Climbers/Vines

Ivy: Friend or Foe?

Hederacolchica'Dentata Variegata'-26704

Ivy is a plant that divides opinions. Attractive foliage, good for wildlife, cools buildings… Invasive, ruins walls, harbours pests…. Research and opinion on all these issues has been in the news increasingly in recent years and now the most comprehensive book on ivies ever produced has been published by The Royal Horticultural Society.

Hedera: The Complete Guide by Hugh McAllister and Rosalyn Marshall is exactly that – the complete guide. With more than four hundred pages, and impressively illustrated in colour throughout, this is the second in the RHS Horticultural Monograph series which began with last year’s excellent book on kniphofias.

This is an attractively designed book – far more appealing than most gardeners expect from a serious plant monograph even though the predominant colour of ivies is, well, green. All the species are described in detail, but not in torrents of baffling technical language; two hundred cultivars are illustrated and described, and the fat descriptive checklist covers all the other names that have ever been used, over two thousand of them.

One very useful feature of the book is its use of the Pierot system of classification. This was created by Suzanne Pierot, the first President of the American Ivy Society, in the 1970s and divides ivies into nine convenient groups based on easily-seen features of the foliage. Brits are largely unfamiliar with this approach so its use in this book should help it stick.

HederaBookCover9781907057731But what does the book have to say about those pros and cons?
Attractive foliage? Obviously.
Good for wildlife? Yes. “Ivy berries are eaten by at least 17 species of bird in Britain indicating the importance of this plant group for the support of vertebrate wildlife…. They have a high energy, though low protein, content and form a large part of the diet of several species at this time of year (winter).” “The autumn flowering of ivy provides nectar for a wide range of invertebrates at a lean time of year.” Not to mention ivy as a valuable nest site.
Cools buildings in summer, warms buildings in winter? Yes. “Measurements on ivy-covered stone walls across several historic sites in England… showed that an ivy covering resulted in cooler walls in summer and warmer walls in winter.” “Recent research on the climate of southeast UK… suggests that a 21-37% reduction in winter heating could be achieved.”

Invasive? Sometimes. While most ivies can develop vigorous growth in their native habitats, it is almost always H. hibernica that causes problems as a non-native plant. “All ivies need not be banned in climates where invasive ivies are a problem. There are enough dwarf, miniature and slow-growing cultivars of H. helix to provide a good range of safe and attractive plants for indoor and outdoor use.” In my Pennsylvania garden, as soon as an ivy shoot penetrates the deer fence the deer eat it.

Damages walls? Sometimes. “Any increase in relative humidity due to wall plant cover is offset by lack of rain reaching the building.” But: “ivy can root into weakened historic walls or buildings, and can lift blocks of stone off walls” and also damage walls built and pointed using soft mortar.

Harbours pests? Sometimes. Ivy is attacked by viburnum scale which also attacks Viburnum tinus. “In pots, by far the most serious pest of ivy is vine weevil” – which attacks a wider range of other plants. I’d be interested to know if outdoor ivy has a role as a reservoir of vine weevil infestation.

This is an impressive book by one of our most seasoned horticultural taxonomists and a relatively young recruit to the RHS botany team. The RHS has more in the series on the way, I look forward to the series building into an invaluable resource.

Hedera: The Complete Guide by Hugh McAllister and Rosalyn Marshall is published by the Royal Horticultural Society at £40.00/$53.45.

You can read more about ivies in gardens and in the wild in these Transatlantic Gardener posts.
Ivy is not always a menace
Ivy reveals how nature is nuanced
Ivy goes green

 

 

                         

The fruits of the autumn hedgerow

Black bryony, Tamus communis, in a Northamptonshire hedgerow. Image © GardenPhotos.comI’ve been trying to get out for a good walk every day - weather permitting - since I’ve been here in Britain and since a few chilly nights brought the last of the fall foliage to the ground the hedgerows are revealed as dripping with fruits.

Two plants stand out, their vivid red fruits shining brightly in the low late autumn sun.

There are two unrelated forms of bryony and the one with the crowded clusters of scarlet fruits now at their peak in the British hedgerow is known, perversely, as Black Bryony, Tamus communis (left, click to enlarge). Closely related to the yams of the tropics, this is a vigorous twining plant, snaking its way through woody hedge plants. As well as its scarlet berries it has fat tuberous roots, deeply ribbed triangular leaves, small green and white flowers – with male and female plants on different plants… And every part of the plant is poisonous.

