Perennials

Everlasting pea: an undervalued garden climber

Lathyrus latifolius 'Rosa Perle', as grown at East lambrook Manor in Somerset many years ago. Image © GardenPhotos.comSometimes, people ignore plants simply because they're common. We see them all the time, even growing by the side of the road, and they sink into our subconscious and simply fail to emerge.

What is sometimes called the perennial sweet pea, or everlasting pea, is a case in point. Lathyrus latifolius is easy to grow, we see patches thriving along sunny roadsides in Britain and in North America, and in gardens it may annoy us as it can be uncomfortably vigorous. But it’s very colourful, very productive, clings to fences or shrubs with its tendrils and is a splendid long lasting cut flower. If it were scented there’d be hundreds of varieties.

It’s been used to control erosion in North America, and its ability to prevent the germination and development of shrubs has led to its planting along utility lines to ensure access remains unblocked by shrubby growth. A variety has even been developed, ‘Lancer’, specifically for practical use. It grows more upright than others, has superior seedling vigor, is a good seed producer and also has a better blend of colours than other mixtures.

In a few parts of the US it’s seen as a noxious weed but, on the other hand, the United States Department of Agriculture provides detailed instructions on how best to sow it and grow it when using it for erosion control etc.

In gardens it can be quite a spectacle, and is lovely clinging to a rustic fence or to a robust old shrub rose (right, click to enlarge). Lathyrus latifolius 'Blushing Bride' with the rose 'Suffolk', also known as 'Bassino'. Image © GardenPhotos.comThere are three basic color forms – magenta, pale pink and white – but, in his book on sweet peas, Roger Parsons lists ten varieties (plus a number of synonyms) although the names are not now applied with much care or precision, especially with regard to flower size. But look for ‘Blushing Bride’ (blushed white), ‘Rosa Perle’ (pink, above - click to enlarge), ‘Red Pearl’ (magenta) and ‘White Pearl’ (white). And if you come across ‘Wendy’s Joy’, with mauve flowers, grow it and pass it round – although dividing the root is the only way to be sure it stays true.

Lathyrus latifolius also makes a long lasting cut flower, with up to a dozen flowers on a spike, and is valuable in itself and also to fill out bunches of scented sweet peas. The challenge is to control the vigor of the beast and encourage it to produce long stems. Training the stems on wires does the trick and tends to create long straight flower stems which are easy to reach for picking.

So next time you notice Lathyrus latifolius flowering by the side of the road (as in Suffolk in eastern England, below, click to enlarge) remember what a fine garden plant it is and look out for the best varieties.

Lathyrus latifolius growing by the roadside in Suffolk, England. Image © GardenPhotos.com



Intriguing recent plant discoveries

Asclepias tuberosus (butterfly weed) with golden leaves. Image ©GardenPhotos.comMaking the hour’s drive back and forth to my cardiac rehab three times a week, and often walking woodland trails on the other days, I’ve spotted some interesting plants along the way.

A couple of years ago I wrote about a yellow-leaved form of common milkweed, Asclepias syriaca, which I spotted growing by the side of the road and last week in a quiet area at the back of the radiology unit (yes, I was just poking around…)  I found a yellow-leaved plant of a different Asclepias species – A. tuberosa, butterfly weed. As you can see (left, click to enlarge) it looks very dramatic and doing very nicely amongst the crown vetch (Coronilla varia).

There were also normal green-leaved plants scattered about the area, which had clearly been disturbed during construction work so we’ll see if that coloring was the freak result of something nasty in the soil or a genuine mutation. I’ll stop back later in the summer for another look.

A white-flowered form of wild bergamot, Monarda fistulosa. Image ©GardenPhotos.comWhite flowered monarda

Just at the moment our local wild bergamot, Monarda fistulosa, is in full flower. This seems to be a “first respondent” if you like, one of those plants that quickly arrives in freshly disturbed soil on open sunny sites. It occurs as a few plants or in huge drifts which, when you look closely, include an occasional plant with darker, or paler flowers.

But this week I screeched to a halt as I spotted a plant - just one - with white flowers (abiove right, click to enlarge). It turned out not to be the white flowered species M. clinopodia (which has a few purple spots on the flowers), but a genuine white-flowered form of M. fistulosa (wild bergamot). There were only a few plants in that location, but I’ve marked it and will collect some seed later.

UPDATE That was a few days ago - and yesterday I found another one, twenty miles farther south. I've been all these years and never seen one white one, and now I come across two.

