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Quotes

A garden is always a series of losses set against a few triumphs, like life itself.
-Mary Sarton

Bags-I a Black Poplar

With trees in young leaf and their flower pollen dusting the air, I re-visited Russell Square’s Black Poplar to determine its sex and true identity.  It was heartening to see the naked, lanky specimen of my winter visit fully clothed in semi-lustrous foliage and looking more like the noble tree of our lowland river valleys.

Black poplar in spring leaf

Black poplar in spring leaf

Black Poplar leaf gall

Black Poplar leaf gall

Examination of the blunt-toothed leaf with its twisted petioloes suggests that this is no cross-species but true Populus Nigra. These contortions are caused by the spiral leaf gall aphid, Pemphigus spyrothecae, which apparently do not occur on any of the Cotton Wood or Balsam Poplar hybrids.

The pointed, triangular leaf shape and furrowed, heavily bossed bark also make an identity match and only the lack of pubescence on the foliage raises some doubt as to this being from native wild Black Poplar stock.1 It could be a sub-species hybrid but without DNA testing at my disposal I cannot discern a betulifolia from sbsp nigra.

Black Poplar fruit

Fruity Female

Black Poplar fallen seedheads

Fluffy female

Although not a racing certainty, I had assumed that the Russell Square tree would be  male. The prejudice against planting female Poplars especially in urban settings  arose from the annoyance of having fluffy seeds wafting around. Populus nigra subsp.betulifolia are currently more endangered due to this sex selection; of the estimated 7000 in the UK, only 600 are female.

Flowers appear before the leaf and so with the season prematurely advanced, I had expected to see red ‘devils fingers’ of spent male catkins lying on the ground. A  few stray fallen seeds confirmed instead that ITS A GIRL.

High up in the canopy the yellow-green catkins were already fertilised and fruiting as small grape-green clusters. The towering height provided no opportunity for a closer look but true to the saying: “it’s an ill wind that blows nobody any good”, the day’s strong Easterly had broken off a 6 foot length. Naturally I brought the branch home for further study although carrying it required a certain nonchalance and dexterity.

Branch of Black Poplar

Branch of Black Poplar

green berries of Black Poplar

Green berries

Propped against the wall and looking extremely top heavy in a large flower vase, life was nevertheless temporarily resumed.

In close-up the textured berry-shaped fruit bears the residual two-tipped stigma, which  received the wind-blown pollen. Although there is no male tree intimately close by, the estimated radius for pollen travel is about about 9 miles 2 putting other London Black Poplars within pollinating distance, including Green Park, Islington and even possibly those on the Hackney marshes.

Interestingly scientific studies confirm that where there are both male Black Poplars and poplar hybrids in equal proximity, P. Nigra preferably accepts pollen of its own species. Otherwise cross-pollination will occur. 3 Given the proximity of the Black Italian Poplar in Hyde Park for example, it is just as likely that the Russell Square poplar has been fertilised by a hybrid interloper.

Black poplar berries opening

Black poplar 'cotton tree'

ripe seedcase of Black Poplar

seedcase & silky filaments

Progressing rapidly on, the seedpods burst open within 24 hours, revealing the tell-tale powder puffs of white down, after which its close relatives, Cottonwood trees, are so-named. With an uncanny resemblance to new born stars in a cosmic Magellanic Cloud, the white seeds can be clearly discerned within. Unfurling on tangled, silky filaments, these are eventually frothed out, descending in cumulus clumps. The tree’s resin helps the seeds to stick where they fall.

Black poplar seeds dispersing

seed dispersal

Black Poplar seeds

seeds are born!

Germination of the short-lived wind-blown seeds requires a wet, bare, alluvial ground but much of the flood-plain conditions on which they rely have disappeared, due to changes in practice of managing our waterways.

Evidently the tended, crowded bedding of Russell Square affords no chance of propagation for this Black Poplar. It is also possible that the fruit will be sterile if it has hybridised. Nevertheless I shall attempt to bag at least one Black Poplar from this seed collection even though emulating the natural conditions of germination is going to be a major challenge.

p.s. I’d be interested to know from any others who have grown a tree from seed – not counting the fecund sycamores, tree of heaven or Horse chestnut which propagate against my will, in the garden.

p.p.s. this post is inspired by b-a-g, an engineer who likes to weigh, measure and generally Experiment with Plants

Related Posts:
Black Poplar in winter Hunting the Black Poplar
Black Italian Poplar For the Love of Poplar

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Notes:
1. Black Poplar also known as Downy Poplar, Water Poplar, Willow Poplar and Cotton Tree
2. Black Poplar Biology
3. Journal of Forest Science 2002 ‘Introgression in black poplar (Populus nigra L. ssp. nigra) and its transmission 

Further Reading:
The Forestry Authority: Black Poplar: the Most Endangered Native Timber Tree in Britian
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©Copyright 2011 Laura Thomas.
All rights reserved. Content created by Laura Thomas @PatioPatch
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10 comments to Bags-I a Black Poplar

  • Laura, I know this post was perfectly serious, and it was very interesting, but I just kept laughing. Laura’s baby girl poplar (It’s a girl!!!) is already mating and possibly in a very promiscuous way with an unknown interloper. Couldn’t you have supervised her more closely? What’s wrong with me tonight? Carolyn
    Carolyn @ Carolyn’s Shade Gardens read my post..Miniature &amp Small HostasMy Profile

    • Botany takes me that way, Carolyn – too serious and it’s just a dry topic. It’s the school girl within us both I suspect that sees the fascinating but funny side of progeniture. :)

  • I too was thinking the same a Carolyn. ‘It’s a girl’, seemed like you were quite pleased and so glad a suitor found her.
    Donna read my post..Prunus x ‘Hally Jolivette’My Profile

  • Quite the informative post…I was so excited it was a girl…I love the seeds…we have something similar called an Eastern Cottonwood tree that once it produces the cottony flowers with seeds it blows them everywhere and it looks like snow…quite a mess in the yard but lovely in the wild…
    Donna read my post..JudgementMy Profile

  • - Well, Donna, I would not be able to try growing seeds if it was a boy ;)
    - I assume male cottonwoods would be preferable for the yard, Donna, but actually the fluffy debris is no worse than the London Plane seeds currently coating our pavements

  • Laura , I can honestly say that I have never inspired anyone before and I had to check the link just in case there was another bag that you were linking to. I am honoured.
    Your(brilliant as usual)post reminded me of a flower project I worked on when I was small. A book referred to male and female parts of a flower and I got really confused. I asked my mother about it, she told me to ask my father. In the end, I had to find out about flowers from a biology textbook and about the birds and the bees from the school playground.
    b-a-g read my post..Foxgloves 03 MAY 2011My Profile

  • Good luck with growing a baby poplar! I have never intentionally grown a tree from seed, but there are plenty of seedlings of all sorts in my yard. Thanks for the info on black poplar, which i knew little about.
    debsgarden read my post..Gardening with Texture and ColorMy Profile

  • Well that will teach me to not get around to catching up with your blog for so long – I read your wonderful Perpendicular Praise posting but couldn’t comment! Any chance you could add a “subscribe by email” button to help us email-driven readers keep up?!

    Love the berries and fluffy seeds. How sad that such a lovely tree has fallen victim to sex discrimination and changing land management. Great post Laura, I always learn something from you.
    Janet/Plantaliscious read my post..Malvern – the show gardensMy Profile

  • - will need luck and great skill, Deb
    - nice to know you missed my posts, Janet! thanks as always for your lovely comments. Have feedburnt a subscribe by email (see header)though not sure it works