1 like = 1 fact about weeds! For each like, I'll tweet 1 fact or observation about weeds, their impacts, or their management. https://t.co/WQkVWBkZQc

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1. Weeds are plants, which is obvious, I know. But important to recognize that...

2. there is no single biological trait that separates weedy plants from non-weeds. "Nature knows no such category as weed." - Zimdahl

3. The concept of weeds is a human construct. Weeds cause us problems. All definitions of "weeds" include the human component.

4. Nearly all traits we consider "weedy" contribute to persistence or pernicious-ness.

5. Native, non-invasive plants can be weeds, depending on what we're doing with the land. Like larkspur, which is toxic to cattle.

6. Many weeds are beautiful! In fact, a number of them are escaped ornamental plants (like toadflax, for example). https://t.co/3URru34jrE

7. Weed scientists often have the weediest yards in town. No joke. https://t.co/PjW8xIFyVx

8. Speaking of weed scientists - weed science is an actual scientific discipline. Think of it as applied ecology or applied botany.

9. We have scientific journals and everything! Weed Science, Weed Technology, Invasive Plant Science & Management https://t.co/gUlfNRSBPS

9b. (Those are just the WSSA journals from North America, there are others too, like Weed Research from Europe)

10. I have a twitter list called "Tweeders" that includes weed-knowledgeable folks on twitter: https://t.co/2kDpxezijj

11. This has already gotten **WAY** more likes than I expected... Might take me longer than I anticipated.

12. If uncontrolled, weeds would cause more crop damage than any other pest group (insects, diseases, rodents, etc.) https://t.co/2F9IZ6EiZS

13. Even so, there are FAR fewer weed scientists at land-grants compared to entomologists or plant pathologists: https://t.co/hm9y2CNBlt

14. Velcro was invented after looking at a weed (burdock). https://t.co/LsqgoIXvYU https://t.co/xrwV7L2n1I

15. "A plant whose virtues have not yet been discovered" (Emerson 1912) is without question the worst weed definition ever.

15b. (I said facts *or* observations... my thread, my rules.)

16. We know *many* of the virtues possessed by weeds. That doesn't make them less problematic.

17. Many of our worst weeds (like kudzu) were introduced intentionally *because* of those virtues! https://t.co/CACxPnbIdU https://t.co/gzpTfdf0hb

18. Johnsongrass, another bad weed introduced on purpose, has a fascinating history: https://t.co/qhmqfyhNlO (not open access, I'm afraid)

19. Most weeds cause problems because they compete with the desirable plants (like crops), and displace them or reduce their yield.

20. But some weeds are problematic for other reasons. For example, nightshade berries can stain edible beans, and make them less salable. https://t.co/hrPGbsLnDR

21. Many German/Russian communities in the US eat this particular weed. Black nightshade = "German blackberries" https://t.co/LSrGZoKS5P

22. My favorite meal growing up was blackberry dumplings. Had no idea they were a nightshade species till I studied weed science in college.

23. The nightshade family (Solanaceae) has some of the most beloved foods (tomatoes, potatoes) & also some of the deadliest weeds (Atropa).

24. One of my most hated experiences growing up was pulling nightshade berries out of pinto bean windrows before harvest.

25. Every time I mention this, my dad reminds me "I only made you do that once!" That one time apparently made quite an impression on me...

26. Almost EVERYONE has some experience with (and an interest in) weeds, even if they don't immediately realize it.

27. One of my favorite parts of my weed science class is learning about students' previous experiences with weeds.

28. Of the ~300,000 known plant species in the world, only about 250 species are major problems in world agriculture.

29. In any given crop, there are only about 25 weed species that will cause major damage. #NotAllWeeds

30. "Noxious" weeds are plants that have been designated by a legal authority (like state or federal gov'ts) as being problematic.

31. Noxious weed laws vary quite a bit by state in the US, and there is also a federal noxious weed law. https://t.co/LvV6cq5jnj

32. Weeds are referenced in the bible (Genesis 3:18) as a curse for eating the forbidden fruit. "Thorns & thistles shall it bring forth..."

33. The first US law requiring weed control (1726, Connecticut) was actually enacted to help control a wheat disease (stem rust).

34. Barberry (Berberis vulgaris) plants allow the stem rust pathogen to survive and spread; the 1726 law required killing barberry.

35. Many weeds act as alternate hosts for crop pathogens and insects. Which is another reason weed control is so important.

