Wednesday wildflower: old man's beard.

“Old man’s beard must go,” said the not-so-young bearded botanist David Bellamy some years ago on TV, and we all knew this was a serious weed that threatened to smother our native forests.  Since then, it’s not as common as it used to be.  The efforts of the Department of Conservation, local and regional councils, community groups, and individual landowners have largely seen off the worst infestations in many places.  But around Wellington city, and probably many other places, there are little pockets of old man’s beard everywhere.  My guess is it’s waiting for our vigilance to let up and it’ll be back with a vengeance.

Old man's beard fruits, Northland, Wellington.

Old man’s beard is called traveller’s joy in England, which goes to show that one country’s wildflower is often another’s weed.  The local name refers to the fluffy white plumes on the seeds.  More accurately (with my pedantic botanist’s hat on) these aren’t seeds but fruits, each bearing a single seed inside a loose-fitting fruit wall.  The flower, like many in the buttercup family, has multiple separate pistils, each with its own ovary, style and stigma.  After pollination, the pistils from a flower mature into a cluster of separate 1-seeded fruits, each with the fluffy remains of the style to form a plume that assists in wind dispersal.

One of the practical problems with a public eradication campaign is that people need to be able to recognise the target weed, and not try to eradicate look-alikes.  Many people worry that they might be pulling up one of the native Clematis instead, so I thought this week a few notes about these plants might be useful.

First, old man’s beard (Clematis vitalba) is one of just two species in New Zealand with once-pinnate leaves; they have a central axis with a terminal leaflet and two pairs of lateral leaflets.  The other species that’s characterised by once-pinnate leaves is C. maximowiciana, but its leaves are more leathery than the leaves of old man’s beard; also it has larger flowers, 30–50 mm diameter.  Most of the other species have three leaflets although these can be quite finely divided.  Two species, C. tangutica (yellow flowers) and C. flammula (white flowers), have twice-pinnate leaves (the pinnae [leaflets] are themselves pinnately divided).  The native C. afoliata has no leaves at all, just the leaf stalks that twine around supporting shrubs’ stems.

Old man's beard flowers, Kakariki, Manawatu.  They are mostly 12–25 mm diameter

Secondly, the introduced species mostly have 4 sepals in each flower, but many (not all) of the native ones have six.  All the introduced Clematis have hermaphrodite flowers (with functional stamens and pistils) whereas the natives all have unisexual flowers on separate plants (flowers have either stamens or pistils, but never both).

Clematis forsteri, a native species.  Pale yellow male flowers with 6 sepals.  If you see these, don't just look, sniff too: many are sweetly scented.

Most of the native Clematis flower in the springtime or even late winter (some plants of C. forsteri are in flower now in late July).  Old man’s beard is a summer-flowering plant, mostly from December to May.

Clematis paniculata, another native species, male flowers.

Old man's beard flowers are greenish white.  Most natives have pale or greenish yellow flowers, although the large (and unisexual) flowers of C. paniculata are pure white, C. marata and C. marmoraria are white or greenish, and C. marata quadribracteolata (corrected 4 September 2013) brown or purplish brown.  Finally, the introduced Clematis are all deciduous whereas the natives are all evergreen (except poor C. afoliata, which hasn’t got leaves to lose).

Old man's beard still must go, but let's hope no native Clematis get pulled out instead by well-meaning weed-busters.  The Flora treatment for their identification is on line at Landcare Research's website and you can find pictures identified by botanists at the Naturewatch site..

Wednesday wildflower: Red carpet, brown carpet

When I use the term wildflower, it's often to avoid the judgmental term "weed".  I like most plants, and if other people have species they don't like, well, that doesn't necessarily stop me enjoying them.  Furthermore, plants we designate as weeds are often biologically very interesting.  To a botanist, the term "weediness" has an ecological meaning that signifies more than a nuisance plant.

Pōhutukawa flowers

One of the interesting things weeds do well is reproduce.  All that any plant or animal needs to do is to reproduce itself at least once, but because an outcrossing sexual plant or animal contributes only one of its two sets of genes to each offspring it must do it twice to break even.  Even then, reproducing a few times doesn't guarantee the survival of all your genetic material, because which copies of genes get into a sperm or egg is random.  But some plants seem to reproduce in overdrive.

Weeds often succeed because they out-reproduce other plants.  Some are long-lived and may spread vegetatively, but others produce huge numbers of seeds.

A few red stamens have accumulated in the gutter beneath these trees, but sometimes, if it's not windy, a thick red carpet can build up.

Today's wildflower is a weed in the biological sense, but to New Zealanders it's a much-loved native flowering tree, the pōhutukawa, Metrosideros excelsa.  Pōhutukawa puts a lot of effort into reproduction, and that's probably why it's an unwanted weed in some other parts of the world where it has been introduced as an ornamental, like South Africa and Hawai'i.  Some people also consider it a weed in parts of New Zealand that are outside of its native range, such as Wellington, because it's invasive and aggressive there too.

A cluster of pōhutukawa flowers; each individual flower has about 25 red stamens (with yellow anthers) and one red style.

