Trials and Awards

Last days of the pampas grass trial

Graham Rice — Wed, 18 Nov 2009 14:34:00 GMT

The trial of Cortaderia, pampas grass, has been both dramatic and intriguing. As it comes to a close, with some entries still looking good very late in the year, there was one that stood out above all the others - ‘Evita' (click the picture to enlarge). Except part of the point is that it didn't "stand out" at all - some varieties are huge, 3m/10ft tall, but ‘Evita' is altogether more manageable.

Reaching just 4-5ft/1.2-1.5m high, it combines vigour, dwarf habit, prolific flowering with plumes of good substance and also flowers as a young plant - a very valuable feature. Another notable feature is that ‘Evita' plants are female, but are not known to produce seed. I'm certain this will get an Award of Garden Merit.

One of the interesting things about cortaderias is that plants are either male or female so any seedlings produced will be hybrids. So when nurseries raise named varieties from seed the resulting plants will not come true - and there was some dramatic evidence of this in the trial; no awards for those entries.

But others that looked especially good included. ‘Highfield Pink' which was seen as the best pink-flowered form - and one assessor said it had an "Afghan Hound quality"! The variegated ‘Pink Phantom' also impressed.

Those with variegated foliage must obviously be propagated by division and two of these stood out. Silver Feather (‘Notcort') is a white variegated form of C. pumila and the overall impression of the rather discreetly marked leaves was of grey foliage. It flowered well, did not grow too high (in fact it was one of the smallest) and its foliage was excellent.

The other good variegated plant was ‘Gold Band'. More vigorous than other variegated types, the overall effect was a wonderful golden colouring and the flowers were excellent too.

These were the stars of the trial and as well as identifying some excellent plants small enough for most gardens and which will give colour from both flowers and foliage, it really highlighted the necessity for nurseries to propagate by division and not seed.

I'll bring you news of the final awards once they're confirmed. In the meantime, take a look at the full list of plants in the Cortaderia trial.

Two fine late flowering kniphofias

Graham Rice — Wed, 11 Nov 2009 12:31:00 GMT

A week or two back I wrote about delphiniums which came back for a second burst of flowers long after their main flush in June. The last couple of times I was taking a look at the Wisley flower trials I also noticed some other perennials looking good late in the season.

The Kniphofia trial has been a difficult one to assess because these pokers flower over such a very long season - some are at their peak in late spring, some in mid autumn.

In September and October Kniphofia rooperi (above, click to enlarge) has been spectacular. You can see from the picture how vivid it is and how few other kniphofias there are flowering in the background. This is a splendid plant for autumn colour and because this form in the trials, sent to the trial by the Hampshire nursery MacGregor's Plants for Shade, was so good it was decided that it needed its own cultivar name. As yet, we don't know what that will be. But this plant was certainly better than the variety ‘Torchlight' growing alongside.

The other poker at its peak late in the season was K. caulescens, and in particular the form loosely known as "from John May". This is very different from many pokers in that not only are its spikes at their best in the autumn, but its impressive foliage is a valuable feature for many months.

Its leaves are relatively broad and noticeably greyish in colour, sometimes they look rather like the leaves of leeks, and can be very dramatic. You can see them in the background in the picture. And it turns out that his plant is unusual in another way: in South Africa, where it grows wild, it's seen in large colonies in bogs - far wetter conditions than we normally associate with kniphofias.

Both these late flowering pokers look to be well on their way to gaining the Award of Garden Merit and will bring a little fiery style late in the season.

Awards for irises

Graham Rice — Fri, 06 Nov 2009 12:09:00 GMT

Tall Bearded Irises are amongst the most dramatic and colourful of perennials so the very best of them must be really impressive. And they are.

The RHS Iris Sub Committee - yes, there's a sub committee just for irises - has recently had its latest awards ratified and three Tall Bearded Irises performed so well in the trial at Wisley that they've been given the Award of Garden Merit.

They were planted in 2007 on the Portsmouth Field, usually known just as the trials field, and were assessed regularly during the flowering season. Using a points system, four specific qualities assessed: the overall quality of the plant, stem quality (robustness and branching), flower quality and the presentation of the flowers.

