Transatlantic Gardener

Choosing the best delphinums

Back in the spring, I posted here about the generally poor quality of delphiniums raised from seed and how Terry Dowdeswell’s New Millennium delphiniums were really the only top quality option.

But, of course, the traditional way to propagate the best named delphiniums is from cuttings, that was the method used for so many of the fine plants seen towering at the back of traditional British herbaceous borders over the years. The problem is that individual delphinium plants produce so few cuttings that, again, they can be expensive to buy a nd uneconomical for nurseries to produce.

But now there is another form of vegetative propagation that will guarantee top quality: tissue culture. Plants in the buttercup family (Ranunculaceae) have been famously tricky to propagate in the laboratory by tissue culture but now Clematis are routinely produced in this way, along with some hellebores, mainly hybrids of H. niger. There has not been success with Aquilegia, Hepatica or Ranunculus but a few - just a few - delphiniums have yielded to this technique.

The first of the Elatum Hybrids to be tissue-cultured were the pink-flowered cultivars, the University Hybrids, developed in a long-running breeding program by Professor Legrow, and concluded at the RHS Garden at Wisley. The first, Princess Caroline (‘Odabar’), was launched at the 1994 Chelsea Flower Show and, although a poor garden plant, its availability through tissue culture led to its widespread use as a cut flower. It was followed by ‘Red Caroline’(above, click to enlarge), ‘Red Rocket’ and ‘Coral Sunset’.

Much more recently the Highlander Series has become available. Developed in Scotland by Tony Oakley, this is a new series of five cultivars with a superficial similarity to one of my favorite of all perennials, ‘Alice Artindale’. Each sterile flower is fully double, with about fifty slender petals creating a flower like a frilly button. The flowers are carried in spikes of about thirty or more and five cultivars are currently available: ‘Blueberry Pie’ (deep lilac with a green center), ‘Crystal Delight’ (a very frilly pale lilac with a yellow-green center - right), ‘Moon Light’ (pale lilac bordered in blue with green center), ‘Morning Sunrise’ (white with a green center), and ‘Sweet Sensation’ (deep mauve-purple, tinged with blue-green). Without tissue culture they would be almost impossible to buy.

So, as we think about buying delphiniums, we must choose: pay the proper price for a really good plant, or buy a second rate plant for a cheap price. There’s only one answer, really. One really good plant is worth any number of second rate ones and now, with tissue culture, good plants are becoming easier to buy.

In the UK, a wide range of superb award-winning cuttings-raised delphinium cultivars is available in limited numbers from  Larkspur Nursery  Plants of the Highlander Series are available from Hayloft Plants and elsewhere; Princess Caroline (‘Odabar’) and ‘Red Caroline’ are available Burncoose Nurseries. In North America, even tissue-cultured delphiniums are very hard to find although ‘Crystal Delight’ (Highlander Series) and ‘Coral Sunset’ are available mail order from Hirts. There are clearly some great opportunities for mail order retailers.

* This is the second part of a piece entitled Buying Good Delphiniums which appears in the current issue of the Newsletter of the Ranunculaceae Group of the Hardy Plant Society. Anyone with an interest in hardy plants in the Buttercup Family (Ranunculaceae) should join. The first part was posted here in April.

 

 

Native or non-native: which plants are best for insects?

When, a couple of years ago, I wrote about non-native plants often being better for wildlife than native plants it prompted a lot of comments, for and against, and also private emails – mostly against, including some that were unexpectedly unpleasant.

Undeterred, I bring news of an article by Dr Ken Thompson in Britain’s Which? Gardening magazine, published by the impartial, non-profit Consumers’ Association (similar to Consumer Reports in the US) which says the same thing: “Recent research shows that non-native plants can be just as attractive to wildlife as native ones – if not more so.”

Ken Thompson, of the University of Sheffield, is a biologist with a special interest in the science of gardening. He’s examined recent research at the Social Insects Lab at the University of Sussex, and at the Royal Horticultural Society’s Plants for Bugs project and reports that “pollinating insects have no clear preference for the flowers of native plants”.