36. The first regional weed society was started in 1938 (Western Weed Control Conference), and is still active (https://t.co/hz1Xm94s8o).

37. I just had to take a break from tweeting to help identify a plant that's killing cattle. Some sort of Astragalus (locoweed).

38. As the common name might suggest, locoweeds (a group of MANY Astragalus and Oxytropis species) are neurotoxic.

39. Y'all need to chill out liking that original tweet now....

40. I conduct lots of herbicide studies as part of my job. It is simultaneously one of the most important and least fun parts of my job.

41. Herbicides are the most important (and relatedly, most over-relied-upon) tools for weed management in most of the developed world.

42. Regardless of what you think of herbicides, the alternatives all pretty much suck too, each in their own way.

43. Tillage is really effective for controlling weeds. But it contributes to soil erosion.

44. Hand labor is really effective for controlling annual weeds. But hand-weeding is perhaps one of the worst jobs in the history of humans.

45. Crop rotation can help a lot for controlling some weeds, but is minimally effective for others, and has other costs (and benefits).

46. Persistence (the ability of weed populations to survive) is among the most important characteristics for species we consider weeds.

47. The most common persistence mechanism for weeds is seed production. Weed seeds can live a LONG time in the soil.

48. A few long-term seed burial experiments have been established, the most famous is probably the Beal study: https://t.co/f79bnysEZA

49. Two species survived 120 years of burial. MANY weed seeds germinated after 40 years (pigweed, ragweed, mustard, purslane, curly dock).

50. Salt (yes, regular old NaCl) was among the first chemicals used as a herbicide.

51. In 1940's Kansas, weeds were controlled along railroad and highway rights of way by applying 20 TONS PER ACRE of salt.

52. 20 tons is a lot of salt.

53. Today, some highly effective non-selective herbicides are applied at less than 2 ounces per acre. About 500,000 times less than salt.

54. The rodweeder is noted as the first piece of equipment specifically designed for weed control (early 1900s). They're still used today.

55. I'm extremely curious how many people have muted me today...

56. Herbicide marketing can be both hilarious, and infuriating for those of us in the public sector.

57. The same herbicide active ingredient (imazapyr) is sold as: * Arsenal (KILL EVERYTHING!) * Habitat (WE LOVE THE EARTH!)

58. AND, imazapyr is sold as: * Stalker (for application to 'stalks' of trees) * Chopper (for application to trunks of chopped down trees)

(57 & 58 are examples of funny, clever, and effective herbicide marketing, by the way. I'll probably get to the infuriating examples later.)

59. Each year, I take my class on a 'weed walk' for 40 min and we ID 25 to 40 different weed species within 4 blocks of the classroom.

60. Weeds are literally everywhere. Including in this brick wall I just walked by. https://t.co/9VLSQ9cu3F

61. They get everywhere because many weeds have really cool dispersal mechanisms. Like dandelions whose seeds float with the wind. https://t.co/z1LhMqVRBr

62. Weed seeds have been found up to 140 meters above the earth's surface. Seeds can move a LONG distance at that height.

63. Some weeds make their seeds sticky to move with passersby. Here's curlycup gumweed, with its sticky goo. (botanical term) https://t.co/4f6qxIexQN

64. And then there's the more obvious pokey/ouchy dispersal mechanisms, like puncture vine which has ruined countless bike tires (and feet). https://t.co/vqJpL0LgR5

65. Tumbleweeds, like kochia and Russian thistle, spread seed as they are blown across the plains. (photo @AndrewWiersma) https://t.co/c5CLWUKsZG

@AndrewWiersma 66. Downy brome (also called cheatgrass) is great at digging into socks and shoelaces to hitch a ride. https://t.co/aMFONJzcWT

67. Wild oats (and some other species) have twisted awns that unwind when wet. This helps them bury themselves to aid establishment. https://t.co/un0b8EE7Os

68. (Here's a video I took of a wild oat seed untwisting when placed on a moist towel) https://t.co/ePFtAqQeFG

69. Kochia seed can germinate and grow *VERY* quickly when conditions are right. Beets (left) vs kochia (right): https://t.co/hIXpFxwmJT

70. Leafy spurge flowers are FREAKING AWESOME. https://t.co/WNf0wBXZch

71. "Blue mustard" (Chorispora tenella) is actually purple. https://t.co/NnTGDkPPOs

72. Some evergreen trees show a spiral pattern when injured by soil-applied systemic herbicides. https://t.co/BNtwJcnEik

73. Shattercane, a common grass weed, is the same species as grain sorghum (Sorghum bicolor).

74. There's also a wild proso millet, which is the same species as the crop of the same name (Panicum miliaceum).

75. Dig them up and see how big the root is. https://t.co/ie5SKefgmt

76. That was only partially in jest. Sometimes the quickest way to ID a weed is to yank it up and look for seed carcass, rhizomes, etc.

