Perennials

New ways with phlox

PhloxEarlibeautyZenithDaughterofPearl
The tall and colorful American native summer phlox, Phlox paniculata, has been popular for more than a hundred years. In 1917 five hundred and eighty four (yes, 584) different varieties were grown in the USA and in 1907 one Scottish nursery alone listed well over three hundred varieties. In Britain, the Royal Horticultural Society currently has a grand total of 577 in its database.

Most of these have now vanished, but there are a number of impressive breeding programmes, many using other species in addition to P. paniculata, going on in both North America and in Europe. Hans Hansen at Walters Gardens in Michigan, with his Opening Act and Fashionably Early series, and Charles Oliver at The Primrose Path in Pennsylvania, with his Earlibeauty Series (above), are leading the way along with Gosen Bartels in The Netherlands with his Flame Series.

But some of the best known varieties of the summer phlox have arisen in another way – they’ve been spotted in the wild or in abandoned gardens by plants people with a good eye, and an appreciation of something special.

I’ve mentioned these in my article about phlox in the current issue of The American Gardener but space was tight so I thought you’d be interested in a little more detail. These were all chosen for their freedom from mildew, but it’s important to remember that mildew resistance is not constant. I’ve seen ‘David’, and ‘David’s Lavender’, completely ruined by mildew.

‘Common Purple’ Found in 1982 by Marc Richardson and Richard Berry, founders of Goodness Grows Nursery, at an old abandoned homesite in Greene County, Georgia. The plant was in full bloom, with no sign of disease or problems. It was introduced by Goodness Grows in 1984.

PhloxSpeedLimit45‘David’ Selected at the Brandywine Conservancy, Chadds Ford, PAennsylvania by nurseryman Richard Simon and the Conservancy’s Horticulture Coordinator Mrs. F. M. Mooberry for its unusually large white flower heads and freedom from mildew. ‘David’s Lavender’ is a sport discovered in 2002 by Kathryn Litton at ItSaul Plants, Georgia.

‘Jeana’ Found in the 1990s by Jeana Prewitt of Nashville, Tennessee, growing mildew-free among "many thousands" of mildew-covered wild plants. Introduced in 2001 by the much missed Seneca Hill Perennials.

‘Speed Limit 45’ Spotted by Pierre Brunnerup, in the company of Allen Bush, by the sign on the roadside near Bush’s nursery in North Carolina and seen to be mildew free. Propagated by Bush and introduced in 2003.

These are exciting time for phlox enthusiasts, with so many new introductions. Those such as the Earlibeauty Series, with no P. paniculata in their background, seem best placed to remain mildew-resistant in the long term.

* Thank you to Charles Oliver and Allen Bush for the pictures.


Chocolate cosmos alive and well in Mexico, not extinct!

Chocolate cosmos growing in the wild in Mexico. © Universidad de Guadalajara

Since the chocolate cosmos, Cosmos atrosanguineus, began to be widely grown in the 1980s we’ve all assumed two things: that it was extinct the wild and that there was only one clone grown which never set any seed. Well, that’s what the Royal Botanic Gardens at Kew and others told us. They even participated in a plan to reintroduce it to the wild. It was all part of the mystique attached to this captivating chocolate-coloured and chocolate-scented plant.

Now, it turns out, Chocolate cosmos has been growing happily in Mexico all this time, and in a number of different locations. So it has no need of re-introduction. And, in New Zealand, chocolate cosmos has been grown from seed since 1990.

Mexican botanist Dr Aarón Rodríguez and his team found eleven relatively recent records of C. atrosanguineus, the earliest of which was from 1986, and the locations mentioned in the records led them out to find the plant in the wild. Dr Rodríguez told me: “The populations are quite numerous. Plants grow in mixed pine and oak forest.” They were found in three different Mexican counties.

From around the same time Dr Russell Poulter, a geneticist in New Zealand, has been raising plants from seed and working to ensure that the plants resembled the original wild form.

Dr Poulter’s work is the origin of the seed raised varieties now available, ‘Black Magic’ from Jelitto Perennial Seeds, and an unnamed form from Plant World Seeds. At least one more is on the way. His plants have also led to the introduction of new cuttings raised varieties including Dark Secret (‘3013/01’), Eclipse ('Hamcoec') and Spellbound (‘Hamcosp’).

