pea-‐like.
- 10. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 9 -‐ April and May Virginia Copperleaf Acalypha virginica A summer annual with distinctive copper-‐colored opposite leaves. Flowers are greenish and on the stems. Insects often eat the leaves. Can you see lots of little holes in the leaves? Common Chickweed ! Stellaria media Chickweed likes cool moist areas. One or two generations can reproduce from seed each year. The leaves are small, light green and oval-‐shape. The flowers are white stars. Other common names for Chickweed are Starweed and Starwort. Its Latin name “stellaria” also means “star”. Chickweed is edible, and you might add it to a salad. Buttercup Ranunculus bulbosus Buttercups have beautiful glossy 5-‐ petalled yellow flowers. The leaves are three-‐lobed and indented. Below ground the buttercup has a thickened corm base. Buttercups reproduce by seed and overwinter as corms. Pick the flowers to enjoy in a vase and then dig out the corm!
- 11. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 10 -‐ April and May Wild Grape Vitis species There are several kinds of native Wild Grape. The vines can grow up to 10 meters and need space to climb. Grapes provide food for wildlife, and spread through seed dispersal by birds. Wild Grape leaves are large and have toothed edges. Note forked tendrils for climbing. Can you tell the difference between Wild Grape and Porcelainberry? Porcelainberry is invasive in this area, so remove it if you can. Wild Grape has habitat value, and is only a weed if you are unable to accommodate a vine in your garden. Carolina Geranium ! Geranium carolinianum Geranium is usually a biennial: the native plant forms a rosette of leaves one year, and then flowers the next. Leaves are deeply lobed. The flowers (May to August) are pink and there are two or more on a stem. The seeds look like a bird’s beak, hence a common name for Geranium is “Cranesbill”. Geranium maculatum is native to Northern Virginia. False Strawberry Duchesnea indica False Strawberry has yellow flowers, and is a low-‐ growing plant with trefoil leaves and red fruit found in moist locations. It spreads via above ground stolons and seed dispersal via animals. The native-‐to-‐Virginia Strawberry, Fragaria virginiana, and cultivar strawberries have similar trefoil leaves but are distinguished by white flowers.
- 12. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 11 -‐ April and May Orchard Grass ! Dactylis glomerata Very dense and fibrous root system. Reproduces by seed. So take it out if you can before it flowers and seeds. Crabgrass Digitaria sanguinalis Reproduces mainly through seeding. Leaves are light green and have stiff hairs and are rough to touch. The flowers and seedheads are 3 to 5 wire-‐like spikes on a stem. Nutsedge Grass Cyperus esculentus Recognize Nutsedge by its three-‐cornered stem and pattern of three leaves and bright green color. It reproduces mainly by tubers that can remain in the soil for 10 or more years. A single plant can produce 100s or several thousand tubers in a season. That’s why it is worth weeding Nutsedge out of the garden, while it is young! Native Americans ate the tuber. It tastes nutty, like almonds. Nutsedge is also grown as food crop in other places, e.g. Spain and West Africa
- 13. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 12 -‐ April and May Mulberry Morus alba Mulberry has irregular leaves, some are lobed as in the photo, and others are heart-‐shaped. The leaves have serrated edges. Mulberry fruit are edible and birds enjoy them. The leaves can be food for domesticated silkworms. The Mulberry tree spreads rapidly through birds dispersing the seeds. If you recognize young Mulberry seedlings in your garden pull them out. Are the roots bright yellow? Yellow roots are an identifying characteristic of Mulberry. Bindweed Convolvulus or Calystegia species There are several kinds of Bindweed. All have trailing stems and tendrils, triangular heart-‐shaped leaves and flowers like a Morning Glory. Bindweed spreads both by seeds and by underground stems, rhizomes. You need to dig out the whole plant as Bindweed can reproduce from even a small piece of broken stem. Lambsquarters ! Chenopodium album Lambsquarters is a delicious and nutritious plant and can be left to grow to harvest the leaves as a spinach-‐like vegetable. If you choose to harvest for eating make sure it’s been growing in a pesticide-‐free and safe place. Or you can weed out as a seedling.