An Asian bush honeysuckle with attractive amber berries. Image ©GardenPhotos.comAsian bush honeysuckles

I’d never stopped to look closely at all the shrubby honeysuckles along the roadside (please forgive my severe dereliction of botanical duty), they’re growing along a stretch of road where it’s not safe to stop the car. But they’re quite a sight in May when covered in white or cream or pink or red flowers, and again now when they’re in fruit.

Then in a parking area the other day I spotted a plant with lovely amber orange berries (left, click to enlarge). Frankly, I’m not sure if it’s Lonicera maackii, L. morrowii, L. tatarica, or L. x bella (the hybrid between L. morrowii and L. tatarica)  – all of which are collectively known as Asian Bush Honeysuckle; I’ll have to make more of an effort to check them when they flower next year. But, although I know they’re all rated as invasive, they’re very attractive especially those with brilliant scarlet berries (rather than a dull and dirty red) and this pretty amber berried form.

Variegated oak

And finally, on the way up the hill to the ledge from which I shot this wonderful picture of a field of Black-eyed Susans (Rudbeckia hirta) – a variegated oak seedling (below, click to enlarge). I think this may be the only one I’ve ever seen outside a botanic garden, and here it is growing by a woodland trail in Pike County, Pennsylvania.

Variegated seedling of red oak, Quercus rubra. Image ©GardenPhotos.comIt’s a seedling of red oak, Quercus rubra, and a quick online search for variegated red oaks reveals only ‘Greg’s Variegated’ and one named as 'Foliis Variegatis' in the Journal of Arboriculture in October 1987. It’s growing very near the trail; I may have to move it to the garden in the fall.

The only other one I’ll mention here is the vanishing trumpet vine (Campsis radicans). There are occasional plants all the way along my drive, all with the usual orange flowers. But, last week, I spotted one cluster of purplish red flowers.

There was too much traffic to stop examine it but it turns out this is a known variation - ‘Atropurpurea’ – but very rarely seen. So rarely seen, in fact, that when I did stop a few days later – I couldn’t find it!


$20 makes for a pricy perennial

xHeucherella Copper Cascade: retailing at $19.95! Image ©GardenPhotos.com
I’d read about xHeucherella ‘Copper Cascade’ and it sounded wonderful. A small-leaved trailer or ground cover with rosy coppery gold leaves all the year round. It seemed ideal to cover the bare soil around the edge of one of our dark-leaved Physocarpus opulifolius ‘Mindia’ – known as Coppertina in North America and as Diable d’Or in Europe – with its amber shoot tips.

So when I spotted a ‘Copper Cascade’ in a nursery on my way back from cardiac rehab a few weeks back – I immediately put it in the cart. But I should have looked more carefully. OK, it was in an 8in pot, but when I got to the checkout I discovered, to my shock, that the price of this one plant was – $19.99! (plus sales tax). Twenty bucks! I’m glad my creaky heart could take the shock. For Brits that’s £11.73.

Now, over the years, I’ve more than once said here that plants are too cheap but twenty dollars for one Heucherella is just too much. I’m not sure how much the White Flower Farm branding has upped the price - they have to take their cut, after all – but don’t you think that price is a bit steep?

White Flower Farm are not offering ‘Copper Cascade’ on their website, but the related ‘Redstone Falls’ sells for $19.45 (plus $9.95 shipping) (£17.14) in a 3in pot which is even less of a bargain. Almost thirty dollars for one heucherella in a 3in pot…! Come on, be reasonable…
xHeucherella 'Copper Cascade' - you can see why I was tempted. Image ©Terra Nova Nurseries


Multicolored newcomers

HibiscusSummerificCherryCheesecake-700Every year the good people at Proven Winners send us some new plants to try. This year’s parcel arrived recently and there are two plants that look especially tempting so I thought I’d mention them straight away – before they’re even planted (torrents of rain today).

Hibiscus ‘Cherry Cheesecake’ (left, click to enlarge), in their Summerific® Series, is nothing if not dramatic, and gorgeously colorful. It’s a hardy perennial hibiscus with flowers 7-8in/20cm across set against dark green maple-like foliage on plants about 4-5ft/1.4-1.5m high. And it blooms all the way up the stems, not just at the tips.

It's tough, too; a few years ago I saw the field in Michigan where breeders Walters Gardens test all the their new seedlings; it’s cold, plants are hardy to zone 4/-34C. For British gardeners it’s more the summer that’s the problem: is it hot enough for these plants? Well, we’ll soon see as a British grower has been testing the whole Summerific® Series and if they thrive we’ll see all four varieties in nurseries in a year or two. In North America, you can order Hibiscus ‘Cherry Cheesecake’ from the Vermont Wildflower Farm.