And out of 110 entries into the trial three gained an AGM, while one other had its AGM withheld until it becomes available to buy.

The lovely ‘Helen Dawn' (above, click to enlarge) is almost pure white. Reaching about 90cm/3ft, with six to eight buds on each stem, the standards (the three upper petals) are almost pure white while the falls (the three lower petals) are slightly creamier with an attractive network of pale veins. The white beard is yellow at the tip, deepening almost to orange in the throat, and the flowers have what iris-expert Claire Austin calls a "heavy sharp scent".

‘Helen Dawn' was raised by Australian breeder Graeme Grosvenor and registered back in 1998. It's a cross between ‘Skating Party' and ‘Scandia Delight'.

‘Diabolique' is almost the opposite in colour. The nearly-black buds open to heavily ruffled deep wine purple flowers, the falls slightly richer and more vinous than the standards. The blooms have good substance so are unusually weather resistant while the deep blue beard is short, but its colour stands out well. Reaching about 38in/97cm and with up to nine flowers on each stem, ‘Diabolique' makes quite an impact.

Raised by the prolific Schreiner's Gardens in Oregon, ‘Diabolique' has ‘Amethyst Flame' and ‘Melodrama', amongst others, in its background.

Also from Oregon is the last of the three Tall Bearded Irises to be given an AGM for 2009, ‘Paul Black'. This is taller, at 4ft/1.2m, with up to six buds per stem and is basically dark purple-blue with a fiery orange beard - like a flame in the night. Both the standards and the falls have a slightly inky look but fade to white in the throat. ‘Paul Black' was raised by Thomas Johnson and named for his partner at their iris nursery Mid-America Garden in Oregon.

Dahlias in containers

Graham Rice — Wed, 28 Oct 2009 11:29:00 GMT

This year's dahlia trial at Wisley has been unusually fascinating and I'll be reporting on a number of its features over the next few weeks. Picking up on recent trends, this year twenty one of the entries were grown as individual plants in pots to assess their value as container plants.

Immediately one thing is obvious. These plants, of course, are smaller than most dahlias - if they were 4ft/1.2m tall, as are many varieties, they'd be far too large for most containers. So we tend to look down on the flowers from above. But many varieties hold their flowers so they face sideways - ideal on a tall plant which is viewed from the side but the impact is much reduced when you look down at the flowers on a short plant from above.

‘Spanish Conquest' (above, click to enarge) was one whose flowers are more upward facing and which made a real impact. The colour is wonderful too, with red buds opening to old gold flowers with burnt orange centres. The plants were prolific and seemed to cope with dry conditions better than many. I thought it the best of all those grown in containers this year.

On the other hand there was ‘Keith's Pet'. This is a lovely dainty little dahlia with neat dark purplish foliage and bright white flowers with just a hint of pink showing through from the backs of the petals. But the flowers face sideways and unless you get down on your hands and knees - as I did to take the photograph - you never get the full impact of the flurry of flowers.

Other outstanding varieties in containers were ‘Exotic Dwarf', a single yellow with upward facing flowers, ‘My-nute Blend', a very prolific red and yellow double, and also ‘Gallery La Tour', with upward facing pink and white double flowers over dark leaves.

There were a couple of other points that came out of this trial of container grown dahlias. There was no watering system set up, no drip nozzles so that the pots could be easily watered at the turn of a tap. The result, I'm afraid, was that with pressure of work meant that the watering can just didn't come out often enough and many varieties would have been a great deal more impressive if properly watered.

And as we assessed them we also noticed the compost in the pots. It had shrunk so much that there was a large space between the tops of the pots and the compost. We concluded that the peat-free compost had already started to decompose and so had shrunk - not good for the plants. The begonias hated the peat-free compost this year as well. Sometimes, nothing but peat, or at least a good proportion of peat, will do.

Of course the varieties that could cope with these problems really were impressive.