So we gardeners can rest easy. If we’re looking to attract insects and other wildlife to our gardens, garden plants are often better than native plants. And there seems to be no argument that, especially in densely populated areas, gardens make crucial contributions to the success of so many birds and insects

So what to grow? To attract pollinators, Ken Thompson recommends these four plants:
Borage - “The ultimate honeybee plant” (left, click to enlarge)
Buddleia – “For butterflies, you still can’t beat buddleia, which is also used as a larval food plant by at least 19 different moths”. [Note: Buddleia is invasive in some parts of the USA, where only varieties that do not produce seed should be planted.]
Catmint – For bumblebees “for sheer attractiveness over a very long flowering season”
Shrubby hare’s ear (Bupleurum fruticosum) – For hoverflies, “a plant you’ve almost certainly never heard of”. (top)

So these are the first plants to try. And the number of hoverflies you’ll find on that bupleurum is amazing.

Ken Thompson’s article Native vs non-native plants: which are best for wildlife? appears in the June 2013 issue of Which? Gardening magazine. It is not available online.

You can subscribe to Which? Gardening here

You can check out books by Ken Thompson on amazon.co.uk

You can check out books by Ken Thompson on amazon.com

Powerhouse Plant For All Seasons - Kolkwitzia Dreamcatcher

This is my third monthly piece about Powerhouse Plants, Plants For All Seasons which don’t flare and fade with two weeks of flowers and fifty weeks of boring leaves. These are plants which provide color and interest for at least two seasons of the year and not just a quick flush of flowers. So when you look at a plant in flower at the nursery or in a catalog, always ask: What else does it do?

My new book, Powerhouse Plants, includes details of over five hundred plants that do something else at another season. And every month in Gardener’s World, Britain’s top-selling garden magazine (and also available in the US) I focus on one very special Plant For All Seasons, highlighting three features which bring color to the garden at different times of the year. And every month here on my Transatlantic Gardener blog I bring you details of yet another – this time, Kolkwitzia amabilis Dreamcatcher (‘Maradco’).

Basically, this is a much improved version of a familiar beauty bush, Kolkwitzia amabilis, which flowers for just a few short weeks in late spring and early summer. Dreamcatcher adds months of fascinating changing foliage color.

In spring, the new shoots are coppery red, then the foliage turns yellow as it matures. Later, it becomes chartreuse with gold hints through summer and in the autumn, and it changes again becoming orange and gold in a final fall flourish.

In my experience Dreamcatcher also makes a lower, more spreading plant than ‘Pink Cloud’, the usual form seen, and the larger of our two seven year old specimens is about 3ft/90cm high and noticeably wider. More widely grown in North America than in Britain, British gardeners should hunt it out.

You can read more about Kolkwitzia amabilis Dreamcatcher (‘Maradco’) in a blog post here back in 2010.

Please take a look at Plants For All Seasons in Gardeners World magazine each month. And check back here for occasional posts about other Powerhouse Plants – the Plants For All Seasons.

You can order my book, Powerhouse Plants in Britain from amazon.co.uk

You can order my book, Powerhouse Plants in North America and the rest of the world from amazon.com

 Or you can find out more about the book at the Powerhouse Plants webpage.

 Subscribe to Gardeners' World magazine

Chelsea Flower Show Plant Of The Year Winner: Mahonia 'Soft Caress'

The winner of the Chelsea Flower Show 2013 Plant Of The Year was announced late on Monday. The award goes to Mahonia eurybracteata subsp. ganpinensis 'Soft Caress'. A selection of a Chinese species, made in Georgia, I feature it on my Royal Horticultural Society New Plants blog in September last year. This is what I said:

Mahonias are amongst the most impressive and dependable of flowering shrubs – but they have a problem. They’re spiny, sometimes viciously spiny. Not any more.

Mahonia eurybracteata is a modestly sized evergreen shrub that grows wild in five provinces of south west China. Reaching 3-4ft/90-120cm in height, and about as wide creating a more or less rounded plant, the long slender divided foliage is slightly greyish green, soft to the touch and not at all spiny or holly-like as so many varieties are.

From August until October the flowers appear, upright clusters of spikes at the tips of the shoots are lined with slightly fragrant, bright yellow flowers that last for many weeks and are followed by blue berries.

‘Soft Caress’ is a new form selected for its extra hardiness and for foliage which has a more noticeably silvery sheen. The leaves may also take on reddish tints as the days shorten and the nights become cooler. ‘Soft Caress’ is neat enough to be grown in a container, or is happy in a sunny or partially shaded border where it appreciates fertile, but well-drained soil.

‘Soft Caress’ was selected by Ozzie Johnson and Karen Stever from a group of seedlings of Mahonia eurybracteata grown at ItSaul Plants in Chamblee, Georgia.