- 14. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 13 -‐ June, July, August and September Porcelainberry Ampelopsis brevipedunculata The leaves can vary and be deeply lobed – the photo shows heart-‐shaped leaves. Porcelainberry was introduced for its beautiful sky-‐blue to purple berries. Seeds are dispersed by birds and other wildlife. Porcelainberry is considered invasive as it spreads rapidly in the mid-‐ Atlantic area and can grow up to 5 to 7 meters. Spurge ! Euphorbia species There are several kinds of Spurge. All in this area are non-‐edible plants with caustic and toxic white latex sap. Do not confuse Spurge with the edible Purslane (shown below). Common Purslane Portulaca oleracea Purslane has thick succulent stems and leaves that store water. Purslane is very high in vitamins E and A, and omega 3’s. You can eat Purslane in salads and stir-‐ fries. It tastes lemony. Purslane grows well in light, hot places and sandy soils. It grows prostrate, that is low to the ground, and has yellow flowers.
- 15. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 14 -‐ Year Round Poison Ivy Toxicodendron radicans Here is a photo of Poison Ivy leaves in early fall. Poison Ivy is a climbing trailing vine or shrub with green leaflets grouped in threes. Note that Virginia Creeper leaflets are grouped in fives. Poison Ivy leaflet shapes are quite variable. Many people (50-‐60% of Americans) have severe skin allergic dermatitis reactions to the chemical resins, urushiols, present in all parts of the Poison Ivy plant. Urushiols from Poison Ivy can remain in surrounding soil and in dead plants for over a year. Take to heart the saying, “Leaves of three -‐ let it be”. Poison Ivy is native to this area, and has wildlife habitat value: some birds and animals like to eat the leaves or white berries. If you do touch Poison Ivy, you can try rubbing the spot with leaves from Jewelweed as an antidote, or rinse off the oils as soon after contact as possible with a Tecnu™-‐type soap and cool water. Be careful to dispose of Poison Ivy safely if you take it out. • Identify the plants in this photo growing with the white flowering Weigela shrub? (Answers on next page) • Why would you weed out the plants competing with the Weigela? Weed Identification Quiz
- 16. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 15 -‐ Answers to Weed Identification Quiz on previous page: Chickweed, Common Daylilies (now considered invasive in parks), Mugwort, Dandelion, Virginia Copperleaf. Photo credits All photos are by Mary Van Dyke except as noted below. Other photos credit as follows: Henbit; Wikipedia By Kaldari (Own work) [CC0], via Wikimedia Commons http://commons.wikimedia.org/wiki/File%3ALamium_amplexicaule_Kaldari _01.jpg Mugwort by Sue Sweeney http://www.inmygarden.org Crabgrass by Richard Norton, http://commons.wikimedia.org/wiki/File:Crabgrass.JPG Chickweed flowers by Kaldari, Stellaria media 01-‐ Own work. Licensed under CC0 via Wikimedia Commons -‐ http://commons.wikimedia.org/wiki/File:Kaldari_Stellaria_media_01.jpg#m ediaviewer/File:Kaldari_Stellaria_media_01.jpg Chickweed plant by Hugo.arg -‐ Own work. Licensed under CC BY-‐SA 3.0 via Wikimedia Commons -‐ http://commons.wikimedia.org/wiki/File:StellariaMedia001.JPG -‐ mediaviewer/File:StellariaMedia001.JPG Sowthistle from Virginia Tech Weed ID Shepherd’s Purse http://northernbushcraft.com/topic.php?name=shepherd%27s-‐ purse®ion=ab&ctgy=edible_plants Bindweed, Convolvulus arvensis by Graham Calow http://www.naturespot.org.uk/species/field-‐bindweed
