PIRRI-PIRRI-BUR

Acaena novae-zelandiae

Rose Family [Rosaceae]

month8jun month8june month8jul month8july

status
statusZneophyte
 
flower
flower8bicolour
 
flower
flower8green
 
inner
inner8white
 
inner
inner8purple
 
morph
morph8actino
 
petals
petalsZ0
 
type
typeZglobed
 
stem
stem8round
 
contact
contactZlowish
 

Date: Unknown, Location: Unknown Maceay Grass Man  Photo: © CC by 2.0
The flowers totally lack petals, but they do have four green sepals, two stamens and a single stigma each. They flower-heads are globular and maybe 10-20mm across and contain maybe about 80 flowers. The off-white doubled anthers are the obvious parts, less obvious are the shorter white styles tipped with their white hairy stigmas.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
The herbaceous stems are ascend up to 15cm whilst the woody stems are procumbent and form mats.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Perhaps these specimens have woody stems and are therefore procumbent, and mat-forming. In this small area there are 16 that can be discerned (and possibly some more which are hidden). Some, (top right corner) are very small, spineless and presumably still developing.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
These fruiting flower heads are ascending, but viewed from above. The pinnate leaves with toothed oblong glossy-green leaves (from above only) are the leaves.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
The leaves are mostly procumbent and growing rather long spreading stems.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
After flowering the stamens and style wither leaving the four empty sepals. Spines grow from beneath the sepals. In this species, Acaea novae-zelandiae, between 3 and 4 spines per flower sprout. Later they also acquire their backwardly-directed barbs.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Each flower has four sepals, and underneath those, at more or less right-angles to each other are four red-purple spines tipped with barbs (centre flower). With 3-4 spines per flower.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Each flower has 4 sepals, more plainly seen when the flowers have withered, as here.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
The tiny white backwardly-pointing barbs are like the spokes of a miniature partially-opened clothless umbrella. Their shape ensures that penetration of fur occurs easily, but extrication is more difficult. The detached spines, complete with seed are thus carried far and wide by animals before being dislodged, to perchance grow elsewhere.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Long gaps between separate leaves.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Leaves alternate up the stem, with an extra smaller leaf growing in the axil of the main leaves.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Leaf with smaller leaf in axil. Leaves very much like those of Fodder Burnet - both are members of the Rosaceae family. There are between 9-13 (up to 15) leaflets in a pinnate leaf. Leaves glossy on the upperside, but matt and paler on underside (top right, but out of focus)


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Leaves have forwardly-directed sawtooth-teeth which have an acuminate tip.


18th July 2016, near The Pole, Stanage Edge, Hathersage, Derbs. Photo: © RWD
Leaf stems are hairy.


Not to be semantically confused with : Piri Piri [an African word for Chili Peppers from the Capsicum genus and also a Portuguese hot chili sauce. Note the differing spelling from Pirri-pirri-bur, although note also that the American spelling for this plant is indeed Piri-piri-bur (!).]

The Pirri-pirri-bur (Acaena novae-zelandiae) shown here has: 9-13 (up to 15) leaflets - those at the tip of a leaf being 1.8x to 2.5x longer than wide, 5-20mm long with 5-12 (up to 15) teeth. 3 to 4 spines per flower. Spines 6-10mm long, often with 1 or 2 much shorter. Compare this with the Pirri-pirri-burs listed below.

Easily mis-identified as :

  • Bronze Pirri-pirri-bur (Acaena anserinifolia) but that invariably has bronzed (not glaucous) leaves. The pair of leaflets at the tip of a leaf are only 3-10mm long. Spines only 3.5-6mm long but often one or 2 much shorter.
  • Glaucous Pirri-pirri-bur (Acaena caesiiglauca) with blue-greem glaucous leaves often tinged purple. The pair of leaflets at the tip of a leaf are only 6-14mm long. Spines only 4.5-7mm long.
  • Two-spined Pirri-pirri-bur (Acaena ovalifolia). With (7) 9-(11) leaflets in a leaf; the pair of leaflets at the tip of a leaf are longer at 10-30mm, are 1.7 - 2 x longer than wide and have more teeth ((11) 17-23. Only 2 spines per flower.
  • Spineless Pirri-pirri-bur (Acaena inermis) without spines, or with imperfect spines, or spines are not barbed, usually zero per flower, but sometimes 1-4 per flower. Leaves bluish-grey-green, the pair at the tip being very small, just 2-8mm long, and are as long as they are wide, with 5-10 teeth.
All are introduced and naturalised and most are grown in gardens. All are invasive, and hard to eradicate once they get into the landscape. There is still a chance of eradicating the outbreak just north of Stanage Pole since at the moment your Author only saw it over a 100 yard section of paved pathway, but then, it is hard to see amongst any taller vegetation which is plentiful around here, such as Heather, Bilberry, grass, etc. Your Author could hardly see it even amongst short grass, so it is possible it has already spread deeper into the acidic moorland common around those parts. Get digging...

A hybrid between Bronze Pirri-pirri-bur (Acaena anserinifolia) and Spineless Pirri-pirri-bur (Acaena inermis) is also grown in gardens and can escape. These have 2 stigmas and develop spines.

Some similarities to : Salad Burnet (Sanguisorba minor) which also has similar pinnate leaves and a similar flower-head, but the flower-head is smaller, red and lacks the spines. Fodder Burnet (Poterium sanguisorba ssp. balearicum) has more similar (more oblong) pinnate leaflets but a longer flower-head, again lacking spines. Both plants are in the same Rosaceae family as the Pirri-pirri-burs.

Unusual for a plant belonging to the Rose family Rosaceae in that it has flowers with zero petals (rather than the usual complement of 5), but it does have 4 (rather than the usual 5) sepals, which are green. The anthers are white and prominent whereas the style, although also white, is much smaller with a hairy stigma. Like most plants it is bisexual.

The stems themselves are spine-less, with all the spines appearing in the flower-head when it is fruiting. There are 4 spines per flower (on Two-spined Acaena (Acaena ovalifolia) there are only 2 spines per flower). The spines are burred and adhere to clothing or the fur of passing animals, which spreads the seeds (which are attached singly to each bur).


  Acaena novae-zelandiae  ⇐ Global Aspect ⇒ Rosaceae  

Distribution
 family8Rose family8Rosaceae

 BSBI maps
genus8Acaena
Acaena
(Pirri-pirri-burs)

PIRRI-PIRRI-BUR

Acaena novae-zelandiae

Rose Family [Rosaceae]