File Name: weeds and what they tell .zip
See the Latest Publications. Browse All Publications. Download PDF. Rodney G. Lym Professor Department of Plant Sciences.
See the Latest Publications. Browse All Publications. Download PDF. Rodney G. Lym Professor Department of Plant Sciences. North Dakota is being threatened by three noxious weeds that could infest more acreage in the state and at a faster rate than leafy spurge.
Members of this trio include spotted, diffuse, and Russian knapweed. These three knapweeds already infest more acreage than leafy spurge in Montana and Minnesota, and have been found in over 20 counties in North Dakota.
Knapweeds are related to thistles and can spread even faster. For instance, spotted knapweed infested approximately 25 acres in eight North Dakota counties in ; by it had spread to more than 1, acres in 14 counties, and was found in 18 counties in and infested more than 30, acres.
Diffuse knapweed can spread as quickly as spotted knapweed, but Russian knapweed spreads much slower. Yellow starthistle Centaurea solstitialis L. Knapweed infestations in North Dakota have been found primarily along highways, waterways, railroad tracks, pipelines and recently constructed utility lines.
Knapweed often spreads to a new site by seed in hay, on vehicles, or in contaminated seed Figure 1. Watch for new infestations along any publicly traveled route, where livestock are fed, or in disturbed areas. Control methods vary depending on the knapweed species and proper identification is the first step towards stopping the spread of these noxious weeds. Figure 1. People are the major cause of knapweed spread from one location to another.
Inspect vehicles, hay, gravel, etc. Spotted knapweed [ Centaurea stoebe L. Spotted knapweed is an aggressive, introduced weed species that rapidly invades pasture, rangeland, and fallow land and causes a serious decline in forage and crop production. Spotted knapweed has few natural enemies and is not preferred by livestock as forage.
The sap of spotted knapweed can cause skin irritation in some people. Spotted knapweed infestations in North Dakota can largely be traced to seed or hay brought in from neighboring states. Researchers in Montana have observed that spotted knapweed may remain in a confined location for several years and then spread rapidly to adjacent areas. It is important to control spotted knapweed plants when they are first observed and monitor the site for several years to prevent reinfestation from seed.
Spotted knapweed generally is a short-lived perennial, reproducing solely by seeds. It is a prolific seed producer with 1, or more seeds per plant.
Seed remains viable in the soil five years or more, so infestations may occur a number of years after vegetative plants have been eliminated. The seeds can germinate from spring through early fall. Seedlings emerging in the fall often overwinter as a rosette of leaves, resuming growth again in the spring Figure 2. Rosette leaves are deeply lobed. The plant grows 2 to 4 feet tall and can have one or more stems with pale green leaves which are 1 to 3 inches long.
The surfaces of the upper leaves and stems are rough. Flower heads are solitary and produced from early July through August. Flowers are pink to light purple rarely cream colored and the petals are surrounded by stiff, black-tipped bracts, giving the flower head a spotted appearance Figures 3 and 4. The black tipped bracts found below the flower petals are the key feature to distinguish spotted knapweed from other knapweed species.
Figure 2. It is very difficult to distinguish knapweed species based on the rosette alone. Diffuse knapweed Centaurea diffusa Lam. Diffuse knapweed is generally a short-lived perennial or biennial in North Dakota and invades habitats similar to spotted knapweed. Diffuse knapweed was found in one North Dakota county in and infested approximately 20 acres. Diffuse knapweed had spread to four counties by and infested nearly acres.
The physical appearance of diffuse knapweed is similar to spotted knapweed, except diffuse knapweed is generally shorter and more highly branched. Also, rosettes of diffuse knapweed have more finely divided leaves than those of spotted knapweed Figure 2. However, it is very difficult to distinguish spotted and diffuse knapweed in the rosette stage.
If the plant is not flowering, search for last seasons flower stalk and identify the plant based on the flower bracts. Flower bracts are the key distinguishing feature between spotted and diffuse knapweed. Diffuse knapweed bracts have a rigid terminal spine about one-third of an inch long with four to five pairs of shorter, lateral spines Figures 3 and 4. The spiny bracts resemble a crab in appearance, are very sharp, and can puncture skin if touched. The flowers can be white or purple, so flower color is not a distinguishing feature between knapweed species Figure 5.
