Plant trials

Ageing disgracefully

Argyranthemum,,marguerite,cobbitty daisy, fading. Images ©
I was looking at the trial of marguerites, Argyranthemum, sometimes known as cobbitty daisies, at the Royal Horticultural Society's garden at Wisley near London this week. One hundred and seven different varieties from around the world all grown in one place. A great opportunity to compare.

Two things struck me. Firstly, the old varieties like 'Jamaica Primrose' were only just starting to flower while modern varieties were covered in flowers. And already plants of the old varieties were generally much larger. But, more importantly, I was struck by the fact that while the flowers of some faded harmoniously the flowers of others deteriorated badly and as they faded they detracted from the display.

This is important because if you have to pinch off the flowers before they're finished the impact is dramatically reduced.

In the picture, the plant on the left is Summit Pink ('Cobsing') and the single flowers open in rose pink then fade to white. Very pretty and with a bonus: as the flowers finally die, the petals roll back as they turn brown and are hardly visible at all so no deadheading is needed.

On the right, San Vicente ('Ohmadsavi') opens a deep magenta rose then becomes paler and paler at the tips of the petals at the same time developing an odd little white crest in the middle. The result is a mess which could only be improved by cutting off half the flowers in the picture. What's more, as you can see, as the petals turn brown they remain on show. Not good.

The classic plant for ageing disgracefully is Achillea 'Fanal', often known as 'The Beacon'. As the tiny flowers first open, the flat heads are a brilliant scarlet. Then it all goes wrong, and as the later flowers are at their peak the earlier ones have turned the colour of dirty dishwater. Of course, you cut them off – but then the display is certainly much brighter, but very very thin.

The ability to fade harmoniously is not always a feature that can be easily appreciated when you come across an unfamiliar plant in flower in the nursery. But look carefully at all the plants on offer and it's often possible to look into the future and see how the flowers will mature.

The Dead Plant Society

DeadPlantCoffeCan I’ve been taking a look at the coffee can on the shelf where all the labels collect, the labels from the plants which are no longer with us. The Dead Plant Society. It's not necessarily as sad as it sounds.

Needless to say, it’s been added to recently as the fall clean up confirms the absence of plants which never peeped through on time in spring. But, also, a space behind a label may reveal something else.

Some plants are definitely very very dead, including the white mophead Hydrangea ‘Queen of Pearls’. It’sHydrangeaTag odd, some mophead/Hortensia hydrangeas do well here in chilly zone 5 and others get clobbered. “Can be grown in Zone 5 with good winter protection” says the website. No, I’m not going to protect some hydrangeas when others are happy without it. ‘Princess Lace’, in the same series, and ‘Forever and Ever Red’ are not dead.

Also very, very dead are:
Echinacea ‘Lilliput’ – not all echinaceas can cope with a combination of not quite enough sun and drainage not quite good enough either.
Aster ‘Marie III’ – don’t really care for these Yoder asters, the flower form is poor and I hate the way they go from ‘Marie’ to ‘Marie II’ and so on as they “improve” the individual colors. There‘s ‘Peter III’ as well, also dead!
Chrysanthemum ‘Will’s Wonderful’ – mentioned often on TP, most recently here. A great loss.
HibsicusTag Hibiscus ‘Peppermint Schnapps’ – yes, gone gone gone. Bred in tropical Florida. Not a good candidate for the frozen north. Stick with those from bred in icy Michigan by Walters Gardens.
Ranunculus ficaria ‘Double Bronze’ (and others) – I shipped just about all the double, and therefore non-invasive, varieties over from England but every one has now died. The single one thrives all too well on a river bank 150 miles away.

Also genuinely gone are some heucheras: weevils munching through the roots, I fear; Helleborus argutifolius: well, it does come from Corsica, zone 9; and all but two buddlejas… invasive? Hah! Not here.

But sometimes there’s just nothing behind the label
Achillea ‘Pomegranate’ – The deer ate (yes, I know achilleas are supposed to be deer-resistant)… The deer ate the ones planted outside the fence while they were soft and succulent and not sufficiently pungently off-putting. Those inside the fence are fine.
Aster novae-angliae ‘Snow Flurries’ – lovely white form of the New England aster found along a lonely road in Cattaraugus County, New York. Actually, it’s thriving. The birds moved the label to another bed. Thanks guys.
Athyrium ‘Ghost’ – It’s there, it’s gorgeous, its tag is fluttering down the driveway.AthyriumGhostTag
Vinca ‘Giant Steps’ – I think it grew so violently that it flung the label across to the other side of the garden. Currently escaping through the deer fence and looking at total eradication in the spring. So, yes, dead – one way or another.

And that’s only a sample from one coffee can… How many more cans are there?!

