Family: Willowherb [Onangraceae]


Chamerion

Circaea

Clarkia

Epilobium

Fuchsia

Ludwigia

Oenothera

Zauschneria



[EPILOBIUM] Willowherbs

 

EPILOBIUM HYBRID CHART (shrunk)
Hybrid Chart: WILLOWHERB (larger)

Missing from the above chart are two triple hybrids, namely
Epilobium montanum × obscurum × parviflorum
Epilobium montanum × parviflorum × roseum
which are over-lapped on the chart by other normal hybrids.

Epilobium SPECIES LACKING HYBRIDS
(Epilobium komarovianum) Bronzy Willowherb
(Epilobium lactiflora)

Most of the Willowherbs hybridize freely with one another. The above is a chart of all the known hybrids of the Willowherbs with other Willowherbs. Note how Bronzy Willowherb has no known hybrids, and that Rosebay Willowherb does not appear in the chart, for it has no hybrids either and although in common parlance it is a 'Willowherb', it is not in the Epilobium genus. Rockery Willowherb has only one hybrid, that with Broad-Leaved Willowherb, whereas Broad-Leaved Willowherb has many hybrids. Together, Short-Fruited and Broad-Leaved Willowherbs have the most known hybrids, totalling 11 (out of a possible 12). The empty dark-brown squares show that there is plenty of opportunity for much more promiscuity between willowherbs.

N.B. Due to the symmetrical nature of the chart, being folded about the black diagonal, each hybrid appears twice.

All Willowgerbs have long seed pods, which when ripe split open like a banana to reveal hundreds of seeds with long feathery plumes, ready to be borne on the wind to set seed in far-off places. a single plant can produce up to 20,000 seeds. Little wonder then that once a willowherb has a foot-hold in a garden, it is almost impossible to eradicate, for the plants grow faster than gardeners on a fortnights holiday can control. The smaller varieties have set seed before the gardener is even aware of their presence.

The characteristics by which Willowherbs can be differentiated from one another concern the shape of the stigma (club-shaped or '+'-shaped) the type of hairs, the branching, if any, the usual colour of the flower, and its size and shape. Also the shape of the leaves. The shape of the stem (round or square) is also an important ID feature in Willowherbs (although seemingly not used in some keys). The presence or absence of either runners above the soil surface or rhizomes below it are also indicative features.

All willowherbs have long fruits which are square in cross-section and contain rows of seeds with long overlapping white hairs, the pappus, to aid its dispersal in the wind. When ripe the fruits split open along the four edges like an un-zipped banana revealing the seeds with pappii. After drying they are able to flee on a slight breeze.

Willowherbs hybridize freely with one another species, their hybrids commonly occurring where two (or more) compatible Willowherbs occur in the vicinity. They are usually recognised by their larger and more branched nature, their longer flowering season, by their unusually large or unusually small flowers and by the darker coloured tips of petals. Their fruits are either partially or entirely abortive, but some seeds within are fertile, able to back-cross or form a triple (or even a quadruple) hybrid with other compatible species of Willowherbs.

Most hybrids are intermediate in character between the parents., most notably in the shape of the stigma (club or cross) and the type of hairs.



[CHAMERION] Rosebay Willowherb

Rosebay Willowherb. (Chamerion angustifolium) Photo: © RWD



[EPILOBIUM] Willowherbs

Great Willowherb. (Epilobium hirsutum) Photo: © RWD



[EPILOBIUM] Willowherbs

New-Zealand Willowherb (Epilobium brunnescens) Photo: © RWD

American Willowherb (Epilobium ciliatum) Photo: © RWD

American Willowherb (Epilobium ciliatum) Photo: © RWD

Broad-Leaved Willowherb (Epilobium montanum) Photo: © RWD



[OENOTHERA] Evening-primrose

The flowers of Evening-primroses tend to close up by mid morning and open up at night, when they are most fragrant. Perhaps Fragrant Evening-primrose is more fragrant than the others. They are all non-native plants originally from North America, but recently introduced to the British Isles, thus neophytes.

They have 4 petals and unusually, 4 sepals too, which are sometimes red depending upon the species. They have 8 stamens and just one stigma. It is the relative heights of these two organs which give one way of discriminating between some of the Evening-primroses: style higher or lower than the stigmas, or about equal in height. It is only when the style is shorter than the stamens where 3 possible species emerge (but rampant hybridization will confound any conclusions).