Double display from delphiniums

Graham Rice — Wed, 21 Oct 2009 12:57:00 GMT

One of the glories of the Wisley trials field in early summer are the delphiniums. Tall and magnificent - taller than they ever get in most people's gardens, I have to say, what with all that manure - they're a real spectacle. But then after a few weeks of glory, they're gone. Or are they?

I went back to take a look at the delphinium trial in mid September, and then finally at the very end of the month, and found some varieties again looking very impressive. OK, the quality of the individual spikes was not up to the standard of the main display but they nevertheless made a real impact.

On my first September visit ‘Ann Woodfield', blushed white, and ‘Kestrel', electric blue with a dark eye, stood out while at the end of the month ‘Jenny Agutter' (right), in rich pink, and ‘Amadeus' (above), in deep purple blue, were the stars.

So what can we do to help ensure we get a double display from our delphiniums? First, cut off the main spike as it fades and then when the shorter, slimmer secondary spikes that follow also fade away - cut the whole plant back down to ground level.

This may seem an odd thing to do in mid summer but if the plants are kept watered, and fed with a high nitrogen fertiliser if the soil is not as rich as that at Wisley, they will soon sprout fresh new leaves. These are valuable in themselves and then followed by more flowering spikes later. Be sure to look out for mildew in hot dry spells and also for caterpillar damage. Then you've every chance of getting a double delphinium display from your plants.

New (free!) dahlia bulletin

Graham Rice — Mon, 12 Oct 2009 15:52:00 GMT

Dahlias are becoming increasingly fashionable. In particular, single-flowered and collarette dahlias are catching everyone's eye so after trialling many of them in recent years the RHS has produced a twelve page full colour bulletin entitled Open-centred Dahlias.

Written by Wisley's Sue Drew, from RHS Trials Office, who has special responsibility for the dahlia trials, the bulletin covers both single-flowered types and collarette dahlias (collarettes are those with additional shorter petals around the eye).

This excellent guide starts with a short history of the dahlia and then illustrates all the thirteen different flower forms, to show the amazing range available. A wide range of the best singles and collarettes is illustrated and each is briefly described, all those chosen have either already been honoured with an Award of Garden Merit or look well set to gain the award soon. Suppliers are noted for each variety - very useful. There's also a very good guide to growing dahlias, a discussion on breeding new dahlias and some thoughts on planting partners for single dahlias.

The whole bulletin provides a valuable introduction to these long flowering and prolific plants, all written in an easy to follow style and with plenty of excellent pictures.

What's more, you can download this new Dahlia bulletin FREE from the RHS website. Or check out the RHS Plant Bulletins page for a list of all the free Plant Trials Bulletins on offer.

Yet another excellent RHS Plant Bulletin based on the society's trials.

Intriguing ipomoeas

Graham Rice — Wed, 07 Oct 2009 14:54:00 GMT

The trial of annual climbers at Wisley has thrown up some stars and some disappointments. Both extremes are to be found amongst the ipomoeas.

In recent years botanists have decided that, although superficially it looks very different, Mina lobata is so closely related to Ipomoea that it should be moved into the genus Ipomoea as Ipomoea lobata (left, click to enlarge). It's been a real star, with spikes of flowers featuring bright red buds opening to cream. Three very similar entries were included in the trial and in recent weeks all three have been stunning and all three look to be on track for an Award of Garden Merit. And all three looked impressive all day.

Also pretty impressive was Ipomoea ‘Ismay Soft Blue' (below, click to enlarge), with its white flowers neatly barred in blue and late in the season it seemed to have the most flowers on show of any ipomoea. The deep purple ‘Kniola's Black Night', with its white throat, set against small, dark foliage was also good. This and the other familiar trumpet-flowered ipomoeas all open very early in the day and on hot sunny days have crumpled by lunch time although on cool days ‘Ismay Soft Blue', in particular, lasted till the end of the day.

However our old favourite ‘Heavenly Blue' - such a stunning colour - and many of the other ipomoeas proved too leafy on the rich Wisley trials field soil and, as happens with nasturtiums, the leaf stalks stretch and so the leaves tend to hide the flowers. The same thing happened with the thunbergias. The ipomoea leaves themselves also grew larger than normal and there seemed to be far more of them. The result of all this extended leafy growth was that the flowers were often hidden. Some were also rather variable in their flower colour or patterning and these included ‘Flying Saucers' and ‘Azzurro di Venezia'.

