How to tell Smaller Cat’s-tail (Phleum bertolonii) from Timothy (Phleum pratense)

How small is smaller? Is it just the hot weather? Is it the shade?

*Beads of sweat appear on your forehead*

During our Worcestershire Flora Group meeting at Alfrick, I collected a suspected smaller cat’s-tail Phleum bertolonii to measure back at home, tea in hand. Attendee Sam Groves kindly curated some typical Timothy Phleum pratense, so I took both back for comparison. As we suspected, we had both species.

This was a fun learning experience, so I’ll leave it here for future use, for a sweaty-browed botanist somewhere…

Comparison of Phleum bertolonii and Phleum pratense

In principal, P. bertolonii is smaller in all parts and stature (10-50cm) than P. pratense. It’s important to sample and measure many of the floral parts to make a true determination.

In the simplest terms, if a plant is short, has spikelets (including awns) less than 3.6mm long, panicles 3-6mm wide and leaves 2-6mm wide, you have P. bertolonii. Below, I’ve provided the differences as listed by Stace, the measurements of our specimens and photo comparisons. Enjoy!

	P. bertolonii	P. pratense
1. Spikelet and awn lengths	2-3.6 (3.8)mm including awns 0.2-1 (1.2)mm	(3.5)4-5.5mm including awns (0.8) 1-2mm
2. Panicle width	3-6 (6.7) mm	5-10mm
3. Leaf width	2-6mm	3-9mm
4. Ligule shape (usually)	Acute	Obtuse

Our specimens of P. bertolonii had:

Spikelets around 2-2.5mm, with a short awn around 0.5mm.
Panicle width of ~ 5mm
Leaf width of 2mm

By comparison, our specimen of P. pratense had:

Spikelets ~ 5mm, with a longer awn around 1.5-2mm
Panicle width of ~8mm
Leaf width of 6mm

Comparison Photos

Spikelet and awns

**Left**: *P. bertolonii* 2-2.5mm, short awn c. 0.5mm. **Right**: *P. pratense* 5mm, longer awn

Panicle width

**Left:** *P. bertolonii*, 5mm wide. **Right:** *Phleum pratense* ~8mm wide.

Leaf width

All of which fit well within the specifications given in Stace.

Tom the Botanist