HYBRID SWARMS

Where many species of Evening-primrose are present, such as on the Sefton Coast, a 'hybrid swarm' is likely to develop (and is in full swing on the Sefton Coast). This is when the so-called 'Reciprocal Interchange Balanced Heterogenesis' (which in the case of the UK, is limited to Oenothera species) forms hybrids [your Author has asked over 3000 botanists and not one has explained what this is or how it works!]. There are many other ways in which hybrids can form naturally, but this modus operandi results in a so-called 'hybrid swarm' where all the participating species are able to hybridize with each other, and moreover, the hybrids themselves are fully fertile and able to fertilise with each other. In fact, this hybridization process is so vigorous on the Sefton Coast that very few pure species still exist there; they are mostly all hybrids. This particular and special hybridization process produces hybrids which are each a new taxon in their own right. The number of species increases exponentially with each hybridization. It is called a 'hybrid swarm' for this reason. Hybrid swarms are likely to occur anywhere there are two (or more) species in the vicinity. So it seems that classification of individual plants in a hybrid swarm is thus almost impossible, but Phil Smith succeeded in finding a group of us some 'good' specimens to photograph which could be so reasonably categorised.

But apparently, species of Columbine (Aquelegia) can also form hybrid swarms, in direct contradiction of an earlier assertion that Evening-primroses are the only species able to do this which are present in the UK. But just because they are capable of doing this, doesn't actually mean that they do in the UK. (Both are alien neophytes).

This article on Wikipaedia may help understanding:  Hybrid Swarm, since it does not (as of October 2017) mention anything about 'tranaslocation heterozygotes', 'balanced lethals', 'Renner complexes', 'homologous complexes', 'reciprocals of hybridization', 'genotypes' or 'selfing' - so accessibility is not up to Wikipaedias usual standard of rampant obfuscation and chronic incomprehensiveness when it comes to technical 'enlightenment' :-)

A few Evening-primroses do not seem to engage much or at all in this frolicking, among them Fragrant Evening-primrose, perhaps through lack of opportunity (there may be no other Evening-primroses nearby with which to engage), or through lack of the requisite ability (?).

 

[Oenothera]
EVENING-PRIMROSE HYBRID CHART
[Oenothera]
EVENING PRIMROSE
HYBRIDS
BSBI MAPS
Common
Evening-primrose

(biennis)
Small-flowered
Evening-primrose

(cambrica)
Large-flowered
Evening-primrose

(glazioviana)
Large-flowered
Evening-primrose

(glazioviana)
Oenothera
×
fallax
Oenothera
×
britannica
Small-flowered
Evening-primrose

(cambrica)
biennis
×
cambrica
Oenothera
×
britannica
Common
Evening-primrose

(biennis)
biennis
×
cambrica
Oenothera
×
fallax

In addition a hybrid between all three Evening-Primroses shown in the above hybrid chart is called Oenothera biennis x cambrica x glazioviana. It is thus a triple hybrid which cannot be shown on a 2-dimensional chart.

The Sefton Coast is renown for the hybrid swarm between Common Evening-primrose and Large-flowered Evening-primrose, the hybrid is commonly called Intermediate Evening-primrose and shown on the chart as Oenothera × fallax. Reciprocal crosses also occur between O. glazioviana and O. cambrica.

The hybrid between the hybrid Intermediate Evening-primrose (O. x fallax) and a female Large-flowered Evening-primrose (O. glazioviana) is known as O. × brittanica (and is thus another triple-hybrid, which cannot be shown on a 2-dimensional chart).

Oenothera SPECIES LACKING HYBRIDS
(Oenothera agg.) Evening Primrose agg.
(Oenothera grandiflora)
(Oenothera laciniata)
(Oenothera missouriensis) Missouri Evening Primrose
(Oenothera oakesiana)
(Oenothera parviflora)
(Oenothera renneri)
(Oenothera rosea)
(Oenothera rubricaulis)
(Oenothera salicifolia)
(Oenothera stricta) Fragrant Evening-primrose
(Oenothera tetraptera)

Fragrant Evening-Primrose (Oenothera stricta) Photo: (CC by 2.0) Geoff Toone

A Hybrid Evening-Primrose (Oenothera glazioviana x cambrica) Photo: © RWD

Common Evening-Primrose (Oenothera biennis) Photo: © RWD

Large-Flowered Evening-Primrose (Oenothera glazioviana) Photo: © RWD

Triple Hybrid Evening-Primrose (Oenothera cambrica x biennis x glazioviana) Photo: © RWD



[FUCHSIA] Fuchsias

Hedge Fuchsia (Fuchsia magellanica) Photo: © RWD

Family: Willowherb [Onangraceae]

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