Those Ipomoea lobata may have started later than most of the annual climbers but the autumn display is amazing.

Amaranthus - bold and beautiful

Graham Rice — Wed, 30 Sep 2009 09:34:00 GMT

We all know the old cottage garden annual Love Lies Bleeding, Amaranthus caudatus. But down on the Wisley trials field right now is a trial of these impressive and easy-to-grow annuals - with almost thirty other entries alongside that familiar favourite.

They come in an amazing variety. As well as the long deep red tassels of Amaranthus caudatus there's a pale green form and a spectacular range of type with upright plumes in crimson, green, and biscuit brown plus some with tight, upright rather nobly flowers heads. There's also a range of varieties with coloured foliage.

One striking thing about the trial is that the mixtures are all noticeably poor compared with the single colours. They vary so much in height and style of flowering that in a group they just look terrible. So forget about ‘Mixed', ‘Ribbons and Beads' and ‘Pony Tails'.

Amongst the those with biscuit brown plumes ‘Golden Giant' (above) was definitely the pick. ‘Marvel Bronze' features tall deep red plumes and bronze-red foliage which makes a great combination as does the rather similar ‘Oeschberg' (left).

A few varieties of the less robust Amaranthus tricolor were also included, these are the ones with multicoloured foliage but insignificant flowers. ‘Early Splendour' was probably the pick but they all develop a rather ungainly habit and none had the impact of the flowering types.

One thing to keep in mid is that most of these make big plants - 90cm-1.2m/3-4ft is common so they need space. But in a large container, slipped into spaces in mixed borders or as part of a tropical style summer border these are very effective.

You'll enjoy seeing these impressive annuals, take a stroll down to the trials while they're still looking good. And there are voting forms at the back of the Trials Pavilion so you can tell us which is your favourite.

Late flowering pinks

Graham Rice — Wed, 23 Sep 2009 07:39:00 GMT

One of the benefits of looking over the trials regularly through the season is that it's possible to pick up points that would be missed by simply checking the trials while they're at their most colourful. So the other day I cast my eye over the trials of pinks, three months after their peak flowering period, to see which varieties were still performing well.

In general it was very obvious that the dwarf pinks, most of which are relatively new varieties, had far fewer flowers than the garden pinks - most of which have been around for a few years.

So the two with the most impact at this late point in the pinks season were ‘Gran's Favourite' (above) and ‘Houndspool Ruby' (below left), both well known varieties and both already holding the Award of Garden Merit.

Others that stood out were ‘Doris', ‘Moulin Rouge' and ‘Valda Wyatt' - again all three already hold the Award of Garden Merit and I expect that these long flowering qualities have already been noticed by the experts who've been assessing this trial over the years.

As I say, the more modern dwarf pinks were less impressive this month compared with June and July but the three that featured the most flowers were ‘Red Star', ‘Passion' and ‘Starburst'

But the lesson seems clear. If you'd like to have pinks which are not only covered with flower in their peak period in early summer but which carry on their display into the autumn, choose AGM winning garden pinks like ‘Gran's Favourite' and ‘Houndspool Ruby'. But remember too: all pinks will flower more prolifically if regularly dead-headed

Dazzling celosias

Graham Rice — Wed, 16 Sep 2009 09:48:00 GMT

Celosias used to thought of mainly as pot plants, and they were also favourites for decorating events at town halls and other municipal venues.

But I grew celosias as summer annuals in mixed borders a few years ago and they were superb. As the summer climate improves and as more adaptable varieties are introduced, growing a trial out in the open on the trials field has provided one of the most colourful of the summer's trials. They come in two types, the feathery plumes of the Prince of Wales Feather type, and the Cockscomb type with congested flower spikes that, some people say, look like the inside of your brain!