In Britain you can order Mahonia eurybracteata ‘Soft Caress’ from Crocus and from Gardening Express.

In North America you can order Mahonia eurybracteata ‘Soft Caress’ from Wayside Gardens and from Springhill Nursery.

Plant Of The Century

It’s a hundred years ago this year, in 1913, that the most famous flower show in the world, The Chelsea Flower Show, was first staged and to mark the centenary of the show the Royal Horticultural Society is asking gardeners to vote for the Plant Of The Century.

They’ve chosen a plant from each decade, and each is introduced on video by a gardener of the appropriate generation - from a 92 year old ex-paratrooper to an eight year old schoolgirl. Anyone can go online and vote for their favorite. These are the plants.

Saxifraga ‘Tumbling Waters' (1913-1922)











Pieris formosa var. forrestii (1923-1932)

Lupinus Russell hybrids (1933-1942)





Rhododendron yakushimanum (1943-1952)





Rosa Iceberg (‘Korbin’) (1953-1962)





Cornus ‘Eddie’s White Wonder’ (1963-1972)











Erysimum ‘Bowles's Mauve’ (1973-1982)





Heuchera villosa ‘Palace Purple’ (1983-1992)





Geranium Rozanne (‘Gerwat’) (1993-2002)





Streptocarpus ‘Harlequin Blue’ (2003-2012)





Not everyone is happy with this list, I have to say. As one Royal Horticultural Society insider (who had better stay nameless) has already emailed me: “Typical RHS, they’ve ignored all the annuals and patio plants that people actually grow and included two shrubs that only grow on acid soil which most of the country doesn’t have.” Hmmm… Got a point, there…

Me? I’d probably vote for Iceberg rose although now that the sulfurous pollution that kept mildew and blackspot at bay in the 1950s is gone it’s a martyr to disease. Or the Russell lupins. But I think Geranium Rozanne will probably win, especially as the nursery that sells it has its PR firm campaigning on its behalf.

Click on the images to see each one enlarged. Check out all ten plants on the Plant of The Century webpage, or click the plant links above to see details of each plant an cast your vote. Voting closes at 12 noon BST Friday 24 May, 2013. Which do you think is Plant Of The Century?

 

 

 

 

 

 

Actaea rubra: Powerhouse Plant For All Seasons

Powerhouse Plants are Plants For All Seasons, plants which don’t simply do their one thing and then sit there looking dull for the rest of the year. These are plants with impact at two, three or perhaps four different seasons. They provide so much more than just a few short weeks of flowers. So when you look at a plant in flower at the nursery or in a catalog, always ask: What else does it do?

You can find details of over five hundred plants that do something else at another season in my new book Powerhouse Plants. And every month in Gardener’s World, Britain’s top-selling garden magazine (and also available in the US) I focus on one very special Plant For All Seasons, highlighting three features which bring color to the garden at different times of the year. This month, it’s Viburnum plicatum subsp tomentosum 'Mariesii'. But here I thought I’d show you another, a perennial: Actaea rubra, the red baneberry.

First, the bright juicy spring shoots emerge and then around this time of year, depending on the season, and this season is a late one, the leaves have expanded and make a fine fresh green background to the fluffy heads of white flowers opening from creamy buds.

Then it’s not long before the rather dramatic change takes place; the flower heads stretch and the berries form, in bright and shining and scarlet red. Quite a different look, two quite different appeals from the same plant.

You might also like to take a look at Actaea pachypoda ‘Misty Blue’ (‘Pewter and Pearls’ is similar): the same white spring flowers; then white berries held on red stems – but with the bonus of blue-tinted foliage.

Please take a look at Plants For All Seasons in Gardeners World magazine each month. And check back here for monthly posts about other Powerhouse Plants – the Plants For All Seasons.

You can order my book, Powerhouse Plants in Britain from amazon.co.uk

You can order my book, Powerhouse Plants in North America and the rest of the world from amazon.com

Or you can find out more about the book at the Powerhouse Plants webpage.

Subscribe to Gardeners' World magazine In North America,Gardeners' World magazine is also available in Barnes & Noble and other good bookstores.

 

Have you seen these double primroses?

In the last ten years, many of the old, double flowered primroses have vanished from our gardens, on both sides of the Atlantic. A combination of virus disease and relentless weevil attack has led to the disappearance of many of these captivating, and very hardy, spring perennials. Grown in Britain. Brought to America they’re part of our horticultural heritage. But they’re disappearing.