Ornamental rhubarbs - send your pictures to the RHS

Rheum trial RHS. Image: GardenPhotos.comThe ornamental rhubarbs, Rheum, are dramatic flowering and foliage plants making bold specimens with, at their best, a very long season of interest. They're related to the culinary rhubarb, of course, but look better! You can help the Herbaceous Plant Committee of Royal Horticultural Society with our research on these plants.

After the trial of ornamental rhubarbs held at the RHS garden at Wisley, just outside London, ended in 2006 the plants were moved for further assessment and we took a look at them a few days ago. Frankly, they're a bit of a muddle. It's not as if there's a huge number of them, but the problem is that they've become so mixed up that when you buy a plant under a familiar or promising name you've little idea of what you're actually going to get. It was clear that many of the plants we assessed were wrongly named and some good plants were not represented.

These plants have five good features: the unfolding spring foliage can be very colourful, often dark red; the mature leaves can be impressive too, especially if they retain their red colouring on the upper surface and have an attractive shape; the flowering heads can be bold and colourful; the seed heads can also be impressive; and the whole plant can make a fine and imposing specimen.

So we'd like you to send us pictures of really good ornamental rhubarbs. If you have plants which are especially impressive in one, some or all of these ways - please send me a picture. Tell me the plant's name, where you got it and when you got it and it will help the Herbaceous Plant Committee of the RHS understand the range of plants which are actually being grown around the country - and under what names. Please don't send plants! Just email pictures.

Thank you! I'll report back here as we continue the research.


Trials judging postponed by snow

Royal Horticultural Society judges were due to assess the winter foliage of the bergenias in the trial at the Society's garden at Wisley near London today. No such luck - can't do much judging when the plants are completely covered in snow!!


In January, some plants in the Cortaderia trial were also still looking good, with their fluffy plumes still intact. Not today.


I don't think the judges were expecting to be assessing the Kniphofia (red hot poker) trial today - but it will be interesting to see if the results of the cold weather and unexpected snow covering.


Thank you to Ali Cundy of the RHS Trials Office at Wisley for these great pictures.

My new blog on plant trials and awards

TrialsViewJune06AliCundy700 One of the most important activities of the Royal Horticultural Society is its plant trials. From hydrangeas to sweet peas, hardy geraniums to lettuces - plants of all kinds are compared side by side at its garden at Wisley in Surrey, just south of London, and at other gardens around the country. The best are awarded the Award of Garden Merit.

It’s a great spectacle, as well as an invaluable resource.

Now, after many years judging the flower trials, and writing about some of them in the RHS magazine The Garden, I’ve now started blogging about them regularly on the Royal Horticultural Society’s website. (My RHS New Plants blog continues.)

I’ll be covering the latest awards, which trials are at their best, the free-to-download reports published by the RHS, events at the trials and more. Be sure to take a look.

Now… readers outside Britain may think that there’s not much in it for them. How relevant can trials in England be to gardeners in Nebraska or New Zealand? Well, it’s true that some plants which thrive at Wisley may not even be hardy in Norway or Nova Scotia and plants grow differently in different conditions, of course.TopDahliaBlogPost

But some factors are fairly universal: messy double flowered varieties are messy everywhere; varieties that flower for just two weeks when all the others flower for eight do not suddenly reform; if a plant rampages at Wisley, you can be sure there are many other places it will smother its neighbours; an annual mixture which turns out to be almost all one color won’t suddenly be harmoniously balanced when grown elsewhere. Some things about plants are just universal.

And all the work on correcting names, proving (or disproving) the point when two varieties seem identical, and describing plants so it’s easy to distinguish one from another – it’s all part of the RHS trials and will all be covered on my new Trials and Awards blog. Give it a try.

Wisley visitors vote for their favorite bulbs

TulipWorldExpressionRHS There’s been a recent innovation at the Royal Horticultural Society’s trials at Wisley – the judges give the awards, but visitors now also get to vote for their favorites.

Clearly this would be a little impractical with, say, carrots which have to be dug up and tasted. But voting took place for tulips and hyacinths grown in the open ground this spring and there will be more opportunities during the summer and fall.

Top of the list of tulips was ‘World Expression’ with ‘Dordogne’ second out of the 196 entries on trial with RHS Award of Garden Merit winner ‘Maureen’ only getting one vote! Of the hyacinths, ‘King of the Blues’ came out top with ‘Blue Jacket’ second out of twenty seven entries on trial.

Voting is taking place for garden pinks now, while buddleias will follow. And if you’re visiting Wisley and look for the signs by the Wisley gate later this month. There will be opportunities to taste the raspberries on trial and vote for the tastiest – but only on days when crops are available.

My new blog on new plants

Rhsscreengrab1 I’ve started a new blog.

Going by the impressively catchy title of New Plants and Trials, it began last week on the Royal Horticultural Society’s website. You’ll find it here.

