![](https://images.ctfassets.net/l2hapltrg3cz/2SvAAy5IYmImvuM9QpoCgN/3d675a78f8d0175291d4d99ce8ba6bc9/fog-2-d.jpg?fm=webp&w=1080&q=85)
Onion couch/False oat-grass
Arrhenatherum elatius
Auricles
Absent
Importance
False oat-grass is very common in grassland and in hedgerows throughout the British Isles. The onion couch variant is a more localised problem, generally in loams of more open texture. Once present it is very difficult to totally eradicate as each root nodule can develop into a new plant and they are very resistant to dry conditions.
Leaf blade
Long, narrow, rough and sparsely hairy above, or hairless.
![](https://images.ctfassets.net/l2hapltrg3cz/6wAbe63YmgsRsh3S1Z07Ag/512a8d99a08c62baef0e596bc381dc48/onion_couch_03.jpg?fm=webp&w=1080&q=85)
![](https://images.ctfassets.net/l2hapltrg3cz/58681ptdSEndxpZD4LLdxy/e23657cb5e1cc5e39a35fb89d13c1e10/onion_couch_02.jpg?fm=webp&w=640&q=85)
![Onion couch/False oat-grass ligule. Photo © HGCA.](https://images.ctfassets.net/l2hapltrg3cz/4lqTPJsUD5jMMPLtCSRu7S/0c4660c3c8a062e71505ccf480b4c6e5/onion-couch-ligule.jpg?fm=webp&w=750&q=85)
Onion couch/False oat-grass ligule. Photo © HGCA.
![Onion couch with distinctive swollen bulbous nodules at base of stems. Photo © Blackthorn Arable.](https://images.ctfassets.net/l2hapltrg3cz/7FrJGmc3VQm6V5Zv4z4Tll/f087d0ba43f3e48570aa59e8a6fc0a76/onion-couch.jpg?fm=webp&w=750&q=85)
Onion couch with distinctive swollen bulbous nodules at base of stems. Photo © Blackthorn Arable.
![Onion couch/False oat-grass flower heads. Photo © Nigel Caittlin/Alamy.](https://images.ctfassets.net/l2hapltrg3cz/3wfpRSRWDj3vUKRxKUkTDi/df899f4e2ab99a65308d5d7ab698335a/onion-couch-false-oat-grass-mature.jpg?fm=webp&w=750&q=85)
Onion couch/False oat-grass flower heads. Photo © Nigel Caittlin/Alamy.
Ligule
![](https://images.ctfassets.net/l2hapltrg3cz/4Y6tAdib3bPD99MRND1KY1/21859c82b30d426be6e032bc01361f03/onion_couch_01.jpg?fm=webp&w=3840&q=85)
Short to medium: up to 3 mm.
Description
Very tall perennial 60-150 cm. Swollen bulbous nodules at the stem-base indicate the onion couch variety of false oat-grass. Panicle is like miniature wild oat head but more upright condensed and narrow.
![](https://images.ctfassets.net/l2hapltrg3cz/3eRUCTw0jmsX4ze8jAKMFB/c9bf16efc9e3f471b1c417f0199ac077/fog-2-d.jpg?fm=webp&w=1920&q=85)
Young onion couch © Blackthorn Arable
![](https://images.ctfassets.net/l2hapltrg3cz/2dNMHPiix4ULJ8OREKBlWi/e9cf02e0ebec30860d61e5fbfb6dd0f3/fog-3-d.jpg?fm=webp&w=1920&q=85)
Ligule © Blackthorn Arable.
![](https://images.ctfassets.net/l2hapltrg3cz/3fLcmJKOTesCOutktCoxi6/742c484d66c7f22d66e2a604ece0368e/onion_crouch_yp.jpg?fm=webp&w=1920&q=85)
Onion couch with distinctive swollen bulbous nodules at base of stems. © Blackthorn Arable.
![](https://images.ctfassets.net/l2hapltrg3cz/1h0qvud54Zy9GzLekPOd5R/677728ff5c36c4492f44e69e75b97e83/FieldMate_Promo_Mobile.jpg?fm=webp&w=3840&q=85)
![](https://images.ctfassets.net/l2hapltrg3cz/3CvKagUshwoSyxEDqRj52c/bd6e3be09e808d22cf4c4c324b6d4ac7/FieldMate_Promo_Desktop.jpg?fm=webp&w=3840&q=85)
![](https://images.ctfassets.net/l2hapltrg3cz/3CvKagUshwoSyxEDqRj52c/bd6e3be09e808d22cf4c4c324b6d4ac7/FieldMate_Promo_Desktop.jpg?fm=webp&w=3840&q=85)