Forty eight entries were grown, all started from seed in March and treated as half-hardy annuals. Most were of the feathery type and come in vibrant red, orange, gold and yellow shades and their dazzling colours catch the eye as soon as the trials come into view. There are a few softer colours, though these seem less effective, and one lovely tall pink and white form.

Looking them over yesterday, we had an eye for both flower and foliage colour, long flowering season and an effective display of plumes. Uniformity is also important, in two ways: there should not be too much variation in colour of the single colour types and if the flowers were supposed to be feathery plumes there should be no cockscomb types creeping in to spoil the impact.

There were five which especially caught the eye of the assessment panel. ‘Smart Look Red' featured long lasting bright red flowers set against rich burgundy foliage to create an unforgettable combination. The vivid slightly pinkish red spikes of ‘Glow Red' were much admired while ‘Century Red' was neat enough for small containers or small sunny beds around the patio with bronze foliage setting off the bright red flowers. The vivid marmalade coloured plumes of ‘Fresh Look Orange' were very striking set against fresh green leaves.

‘Flamingo Feather' (above, click to enlarge) was rather different, taller than most of the others and with masses of slender spikes, the carmine buds open to pink flowers fading to white. Good for cutting, it also integrates especially well with perennials in mixed borders.

The assessors rated those five especially highly, but you can vote for your own favourites. Pick up a voting form in the new logia at the bottom of the trials field, make your choice, add your comments and leave it in the box alongside the celosia trial itself.

Kniphofia (red hot poker) Open Days

Graham Rice — Mon, 07 Sep 2009 21:39:00 GMT

Alongside a new look Wisley Flower Show, starting this coming Friday morning and closing on Sunday afternoon, the RHS Herbaceous Plant Committee is running a series of three Kniphofia Open Days. Kniphofias are dramatic, colourful, sometimes statuesque perennials which are currently enjoying a revival so this is an ideal time to combine a visit to the Wisley Flower Show with finding out more about these essential autumn perennials. There are two parts to the event.

In the loggia at the end of the Wisley Canal, just a short walk from the main entrance to the Wisley Garden, there'll be a series of illustrated display boards giving a thorough and easy-to-follow introduction to kniphofias. Members of the RHS Herbaceous Plant Committee will be on hand each day to provide expert advice so, to mention just three, you'll get the chance to pick the brains of Sarah Cook, former Head Gardener at Sissinghurst, Ivan Dickings former Chief Propagator at Notcutts Nurseries and plant breeder Simon Crawford.

They'll be able to tell you about where kniphofias grow in the wild, how best to grow them in gardens, which varieties did well in the trial and answer your questions about kniphofias, how to grown them and the plants that look good with them.

Also, at 11am and 2pm each day, meet at the loggia for a Guided Walk through the Kniphofia trial where you'll be able to see every one of the one hundred and twenty seven (yes, really - I know, you had no idea there were so many!) entries in the trial and get an insight into why some got high marks in the trial and some did not. There'll be some stupendous varieties at their peak.

So that's Friday 11th, Saturday 12th and Sunday 13th of September - start at the loggia at the end of the Wisley canal: enter the gardens, turn right along the back of the main building and look to your left towards the end of the canal.

Annual climbers

Graham Rice — Wed, 02 Sep 2009 11:40:00 GMT

Most trials concentrate on a particular type of plant - usually one genus like Dahlia or Dianthus. But occasionally a whole group of similar plants from a wide variety of genera is trialled together because they have useful similarity - and this year it's the annual climbers.

These are invaluable in creating a quick feature in a new border, rapidly clothing a fence or wall, or for adding a secondary colour to a mature shrub or climbing rose.

There are one hundred and fifteen different entries covering about twenty different genera grown on wire towers and they've been fascinating. The site is perhaps a little too exposed for some of them, but many are thriving - indeed the Eccremocarpus are thriving a little too enthusiastically, they're very vigorous and the rich soil is helping create large plants.

Not many years ago Rhodochiton astrosanguineus (above) was mainly grown in pots in the cold greenhouse as it was considered impractical to grow it outside - on the trial, it thrives. In recent years more robust forms have been selected.