I’m sharing the space with the Trials Office at the RHS garden at Wisley: I’ll be posting about new plants and Ali Cundy, Trials Recorder for the RHS at Wisley, will be posting about the many and varied trials on flowers and food crops which the RHS runs every year.

Why not take a look? I've just started a series of three posts on new hardy geraniums. And while you’re there look over the other RHS blogs including one by the Curator of the garden at Wisley, Jim Gardiner. I’ll post an occasional catch-up list here – just so you know what you’re missing if you don’t pop over and check it out.

That’s my new blog - New Plants and Trials - over on the Royal Horticultural Society’s website.

Delphiniums on trial

Delphiniumtrial500 There’s no doubt that the very best delphiniums are those propagated by division or cuttings. But it’s impossible to produce them in the large numbers gardeners need by these methods and tissue culture, which works so well for so many perennials like heucheras, campanulas, coreopsis and so on, doesn’t yet work for delphiniums. I’m sure they’ll crack it eventually, but in the meantime the only way to raise delphiniums in the numbers that nurseries and gardeners really need is from seed.

One of the best was ‘Aurora Light Purple’Delphauroralightpple400 – lovely colour, good flower form and no off-types – but there’s one big problem with delphiniums from seed: they are very difficult to keep true to colour, superior spike quality and good garden performance. So the trial of seed-raised delphiniums under way at the RHS garden at Wisley is very useful. Even in this first year, it’s clear that some entries are much more uniform than others. There are forty-six in all, and they’ll be judged this year and again next year.

But even if the colour is uniform if the structure of the plant is poor, then it’s still not a good garden plant. ‘Clear Springs Lavender’, for example, produced a lot of lovely, well-formed spikes but the display was spoiled by the secondary spikes growing up around the main spike while it was still at its best. It may sound a like a small thing, but in the garden it makes a big difference.

The trial continues through next year, I’ll report the results when they’re in.

Petunia trial

Petuniatrialafterdeluge500 The most colourful trial at the RHS garden at Wisley this year is the trial of multiflora petunias. Well, let me re-phrase that: ...sometimes the most colourful trial...

The first time I looked at the trial was following an absolute deluge… and out of 202 entries to the trial only a very few were looking good – the low, spreading, ground-hugging types in the Opera Supreme and Shock Wave series. The rest were just battered by the rain and had not recovered – the very worst affected were probably those with white edges to the petals.

Petuniatriallater500 Two weeks later, the trial was transformed – a sparkling vision of colour - even though there’d been a shower the day before which had left the flowers of many entries spotted. The veined types, by the way, seemed to resist spotting most effectively. Again the Opera Supreme and Shock Wave series were outstanding.

Over the two visits these were the most colourful varieties, the most uniform, and came back after rain or resisted the rain most effectively; ‘Opera Supreme Purple’ stood out above them all for resisting the deluge and coming back well and for not spotting after the shower, other exceptional ones were: ‘Celebrity Pink’, ‘Celebrity Mid Blue’, ‘Hurrah Salmon’, ‘Hurrah Coral Fire’, ‘Frenzy Pink Morn’, ‘Frenzy Light Blue’, ‘Prime Time Pink’, ‘Prime Time Lavender’, ‘Horizon Bright Rose’, ‘Horizon Lavender’, ‘Baby Duck’, ‘Pink Lady’ plus, in the Opera Supreme Series, Pink Morn, Lilac Ice, and Blue, as well as ‘Shock Wave Pink Vein’ and ‘Shock Wave Purple’.

The summer still has a lot to throw at them – heat, as well as rain, I expect – but already this trial proves that there are some varieties that deal with the worst weather outstandingly well.

Dark-leaved dahlias

Dahliahappyfirstlove500 The annual Royal Horticultural Society trial of dahlias held at Wisley is always spectacular. It includes plenty of traditional large-flowered exhibition types but increasingly features small plants with smaller flowers - more suited to containers and small mixed borders.

This year there’s quite a range of short, dark-leaved dahlias on trial and one in particular stood out – ‘Happy Single First Love’. This is one of a series of single-flowered, dark-leaved dahlias from Holland, all of which looked excellent. But the unique colour of the flowers of ‘Happy Single First Love’, set against the rich foliage, made a knockout combination.

Footnote. While bending over to photograph these dahlias my phone slipped out of my pocket. I didn’t notice till later. I went back… but what are the chances of finding a black phone amongst all that dark foliage? And I wasn’t exactly sure where I’d lost it. In fact I looked in vain for so long that I was locked in the garden after closing and had to exit through the restaurant delivery bay! Next day, I borrowed my mother’s phone and went back.

I dialled my phone up and down the delphinium trial… amongst the monardas… finally I heard my phone ringing amongst the dahlias. And there it was, caught in the bushy growth of a dark-leaved Happy dahlia. Thank goodness they hadn’t had the irrigation on.