It’s a little baffling that these two fundamental facts have slipped us by all these years. But it’s great news that this lovely plant remains established in the wild and that new introductions are being developed from seed-raised plants.

* Find out more in the June issue of the Royal Horticultural Society magazine The Plantsman, where I describe the horticultural history of the chocolate cosmos from its introduction to Britain in 1861 to the confirmation of its status in the wild and recent development of new cultivars, including those raised from seed. Please subscribe here.
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The foxglove revival

Digitalis Goldcrest (left), Knee High Lavender and Foxlight Ruby Glow
Almost two hundred years ago Alexander Campbell, curator of the Manchester Botanical and Horticultural Society’s Garden, crossed a foxglove and a gloxinia (Digitalis grandiflora and Sinningia speciosa) to create what was known as Campbell’s hybrid foxglove.

It looks a little like a rusty D. grandiflora (below, right) but pollen from another foxglove - D. obscura, perhaps? - must have achieved the fertilisation that pollen from a gloxinia could never manage.

The first genuine foxglove hybrid between, D. purpurea and D. grandiflora, was made in 1849 but the seedlings were all sterile and it was not until 1924 that two hybrids that are still grown today were created at England’s John Innes Horticultural Institution: D. × mertonensis and D. ‘John Innes Tetra’.

Campbell's Hybrid Foxglove from 1825, said to be a cross with a gloxiniaSince then a large number of hybrids between different foxglove species have been created although, sadly, many have been lost including an interesting range created by the short lived Europa Nursery (anyone know where the owners, Tim Branney and Adam Draper, are now?).

Now, digitalis breeding is enjoying a bright revival with new hybrids being developed on both sides of the Atlantic. Goldcrest (‘Waldigone’) (above, left) was one of the first recent hybrids to make its mark. Three different breeding programmes in The Netherlands, in Suffolk (UK), and in Michigan, bring together the familiar British Native foxglove, D. purpurea, and D. canariensis from the Canary Islands. Foxlight Ruby Glow (‘Takforugl’) (above, right) is one of them. And, please, both parent plants are Digitalis. Let's not mess around with creating an imaginary new genus – Digiplexus.

Two new series of prolific dwarf hybrids are also just coming on to the market, the very short Knee High Series (‘Knee High Lavender’ above centre) from England and ‘Lucas’ and ‘Martina’ from The Netherlands.

I’ve recently published a long piece about the history of foxglove hybrids, from that early attempt using pollen from a gloxinia to the very latest developments. It appears in the current (March) issue of The Royal Horticultural Society magazine The Plantsman.

You can read my piece on foxglove hybrids online, but please take a moment to subscribe to The Plantsman: you can subscribe to The Plantsman here.


Seeds and plants by mail order: It’s not too late!

Cotwold Garden Flowers catalogue with too may plants tagged for ordering! ©GardenPhotos.com
Easy online ordering is a huge boon, but there’s nothing quite like scanning printed catalogs by a winter fire (or in the smallest room in the house) and tagging the tempting plants. And it's too late to order for the coming season.

And you can see from my post-its marking the must-have plants in England’s Cotswold Garden Flowers plant catalog just how many tempting plants there are!

Owner Bob Brown has a fine eye for a good plant, picking out the best of the old favorites, the best newcomers and landing his eye on undeservedly neglected species. Bob also breeds new crocosmias, kniphofias, aconitums, and other plants and his son Ed has some developed some intriguing new Sambucus (elder) varieties.

One of those tags marks a rare hardy (zone 6a) climbing tuberous perennial cucumber I remember from Kew decades ago and have always wanted to grow - Thladiantha dubia. No edible cucumbers unless you have male and female plants, I’m afraid, but well worth growing for its yellow flowers.

And one of Ed’s elders will definitely go on the order: ‘Gate Into Field’ (!) is described as: “A very vigorous elder hybrid, very large heads of pink-flushed deliciously scented flowers later than normal, July – September, dark pink flushed foliage with pale midribs.” OK, it grows to 5m… I’ll just have to knock down the shed to make space, I suppose. Order going in just before I post this – so you don’t grab the last of the plants I’m ordering before I do!

