The following dichotomous key can be used as a guide to identifying a particular blown-grass species. The key works by selecting one of the two choices given for each pair of descriptions, which lead to either another pair or the identification of your species.
| 1. | Leaves flat when fresh | ................................................................................................ | 2 |
| 1. | Leaves inrolled or closely folded | ................................................................................................ | 3 |
| 2. | Leaves less than 3 mm wide | ................................................................................................ | Lachnagrrostis filiformis (Common Blown-grass) |
| 2. | Leaves greater than 3 mm wide | ................................................................................................ | Lachnagrrostis billardierei (Coast Blown-grass) |
| 3. | Florets awnless or with short non-bent awns | ................................................................................................ | 4 |
| 3. | Florets with long, sharply bent awns | ................................................................................................ | 5 |
| 4. | Florets more or less awnless | ................................................................................................ | Lachnagrrostis leviseta (Awnless Blown-grass) |
| 4. | Florets with awns 1.5-3mm long | ................................................................................................ | Lachnagrrostis adamsonii (Adamson’s Blown-grass) |
| 5. | Upper part of florets with rough surface | ................................................................................................ | Lachnagrrostis robusta (Salt Blown-grass) |
| 5. | Upper part of florets smooth | ................................................................................................ | Lachnagrrostis punicea (Purple Blown-grass) |
![]() Purple Blown-grass (L. punicea ssp. punicea) | ![]() Salt Blown-grass (L. robusta) | ![]() Adamson’s Blown-grass (L. adamsonii) | ![]() Common Blown-grass (L. filiformis) |