Previous month:
April 2010
Next month:
June 2010

May 2010

Is this plant really dangerous?

Hesperis matronalis, dames rocket, in partially felled forest in PA. (click to enlarge) Dame’s rocket, Hesperis matronalis. Also called sweet rocket and many other pretty names. Delightful biennial. Brought to America from Europe in about 1600 and much loved by gardeners for its color, its fragrance and for being so easy to grow. Now naturalized in most US states.

Banned in Colorado, Connecticut, and Massachusetts as an invasive species.

And here it is in north east Pennsylvania (left, click to enlarge), a delightful image of color and fragrance glimpsed in the distance through the remains of some natural deciduous forest of a bright and blazing afternoon. True, there are quite few plants here – though very few if you think of the forest as a whole. It’s not a very likely candidate as a dangerous invasive, is it. Yet some people want it ripped out.

It doesn’t make a smothering mass of foliage like vinca or Japanese knotweed. In flower, each plant often sends up just one vertical flowering stem. Not much smothering there. (In gardens it tends to be bushier.) True, in a mass they might shade out other plants. But for how many weeks in the year?

With some plants it’s their winter rosettes which are the problem – dandelions, and other similar members of the daisy family, often develop broad, leafy, ground-hugging rosettes which very effectively crowd out Hesperis matronalis, dames rocket,invasive,rosette. Image: This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License. neighboring plants. Some of these are important weeds of lawns, crowding out the lawn grasses. But the rosette of dame’s rocket is a relatively puny thing (right, click to enlarge).

And it’s not even a long-lived, ever-increasing perennial. It’s a biennial so plants don’t get bigger and bigger each year – they mostly die in their second summer.

But even the agencies warning us of its terrors don’t seem convinced. The Invasive Species pages of Wisconsin’s Department of Natural Resources, for example, tell us: “The effects of dame's rocket invasion are not known, but it may compete with native species…. Dame's rocket has not been studied extensively. In fact, it is not yet widely recognized as an invasive plant in the Midwest.” So why do they insist that “any plant whose seed may escape to roadsides or woodlots should be eradicated or prevented from going to seed by cutting the flower heads after they bloom”.

And let’s take a look at one interesting piece of research undertaken by the US Geological Survey and presented at their 93rd annual meeting just a couple of years ago – as it happens, in Wisconsin. In summary: They marked out twenty plots in which dames rocket was growing; they measured the cover for every plant species present in each plot; they pulled the dames rocket out of half the plots; then for three years they assessed the flora in both sets of plots.

The result: “Removal did not significantly affect species richness and species diversity”. “In the three years, neither native nor exotic forbs, nor native woody plants, significantly responded to the removal of H. matronalis.”

Hesperis15371 OK, got that? Pulling out the dames rocket made no difference. You couldn't make it up, could you. So enjoy their attractive flowers (left, click to enlarge).

Here in Pennsylvania, the situation I examined the other day gave a fat clue as to why some non-native plants proliferate. Many of the trees in the area of forest where the dame’s rocket was growing had been felled a few years ago so the tree canopy was very thin and gappy. This is also an area with a very high deer population. The most widespread plant in this patch of forest was a more troublesome non-native plant, garlic mustard (Alliaria petiolata). There were also quite few plants of multiflora rose (Rosa multiflora). Dames rocket, garlic mustard and multiflora rose are all non-natives and all, to varying degrees, deer resistant.

The one striking native perennial I came across was Erigeron philadelphicus: one plant, surrounded by tree trunks – and so protected from the deer.

My point? If the area had been fenced to keep the overabundance of deer out after the trees were felled then the diverse local native flora – which the deer love to eat – would have established itself and the deer-resistant non-native plants would have been much less likely to take hold.

But hey, let’s rip out those nasty non-natives (sorry, alien invasives) anyway.

Chelsea Plant of the Year winners

Streptocarpus 'Harlequin Blue'. Image: ©Dibleys Nurseries. All rights reserved. The winner, and runners up, of the very first Chelsea Flower Show Plant of the Year have been announced this morning. The award is specifically for new plants introduced in the last year and not seen before at a British show.