The other plant that caught my attention amongst this year’s Proven Winners samples is Calibrachoa Superbells® ‘Frostfire’ (below, click to enlarge). There have been some gorgeous multicolored calibrachoas introduced in recent years, I especially like Superbells® ‘Lemon Slice’, which was such a success last year, and also Superbells® ‘Tangerine Punch’. In ‘Frostfire’ the white flowers have a yellow throat streaked in red. Unique – but not available until next year.

These newcomers have something in common: the flowers are multicolored, white and cherry red, or white and yellow and red. This gives you a clue as to what to grow with them. Choose plants with white or red flowers alongside the hibiscus, and plants with white yellow or fiery red flowers in a basket with the calibrachoa. That’s the way to create a harmonious look.
CalibrachoaSuperbellsFrostfire-700



Virginia bluebells in blue - and pink

Mertensia virginica growing on a streamside in PA. Image ©GardenPhotos.com
Driving close to where I spotted those naturalized snowdrops I mentioned here a few weeks ago – on my way back from my first session of cardiac rehab – I stopped for another look and found that the snowdrops, of course, were being overwhelmed by other vegetation including a star of our spring flora here in Pennsylvania – Virginia bluebell, Mertensia virginica (above, click to enlarge).

I haven’t come across lovely perennial this too often in this area but here it was growing in damp soil near a seasonal stream (dry at the moment). There were mature clumps, small plants and young non-flowering plants so it seems to be doing well.

Then, when I got home and was looking round the garden, I found that one of our clumps of the same plant A pink flowered shoot on a plant of Mertensia virginica in the garden. Image ©GardenPhotos.comhad produced two shoots with pink flowers (left, click to enlarge). Even on the usual blue-flowered plants the buds are pink, but soon mature to blue as they open. On these two shoots the flowers remained pink, though they seemed a little smaller than the nearby blue flowers.

White flowered forms with pale green leaves are also known, as well as plants with very pale blue flowers, and years ago I also saw plants with smoky bluish-purple purple flowers. They were all lovely. As soon as the clump sporting both pink and flowered shoots dies down in summer, I’ll lift it and split it to isolate the pinks. Not I just need to get my hands on the white one and the smoky one and the pale blue one…

There’s a fascinating chapter on these plants in Carol Gracie’s superb book Spring Wildflowers Of The Northeast.


Hellebore surprise in the Pennsylvania woods

Green hellebore, Helleborus occidentalis, in the Pennsylvania woods. Image ©GardenPhotos.com)
Out walking in the woods again yesterday, and I found ten clumps of hellebores! They look to me like a form of green hellebore, Helleborus occidentalis, with unusually large flowers; there was one very prolific clump (above, click to enlarge) and the rest were smaller, with some clumps too small to be flowering. All were scattered across an open east facing bank. Now hellebores are not native to North America – so what were they doing there? A couple of miles from the nearest house.

Actually, it was pretty obvious. The bank was at the edge of an unusually flat area; other non-natives were around including dense thickets of forsythia (below, click to enlarge - usually a sign of an old homestead), broad patches of Japanese pachysandra (Pachysandra terminalis) and bugle (Ajuga reptans), and three individual grape hyacinth (Muscari botryoides) bulbs with a single spike of flowers on each.

I’d say it was the site of an old homestead and this was confirmed by the fact that the whole area was relatively open compared with the surrounding forest. There was also what seemed to be the remains of a stone built water cistern, sunk in the ground and partially overgrown. And the trail along which I’d been walking when I spotted the hellebore clumps in the distance turned out to be a paved road that had been closed and become overgrown.

So, even though there was no sign of tumbledown walls, at some point in the past there must have been a house there and either the timber construction had simply rotted away or it been removed to be used again elsewhere. Helleborus occidentalis has a number of medicinal uses so it’s not surprising to see it on such a site.

Still – flourishing hellebores growing in the Pennsylvania woods 3000 miles from their native home in western Europe (including Britain) was quite a sight to see. Of course there are some people who’d have them ripped out as “invasive aliens” – see my recent piece on snowdrops. So I’m not going to say exactly where they are!
Forsythia growing in the woods is usually a sign of an old homestead. Image ©GardenPhotos.com



Woodland native that's good in the garden

Anemonella thalictroides growing in an unexpectedly damp place. Image ©GardenPhotos.com
Off out for my daily, cardiologist prescribed walk in the Pennsylvania woods yesterday, I came across two plants - uneaten by the deer that abound in this area – that while interesting to see in the woods are also good to grow in the garden.