- 17. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 16 -‐ Resources Plant NoVA Natives online and published guide http://www.plantnovanatives.org for plants native to Northern Virginia Weeds of the Northeast, book by Richard Uva et al, 1997 Virginia Tech Weed Identification online, http://oak.ppws.vt.edu/weedindex.htm A Field Guide for the Identification of Invasive Plants in Southern Forests, by James Miller et al, 2010, USDA publication http://www.srs.fs.usda.gov/pubs/35292 Terrestrial Invasive Plants of the Potomac River Watershed, brochure by The Nature Conservancy and partners http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/maryland_dc/ explore/mdinvasivebrochure.pdf Plant Invaders of Mid-‐Atlantic Natural Areas, fourth edition 2010, by National Park Service, U.S. Fish and Wildlife Service and other partners http://www.nps.gov/plants/ALIEn/pubs/midatlantic/index.htm Wild Food from Your Yard and Neighborhood by Mary Van Dyke, July 2014 in http://tmiliving.com/2014/07/17/wild-‐food-‐from-‐your-‐yard-‐and-‐neighborhood/ Weeds: In Defense of Nature’s Most Unloved Plants, book by Richard Mabey (hardback 2010, paperback 2012) Virginia Invasive Plant Species List, VA Dept. of Conservation and Recreation, two page list, 2014 http://www.dcr.virginia.gov/natural_heritage/documents/nh-‐invasive-‐plant-‐list-‐ 2014.pdf Credits To my mother and father: both great gardeners, And my family, To my many garden, school and naturalist friends And to Kirsten Buhls, Agriculture and Natural Resource Extension Agent, Virginia Cooperative Extension; Thank you for sharing your love Of plants, community, and knowledge.
- 18. WEED IDENTIFICATION for SCHOOLS WEED IDENTIFICATION for SCHOOLS Green STEM Learning – January 2015 -‐ 17 -‐ Index Bluegrass, Annual 3 Bittercress, Hairy 6 Broad-‐Leaved Plantain 6 Bindweed 12 Buckhorn Plantain 6 Buttercup 9 Carolina Geranium 10 Chickweed, Common 9, 15 Common Chickweed 9 Common Plantain 6 Common Purslane 13 Clover, White 3 Crabgrass 11 Cranesbill 10 Dandelion 6, 15 Daylily, Common 14 English Ivy 4 English Plantain 6 Garlic Mustard 5 Garlic, Wild 5 Geranium Carolina 10 Grape, Wild 10 Grass, Nutsedge 11 Grass, Orchard 11 Groundsel, Common 3 Hairy Bittercress 6 Henbit 4 Ivy, English 4 Lambsquarters 12 Morning Glory 12 Mugwort 5, 15 Mulberry 12 Nutsedge Grass 11 Orchard Grass 11 Persian Speedwell 3 Plantain 6 Poison Ivy 14 Porcelainberry 13 Purslane, Common 13 Shepherd’s Purse 7 Sowthistle, Annual & Perennial 7 Sowthistle, Spiny 7 Speedwell 4 Spurge 13 Starweed or Starwort 9 Strawberry, False 10 Strawberry, Virginia 10 Vetch 8 Violet 8 Virginia Copperleaf 9, 15 Virginia Creeper 14 White Clover 3 Wild Garlic 5 Wild Grape 10 Woodsorrel, Creeping & Yellow 8 Acalypha virginica 9 Alliaria petiolata 5 Allium vineale 5 Ampelopsis brevipedunculata 13 Artemisia vulgaris 5 Calystegia species 12 Capsella bursa-‐pastoris 7 Cardamine hirsuta 6 Chenopodium album 12 Convolvulus species 12 Cyperus esculentus 11 Dactylis glomerata 11 Digitaria sanguinalis 11 Duchesnea indica 10 Euphorbia species 13 Fragaria virginiana 10 Geranium carolinianum 10 Geranium maculatum 10 Hedera helix 4 Lamium amplexicaule 4 Morus alba 12 Oxalis corniculata 8 Oxalis stricta 8 Plantago lanceolata & major 6 Poa annua 3 Portulaca oleracea 13 Ranunculus bulbosus 9 Senecio vulgaris 3 Sonchus oleraceus 7 Stellaria media 9 Taraxacum officinale 6 Toxicodendron radicans 14 Trifolium repens 3 Veronica persica 4 Vicia species 8 Vitis species 10