From a shortlist of twenty potential winners. The winner is Streptocarpus 'Harlequin Blue', the latest in the long line of compact and prolific streptocarpus intended as house plants and raised by Lynne Dibley of Dibleys Nurseries in Wales. At each year’s Chelsea and Hampton Court Palace Flower Shows she always seems to have a new introduction. This is the first bicolor streptocarpus whose flowers open relatively flat and show of their delightful coloring effectively - with primrose yellow on the lower petals contrasting effectively with the pale blue upper petals. A compact plant with masses of flowers, it really looks gorgeous.

Streptocarpus 'Harlequin Blue' is available from Dibleys Nurseries.

The runner’s up prize went to Gaura lindheimeri 'Ruby Ruby', the most recent of the selections of Gaura Gaura lindheimeri 'Ruby Ruby'. Image: ©Hardys Cottage Garden Plants. All rights reserved. lindheimeri made by Rosy Hardy at Hardy’s Cottage Garden Plants. ‘Ruby Ruby’ combines dark ruby pink flowers held on dark red stems, with dark red foliage in a rich combination.

Gaura lindheimeri 'Ruby Ruby' is listed on the Hardy's Cottage Garden Plants website but is, unfortunately, currently out of stock.

Finally, in third place, an especially good form of the rare white flowered variety of Cypripedium flavum. This delightful orchid from China is usually seen, when it’s seen at all, with yellow flowers and with the each of the two more or less horizontal side petals swept back and, sometimes, the upper petal rolled down over the lip. In this form, from McBean’s Orchids, not only are the flowers pure white but the side petals stand out straight and the upper petal stands straight up. The effect is much more bold.

Cypripedium flavum (white form) Image: ©RHS. All rights reserved. This white form of Cypripedium flavum is, unfortunately, not listed on the McBean’s Orchids website and does not have a cultivar name. A white form of Cypripedium flavum is listed in the RHS Plant Finder as being available from Edrom Nurseries – but it not listed on their website earlier. Such a form is listed on the Easy Orchids website.

So here’s the thing. This award is a great idea. It was a great idea when the RHS turned it down flat, complete with sponsorship, over ten years ago! And it will surely help counterbalance the media coverage which is usually biased in favor of the show gardens and often ignores the vast variety of beautiful and intriguing plants in the floral pavilion.

The winner is delightful, available by mail order and not expensive - £4 per plant. Unfortunately the second placed plant, though lovely, well-worth growing and listed on the Hardy’s Cottage Garden Plants website is, as I write, out of stock with no note of when it will be available. This is not only a missed opportunity for those of us who’d like to grow it but a missed opportunity for Hardy’s who are unable to capitalize fully on their award. All their other gauras are also out of stock.

And the third placed plant, that rare and distinctive form of Cypripedium flavum, not only has no cultivar name but is not listed on the nursery’s website. And the usual form of C. flavum is listed at £35 per plant plus £15 shipping. That’s out of reach of most gardeners – and how much will be the choice white form be?

So – a good first year, but flawed.

And by the way: An extra element in that original proposal for this competition was the chance for the show visitors to vote on their own favorite. Let’s hope the RHS can add that element next year.

What? Not at the Chelsea Flower Show?

Cypripediumacaulae3552 Press Day at the Chelsea Flower Show today – and we’re not there. An unexpected conjunction of circumstances (that’s code for “I’m not going to go into all the details”) results in us not being there this year.

And it was thirteen years ago today, that my wife judy and I met – on Press Day at the Chelsea Flower Show – when she was running the very first online coverage at the Show for Time Warner’s late lamented Virtual Garden website. She was helped by expert gardening editor Fiona Gilsenan and joining me in the British reporting contingent was the man who is now Vice-Chair of the RHS Nigel Colborn!

“A baker’s dozen of years,” says judy. “Which one was the free one, I wonder?”