77. Winter wheat and jointed goatgrass seedlings look remarkably similar (they're closely related). But the seeds are very different. https://t.co/4s31FnllrQ

78. Turf weed scientists get to do fun shit like putt golf balls to see if weeds change the ball speed/direction. https://t.co/hPJ1qsXjVF

79. Speaking of turf, if you've been spraying glyphosate, you should wash your shoes before walking on the green. https://t.co/6BAlvROH6g

80. Holm et al. wrote a book in 1977 called the "World's Worst Weeds" and it might be the most widely cited text among weed scientists.

81. Holm detailed 200 of the world's worst weeds. Of those, 38% came from just 2 plant families: Poaceae (grasses) & Asteraceae (sunflower)

82. Dinitroaniline herbicides are yellow. Like, super yellow. If you're not doing a good job with PPE, you'll know it after spraying them.

83. PPE = personal protective equipment. All herbicide labels require PPE to be worn, and it details which PPE is required.

84. ALL herbicides require at minimum: * shoes with socks * long pants * long sleeves * hat More toxic products increase PPE requirements.

85. mixing and handling PPE requirements are usually require more PPE. Gloves & apron & eye protection are almost always required.

86. Herbicides (except for fumigants, which are rare) can't kill weed seeds. they can only control seeds that have germinated.

87. Many weed species produce a lot of seeds. Like, a LOT of seeds. Hundreds of thousands (or even a million) of seeds per plant.

88. I studied common lambsquarters (Chenopodium album) for my PhD. In a crop field, it produced between 50,000 to 300,000 seeds per plant.

89. Common lambsquarters has dense 'bladder hairs' on the leaf surface. (black lines are 1 mm apart) https://t.co/r8EhQSHFX4

90. Bladder hairs basically look like bubbles on pedestals. The bubbles contain fluid similar to what's in the vacuole of plant cells.

91. I suspect, but still haven't confirmed, that bladder hairs contain enough positive ions (like Ca, Mg, Fe) to reduce herbicide efficacy.

92. Nearly all synthetic herbicides (except 2) are negatively charged ions at biological pH.

93. We know that free cations (+) like Ca++ & Mg++ can interact with anionic (-) herbicides to inhibit uptake of the herbicides.

94. So it is possible that these bladder hairs may have enough cations to tie up herbicides; but need to actually do the study to confirm.

95. Many weed seeds are really small. These are common lambsquarters seeds (scale at bottom is mm). https://t.co/dACvMU4HXp

96. Tebuthiuron herbicide was used to kill Auburn's iconic Toomer's Oaks by an Alabama fan. https://t.co/uQLU9hYARe

97. Weed scientist at Auburn (a friend) called to chat about the tissue levels afterwards. My exact words: "Dude, those trees are toast."

97b. https://t.co/58KJgonNBw

98. For my PhD, I planted >300 accessions of common lambsquarters in a field that didn't have any common lambsquarters. (It does now) https://t.co/qAJYsvqkVH

99. Common lambsquarters (Chenopodium album) is one of the World's Worst Weeds (Holm et al. 1977)

100. To do weed science research we make a lot of weird 'equipment', like this adjustable depth rake to plant rows of weeds. https://t.co/0kQKUTZunI

101. And here's how a fellow graduate student studied jointed goatgrass seed predation in the field. https://t.co/aCZllpAY4c

102. That same student (Dr. Gustavo Sbatella) also used RFID tags to track jointed goatgrass movement in the field. https://t.co/XqOjJVG3hG

103. My wife and I went to Yellowstone for our anniversary ~10 years ago, and ALL of the photos from our trip looked like this (weeds) https://t.co/TcV6gntatr

104. The North entrance of Yellowstone has LOTS of Dalmatian toadflax. In some places, it seems to be the only thing that can grow.

105. Weed scientists use radioactive herbicides to study weed physiology, because they're easy to track within the plant.