The Whole Seed Catalog for 2017 - with only the flowers tagged! Image ©GardenPhotos.comThe order to Missouri's Baker Creek Heirloom Seeds, who produce the extraordinary Whole Seed Catalog, has already arrived. The catalog is focused on its vast VAST array or heirloom edibles with a smaller section of flowers in the back. The tags only mark the flowers that appeal; I’d already taken out all the veg tags.

Have to say, this is the most astonishing catalog that I’ve ever seen. OK, it costs $9.95 (there’s a smaller free version). But there’s over 350 full color pages packed with goodies. Tomatoes, of course, feature strongly but there are also forty nine different lettuce varieties including the superb red leaved cut-and-come-again lettuce ‘Merlot’. I grew this last year and have ordered it again. It’s deep deep red in color, cuts for many weeks, tastes great and didn’t bolt. The three foot long Armenian melon from the 1400s is quite something, too.

I’ve also ordered the tall double America/African marigolds intended for cutting – never seen those before – and they also have some superb cut flower zinnias too.

Two oh-so-very-tempting catalogs. Here are the details.

Cotswold Garden Flowers
Order a fee printed catalog 
Order online
Plants can be sent to most of Europe but not North America

Baker Creek Heirloom Seeds
Order The Whole Seed Catalog
Order a fee printed catalog
Order online
Seed can be sent anywhere in the world but they make it clear that sending seed to Europe is expensive and difficult.


Transatlantic plant trials - any value?

Phlox and Sweet Pea Trials at the Royal Horticultural Society's garden at Wisley, near London. Image ©GardenPhotos.com
On both sides of the Atlantic, independent trials of perennials are organized by a number of different organizations. But I’ve sometimes seen the Royal Horticultural Society’s Award of Garden Merit (AGM), often given after trial (phlox and sweet pea trial, above), used in American catalogs and wondered how much relevance this British award has in North America. And does the Plant Evaluation Program run by the Chicago Botanic Garden and, in Delaware, the trials run by the Mount Cuba Center (baptisia trial, below) have any relevance in Britain?

Well, this year I’m chairing a group of experts working to update the list of AGM heucheras for the Royal Horticultural Society (RHS) and I’ve sent all the participants copies of the reports of the heuchera trials at both Mt. Cuba and the Chicago BG.

Of course, the climate in Delaware and in Illinois is, well, rather different from the climate in Britain but, for hardy perennials, if they grow in Delaware or Illinois, they’ll generally grow in Britain. And while modern American heuchera breeding is often focused on suitability for specific climates, the way the plants look when they’re growing well is relatively constant; a harmonious combination of flowers and foliage works well in any climate. So these reports will provide valuable background to our deliberations.

At first I was skeptical, but now I can understand why the AGM appears in American catalogs – it’s one of a number of useful factors that inform choice. The problem is that some gardeners in Texas or Maine, while they may see that the plants look wonderful, may not appreciate that the plants are given their award in a climate that’s closer to that of Oregon or Washington state may not do well for them. In fact they may die their first year.

But it’s not just climate, there’s another thing going on. I suspect that most British gardeners, seeing trial results from Delaware or Illinois, will just assume that they’re of no relevance, or even interest, and ignore them. True, disease resistance in American trials is unlikely to be of value elsewhere as different forms of the same disease are found in different places. But if the flowers are a dingy color in Chicago they’ll be dingy in Britain, too

American gardeners, on the other hand, seem to have a more open attitude and although they may not want to read the detailed reports of the RHS trials in which plants were given the AGM, they’re happy to accept that this is useful information and allow the awards to inform their plant choices as they decide what’s right for their own gardens.

And perhaps, as the dissemination of information about plants becomes more global, these reports help writers and advisors and consultants develop a deeper understanding of the plants so that the guidance we pass on is more informed. And they help nurseries decide what to grow. These trials and their reports are certainly invaluable to me. Even something as simple as paying attention to the factors these reports consider important is useful.

* The Mount Cuba Center is based near Wilmington, Delaware, just over an hour north of Washington DC, and its primary aim is to foster enthusiasm for native plants and their conservation. You can download their trials reports here.