So by way of celebration the plan is to go and check out the last remaining wild local lady's slipper orchids (above, click to enlarge). They almost always flower in Chelsea week, so the upside of missing the Show is the opportunity to see them bloom. The last ones left in this area, I might say, are inside a huge fence which keeps the ravenous deer out.

And we’ll be keeping an eye on the Show, via the rich online coverage that's developed since judy’s pioneering (and highly fortuitous) first visit.

Royal Horticultural Society Chelsea coverage
Daily Telegraph Chelsea coverage
Chelsea coverage in The Guardian
BBC Chelsea coverage (video in the UK only, I’m afraid)
Follow the RHS at Chelsea on Twitter
Follow the RHS Chelsea coverage on Facebook

Matt Appleby of Hort Week on Chelsea
Anne Wareham of ThinkinGardens on Chelsea garden themes

UPDATE: The day turned damp and drizzly - so we went to the supermarket instead. They had a special offer on cans of clam chowder so we bought two! What a day! Ah, married life. Thank you Chelsea.

Chelsea Flower Show Plant of the Year Award - finalists announced

ChelseaAward4FinalistsBette For the first time this year, the Royal Horticultural Society's Chelsea Flower Show, which opens officially on Tuesday (it's sold out, sorry) is giving an award for the Plant of the Year. The award will go to "the most inspiring new plant" at the Show.

The twenty finalists have just been announced this afternoon (this evening UK time), and the RHS Plants Advisory Committee will vote for the winner tomorrow.

The finalists range from an orchid to an egg plant, with two irises, two pitcher plants and two roses amongst the contenders.

But for the plant that's the most appealing to the widest range of gardeners (I wonder if that will be considered - hardly anyone grows tropical pitcher plants, after all) I'd say it's between the Balconita trailing pansies (top picture) bred by ace petunia and primrose breeder David Kerley, the Buzz Series of dwarf buddlejas bred by Thompson and Morgan (second picture), the new disease resistant rose Princess Anne ('Auskitchen') from David Austin Roses (third picture), and the spectacular variegated Impatiens 'Masquerade' (fourth picture).

Check out the full list of twenty contenders. I'll let you know the winner as soon as it's announced.

New variegated culinary sage

Salvia,sage,variegated,La Crema. Image: © All 
rights reserved.How about this for a new sage? Yes, a brand new variegated culinary sage. Doesn’t it look great? It's called 'La Crema'.

Now, I have to say, before you get too excited – it’s only just becoming available in the US in independent garden centers through the Hort Couture brand. And it's not yet available in Britain -  I'll let you know when it is.

But yesterday we received three small plants to try, to assess how good it really is. So the picture is of a little plant just 3in/7.5cm high. But it looks very promising, doesn’t it? It’s a variegated sport of the broad-leaved ‘Berggarten’ and with relatively few forms of the culinary sage available, this looks as if it has a bright future - IF it performs well in the garden. Of course, that all depends on how it looks this summer, how well it comes back after our winter snows here in Pennsylvania, and then how well it performs next year. And will it revert to its non-variegated parent?

I'm hoping it does well, as an enthusiast for colorful forms of culinary plants - after all, I wrote a book on the subject - this is precisely the sort of plant I like to see. If you're growing it, email me later in the year and tell me how it performs for you.

The dream catcher

Kolkwitzia amabilis Dream Catcher (‘Maradco’). Image: © All rights reserved. This is the best new foliage shrub I’ve grown in recent years. OK… a bold claim. But in its habit and its coloring it’s not only unique but supremely effective in the garden. And it’s unusual in a number of ways. I’m talking about Kolkwitzia amabilis Dream Catcher (‘Maradco’).

Now, I expect we all know the familiar K. amabilis ‘Pink Cloud’. It’s a tough, upright shrub with arching growths and in spring every branch is lined with pretty pink trumpets. It makes a spectacular specimen for a few short weeks – after that it’s main use is as a host to summer flowering clematis.