It’s sometimes used as poultice to treat internal injuries but, frankly, it’s best just to admire it from a distance. Gardeners around the world can order Black Bryony seeds from Plant World Seeds.

The other plant that stands out is the dog rose, Rosa canina (below, click to enlarge), a much more substantial, even imposing, feature of the hedgerow with clusters of red hips which are a little less shiny than the black bryony berries so that they gleam in the sun but look more dull in the shade.

Mind you… I say dog rose, Rosa canina… But these hedgerow roses come in a confusing number of micro species, about thirty very similar but slightly different species some of which have five or even six times as many pairs of chromosomes as usual. They also have a slightly quirky form of reproduction known as permanent odd polyploidy – but you and I can both be delighted that I’m not going to try and explain it.

But what I can do is remind you that rose hips can contain as much fifty (yes, FIFTY) times as much Vitamin C as oranges! So those hedgerow rose hips can bring you a genuine health benefit. There’s more about Vitamin C in the hedgerows in a post from September last year. Gardeners around the world can also order seeds of Rosa canina from Plant World Seeds.

The final fruity feature of the Northamptonshire hedgerows along which I’ve been walking these last few days has been the sloes, Prunus spinosa. These are like small plums in both their appearance and their botanical connections – but not in taste. “Tart” is hardly the word but sloes make a fantastic flavored gin, as I discussed here back in 2007.

One other thing I’ve noticed these last few days is that the birds haven't got stuck in to all these fruits yet. But this looks like an exceptionally good year for hips and berries and other fruits, all of which will help so many birds, and small mammals, through the winter ahead – however tough it turns out to be.

Dog rose, Rosa canina, in a Northamptonshire hedgerow. Image ©GardenPhotos.com


Classic tree and shrub reference goes online

Bean's Trees and Shrubs Online.The five volume Trees and Shrubs Hardy in the British Isles by W. J. Bean, usually referred to simply as “Bean”, is a monumental work running to over 4,000 pages. It does what it says: it describes in detail the woody plants (including climbers) that can reasonably be expected to grow outside in Britain (mostly zone 8, some zone 9).

The four A-Z volumes were last revised almost forty years ago, then a supplement appeared in 1988 (see below, click to enlarge), so it does not include recent classification and name changes and recent introductions. Otherwise, it's impressively comprehensive with good descriptions and boundless information on origins and differences between similar plants. It’s invaluable.

Now you can read it - free.

In the first part of a two part initiative, the International Dendrology Society has published the whole thing – all 4,027 pages of it – online. And it’s free: no charge for access. The original four A-Z volumes plus the supplement are currently priced on abebooks.com at £325/$504. Did I mention that the online version is free?

The new online version is easy to navigate and attractively presented. The next step is adding pictures.

You can read more about it on the excellent blog post by John Grimshaw, who’s been heavily involved with the project - and I see he’s had the same idea of including an image of his five volume set as I did!

Take a look at Bean's Trees and Shrubs online - it's invaluable, and it's free.

The five volumes of Bean's Trees and Shrubs. Image ©GardenPhotos.com

And what's coming next? Britain's Alpine Garden Society is well into the process of making its invaluable two volume Encyclopaedia Of Alpines available online. It's currently available from abebooks.com for £150/$250.74. You can track the progress of the operation here.


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



Rampageous wisteria in the Pennslyvania woods

Wisteria floribunda smothering the Pennsylvania woods. Image ©GardenPhotos.comInvasive plants keep turning up on these pages, and often I’m less than supportive of the way the plant police want to rip out any non-native plants that turn up in wild places – as with the snowdrops I wrote about last month - whether or not they’re doing any harm.

Well, here’s one that we can justifiably worry about.

I spotted the bluish purple flowers hanging from the branches as I drove between the woods and the Delaware River in Pennsylvania the other day. That's Wisteria, I thought. I was on a tight schedule and couldn't stop, so when I got home I checked with the Pennsylvania Flora Project website which told me that no wisterias, native or introduced, grow in the area. The USDA plants website said the same thing.