* The Chicago Botanic Garden has been organizing trials of hardy perennials, and other plants, since 1985 under the expert guiding hand of Richard G. Hawke. You can download their trials reports here.

* The Royal Horticultural Society has been running trials of everything from hamamelis to cabbages to marigolds since, it seems, time began. You can search their database of trials here.
Baptisia trial at the Mount Cuba Center. Image ©Mount Cuba Center.


Plants For 2017: Perennials for 2017

Finally, in this week of daily postings on the best of 2016 and looking ahead to 2017, two exciting perennials to look out for in the year ahead.

Hosta 'Branching Out'. Image ©Plant Delights
Hosta
‘Branching Out’

Tony Avent at Plant Delights in North Carolina started out to create a hosta with branching flowering stems back in 1989 and, usig five different parents and after a number of generations of crossing and selection, ‘Branching Out’ is the result. (You can read more on Tony’s blog.)

Its pale lavender flowers on their sturdy 30in/90cm branching stems make an attractive and prolific show in mid summer over broad, heavily veined, dark green leaves. All we need now is added fragrance.

Hosta ‘Branching Out’ is available in North America from Plant Delights, it is not yet available in Britain.


Ajuga reptans 'Choc Ice'. Image ©Monksilver NurseryAjuga reptans 'Choc Ice'
There are few plants with bronze or purple foliage and white flowers. It’s a matter of genetics, the bronze or purple leaf colouring tends come with flowers colours at the same end of the spectrum. Astilbe ‘Chocolate Shogun’ is close, its chocolaty purple leaves topped with pale pink plumes.

And here’s another candidate, a bugle with white flowers held above purple leaves and bracts. OK, it all turns greener late in the season but at flowering season, it looks impressive. Discovered by plantsman Geoff Hitchens.

Ajuga reptans 'Choc Ice' will be available again soon in Britain from Monksilver Nursery. It is not yet available in North America.



Plants Of The Year 5: Cool new primula

PrimulavialiiAlisonHolland-900
Ending the first part of my daily review of the some of the most memorable plants, new and old, from last year we come to the 2016 Chelsea Flower Show favorite – the new white flowered form of Primula vialii .

Primula vialii 'Alison Holland’
As soon as I entered the showground on the Sunday morning before the show opened on the Tuesday, plantspeople were asking me: “Have you seen the new white primula?” So off I rushed to take a look – and it’s lovely. I wrote it up on my RHS New Plants blog back in June. It was shortlisted for the 2016 Chelsea Plant of The Year award.

Basically, instead of the red buds and lilac flowers of the wild Primula vialii from China, ‘Alison Holland’ has creamy green buds and cool white flowers. Gary McDermott of Harperley Hall Farm Nurseries, who introduced the plant at Chelsea, told me that it’s more vigorous and flowers for longer than the usual form. But it hates drought.

‘Alison Holland’ was found in 2011 in his garden in the north east of England by John Holland who named it for his daughter-in-law. Plants never set seed but this form has proved easy to propagate by tissue culture.
 
Primula vialii 'Alison Holland' is available in the UK from Harperley Hall Farm Nurseries.

Primula vialii 'Alison Holland' is not yet available in North America but should be soon.


Plants Of The Year 3: Unique foliage perennial

HeucherellaSolarEclipse
Continuing with the third of seven daily posts about the plants that caught my eye last year, we come to a fine perennial that I noted thriving in a number of different situations.

xHeucherella ‘Solar Eclipse’
With so many heucherellas on the market, its important to take a deep breath before pronouncing one as “unique” – but here goes: xHeucherella ‘Solar Eclipse’ is unique.

This distinctive clump-forming variety has slightly ruffled, prettily scalloped, reddish brown, almost chocolate brown, leaves with a neat minty green margin. It keeps its color well and matures into a clump about 20cm high and 40cm wide. The flowers are white – but not really the point. The cut leaves last quite well in water, too.

Lovely in a terracotta pot, it also looked unexpectedly good in a blue pot and at the front of border in dappled shade. In cool areas with water retentive soil it will grow happily in full sun but is general happier in some shade.