The British garden plant conservation charity, Plant Heritage, once oversaw three National Collections of double primroses in private gardens. These too are gone. But Caroline Stone, a keen gardener from North Cornwall in Britain’s West Country, is determined to establish a new National Collection and preserve those wonderful old double primroses.

“I started with five or six double primroses,” she told me, “and having had some success winning prizes with them at the Cornwall Garden Society Spring Show decided to get a few more. It quickly became obvious that there were very few old varieties being sold - but the more difficult it was to find them, the keener I got. Now, I have around seventy varieties ranging from some of the very old to the modern, and with several that occurred naturally in the wild. I hope to be able to get them growing strongly and propagate them to ensure they survive.”

There are two varieties of double primrose that Caroline is especially keen to track down. ‘Red Velvet’ (above, click to enlarge) was a good red, and was quite a vigorous variety – it may still be around. Many of the reds are a crimson shade, but this was a proper bright red. And the slender red edge to each leaf is very distinctive. But now, not so many years later, the plant has become impossible to find. The other is ‘Torchlight’ (left, click to enlarge)…

Hopleys nursery launched a range of double primroses that had been selected from Barnhaven seed in New Zealand in the early 1980s. One, ‘Torchlight’, a neat upright double yellow, was featured on their catalogue cover and received an Award of Merit from the RHS at Chelsea in 1983. But it too seems to have disappeared.

If you grow either ‘Red Velvet’ or ‘Torchlight’ in your garden, in Britain, North America or, perhaps, New Zealand, Caroline would be thrilled to hear from you. You can email Caroline and tell her about your plants.

Caroline is also looking for quite a few other double primroses that now seem impossible to track down. Here’s her “looking for” list. Please email Caroline if you’re growing any of these varieties:
‘Arthur du Moulin’, ‘Big Red Giant’, ‘Bon Accord Beauty’, ‘Bon Accord Blue’, ‘Bon Accord Brightness’, ‘Bon Accord Elegans’, ‘Bon Accord Jewel’, ‘Bon Accord Lavender’, ‘Bon Accord Lilac’, ‘Bon Accord Purity’, ‘Bon Accord Rose’, ‘Chevithorne Pink’, ‘Crathes Crimson’, ‘Downshill Ensign’, ‘Elizabeth Dickey’, ‘Ethel M. Dell’, ‘Fife Yellow’, ‘Granny Graham’, ‘Ladybird’, ‘Madame Pompadour’, ‘Mark Viette’, ‘Prince Silverwings’, ‘Rhapsody’, ‘Red Velvet’, ‘Torchlight’, ‘Tyrian Purple’.

* The picture of ‘Red Velvet’ - taken by that fine photographer Derek St Romaine, now editor of the excellent new online garden magazine Garden Life Love - appeared in the March 2000 issue of the Royal Horticultural Society magazine The Garden.

What’s this scilla doing in a wood in New York?

Nosing around in the spring woods yesterday, near the east branch of the Callicoon Creek in Sullivan County, NY, I spotted a speck of sparkling blue, amongst fresh foliage and the flowers of Dutchman’s breeches, Dicentra cucullaria. Seemed odd. Took a closer look, and it was a scilla. There were a few leaves and three stems with one flower on each.

The map on the USDA Plants website reveals that the Siberian squill, Scilla siberica (left, click to enlarge), has been found in seventeen north east states but, according to the New York Flora Atlas, never before in Sullivan County. The little trail is part of the Stone Arch Bridge Historical Park, but few visitors pass this way. A quick check with the Pennsylvania Flora Project reveals that it’s been recorded in three places here in PA (For Brits: Pennsylvania is the size of England.).

It’s not native, it comes from Russia. So what’s it doing in a wood in New York? The nearest house – not, it’s clear, occupied by a keen gardener - is hundreds of yards away. In more than ten years I've only once heard of the creek flooding the area in which it was growing, so a flood is unlikely have dumped a bulb. So where it come from?

One flower was already developing its seed pod, which had weighed down the stem so that the pod was resting on the ground. That’s one way for the seed to spread a few inches. It’s growing about 10ft/3m from the narrow trail so seed arriving on footwear seems unlikely.

I often take a walk along this trail in spring, and have never spotted it before. Although the flowers may only last a few days, in hot weather - it can easily reach 70+F/21+C in April.