106. Mostly, we use carbon-14 labeled herbicides, since all synthetic herbicides have carbon, and C14 is very stable.

107. We also once used carbon-13 (a stable isotope) to try and figure out how long undisturbed weed seeds live in the soil. https://t.co/GvjXTbGNOs

108. I've seen 4 tornadoes while doing weed research in Wyoming. Only got photos of 2 of them. https://t.co/uKOYSpoymU

109. YES! YOU CAN MAKE BEER FROM WEEDS! (I have no idea if it is any good...) https://t.co/mgakAHk1Ji https://t.co/ZaYWKhzL3b

110. MANY weeds are edible! Though many are also toxic/deadly. So be sure you know before you taste. https://t.co/mHmy7TKZFh

111. I commissioned a friend/colleague (who is a phenomenal artist) to draw some edible weeds for my kitchen. https://t.co/67veT0N1g8

112. The weeds that are most competitive with crops grow tall, even in Wyoming. This common lambsquarters plant is ~8 feet tall. https://t.co/ZWvmq7Q7b7

113. In the "weird things weed scientists do" department, here we put down weed barrier fabric to place our weeds *on top* https://t.co/CxJwz3kYfN

114. In most crop fields, the most limiting factor for plant growth by the middle of the growing season is light.

115. We give the crop water (if irrigated), nutrients, etc. It is pretty difficult to give the crop more light. So tall plants usually 'win'

116. We see a lot of wildlife doing weed science research in Wyoming. Not all of it is friendly. https://t.co/O0hIpHwEF2

117. Some crops and weeds are considered to be allelopathic, meaning they release chemicals into soil that harm competing plants.

118. Allelopathy sounds cool and gets lots of hype and attention, but...

119. with few exceptions, weed scientists are generally skeptical of the magnitude of allelochemicals in crop-weed interactions.

120. I have an entire refrigerator full of weed seed. And a closet. And a few shelves. And I'm probably at the low among weed scientists. https://t.co/a3SvpNBQzM

121. We spend lots of time planting, growing, harvesting, and cleaning weed seed. Think growing flowers is hard? Try growing weeds.

122. "But weeds grow EVERYWHERE! How could it be difficult?" Because weeds grow everywhere YOU DON'T WANT THEM TO GROW.

123. One problem growing weeds is seed dormancy. Some freshly harvested weed seeds simply won't germinate even under ideal conditions.

124. We can often break that seed dormancy by treating the seed in some way, but not always.

125. Dormancy breaking treatments we use in weed science include heat, cold, sandpaper, acid soak, plant hormones, potassium nitrate...

126. Often it is a combination of those factors. Like heat/cold cycles or wet/dry cycles. Or a 20 minute acid soak followed by prayer.

127. There's a book titled "Germination and Establishment of Weeds for Experimental Purposes" lovingly referred to as Andersen's guide.

128. Andersen's Guide is basically a literature review of all the crazy shit weed scientists have tried to get weeds to grow.

129. Andersen's Guide is indispensable for weed biology/ecology research.

130. Another issue we run into is that there's not really any commercially available equipment for weed seed planting and harvest.

131. We often have to build our own. Or buy things and heavily modify them. This is a unit we use to clean weed seed. https://t.co/3V4rzgmpyz

132. I don't know the origin of that seed blower. It predates me. Probably by a decade or better.

133. We also have a few hundred mounted weed specimens in the lab. Helpful for teaching and identification of unknown species. https://t.co/evPpVwNkiW

134. This contraption is an elutriator. We use it to separate weed seeds from soil. https://t.co/qh7lWcq6Rx

135. Separating weed seeds from soil is obviously not a viable weed control strategy... We use it to quantify weed seed in soil in research.

136. A "typical" cropland soil has anywhere between 600 to 160,000 weed seeds per square meter. THAT'S A LOT OF SEEDS.

137. When you have that many weeds, even getting 99% weed control (which sounds pretty good) can lead to crop failure.

138. Leaving behind 1% of a helluva lot of weeds IS STILL A HELLUVA LOT OF WEEDS.

139. "Acceptable" weed control, then, usually involves lots of decimals. 99.999...%

140. Some plants we think of as weeds provide excellent habitat for pollinators. https://t.co/7mUSl0XMAY

141. However, many plants that serve this function (especially native thistles and milkweeds) aren't really that weedy.

142. This why I think it is important to really think about defining the term "weed" even though it can seem purely academic & impractical.