Pōhutukawa reproduction seems wasteful.  The trees flower profusely around Christmas time in New Zealand and in the later part of each flower's life the bright red stamens fall to the ground where they can form a thick red carpet.  This isn't over-production particularly; it's just that the red stamens are so visible and there are so many flowers producing them.  They can be dispensed with once their pollen has been dispersed.  They're visible for a good reason: pōhutukawa is primarily pollinated by birds (tūī, bellbirds, but also silvereyes and starlings) and the red colour attracts them because birds see well in the red wavelengths.

A bit later in the summer, many of the old flowers themselves fall.  I guess these are flowers that aren't setting seed; they no longer have a function and the plant can discard them.  I don't know whether these are functionally male flowers or simply flowers that didn't get pollinated, but these form a pale grey-green carpet for a time.

Pōhutukawa seeds in the gutter, Kelburn, Wellington

The third big dump of reproductive material is happening about now in Wellington, and that's the dispersal of seeds in their millions.  Most of these are never going to germinate.  They pile up in gutters, on footpaths, and at the bases of walls.  I'd like to do a rough calculation of the weight of stamens, aborted flowers, and seeds produced by a large pōhutukawa tree in a season; I think we'd all be surprised.  Multiply that, whatever it is, by the number of trees in Wellington and that's a lot of biomass falling to the ground each year.

Pōhutukawa seeds.

This prodigious reproductive effort is one of the attributes that makes pōhutukawa such a successful plant, and it's a trait normally associated with weediness.  No wonder then that our Christmas tree has become a pest in places.

Lila's big day out.

It’s ANZAC Day, New Zealand’s day to remember the war dead.  It’s an important day for my family too, because we arrived in New Zealand on ANZAC Day (April 25) 1955 on the MV Ruahine. 

Today it rained on and off all morning, so when the sun came out after lunch we had to get out for a walk.  Rufus was happy inside, but Lila was out in the garden and decided to follow us.  We tried to outrun her, but in the end decided to give in and let her come with us.

So she tagged along quite happily for the first 500m or so and then seemed to get a bit tired.  She was very wary the whole time, probably because she was out of her territory and in a place of new smells and sounds.

You might feel it’s wrong to take a cat into the bush, especially so close to Zealandia.  First, she’s not a hunter (yes I know cat owners always say that, like dog owners say their dogs don’t bite).  Secondly, she was too busy keeping up with us and watching her back.  Thirdly, and I know it’s not a valid argument but I’ll make it anyway, lots of cat-owning households back onto that bush and people walk their dogs there all the time.  I agree with Gareth Morgan that cats should be enclosed so they can’t hunt birds and lizards.

It’s autumn now.  The drought is well and truly behind us and fruits and fungi were the features of this walk.

Favolaschia calocera

Favolaschia calocera is an introduced fungus that lives on dead wood.  It’s become very common around Wellington.  Under the cap are large pores instead of gills.

Under the cap of Favolaschia calocera are honeycombed pores.

Buds of kohekohe, Dysoxylum spectabile.

Kohekohe (Dysoxylum spectabile) is going to have a bumper flowering this year.  The sprays of small white flowers are produced on the tree trunks, and a number were quite low down.  When these open, I’ll easily be able to reach them and get good photos.  Individual trees are either male or female, although some males can set a few fruits.

Outside the bush, the track follows the Zealandia pest-proof fence alongside a clay banks with a nice range of mosses and lichens and a view of the harbour.  We didn’t go far along, because Lila was clearly getting tired by now.

Passiflora fruits, one eaten by birds

Native passion flower (Passiflora tetrandra) was in fruit.  Orange rinds littered the ground where birds had opened the fruits for their meagre pulp and few seeds.  I found one intact one.

Inside the Passiflora fruit are bright red seeds and pulp.

The fruit has three parts (carpels) and the ovules and (later) seeds are attached in three rows to the outer walls where they join.

Home at last, Lila staggered in the door and immediately collapsed on the cool wooden floor.  She’ll sleep well tonight.

A little gift on the doorstep

When you have cats, you have to get used to odd and sometimes gross gifts on the doorstep, but this morning's little surprise didn't come from the cats.

Wētā dropping with embedded seeds.  The New Zealand 10c coin is 20.5 mm diameter

Wētā are large flightless Orthopterans (crickets), and this is wētā poop.  The dropping is about 5 mm diameter, so this is a big insect.  Note the embedded seeds; they've passed right through the wētā's gut. Probably it was a Wellington tree wētā (Hemideina crassidens), which are common in the garden.  These seeds are quite large, and I suspect they're Coprosma robusta.

Coprosma robusta in fruit, Tunnel Gully, Wellington.

I could wash them out and put them under the microscope to confirm their identity, but instead, I've just planted the poop to see what comes up.  I'll report back when I get a result.

A close-up of the seeds.

Duthie et al. (2006) reported wētā dispersal of seeds in New Zealand.  Mostly the seeds dispersed were smaller than these.  The underside of this dropping had several more showing, so I'm expecting up to 8 or even 10 seedlings.

Reference.

Duthie, C., Gibbs, G., Burns, K.C., 2006. Seed dispersal by weta. Science 311: 1575.