Yesterday I was again passing that way and took a closer look. Yes, it’s wisteria – but the Japanese Wisteria floribunda (below, click to enlarge) and not the uncommon Pennsylvania native W. frutescens which flowers later and has much shorter strings of flowers. And it’s not just a plant or two, there must be half a mile of it in half a dozen different places over a stretch of a few miles. It's covering the trees(above, click to enlarge).

This is in the Delaware Water Gap National Recreation Area, where you’d expect some expert oversight of These strings of flowers of the Japanese Wisteria are longer and earlier than those of the native species. Image ©GardenPhotos.comthe habitat that’s being preserved, and one stifling mass of it is by the turn to the Pocono Environmental Education Centre. So why do the distribution maps say that it doesn’t exist in the area? I presume that, like the hellebores I wrote about a few weeks ago, it originated on a now-vanished property. When it was planned to flood this valley to create a reservoir many houses were vacated and removed - but not the plants. But it’s clearly been there a long time, so it’s strange that no one noticed -or, at least, no one reported it.

Of course, it looks spectacular but it completely smothers and weighs down the trees. Clearly anything growing on that scale – 30 to 40ft high, and more, through trees – must be doing some damage. I wonder if anyone has published any before-and-after wisteria research.


Best new plant of the year: Pink Trumpet Vine

Podranea ricasoliana ‘Pink Delight’. Image ©GardenPhotos.comGuest post from judywhite

This year the clear best new plant of the year winner is something we’d never even heard of before. At my favorite local garden center, Fair Acres Farms in Sussex County, NJ , there are always interesting and tempting unfamiliar plants amid the wonderful collection of more recognizable varieties. As the owner, Richard Kaweske, says, “If I can’t try something totally new every year, what’s the point of gardening!” He had brought in plants of Podranea ricasoliana ‘Pink Delight’ (aka Pandorea*) (left, click to enlarge) which he’d never seen or grown before either, but had heard great reports of the big pink trumpet-like flowers. So I bought one. A bargain at about $8. That was early May.

It was about 8in/20cm high at the time, and I planted it in an old cement urn in mostly sun, not realizing that this tropical South African plant was actually a tall, vigorous, rambling shrubby vine with strong long woody stems that arch all over the place. Despite its tight pot (or maybe because of it; Podranea apparently does best well-drained, which the cement planter definitely was), it immediately began to romp away, with beautiful glossy green compound foliage on gracefully open weeping branches. By early June the first of the spectacular candy-pink 3.5in/9cm flowers appeared, and I was hooked for life.

The papery flower buds appear at the very ends of the branches, and stay in bud a long time before the big pink trumpets start opening, which they do sequentially, then stay in bloom an even longer time. They’re supposed to be fragrant, but I never did discern any scent. Didn’t matter in the least.

Each of our branches eventually reached 10ft (3m) or so, and arched all over another wonderful vine, the variegated Ampelopsis brevipedunculata var. maximowiczii 'Elegans' (below, click to enlarge).

Flower color deepens as the weather gets colder. We left it outside until the temperatures dropped to about 36F/2C, which it tolerated fine, flowers and all, then dug it out of the planter, stuck it in a bigger plastic pot and brought it inside to drape all over the hot tub solarium. It’s still solidly in bloom, and didn’t seem to mind all the ruckus. Advice says to prune it back hard after flowering. Next year I think I’ll train it up a trellis against the house.

* In a strange twist, this plant has been known by two names - one of which is an anagram of the other: Podranea (the correct name) and Pandorea.

You can find more details of this fine plant on the Kirstenbosch National Botanical Garden website.
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You can order Podranea ricasoliana ‘Pink Delight’ in North America from Stokes Tropicals.

You can order Podranea ricasoliana ‘Pink Delight’ in Britain from these Royal Horticultural Society Plant Finder nurseries.
Podranea ricasoliana ‘Pink Delight’Ampelopsis brevipedunculata var. maximowiczii 'Elegans' and perennials. Image ©GardenPhotos.com



Four, long season foliage plants

Impatiens omeiana, Hosta 'Maui Buttercups' and Brunnera 'Silver Heart'. Image ©GardenPhotos.com
One of the first plants we bought for our Pennsylvania garden, years ago now, was a hardy Chinese Impatiens species called Impatiens omeiana. It's a hardy perennial related to the colorful Impatiens seen in containers around the world. As you can see (above, click to enlarge), in summer it features these beautifully marked leaves and now we’re seeing clusters of yellow flowers in the tips of the shoots (blow, click to enlarge).