143. Here are 2 missile silo sites in Wyoming. One is active, one isn't. How do I know? WEEDS! https://t.co/udONRF8tbI

144. Weeds cause problems with remotely managed secure sites like this. Weeds blow around and provide habitat for critters that move.

145. If you rely on motion sensitive monitoring equipment, weeds are going to cause problems with false alarms. So you kill the weeds.

146. There is a non-zero chance I get visited and questioned before the end of the day about why I stopped and took photos of these sites...

147. I'm sure that sounds paranoid, but I know from experience guys with M-16s don't appreciate me loitering near these sites. (long story)

148. In number 82, I mentioned that dinitoaniline herbicides are yellow. Here's proof: https://t.co/LJNLSwxXS4

149. Rumor has it that it was the paint division of one company that discovered that herbicide class. No idea if that's true, though.

150. And so now I guess I'm tweeting facts, observations, or unsubstantiated rumors about weeds and other stuff.

151. Rye is a common weed of winter wheat. If we didn't plant the rye, we call it 'feral' rye, but it is the same species as cereal rye.

152. Rye grows taller than wheat, and it's pretty obvious when the crop and weed have produced seed heads. https://t.co/1p0NIXOo8q

153. We can exploit the height differential to help manage rye in the wheat crop.

154. A wick applicator (basically a sponge soaked with herbicide) can be run just above the wheat, and the wick wipes herbicide on the rye.

155. The goal of the wick application is not to kill the plant at this point, but to reduce rye seed production.

156. Rye seed is a problematic contaminant in wheat seed. Rye can impart an off flavor to the wheat (like rye bread).

157. Foxtail barley (Hordeum jubatum) isn't weedy in many ways; native, not very competitive, only grows where other plants won't. https://t.co/NFmcdSmhf3

158. But the foxtail barley seed head has lots of barbs, that causes problems (like mouth sores and infections) when livestock eat it. https://t.co/WwPqMrP6RV

159. Foxtail barley can also be a problem for pets. Dogs that eat it can get the barbs caught in their throat and cause a persistent cough.

160. Quackgrass (a perennial grass weed) has had a LOT of scientific names over the years. https://t.co/3wzbQM491c

161. Plant taxonomists are a tortured people.

162. The Weed Science Society of America has a standard list of weed common names, since scientific names change: https://t.co/sZ3GXancTx

163. I think among weedy species, salsify might be my favorite flower. https://t.co/ve9AXOvBuk

164. Weeds compete with crops for resources. We usually attribute crop yield loss to weeds using water, light, or nutrients the crop needs.

165. But plants interact in different ways, too. For example, by altering light *quality* instead of quantity. https://t.co/9fig9GYQyC

166. These resource-independent interactions are remarkably interesting, but also kind of infuriating to study.

167. To truly isolate the effect of reflected light quality on plant growth, one must grow plants in a *HIGHLY* artificial system. https://t.co/LshCQLqTkU

168. Which always leaves the question about how important/relevant the results from the highly controlled experiment is in the real world.

169. We also find VERY interesting results each year we continue with this line of research. But we're always skeptical they're real.

170. Because in these artificial systems, it is difficult to predict how we might be confounding some aspect of the total plant environment.

171. So we try not to report the results until we're sure the effects are real, repeatable, and attributable to the hypothesized cause.

172. Taking this cautious approach can be really frustrating. Things move slowly, especially when each study takes nearly a full year.

173. Russian olive (Elaeagnus angustifolia) is a drought tolerant, beautiful tree that was planted all over the Western US. Also a weed. https://t.co/zOPIizG9Ba

174. Russian olive pistils kind of look like they lick their own anthers. #kinkyautotrophs https://t.co/CjJtkEtrtW

175. Dicamba is volatile, meaning it can turn into a gaseous state and float away.

176. The absolute worst time to spray a pesticide is when there is ZERO wind. Ideal spray conditions are a 3 to 5 mph breeze.

177. When there is no breeze, it is possible that a 'temperature inversion' exists. That's when a cool air layer is trapped below warm air.

178. When there is a temperature inversion, many spray particles just hang; they don't fall immediately downward like normal.

179. Spray droplets applied during a temperature inversion can move a LONG way off-target, making it difficult to figure out the source.

180. Research from Missouri suggested that temperature inversions are more common than we realized, occurring 24 times in June '16.