Diffuse knapweed flowers from July to September. Russian knapweed [ Rhaponticum repens L. Russian knapweed has infested approximately acres in seven counties in It also is the only perennial of the noxious knapweeds and is the most difficult to control.
The largest infestations generally are found in southwestern North Dakota. It is often found in areas with a supplemental water source such as the Little Missouri and Heart Rivers in North Dakota.
Russian knapweed will also infest roadsides, pasture, and rangeland and is the only knapweed in the state that causes significant losses in cropland. Russian knapweed is a long-lived, deep-rooted perennial with growth characteristics similar to Canada thistle. The weed emerges in the spring from roots and grows 1 to 3 feet tall Figure 2.
Once established, Russian knapweed spreads mainly by underground root stocks as seed production is limited compared to other knapweed species. Two key characteristics distinguish Russian knapweed from spotted and diffuse knapweed.
First, the flowers have rounded bracts with transparent tips Figures 3 and 4. Second, the root of this perennial is dark brown to black in color, scaley as if the plant had been burned, and can grow to depths of greater than 20 feet Figure 6. The flowers of Russian knapweed vary from light pink to lavender Figure 3. Flowering occurs from June to September. People are the major cause of knapweed spread. Knapweeds are spread readily in hay and on vehicle undercarriages.
Producers should exercise caution when using hay from road ditches and when purchasing hay from known infested areas in neighboring states and provinces. Land managers must learn to identify knapweed on their own and neighboring land, especially on disturbed sites, pastures bordering roads and streams, and where hay is fed.
Timely control of a few plants will be very cost-effective compared to treating larger acreage later. The public can assist county weed officials in controlling knapweeds by reporting all suspected infestations.
Figure 3. Spotted knapweed has stiff black tip bracts with purple flowers left , diffuse knapweed has both purple and white flowers and bracts with rigid sharp spines center , Russian knapweed has pink to purple flowers with opaque bracts and the flower heads are generally larger than the other two species right. Small infestations. Spotted and diffuse knapweed confined to small, well-defined areas should be pulled by hand or treated with a herbicide as soon as detected to avoid spread of the weed.
First, all visible knapweed plants should be removed and destroyed by burning or mulching. Then the areas should be treated with a herbicide to prevent reinfestation from seedlings.
Anyone working with spotted knapweed should wear protective gloves and avoid getting sap from the plant into open cuts or abrasions. Workers should wash their hands and exposed skin with soap and water following contact with this plant. Treat an extra 10 to 15 feet around the knapweed patches to control roots and seedlings.
A careful follow-up program is necessary to control missed plants and seedlings. Many attempts to control knapweed have failed because follow-up treatments were not applied. Pasture and rangeland. Herbicides will control spotted and diffuse knapweed plants and seedlings for two to three years. The residual control period may be shorter on gravelly soils and where soil organic matter is high. The optimum application time is when the plant is in the rosette growth stage in the fall or in the bolt to bloom stage in the spring.
Consult the herbicide for use and grazing restrictions. Spotted and diffuse knapweed are generally easy to control with herbicides. However, a treated area must be monitored for several years and retreated as necessary for seedling control. Figure 4. The most reliable way to distinguish the knapweed species is by the bracts.
Black-tipped bracts of spotted knapweed left , spiny crab-like bracts of diffuse knapweed center , and transparent tips of Russian knapweed. Figure 5. An example of why flower color cannot be used to distinguish knapweed species.
Note the spiny bracts on both the purple and white flowering plants. They are both diffuse knapweed. Figure 6. The roots of spotted and diffuse knapweed are taproots similar to dandelion and off-white in color left.
Weeds are plants that grow wild and have negative impacts on primary industries, native vegetation or human health. Many weeds, particularly those that invade bushland, rivers and coasts are escaped garden plants. Weed risk assessment is now used to determine the weed potential of new plant introductions to Australia. Declared plants are weeds that are regulated under the Landscape South Australia Act due to their threat to primary industry, the natural environment and public safety. Plants are declared under the provisions of the Act relating to their movement, sale, notification and control. Landscape boards oversee control programs for declared plants in each region. Some declared plants are also alert weeds because they are not yet established in South Australia and pose a serious threat.
