Science

True from seed?

Pulmonaria 'Dark Vader' (thrum eyed, left, Image © Terra Nova Nurseries) and 'Cleeton Red' (right, Image © GardenPhotos.com)
In this month’s issue of The American Gardener, the membership magazine of The American Horticultural Society, I’ve written a piece about plants that come true from seed – and those that don’t. And, in particular, it set me thinking about pulmonarias.

Many of us know that individual Primula plants have flowers that come in one of two forms: some have “pin” flowers, some have “thrum” flowers. The difference is that in pin flowers, the stigma (which is the female part of the flower where the pollen needs to land) is on a long stalk and so visible in the center of the flower. The anthers, which carry the pollen, are on short stalks low down in the throat of the flower. In thrum flowers, it’s the other way round.

Pollen that a bee picks up on its body from the anthers of a pin flower buried down the tube of the flower is in precisely the right position to pollinate a thrum flower – which has its stigma positioned back down in the tube in exactly the right spot. So when seed is set, the pollen almost always comes from a flower of a different plant. So the seed is the result of hybridization. Who knows where the pollen came from? The only thing that’s almost certain is that the pollen did not come from the plant setting the seed – so the resulting seedlings will be different from the plant that produces the seed.

This is true of primulas - but it’s also true of pulmonarias. You can see it clearly in the pictures at the top. The thrum-eyed American-bred ‘Dark Vader’ (left) with the ring of five anthers clearly visible; and the pin-eyed British-bred ‘Cleeton Red’ (right), with the stigma plain to see, on the right (click to enlarge).

So, the lesson. Pulmonarias tend to shed their seed and often quite a lot of it germinates. But the seedlings The American Gardener - January -February 2013 are likely to be all hybrids and not identical to the seed parent. So please don’t pass the seedlings to friends with the parent plant ’s name on. If you’d like to pass on the plant, pass on a division.

There's more about a whole range of plants, and whether or not they come true from seed, in the latest issue of The American Gardener. So why not join the American Horticultural Society (Brits can join too) and receive every issue of The American Gardener as well as many other benefits? If you’re already a member, you can read the current issue of The American Gardener, including my article True To Seed, on the AHS website.

Organic broccoli: is it really better for you?

Broccoli Marathon - more antioxidants when organically grown? Image ©Marshalls SeedsMany of us feel that organically grown food is better for us then food grown by what have become conventional methods but rarely is it actually proved that organically grown food is more nutritious. Perhaps, says he, because it isn’t more nutritious – it's just that it doesn’t have the chemicals.

But the other day I noticed a small piece in the ResearchMatters column of the British trade magazine Horticulture Week (login required) which summarizes research published in the latest issue of The Journal of Horticultural Science & Biotechnology. And this research finds that organically grown broccoli has higher levels of antioxidants than conventionally grown broccoli.

The variety ‘Marathon’ (above, click to enlarge), popular with both home gardeners and commercial growers, was grown on the same site by both conventional and organic methods. Florets were tested for a range of factors, and organically grown and conventionally grown broccoli showed no difference – except in antioxidant content.

I don’t subscribe to The Journal of Horticultural Science & Biotechnology, perhaps I should, so I’m not able to study the research paper in full but the publically available abstract looks promising. And study reported in Britain’s Guardian newspaper four years ago also shows the promise of organic culture as does a paper on blueberries in The Journal of Agricultural and Food Chemistry.

Of course, I'm not an organic chemist, So I popped downstairs and asked judy, who holds double-major B.S. degree from Rutgers University's College of Agriculture and Environmental Science. She told me: “There is a lot of controversy in the scientific world about how bad most of the studies have been. The broccoli one is not statistically significant. Also, the word “antioxidant” is not even used the same way by different studies; various compounds are given a number of different names and it's not regularized.”

Hmmm… So we have to be a little careful and not get carried away. But whatever proves to be true about the nutritional content, at least we know organically grown food has not been sprayed with chemicals.

Just one other thing… Many years ago, the British organic gardening charity Garden Organic (known back Potato 'Desiree' - more Vitamin C than other varieties. Image ©Marshalls Seedsthen as the Henry Doubleday Research Association) did some studies on the nutritional content of different varieties of potatoes, I think it was, and carrots. They found that varieties varied enormously in their vitamin content.

And I just come across a study from Slovakia which showed that the popular potato variety ‘Desiree’ (right, click to enlarge) can have more than twice the Vitamin C content of other potato varieties.

So the variety you choose to grow may well turn out to be more important, from a nutritional point of view, than anything else.