We’re in US hardiness zone 5 (-29C/-20F) which is off the cold end of the scale of the new British hardiness ratings system launched earlier this year by the RHS. The winters certainly get chilly and occasionally our Chinese Impatiens has taken a hard knock. Some years, in spring, just a few spindly shoots emerge but by summer those few stems are looking luxuriant and the following year there’s again a fat clump. This year, we have a couple of interesting perennials underneath, Hosta ‘Maui Buttercups’ and Brunnera ‘Silver Heart’.

Hosta ‘Maui Buttercups’ is one of the best yellow-leaved hostas and it’s also small, not much more than 25cm/10in in height – it’s a classic “sunshine in a shady place” plant and its coloring connects with the stripe in the Impatiens leaf and with its yellow flowers. A cross between two old favorites, 'Frances Williams' and 'August Moon’, the off-white flowers are, frankly, a distraction; I’d snip them off. This is a plant that suffered in our vole infestation but is now thriving again.

Impatiens omeiana with foliage of Ampelopsis brevipedunculata var. aximowiczii 'Elegans'. Image ©GardenPhotos.comAlso tucked under there is the brand new Brunnera ‘Silver Heart’ which is a new improved form of ‘Looking Glass’ with very heavy duty foliage and a brighter silver sheen – it really gleams.

The foliage shape of both these perennials contrasts attractively with the slender Impatiens leaves, and all are happy shaded from the east, and from the west late in the day.

Farther back, the leaves of a climber in a different shape have made their way over from a pot a few feet away. It’s a climber that goes by a rather heavy-handed name – Ampelopsis brevipedunculata var. maximowiczii ‘Elegans’ (left, click to enlarge), or is sometimes known as the variegated porcelain vine. As well as these very pretty variegated leaves, clusters of porcelain blue berries mature in the fall. The green-leaved version of this plant is invasive in some parts of North America, but here this variegated form has never produced a seedling.

But these four plants have made an appealing plant picture for months – and they’re still going strong at the end of September.

North American gardeners
You can order Impatiens omeiana from Burpee
You can order Hosta ‘Maui Buttercups’ from The Hosta Farm
You can order Brunnera ‘Silver Heart’ from Romence Gardens
You can order Ampelopsis brevipedunculata var. maximowiczii ‘Elegans’ from Digging Dog Nursery (though it may be considered invasive in some parts of North America)

British gardeners
You can order Impatiens omeiana from these RHS PlantFinder nurseries
You can order Hosta ‘Maui Buttercups’ from Mickfield Hostas
You can order Brunnera ‘Silver Heart’ from Coblands Nurseries
You can order Ampelopsis brevipedunculata var. maximowiczii ‘Elegans’ from these RHS PlantFinder Nurseries
Impatiens omeiana in flower in September. Image ©GardenPhotos.com


Delightful transatlantic clematis – which may (or may not) be scented

Clematis 'Betty Corning'. Images ©GardenPhotos.com

Last year, we ordered some clematis from Donahue’s Greenhouse. Most have done well and one of the most appealing has been one of the less flamboyant varieties.

‘Betty Corning’ has scrambled up a black wire trellis, its two-tone, lavender-blue flowers dancing above the border perennials below. The combination of the coloring and shape of the flowers themselves, the elegance of their presentation on long stems and the neat foliage makes this a really lovely plant. Flowering began with a burst from late June, and is still continuing at a lesser intensity.

Each flower is like a lavender-blue bell split into four reflexed lobes with, on the inside, a paler stripe through the middle of each lobe. The first flowers did not set any seed, but it looks as if the more recent blooms may develop seed heads.

‘Betty Corning’ is an unusual hybrid between an American and a European clematis. The American native Clematis crispa, which grows across much of the southeastern United States and is known by the rather discouraging common name of Swamp Leather Flower is one parent. The other parent is Clematis viticella, from Southern Europe. It's sometimes listed under Clematis viticella, but it's definitely a hybrid.