The rue anemone, Anemonella thalictroides, is a lovely spring ephemeral, and a familiar native here in eastern North America where it’s often known as Thalictrum thalictroides - literally, the thalictrum that looks like a thalictrum. Surely that must mean that it’s an absolutely typical Thalictrum and meaning, I suppose, that all the other thalictrums are very definitely different.

Well, long ago that was the opinion. But in Europe and the rest of the world it’s now known as Anemonella thalictroides – in fact it’s considered so different from other thalictrums that it deserves a genus all of its own! This is a case of botanical science moving on and gardeners and botanists around the world taking their time to catch up.

Anyway, I was surprised to see it growing in soggy saturated soil by the side of a small stream as in these parts it’s usually seen in much drier conditions, such as trailside banks and rain-sheltered slopes.

You can see the wild plants I came across yesterday at the top (click to enlarge) but it’s true to say that their flowering season is very short – ephemeral indeed, so less useful in gardens. But like so many plants in the buttercup family - delphiniums, hellebores etc – there are many variants of Anemonella thalictroides and the double flowered forms make far better garden plants that the wild form as they bloom for so much longer.

‘Oscar Schoaf’ (below, click to enlarge) is a good example: not only are its flowers a rich pink, unlike the white or blush shade of wild forms, but they’re fully double so have more impact and last far longer than single forms. The problem is that plants are hard to come by, and they can be expensive. Propagation is by division - by scalpel!

Anemonella 'Schoaf's-Double' blooms for longer than the wild species. Image ©GardenPhotos.com

Oh. I seem to have run out of time for discussing the other US native perennial that was such a standout – next time.





Powerhouse Plant For All Seasons: Cyclamen coum

Cyclamen coum 'Maurice Dryden'. Image ©GardenPhotos.comTime for a look at another Powerhouse Plant, these are Plants For All Seasons - individual varieties which bring colour and interest to the garden for at least two seasons of the year. I feature over five hundred of them in my latest book, Powerhouse Plants, and every month in Gardeners' 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 of a single variety that bring color to the garden at different times of the year. This month, in the magazine, I feature Spiraea ‘Goldflame’ and next month it’s the lovely but long-winded Polygonatum odoratum var. pluriflorum ‘Variegatum’.

And every month or two, here on my Transatlantic Gardener blog, I bring you details of another Powerhouse Plant this month it’s Cyclamen coum (left, click to enlarge).

This unexpectedly tough little plant from Turkey and the Caucasus (hardy to z5, -29C) has two special features. First there are the small, neat, rounded, rather leathery leaves. These can be beautifully silvered, with or without a green edge, but in some cases are a rather dull uniform green – of course, choose the former. They emerge in the autumn and are followed in winter and spring (depending on the climate) by flowers made up of five reflexed petals held above the leaves on individual stems; in some cases, the flowers are attractively scented.

The flowers come in a range of colors from pure white through various pink shades to magenta and including some lovely bicolors like this one (above, click to enlarge) which is ‘Maurice Dryden’ whose pinkish red stems are another highlight.

So, with its long season of silvered foliage partially overlapping with its small colorful flowers, this is an easy and reliable little plant for a shady or partially shaded site and preferably in rich but well-drained soil. In fact this one of the easiest of all garden cyclamen and usually self sows once established. It’s lovely under hellebores with wild crocus such as C. tommasinianus.

There many varieties of Cyclamen coum, and they all set out in Chris Grey-Wilson’s excellent book Cyclamen: A Guide for Gardeners, Horticulturalists and Botanists (available in the UK and also in the US). Varieties to look out for include ‘Maurice Dryden’ (above) and ‘Silver Leaf’ although some nurseries sell them under descriptive names such as “Silver/Pewter Leaves, White Flowers”.

In North America you can order Cyclamen coum from Edgewood Gardens and in Britain you can order Cyclamen coum from Potterton’s Nursery.

North American readers can find out more about Powerhouse Plants here.

British readers can find out more about Powerhouse Plants here.


New begonias - foliage varieties

Begonia Garden Angel Series. Images ©TerraNova NurseriesThere are about nine hundred species of begonias, so it’s hardly surprising that they’re so important to gardeners. And on both sides of the Atlantic new begonias are arriving fast. In the States, it’s mainly foliage types to grow outside in containers, or even as hardy perennials; in Britain it’s flowering varieties for containers, many with blood from B. boliviensis, that are making an impact.

I think that each country should grow more of what the other is already growing. So, today, I’m going to have a quick look at the new foliage types and next time I’ll feature the new flowering types.

So new styles of foliage begonias for use in patio pots and the open garden have been pouring out of Terra Nova Nurseries in Oregon, the world’s leading developer of new perennials. [Terra Nova don’t do retail, ever, so please don’t ask.]