So I wonder how it got there…?

Nepeta ‘Walker’s Low’ – why the unsuitable name?

Working on an article about catmints, Nepeta, recently it suddenly struck me: Why does Nepeta racemosa ‘Walker’s Low’ (left, click to enlarge) have such an unsuitable name? You’d never describe it as “low” growing.

Checking what I said in my own book – my big fat Encyclopedia of Perennials – I see that I gave the height as 24in/60cm. When the Chicago Botanic Garden reported on their trial of nepetas back in 2007, they gave it 30in/75cm. America’s Perennial Plant Association, when it gave ‘Walker’s Low’ its Perennial Plant Of The Year award in 2007 gave its height as 24-36in/60-90cm.

Of course it tends to flop, rather elegantly in fact, and if trussed up to keep the stems vertical would be even taller – though perhaps less appealing. But how did a plant that can reach 3ft/90cm in height come to be called “low”?

I’ve been rooting around trying to find out for the last few weeks – and have not come up with a definite answer. Can anyone help?

It’s often said to have been raised in Ireland or named for an Irish garden, but the leads turn out to be dead ends. The garden writer Jane Taylor (author of The Shady Garden, Fragrant Gardens and of the very useful Drought Tolerant Plants) has been cited as having discovered the plant – but I’ve been unable to contact her. [If anyone has contact details, please email me privately.]

Just to emphasize the fact that ‘Walker’s Low’ is not a short plant – we now have a dwarf version, reaching just 15in/38cm. It’s called Junior Walker (‘Novanepjun’) and was created by “gamma-ray mutagenesis” – tissue-cultured plants of ‘Walker’s Low’ were treated with gamma radiation, then grown on, planted out and assessed. One neat, bushy and prolific plant was chosen, give the code name ‘Novanepjun’ and the selling name of Junior Walker – acknowledging the saxophonist of that name, leader of the Tamla Motown band Junior Walker and the All Stars. It’s just starting to appear in the US, not yet in the UK.

So – does anyone have any ideas - or better still facts! - about how ‘Walker’s Low’ got its name?

* My article on nepats appeares in the May issue of the Royal Horticultural Society's magazine, The Garden.

Book Bullet: Spring Wildflowers of the Northeast by Carol Gracie

This is a fantastic book.

Discussed in rich but readable detail, and profusely illustrated, are thirty of those beautiful and fascinating spring flowers which mark the passing of the snow and ice and the sudden rush of new growth – and not just in the north east, but over much of the country.

Plant by plant, from baneberries to wild ginger, centuries of scientific research are brought together with decades of enlightened personal observation to present detailed accounts of some of our favorite plants. But not just descriptions, far from it. The ways in which these plants fit into their botanical families, their relationships with their habitat, their pollination, their seed dispersal, their medicinal and other practical uses – it’s all there.

And here’s the thing: we know we can trust its combination of science and experience not only because it’s clear that it’s written by a scrupulous fanatic! But also, from her years as a tour leader at the New York Botanic Garden answering the questions of visitors – interested, of course, but not necessarily knowledgeable – Carol Gracie knows how to present her fascinating material in a way that scientists will respect, and everyone else can understand (with occasional help from the excellent glossary).

The book is also packed with wonderful pictures. In fact my only criticism of the book is that, in places, there are too many squeezed on to the page. I don’t think there’s a dud amongst them, but sometimes the page is just too full.

I first looked at entries on plants I’d recently researched myself including skunk cabbage, Symplocarpus foetidus, where her account of the plant’s mechanism for generating so much heat in its early flowers that it can melt snow and keep insects cozy includes an important detail that I’d missed! And I was thrilled to discover that it’s the box turtle, wandering up to 60m a day, that not only distributes seeds of may apple, Podophyllum peltatum, but through keeping them in its digestive system for a week while it wanders also greatly improves their germination.

So… whether you grow these plants in the garden or simply admire them on rural (or sometimes urban) hikes, I’m sure you’ll find this book fascinating. If you need more superlatives, just ask.

Spring Wildflowers of the Northeast by Carol Gracie is published by Princeton University Press.

• The habits and habitats of thirty familiar spring flowers revealed
• Detailed but easy-to-read text
• Huge number of exceptional pictures
• Gardeners and wildflower enthusiasts will be fascinated
• Not just for those of us in the north east US
• Put it on the short list for plant book of the year