Dream Catcher is the opposite, the foliage is almost surreal. Opening vivid yellow with a coral tint then going through a brief soft orange phase it matures to a uniform bright yellow, it’s a spectacular color enhanced by the new shoots having pinkish red stems. And in fall the whole plant turns orange.

But it doesn’t grow upright with the side shoots arching over like ‘Pink Cloud’. Instead it makes an ever expanding mound with the new shoots arching over each other in layers of flat symmetrical branches. The larger of my two plants is about 5ft/1.5m across and 30in/75cm at the top of this year’s new growth. It looks wonderful but it will never get to the 8ft/2.4m I’ve seen ‘Pink Cloud’. Kolkwitzia amabilis Dream Catcher (‘Maradco’). Image: © All rights reserved.

I’ve never pruned either of my two plants and they’re both behaving in the same way. In fact I’m thinking of moving one of them to trail over the edge of a raised bed I’m going to make on a slope. Both are in partial shade and the one in more light has developed more quickly.

I’ve had each about four years but neither has ever flowered. Frankly, I don’t care, I’m not sure that pink flowers would quite suit the yellow foliage. But arching over the dark green leaves of Helleborus x nigercors and over Hosta ‘Gold Standard’ alongside, and with self sown forget-me-nots peeping through, it looks wonderful.

In Britain you can buy Kolkwitzia amabilis Dream Catcher (‘Maradco’) from these RHS Plant Finder nurseries.

In North America Kolkwitzia amabilis Dream Catcher (‘Maradco’) is available from Forest Farm, Sooner Plant Farm and Wayside Gardens to name just three.

Bye bye cherry tree – the easy way

CherryTreeHeave19730 Well, it started back in the winter of 2007 and 2008 and finally it’s done. The last of our ailing thirty year old cherry trees is no more. And this time it was easy, all done in half a day.

In one of the comments to my original post about removing them, Joanna mentioned a winch. Now I just let this go by – I thought they cost a fortune. Then my old friend Bob – ace fisherman and advisor on anything to do with construction and DIY - came to stay and he said: “What you need is a come-a-long”. Never heard of it. Turns out that in Britain we’d probably call it a cable winch. I thought they were huge and cost a fortune; the ones we used on the tree gang at Kew years ago must have done. But no, $38. And in the UK I see you can get one for £11.50! Don't you just love a bargain?

You loop one end of the cable round a nearby sturdy mature tree (I used a big old spruce), attache the other end to whatever you want to pull out – like this old cherry tree - and crank the handle on the device in between (right, click to enlarge). And the tension mounts. ComeAlong19726

Here’s the thing. As soon as the tree starts to move, you can see by the movements in the soil where the roots are. Scrape the soil away, cut the root with a chainsaw or pruning saw – and crank some more. The tree leans more and more (above, click to enlarge), eventually all the roots are cut and the tree topples right over. Log up the remains of the trunk and you have a new batch of firewood waiting to dry out.

Then… You attach the cable to each individual piece of root remaining in the soil. And crank the handle. And it pulls the roots out. Then you’re just left with a hole and a mess to clear up. Brilliant. Thanks, Bob.

Now, what about those birches?

Getting plant names right – and up to date

RHSPlantFinderOnline  We all want to use the correct botanical names for our plants, right? And we know that, as plant science evolves, names sometimes have to change. Well, the annual online update of correct plant names is now available – free to everyone – courtesy of the Royal Horticultural Society.

For British gardeners the RHS Plant Finder reveals which of over 600 nurseries stock each of 70,154 plants. But for gardeners around the world the RHS Plant Finder has wider value as the fount of all wisdom on correct plant names. Overseen and regularly updated by a team of horticultural botanists based in Britain but with connections around the world, the team and its associates look at the naming of plants at all levels.

