Transatlantic Plantsman

My new blog on new plants

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

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’ – 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

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.

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

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.

Flower pouches

I’ve always been a bit suspicious of flower pouches. These are the green bags that you hang on a fence or wall and plant up with trailing plants through the holes. Like a vertical hanging basket – sort of.

But on this week’s first visit to the trial grounds and display garden at Thompson and Morgan, near Ipswich in the east of England, I have to say I was impressed. In the picture you can see the variety of plants that do well: petunias, verbenas, even lavenders, and the superb new trailing viola ‘Friolina’. T&M are trying all sorts of plants in Flower Pouches, and their trials and display gardens demonstrate how well so many do. And they'll fit into the tiniest garden.

The key to success is watering and feeding. For anyone with more than the occasional pot on the patio, installing watering where you just turn on the tap and the water drips into each and every pot – or each flower pouch – is essential. And it’s never allowing flower pouches to dry out that ensures they look so good.

You can buy flower pouches in the UK here

You can buy flower pouches in the US here

Phlox and achilleas on trial

Visiting trials where potential new introductions are being assessed alongside those which are already on the market is always fascinating and my recent visit to Amish Country in southern PA to see the trials shared by Yoder and the US operation of Blooms of Bressingham revealed plenty of exciting potential new introductions.

There’s been a resurgence of Phlox paniculata breeding recently, with the aim of reducing the height and making the plants generally more manageable – for nursery and gardener. Mildew resistance is also an aim along, of course, with impressive color. And perhaps the most colorful part of the whole trial was the comparison of the existing Junior Series and Volcano Series phlox with a new range.

Lettuce – the new dahlia!

You’d never think lettuce could be so colourful. But down on the trials field at the Royal Horticultural Society’s garden at Wisley in Surrey, 49 different cos lettuces are being grown side by side and some of them are as colourful as dahlias.

The whole trial makes a very attractive display. Beautifully grown, as ever, by the Wisley trials team the fresh bright green of those varieties in the more familiar style sets off those with red, bronze, copper or speckled leaves beautifully. Many will more than hold their own in the border with summer flowers.

Top choices? Well, at this stage ‘Freckles’, with fresh green leaves speckled in red freckles, looks very pretty while for more vivid colour the rich red ‘Rosemoor’ looks outstanding. It’s just about the same colour as the dahlia in the bouquet a friend brought to our party last week.

You can find out more about this trial here.

New plants on trial: Perennials round up

Finally, in this survey of plants I’ve had on trial there are just a couple more of perennials I wanted to mention.

Hellebores were a little disappointing. ‘Ivory Prince’, which I’ve had for a few years, makes an excellent foliage plant but its flower buds can’t seem to get through the winter. The same applied to most of the new introductions from Germany, the Immanence Series, I received these in large pots of peat-based compost and I think they simply remained too wet in winter and spring. Those that did flower, and other hellebores from various sources, were mainly encouraging this spring rather than exciting, with 'Double Integrity' perhaps the most promising of all – but they’ll all be better next year.

New plants on trial: echainaceas and coreopsis

I’m growing quite a collection of echinaceas, including most of the new hybrids in orange and mango shades, as I’m researching them for some magazine articles and a book. I also grew many of the new coreopsis last year and even after just one season the results are interesting.

I was nervous about the echinaceas. Most are planted in the one bed, the easier to compare one with another, and it’s a little more shaded and a little more damp than I would have liked; they’re always said to prefer plenty of sun and good drainage. However, the vast majority seem to have come through the winter very well and are growing away nicely although three did not make it through till spring: the variegated ‘Sparkler’; ‘Paranoia’, the first of the hybrids between the purple E. purpurea and the yellow E. paradoxa; and the dwarf ‘Pixie Meadowbrite’.

New plants on trial: Heuchera, Tiarella and xHeucherella

Every year new heucheras, tiarellas and heucherellas appear, often quite a few – mainly from TerraNova Nurseries in Oregon and also from The Primrose Path here in Pennsylvania but also from Europe. They’re amongst the most varied and colorful of foliage plants and I had a number of newcomers, mainly from TerraNova, on trial this last year.

One of the factors that struck me about them was how much, or in some cases how little, the leaves from last year contribute to this spring’s display. Two stood out as really excellent plants.