Read your weeds! If you have large patches of one kind of weed, your garden is trying to tell you something. Here are common weeds and that they say about your soil—plus photos. However, weeds can be very useful.
Weeds are becoming a more and more appreciated component of gardening. We have been reintroduced to eating the weeds, with things like dandelion leaves becoming a niche crop. Also, we are encouraging plants that, up until recently, were viewed as weeds dynamic accumulators like comfrey and pioneering legumes to revitalize our soils. And, many gardeners are once again celebrating weeds as a means of reading the soil. Geoff Lawton says weeds are not the problem but rather symptoms of glitches within the soil.
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Noxious weeds have a destructive impact on Montana's landscape by displacing native plant species, increasing soil erosion, and decreasing wildlife habitat and recreational opportunities. These lands are vital for agricultural production and protecting the integrity of ecosystems. The Department's Noxious Weed Programs offer resources and assistance with the management of state- and county-listed noxious weeds. Both new and continued infestations of these non-native species not only reduce the productivity of cropland and rangeland, infestations of noxious weeds diminish the productivity and biological diversity of ecosystems by negatively impacting wildlife habitat and by affecting the vitality and survival of native species due to competition for space, nutrients and water. To address noxious weeds, you first need to know how to identify the weeds we are dealing with in Montana.
Weed , general term for any plant growing where it is not wanted. Ever since humans first attempted the cultivation of plants, they have had to fight the invasion by weeds into areas chosen for crops. Some unwanted plants later were found to have virtues not originally suspected and so were removed from the category of weeds and taken under cultivation. Other cultivated plants, when transplanted to new climates, escaped cultivation and became weeds or invasive species. The category of weeds thus is ever changing, and the term is a relative one. Weeds interfere with a variety of human activities, and many methods have been developed to suppress or eliminate them.
Еще одна игра слов мистера Танкадо: разница означает результат вычитания. - Верно! - сказал Беккер с экрана. - Может быть, у этих элементов разное число протонов или чего-то. Если вычесть… - Он прав, - сказал Джабба, повернувшись к Соши. - На этих таблицах есть числа. Количество протонов.
Странно. Я вчера говорил с. Велел ему сегодня не приходить. Он ничего не сказал о том, что поменялся с тобой дежурством. У Чатрукьяна ком застрял в горле.
Острая боль пронзила вес его тело, когда он приземлился на бок, но мгновение спустя он уже был на ногах и, скрываемый занавешенным входом, сбежал вниз по деревянным ступенькам. Превозмогая боль, он бежал через гардеробную. У алтаря кто-то кричал, за спиной у него слышались тяжелые шаги. Беккер толкнул двойную дверь и оказался в некотором подобии кабинета. Там было темно, но он разглядел дорогие восточные ковры и полированное красное дерево.
Ты волнуешься о Дэвиде. Ее верхняя губа чуть дрогнула. Стратмор подошел еще ближе. Он хотел прикоснуться к ней, но не посмел. Услышав имя Дэвида, произнесенное вслух, Сьюзан дала волю своему горю. Сначала она едва заметно вздрогнула, словно от озноба, и тут же ее захлестнула волна отчаяния.
Значит, она слышала звук выстрела Хейла, а не коммандера. Как в тумане она приблизилась к бездыханному телу. Очевидно, Хейл сумел высвободиться.
Сьюзан словно отключилась от Хейла и всего окружающего ее хаоса. Энсей Танкадо - это Северная Дакота… Сьюзан попыталась расставить все фрагменты имеющейся у нее информации по своим местам.
По мне, так поделом Стратмору. - Грег, - сказала Сьюзан, стараясь не показать своего возмущения, - этот черный ход позволял АНБ расшифровывать электронную почту, представляющую угрозу нашей безопасности. - Что ты говоришь? - Хейл невинно вздохнул. - И в качестве милого побочного развлечения читать переписку простых граждан. - Мы не шпионим за простыми гражданами, и ты это отлично знаешь.
Спокойно. Он оглядел пустой зал.
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