So the Plant Finder will confirm that the correct name, accepted around the world, for the dreaded Japanese knotweed is not Polygonum cuspidatum nor Polygonum reynoutria nor Reynoutria japonica but is Fallopia japonica – which reflects its close botanical connection with the rampaging mile-a-minute vine, Fallopia baldschuanica. (Fallopia baldschuanica, by the way, is the correct name for what has been called Bilderdykia aubertii and half a dozen other names.)

Laprocapnos,Dicentra,spectabilis. Image: © All rights reserved. This year, after much deliberation, the team has accepted the splitting from Dicentra of a number of species and elevating them into genera of their own. So the yellow-flowered climbing types are moved into Ichthyoselmis and Dactylicapnos and a favorite spring perennial, Dicentra spectabilis (left, click to enlarge) – in full flower now, frost permitting – has been elevated into the genus Lamprocapnos. They have not yet decided to accept the splitting of the American members of the genus Aster into many smaller genera.

But perhaps the most startling of this year’s changes is the transfer of Antirrhinum, Digitalis, Hebe and Penstemon to the plantain family (Plantaginaceae) – which most of us know as wind-pollinated weeds. They may look so clearly very different but the reason for this, and a number of other changes, is explained in a new essay written by RHS Chief Scientist Dr John David. Basically, it’s all down to the analysis of the plants’ genetic material (the genome). Verbascum and Phygelius, by the way, remain in their original family (Scrophulariaceae) where they are now joined by Buddleja.

The essay, although rather long and a little technical for the casual reader, is well worth reading for its overview of the changes at family level.

Name changes will continue. The one downside of the Linnaean system is that when we discover more about the way in which plants are related to each other, the names have to change. At least with the free online RHS Plant Finder we can easily find out what the correct names are.

And you can find out more about the changes in Dicentra in the excellent book from Timber Press called Bleeding Hearts, Corydalis, and Their Relatives. It's very welcome to finally have an opportunity to recommend this invaluable book.

Don't buy hostas from Home Depot

Hosta,Home Depot,Lowe's,wrong name, Image: © All rights reserved. Just back from a trip to Home Depot (for Brits: that's like B&Q only much much bigger).

Naturally, we took a look at the plants and found their hosta labelling in complete chaos  The two hostas in the picture (click it to enlarge) were both labelled 'Albomarginata'. And elsewhere in the display the one on the left was labelled 'Fragrant Bouquet' and the one on the right was labelled 'Golden Tiara'! Even allowing for the fact that all the plants were very soft and had clearly been forced, and for the fact that the foliage of young plants is often not typical of mature specimens - well, it's entirely possible that none of the names are right! 

So go to a specialist for your hostas.

In the interests of balance it's only fair to say that when we stopped later at Home Depot's big competitor, Lowe's, I found the one petunia with two different names. But at least one of them was right.

The first bear of the year

BearSkunkCabbageJW19551 We had our first bear sighting of the season yesterday. The last day of April is unusually late for our first visit but it was good to see this big old male down by our little stream enthusiastically tucking into some skunk cabbage -  you can see the leaf in his mouth! (click on it to enlarge)

Skunk cabbage, Symplocarpus foetidus, is one of the black bears’ favourite early season foods. They not only eat the leaves, as you can see in the picture, but they also dig up whole plants to eat the fat and fleshy roots. Skunk cabbage is a fascinating plant, which I’ve written about here in the past.

But it seemed odd to me, watching from the deck at the back of the house, that he was so random in his choice of plants. Watch a pigeon digging up pea seeds - as I did last week in our garden back in England - and the fat bird starts at one end of the row and methodically goes along the row picking them all out one by one till he's gobbled up them all.

The bear seemed to wander aimlessly through the patch of plants, stopping to eat one, or just part of a leaf or two from a plant, skipping the next one or two, stopping to feed again – is it entirely random or is there some hidden pattern that we mere humans fail to detect? Can the bear make some instinctive determination as to which of the mass of plants are the best to eat?

Bear30April2010 The other thing I noticed was that after the first shot in a series of pictures the bear looked up at me. I was using a long lens but as you can see in this second picture (click on it to enlarge) – one click and he looked right at me.