‘Solar Eclipse’ is sport of ‘Solar Power’ (which has yellow leaves with a red central pattern) and was developed by Janet Egger and Chuck Pavlich at specialist perennial breeders Terra Nova Nurseries in Oregon.

xHeucherella ‘Solar Eclipse’ is currently available retail in the UK from these Royal Horticultural Society Plant Finder nurseries.

xHeucherella ‘Solar Eclipse’ is currently available retail in North America from many suppliers including Bluestone Perennials and Plant Delights.


The day our echinaceas died

Echinacea 'Flame Thrower' © Terra Nova Nurseries
The day the echinaceas died... It was yesterday. And this is how it happened.

Echinaceas, coneflowers, and especially all the fancy hybrids that have come on the market recently, like ‘Flame Thrower’ (above) and all the doubles (below), hate bad drainage in winter. That’s what kills them. But yesterday that’s exactly what they got.

On Sunday night the temperature in our garden here in Pennsylvania went down to -10F (-23C). So, after a temperature almost as low the night before, and low temperatures for a few days before that, the ground was frozen solid to a depth it was hard to assess.

And then it snowed. Not a lot, just a couple of inches and the whole garden looked lovely. But then, yesterday, Monday, it got warmer. A whole lot warmer, and quickly. By early afternoon the temperature had risen to 48F (9C), and the snow had melted and the top inch or two of soil had thawed out as well.

But because the soil was frozen down deep, all the melted snow just sat there on the surface, in puddles – it could not drain away because the soil underneath it was frozen. Our borders were covered in pools of water, yesterday, and they’re still there this morning.

And in those puddles of thawed snow are the crowns of our last remaining echinaceas (this has happened before...) – and echinaceas hate bad drainage. So those last few may well die.

Of course, this is not a phenomenon that comes into play in Britain all that much, or in parts of the USA where the winters bring less ferocious frosts. Because if the soil is not so solidly frozen, melted snow drains away and impacts much less on our, rather sensitive, echinaceas.

But here's what's important: it reminds us that, wherever we garden, it’s bad drainage in winter that prevents us enjoying the vast range of exciting new echinaceas for years and years after we first planted them. Which is a shame, because they really are gorgeous. As you can see.

Double echinaceas from Marco van Noort. ©Luc Klinkhamer


Most Christmas roses used to be pink!

HelleborusGiant-TheGarden-1878
“The Christmas Roses with which one meets in the majority of gardens are not white, but pink, or more or less suffused with pink or dirty purple.”

Really? Well, perhaps it was true in 1878 when a certain Mr. D. T. Fish wrote those words in William Robinson’s epic journal, The Garden, although it seems unlikely. He then goes on to explain in detail how to make Christmas roses (Helleborus niger) white.

Even allowing for the artist’s overenthusiasm, this Giant Christmas Rose, illustrated in The Garden in 1878 (above), is impressive and well illustrates how the coloring works: individual flowers open white and develop pink tones and become richer in color as HelleborusLouisCobbett700they mature. Sunset Group, collected in Slovenia by veteran British hellebore expert Will McLewin was similar (but a whole lot less dramatic). Dark stemmed ‘Louise Cobbett’ opens with pink backs to its flowers and later develops additional pink tints but it’s not the color of the Giant Christmas Rose.

Neither is Blackthorn Group (below), developed by acclaimed hellebore and daphne breeder Robin White from ‘Louise Cobbett’ (right) and ‘White Magic’ although it’s a lovely thing.

Strangely, Josef Heuger, in Germany, who has introduced so many fine forms of the Christmas rose recently - ‘Jacob’ flowers dependably in November here in Pennsylvania - has created no pinks. Most of the pink ones such as ‘Pink Frost’ which listed as H. niger by mail order nurseries are actually hybrids. If Ernie and Marietta O’Byrne of Northwest Garden Nursery in Oregon, who’ve created so many spectacular double and single forms of H. x hybridus, turned their attention to Christmas roses we’d be in for a treat.

Anyway, it’s interesting (if difficult to believe) that pink was once normal in Christmas roses and that detailed suggestions were given in The Garden for turning them white.  And what, in short, were the recommendations: “light soil”, “a warm, sheltered, partly-shaded situation” and “cover them with glass”. Somehow that doesn’t really seem a very convincing way to change their color…

HelleborusBlackthorn2143