Jan 15, 2015
Esperanza Leticia sent me a pic of weeds in her garden at Lismore so I am doing a bit of a tall weed identifying section here..






Pennisetum purpureum renamed Cenchrus purpureus in 2010. is tall as fuck, growing to 4m, can resemble sugar cane when fully mature. Pale green leaves up to 4cm wide with a prominent midrib tapering to a tip. Flowerheads are 30cm in length and range in color from yellow to purple. when you try pulling it out it has a stem like lemongrass a bit. Cenchrus p. will never be declared a pest coz cows love it and its good for them :-). Another unique thing about Cenchrus p. is that it can also grow geniculately ascending - flat then bend up at a sharp angle opposed to decumbent like Eragrostis c. which lies mostly along the ground and with only the extremity curving upward.

1) & 2)







Megathyrsus maximus grows to 200cm tall (unless its a mutant that will die within a year and is 400cm tall). If you take a look at the panicle inflorescence u will see that Cenchrus P (the yellow one) is solid and the spikelets/seeds are sessile (no small branch attaching them) while Megathyrsus has a compound inflorescence (branching into an oblong or pyramid shape) with spikelets/seeds pedicelled (on a small branch).  First picture is from #election2013 and now #qldelection2015. Leaf blades are linear or lanceolate.










Sporobolus natalensis' flower even tho its a compound inflorescence with pedicelled spikelets like Megathyrsus m. looks more like Cenchrus p. because its primary branches are contracted. Of course the inflorescence looks like a rat's tail I recommend looking closer at the flower to ID.





Eragrostis curvula - so if the inflorescence is wide with branched spikelets it could be a Megathyrsus m. or an Eragrostis curvula (they r both around the same size). A spottable difference is if the leaves are filiform (thin like string) or convulute or curled, then you probably have an Eragrostis. Eragrostis can be a bit purple in the green stage of flower so be careful identifying just on flower color.  The other identifiers kind require a magnifying glass but try seeing if the floret is on a bendy stem coming off the branch or a straight stem. Eragrostis c have bendy stems (rachilla). Sporobolus n. and Eragrostis c. are not that good for cows. oh plus. If it's a bushy looking flower then its a Megathyrsus m. its not such a good identifier coz its only a small stage of the flowering process.

NB. Arundo donax (Giant Reed) may be a tall weed too but it grows in and around freshwater, and is handy to burn as a biofuel, someone send me a pic of water weeds and I can do a water weeds section?

Plus coming is a weeds under 1m section and includes several varieties of Paspalum, Rhodes Grass, the shorter American Rat's Tail Grass, Molasses Grass, Para Grass... aargh my head is spinning.