CAPE-PONDWEED

CAPE PONDWEED

Aponogeton distachyos

Cape Pondweed Family [Aponogetonaceae]

month8may month8jun month8june

status
statusZneophyte
 
 
flower
flower8white
 
 
inner
inner8cream
 
 
morph
morph8actino
flowers
 
morph
morph8zygo
petals
 
petals
petalsZ2
~4n-1
[n=1-7]
type
typeZspiked
 
 
stem
stem8round
 
 

28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Leaves long-oval and present April to October. White flowers on long stalks lying down on the leaves close to water. [The flowers on the far-right are of a different garden flower). The leaves can grow up to 25cm x 7cm but these are nowhere yet near that. The tip of the leaf is obtuse to pointed with between 5 and 9 parallel veins going lengthways (but they converge at each end).


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Leaves nearly long-oval; some come to a sharper rounded end. A central main vein with 3 equi-spaced curved veins. Straight wrinkles at nearly right-angles to the veins. Flowers elongated symmetrically about a central origin. The leaves have long stalks (up to 80cm and even 1m)


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Flowers in two tapering radial spikes from a single stem.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Side view of 2 shorter radial spikes of flowers which each grow up to 6cm long, each with up to 10 flowers (but each flower does not have a corresponding set of petals - it seems). They are at an angle to the single stem. The petals (actually tepals) are 10 to 20mm long.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Petals in loosely opposite pairs, getting smaller the further from the central stem. This double spike of flowers has (nominally) 8 paired petals, although there might be the odd unpaired petal...


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Whereas this specimen nominally has 6 loosely-paired petals (again there might be an odd unpaired petal in this specimen?) the number of petals do not correspond to the number of 'flowers' (anthers plus style) for there are between 1 and 2 petals (actually tepals) for each flower. A frog keeps a keen eye on the suspicious proceedings above the pond.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
For instance, this specimen definitely has 5 loosely-paired petals that he can see, but your Author can count at least 8 styles with anthers clustered around and he suspect there are other flowers hidden by curled tepals at each end.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
The stamens are numerous and coloured cream with pollen at first, then turning dark brown as the pollen is lost. In the centre of each set of stamens is a 5-pronged white stigma.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
In the centre of the floating leaves many stems emerge from the depths of the water. Leaves might emerge curled longitudinally first before lying flat on the waters surface.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
One of the smaller and more-pointed leaves. The frog is still a concerned citizen of the pond and could be about to write to The Guardian newspaper about your Author hovering suspiciously above.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
Leaf ends (both). The numerous cross-veins between the longitudinal veins are like a ladder. The leaf underneath (not shown) has many reddish streaks.


28th May 2018, a garden, Poynton, Cheshire. Photo: © RWD
At first the un-opened flowers emerge from the pond upright.


28th May 2018, a garden, Poynton, Cheshire. Photo: © Anne Nesbit
The seed pods will proliferate and smother the pond with new offspring if not removed.


28th May 2018, a garden, Poynton, Cheshire. Photo: © Anne Nesbit
The seed pods are in pairs with a thinner spike each.


Not to be semantically confused with : Cape Pigweed (Amaranthus capensis), Cape-pondweed (), Powell's Cape Lily (Crinum × powellii), Cape Cudweed (Gnaphalium undulatum), Cape Tulip (Homeria collina), Cape Marguerite (Osteospermum ecklonis), Cape Wattle (Paraserianthes lophantha), Cape Figwort (Phygelius capensis), Cape Gooseberry (Physalis peruviana), Caper Spurge (Euphorbia lathyris), [plants with similar names belonging to differing families]

Uniquely identifiable characteristics

Distinguishing Feature :

The strange arrangement of the flowers and petals (actually tepals) is unique. The flowers themselves (anthers and style) are actinomorphic, but the rest of the flower (the 'petals) are not. The flowers are bisexual and hypogynous, the latter term relating to the height juxtapositioning of the various sexual organs.

By reasoned inspection your Author has deduced that the number of petals any double-spike of flowers contains is about 4n-1, where n can assume any value between 1 and 7. However, he has not worked out a suitable formula for the number of flowers that the specimen contains given the count of the number of petals, but thinks it fair to say that the more petals, the more flowers it has room to contain. Cape Pondweed is very unusual in that the flowers lack individually assigned petals like most (all?) other flowering plants. The flowers are counted by the number of styles (which have 5 stigmas) the spike contains. The anthers are grouped around the single styles, but they too are very variable in number. Although the flowers themselves are actinomorphic, the petals around the linear array of flowers are decidedly zygomporphic. Hence both the actinomorphic and zygomorphic designations.

Cape Pondweed is not a very prolific invader of water; being found in isolated spots in the South of England, and in the north of England and Scotland is even thinner on the ground seemingly preferring the coastal spots in just a few scattered locations, but does appear to be spreading slowly. It has been known to reproduce by seed in Britain, but presumably in warmer locations. It grows in still water up to 2m deep and can easily overwhelm small ponds and other bodies of water.

The roots (not shown) are not divided into segments (not septate). The plant produces tubers, which is mostly how it spreads in a pond in the UK rather than sexually (it does not produce seed in the UK) and cannot spread except by human intervention. However once in a pond or other body of still water it can quickly overwhelm it.


  Aponogeton distachyos  ⇐ Global Aspect ⇒ Aponogetonaceae  

Distribution
 family8Cape Pondweed family8Aponogetonaceae

 BSBI maps
genus8Aponogeton
Aponogeton
(Cape-Pondweed)

CAPE-PONDWEED

CAPE PONDWEED

Aponogeton distachyos

Cape Pondweed Family [Aponogetonaceae]