BTW British gardeners can buy both the varieties mentioned from Marshalls Seeds. In North America Broccoli 'Marathon' is available from Harris Seeds, and potato 'Desiree' is available from Seed Savers Exchange.


Harry Potter and the Horticultural Hogwash

Here's a great little video from Dr Markus Eichhorn, an ecologist at the University of Nottingham, pointing out some of the horticultural blunders in the Harry Potter movies.

 

I've seen none of the Harry Potter movies (Hah!) so can't add more.

But I once started keeping a record of all the plants I'd spotted on far and distant planets visited on Star Trek. I began when Captain Picard, I think it was, beamed down into a large field of argyranthemums (marguerites), of all things, and another episode found Captain Kirk and his crew slashing their way through a forest of garden centre sized date palms.

But the truth is I just couldn't face watching every episode of Deep Space Nine on the off-chance of spotting a begonia.


Native plants are not always best for native insects

Wildlife of a garden,Jennifer Owen. Image ©RHS Native plants are not always best for native insects, non-natives also have an important role. That’s the message following a thirty year study in a British garden. For thirty years award-winning ecologist Dr Jennifer Owen studied, identified – and counted! – the insects and other creatures that visited her suburban garden in the English Midlands. And detailed it all in her invaluable book Wildlife of A Garden (Available in North America, and available in Britain) published by the Royal Horticultural Society.

She grew well over 400 different plant species - garden plants and weeds, natives and non-natives - in her garden (below, click to enlarge) which measures just 741square meters (8000 square feet). And she counted 23 species of butterflies, 375 species of moths, 94 species of hoverflies, 121 species of bees and wasps, 305 species of bugs, sawflies, lacewings and related creatures; 21 species of beetles, 122 species of other insects including two ants – all in her suburban garden. And 138 other invertebrates. And 57 birds and six mammals. Wildlife of a garden,Jennifer Owen,garden,Leicester. Image ©RHS

And as well as counting with extraordinary determination and great skill at identifying this vast variety of creatures – she also studied their food plants. And what did she find?

Dr Owens found that non-native species were better as food plants for moth larvae than native species. Moth larvae used 27% of the native species in the garden as food plants, and 35% of the alien plants. And 46 species of moth fed on 40 native plants in the garden, while 75 alien plants provided food for 38 species of moth.

She also looked at the four moth species with the most varied diets and the plants they ate. One ate 78% non-native plants, one ate 83% non-native plants, one 62% and one 79% non-native plants. They definitely didn’t favor natives. Of course, we don’t know how much of each plant each moth actually ate – after all, Dr Owen needs to get a few hours sleep each night.

And finally, what were the most popular food plants for moths? Plants in the rose family come out top, with seven native species and five non-native species used by 27 species of moth. And one of those native species, Potentilla fruticosa, is so rare in Britain it might almost be non-native. Next comes the Buddleja family represented only by the Chinese Buddleja davidii and used by 19 species of moth. The daisy family, the largest family of garden plants, hosts just 13 moth species all of which feed on aliens and only two of which feed on natives. And just to be clear: these are all British native moth species.

Wildlife of a garden,Jennifer Owen,tortoiseshell,aster. Image ©RHS You get the picture. I could go on, but this is just a blog post of a few hundred words. Read the book. OK then, one more thing. Dr Owen reports that of the 15 most widely used food plants in the garden nine are non-natives and only six are native. And some people think that introduced plants have no native larvae feeding on them at all!

This really throws the “natives are best” notion out of the window. We may like to think that natives are best, but they’re just not. And can’t we trust the insects know what they like to eat – wherever the plants come from? So why don’t we plant what the larvae actually like to eat, instead of what we think they ought to like?

This is an extraordinary piece of research summarized in a very readable and well illustrated book.

In my next post here, I’ll be looking at which buddlejas are best for adult butterflies. Because now we know.

           

 

* This post was originally headlined: "Alien plants are better for insects than natives – it’s official!" But after reflecting on the comments below, I modified it and substituted a less sensationalist headline. I also modified the introduction.

* At present, for some reason, amazon.com and amazon.co.uk don't seem to realize they have the books in their own warehouses and are not listing them as being available. They are available for shipping anywhere in the world from The Royal Horticultural Society.


Our bird count results

sharp shinned,hawk,Accipiter striates. Image by Dario Sanches and used here, with thanks, under the Creative Commons Attribution-Share Alike 2.0 Generic license.
The Great Backyard Bird Count is now over here in the US. We didn’t set up an armchair in front of the window but we kept our eyes open and a pen and paper handy for the full four days - which also produced 8-9in/20-23cm of fresh snow on Sunday night.