Of the forty Ipomoea entries, ‘Bohemian Shades', ‘Grandpa Otts' and I. lobata stand out with many of the others also impressing. ‘Heavenly Blue', however, is not showing itself off as well as we know it can and the judges described ‘Split Personality' as "ugly"!

Vote for your favourite

Graham Rice — Fri, 28 Aug 2009 15:52:00 GMT

One of the most exciting developments on the Wisley trials in recent years has been the new opportunity for visitors to vote on their favourite plants.

For a number of selected trials, voting papers and a voting box are set up alongside the trial. Just tell us your favourite, add a quick comments to tell us why you like it - and all the votes will be tallied and published, along with the comments, at the end of the season.

Voting on the Buddleja trial is going on now. It'll be interesting to see how this year's vote compares with last year's voting. The Buddleja trial is not on the trials field with the perennials, annuals and veg. It's at the opposite end of the garden, past the restaurant and through the Pinetum. You'll also find the trial of Weigela down there - this trial focuses on the coloured-leaved forms (purple, variegated etc) which have become so popular recently - along with the trial of Indigofera, much under rated shrubs in the pea family, which is looking good now.

On the main trials field, you can vote for Amaranthus and Celosia. The Celosia trial is especially interesting as this is a plant which is much underused in summer borders - the trial show how good some of them are. And with both flower and foliage appeal, the Amaranthus are also in need of your vote.

Voting on the Dahlia trial is about to start and in October voting will begin on the Cortaderia (pampas grasses).

This is a great opportunity to make your views known, please cast your vote and tell us what you think.

Online pea trial

Graham Rice — Thu, 20 Aug 2009 18:21:00 GMT

Every year the RHS tries to accompany its huge trials programme with ventures at its regional gardens and also at East Ruston. And every year we also try to involve RHS members in a trial, to give gardeners and schools around the country the chance to compare varieties, report back and have their results included as part of the assessment of varieties for the Award of Garden Merit.

This year it was snap peas and sugar peas and 200 members along with schools around the country grew two varieties and kept records of how well (or how badly) they did. The varieties grown were ‘Sugar Ann' (above) and ‘Oregon Sugar Pod', both widely listed in catalogues.

Well, reports are starting to come in. And, without giving the game away before all the results are received and collated, the comments so far have been very interesting. Some people found that just as the seedlings were emerging they disappeared: sounds like slugs or mice or pigeons to me. Some growers re-sowed.

Both were rated "sweet" in reports and also as and "stringy" (!) and interesting details were revealed: one grower reported that ‘Sugar Ann' could be eaten very early or allowed to mature and it seemed that ‘Sugar Ann' was also a favourite with pigeons and slugs. Another reported plants of ‘Oregon Sugar Pod' with pink flowers instead of the usual white - a sign that this variety is deteriorating.

But there are still reports to come - so if you participated in this trial please get your reports in as soon as possible. The hard-working team in the Trials Office (not to mention Thompson & Morgan who generously donated the seeds) have put a lot into this - and you've put a lot into growing and assessing the crop. So please don't fall at the last hurdle, get those reports sent in. the more reports we have, the better picture we can create of how these two varieties performed across the country.

Early favourites in the veg trials

Graham Rice — Fri, 14 Aug 2009 14:03:00 GMT

Lots going on amongst the vegetable trials at the moment.

The all-female cucumber trial is being grown in a polythene tunnel in the way that most keen home veg gardeners will grow them. This is not a sophisticated commercial poly tunnel with heat for chilly early summer night, and fans to keep the air moving and sides which roll up for ventilation. If you need some air, open the doors! So this is a good test of which varieties will suit home gardeners and there are some early leaders.

For flavour, ‘Byblos' (below), ‘Carmen', ‘Emilie', ‘Mini Munch', ‘Naomi', ‘Socrates' and ‘Tyria' stood out. For productivity ‘Cucino' (above) and ‘Mini Munch' got special mention from the assessors, while ‘Tiffany' was appreciated for its even shape. All these were thought to be a cut above the others amongst the twenty two varieties in the trial.