Terra Nova started by identifying a few existing foliage begonias and bringing them to a wider audience. The first was ‘Bentichoba’, a hybrid from Japan originally introduced in 1973, with silver and green leaves, tinted pink when young. This is actually turning out to be unexpectedly tough and is reckoned to be hardy outside in most of Britain (zone 8), dying down in the autumn like other perennials.

They began breeding their own and the interspecific hybrid ‘Metallic Mist’ was their first, with bold dark-veined silvery leaves. It’s thought to be even hardier than ‘Bentichoba’.

Then last year they launched a host of new foliage begonias which will be getting around North America this year and in Britain in a year or two. There are four series: the Garden Angel Series, Shade Angel Series, T Rex Series and the Cool Breeze Series.

The three in the Garden Angel Series (above, click to enlarge) are said to be hardy down to zone 7 (-18C/0F) and look as if they’re derived from ‘Bentichoba’. They’re big, making plants 2ft/60cm high and wide with large maple-like leaves in various combinations of silver, green tones, pink and purple. So, they should make dramatic hardy perennials in many areas.

The first in the Shade Angel Series, ‘Aurora’, is described as having “iridescent foliage in aquamarine, lavender, raspberry pink and cream overlaid with mother-of-pearl”. It’s quite something and would be excellent as a container specimen. Their T Rex series includes three more compact varieties in vivid colors and patterns that are again designed for summer containers outside.
Begonia Cool Breeze Series. Images ©TerraNova Nurseries
Finally, there’s the Cool Breeze Series (above, click to enlarge) in four foliage colors, including the silver leaved ‘Cool Breeze Rouge’ that develops pink tints in summer a little like a Caladium. These are for summer containers and will keep going well into autumn, not being damaged till the temperature is down to 38F/3C.

But I must also mention a seed-raised foliage begonia for summer containers that’s nothing to do with Begonia 'Gryphon' Image ©ProvenWinners.comTerra Nova.

Launched in 2011, ‘Gryphon’ (right, click to enlarge) makes a plant about 16in/40cm high and wide covered in large, jagged, dark glossy green leaves patterned in silver. Superb.

All these begonias should be available this season in North America. ‘Bentichoba’, ‘Metallic Mist’ and ‘Gryphon’ are already available in Britain, these startling newcomers from TerraNova should follow soon.

For more detail on all Terra Nova’s begonias, past and present, take a look at the begonia page on their website.


Powerhouse Plants For All Seasons: Tiarella 'Mystic Mist'

Foliage of Tiarella 'Mystic Mist' - a Powerhouse Perennial For All Seasons. Images ©GardenPhotos.com
We’re past due for a look at another Powerhouse Plant, these are Plants For All Seasons - individual varieties which provide color and interest for at least two seasons of the year and not just a fleeting flush of flowers followed by months of not-very-much. I feature over five hundred of them in my latest book, Powerhouse Plants, and every month in Gardeners' 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, in the magazine, I feature Cornus ‘Midwinter Fire, next month it’s Mahonia ‘Charity’.

And every month or so, here on my Transatlantic Gardener blog, I bring you details of another Powerhouse Plant this month it’s Tiarella ‘Mystic Mist’ (above, click to enlarge).

Today, here in Pennsylvania, we’re snowbound but yesterday the rich red tints of Tiarella ‘Mystic Mist’ caught the eye in a shady corner by the front door, under the spiny, bluish green leaves of the hybrid holly, Ilex x meservae.

Flowers of Tiarella 'Mystic Mist' - a Powerhouse Perennial For All Seasons. Image ©GardenPhotos.comThis is its winter livery, but this plant seems to be in an almost imperceptible but constant state of change. For in summer, its bright leaves are densely dusted in silver speckles, with a rather variable red flash in its central veins. In winter the red and purplish tones are more dominant. In spring, short spikes of fluffy white flowers, opening from pink buds, add a third dimension (left, click to enlarge).

There have been speckled forms before, but ‘Mystic Mist’ is more vigorous and more robust in the garden. It spreads well, although it’s better in soil with good drainage. It throives with us tucked bteween the holly and a rhododenendron.

There’s just one problem. In Britain ‘Mystic Mist’ is available from Heucheraholics and from Plantagogo. But, in North America, its creator has withdrawn it. You may still find it in retail nurseries, but I couldn’t find anyone selling it online. That’s a shame. Let’s hope it’s back soon.

North American readers can find out more about Powerhouse Plants here.

British readers can find out more about Powerhouse Plants here.

And you why not take a look at some more fine Powerhouse Plants, Plants For All Seasons, here on my Transatlantic Gardener blog.