The star of the show was Sunday’s visit from a sharp-shinned hawk (above, click to enlarge). It’s not a rare bird, but we hadn’t seen one here before so it was a treat to see it swooping past the feeders and perching in the nearby birch tree. It caught nothing, though it might have been enjoying the mice I've been catching in the attic and leaving outside on a rock these last few weeks (about 25 in all so far!).

In all we saw fifteen species, here’s the list.

Black-capped chickadee - 4
Blue jay - 6
Cardinal - 2
Carolina wren - 1
Crow - 6
Junco - 6
Red-winged blackbird - 1
Sharp-shinned hawk - 1
Tufted titmouse - 4
Turkey - 1
White-breasted nuthatch - 3
Woodpecker, downy - 2
Woodpecker, hairy - 1
Woodpecker, pileated -1
Woodpecker, red bellied – 1

Missing regulars included goldfinch, various sparrows, purple finch and house finch. Unusual to see just one turkey. It was probably the last of the group, the others out of sight round the corner of the house.

Visit the Great Backyard Bird Count website to check results anywhere from the USA and Canada.

The image of the sharp-shinned hawk is by Dario Sanches and used here, with thanks, under the Creative Commons Attribution-Share Alike 2.0 Generic license. 


Virus-free foliage pelargoniums

Pelargonium,zonal,geranium,Vancouver,Centennial,Pelgardini. Image ©GardenPhotos.com (all rights reserved)
In the comments to my last post about Pelargonium ‘Mr. Wren’, I mentioned the colored-leaved varieties which had benefited so much from being cleaned up – that is, having virus diseases removed. These are marketed around the world by the German plant breeders Elsner pac under the Pelgardini brand.

When I first grew ‘Vancouver Centennial’ (above, click to enlarge) back in the early 1990s it was a weak plant, lovely but very slow to make a good sized plant - which was perhaps surprising as it had only been introduced in 1986. But, nevertheless, it had already picked up some debilitating viruses. I found it hard to root from cuttings too.

Its boldly marked, jaggedly shaped foliage, spreading habit and brick orange flowers marked it out as unique but eventually I gave up.

But this is one of the varieties in the Pelgardini brand and, although less strong than many pelargoniums, it’s now easy to grow, makes a good sized specimen and has even led to a magenta flowered version, ‘Mandala’, raised in Italy by Catia de Tomi and introduced in 2005.

‘Vancouver Centennial’, by the way, was bred by Ian Gilliam, a British pelargonium enthusiast who moved to Canada and named and introduced the plant to celebrate Vancouver’s Centennial year – 1986.

The cleaned up plants in the Pelgardini brand seem most often to be available in nurseries and garden centers than by mail order. Look for “Pelgardini” on the label. Five varieties are included, reduced from about ten a few years ago.


A new weed evolves

peppered moth,evolution,birch,black,white. Image ©Martinowksy. Distributed under the GNU Free Documentation License How often is it that you see natural selection happening before your very eyes? Well, it’s been happening at the Royal Horticultural Society’s Garden at Wisley, just south of London, where a weed has evolved which is less likely to be pulled out by the gardeners!

It’s like the moths in the old industrial north of England. For centuries, the white form of the peppered moth had been the most common, camouflaged against the pale bark of birch trees upon which the moths rested. Then, as industrial pollution grew, the bark became covered in soot and the white moths became highly visible and were snapped up by birds. (Click the image, left, to see white and black forms on birch bark.) The less common black form then became much more common. More recently, as the air became cleaner again, the white form has enjoyed a resurgence.

At Wisley, annual meadow grass (Poa annua) is a persistent weed but the gardeners are diligent in rooting it out and consigning it to the compost  heap. But over the years forms with darker stems and leaves have developed – colours which show up less well against the dark soil and which are less likely to be noticed and pulled or hoed off by gardeners. poa annua,purple,Wisley,evolution. Image ©GardenPhotos.com (all rights reserved) The result has been the development of a distinct brownish purple leaved form known not seen anywhere else. Known as Poa annua f. purpurea, it was first formally described in 2003. Click on the image, left, to see how well camouflaged the purple form is.

On the Rock Garden and on the Portsmouth Field (the trials field) at Wisley this new “invisible” form has become a particular problem, especially now that less chemical weed control is used and control depends more on the gardeners’ sharp eyes. I only noticed the plant in the picture when I bent down to pick up my glasses!