The hybrid between the two was found in 1932 by Elizabeth Corning, wife of Erastus Corning II who was Mayor of Albany, NY for forty years from 1942.

But there’s an odd thing about this plant. The most comprehensive source of clematis info, Clematis On The Web, reports that plants of ‘Betty Corning’ in Britain are well known as sweetly scented, but plants grown in North America are not. The flowers on our plant have have a faint, sharp-sweet scent, but other American reports around the web mention the “sweet scent” or don't mention scent at all. More startling, perhaps, is the variety of colors seen in an image search; some are quite pink.

Anyway, scent or no, this is a lovely plant and much hardier than the origins of its parents might indicate.

In North America, Clematis ‘Betty Corning’ is available from Donahue’s Greenhouse (who don’t mention scent)
In Britain, Clematis ‘Betty Corning’ is available from Thorncroft Clematis (who say it has a “delicate scent”)

Buying clematis by mail order (US style)

Clematis plants from Donahue's Greenhouse. Image ©GardenPhotos.comNot long before I came over to England, I decided to order some clematis. We don’t have all that many and I thought it was high time we added some more. Local nurseries have a very limited selection, and they’re not cheap, so I looked at some mail order suppliers.

I wanted small plants – I prefer not to pay to ship big pots full of soil across the country; if I order smaller plants, much lighter in weight, I can have plants more for the money. OK, I know that what I’m actually paying for when I buy large plants is time, maturity. But they’ll probably have to be cut back to fit in the box anyway.

So, I had a look at some recommended mail order clematis suppliers. One nursery sells two year old plants at $22 each, with 20% minimum shipping: so five plants would cost $132 (£82). That seemed too much, I’d rather have smaller plants. Another mail order specialist I looked at does not give a shipping cost until they ship the plants – so you have no idea how much the shipping will actually be when you order. Two clematis nursery websites I looked at had searches that didn’t work properly.

So I asked Linda Beutler, a fellow Timber Press author who wrote Gardening with Clematis, for advice. And as well as some I’d already tried, she suggested Donahue’s Greenhouse. They don't immediately sound like a clematis nursery, but I’m glad she told me about them.

Donahue’s Greenhouse supply younger plants, in 31/2in pots, all at $10.50 each. Input your zip code and the shipping cost is calculated as you go along – it came to $12 for ten plants. So a grand total of $117.00 (£73). I thought that was great value. Another good thing I sported: Donahue’s Greenhouse absorb the royalty charge levied on some new varieties so both old and new cost the same.

The plants arrived in a USPS Priority Large Flat Rate Box (for UK readers: same charge whatever the weight). They were packed tight – the only way to be sure they don’t move about and damage each other in transit. Each plant was still in its pot, in a protective plastic sleeve, and each plant tied to a short cane. All were well rooted plants, damp but not wet. The soil was a little loose in a few, but they’d travelled over 1100 miles so it’s hardly surprising. They took two just days to get here.

Problems? Not really. They even emailed to ask if their proposed shipping date was OK. True, the website is a little old-fashioned and could do with a new look, but it functions perfectly well. They also need to improve their seaarch engine rankings, when I searched on "buy clematis" they were not in the first 300 results.

So. A day or two to let the plants recover, a little liquid feed for each one, and then into the garden. Some will be flowering later this year.


Ivy reveals how nature is nuanced

Ivy growing on a stone wall. Image ©GardenPhotos.com (all rights reserved)In North America, in spite of uncertainty about exactly which species is involved, ivy is widely condemned as an invasive plant that smothers natural vegetation. And it’s true, whether it’s Hedera helix or H. hibernica that’s causing the problem, ivy can be a menace in some areas although in much of the country it doesn’t grow at all and in other areas it remains well behaved.

But seeing this ivy on the wall of an English stone cottage (left, click to enlarge) reminded me that ivy can cause other problems even in Britain where it’s a valuable native plant popular with insects and birds and a widely popular ornamental climber for walls.

It has clearly once covered this limestone wall but has been cut off at the root and most of the growth removed. But it’s still growing, rooting into the mortar and renewing its hold. Looks like a job for Round Up, now, because the mortar traditionally used between the stones is relatively soft; when it’s pulled off, the mortar tends to come away too. Click he picture to enlarge it and you can see.

On modern walls built of hard bricks and hard mortar, a completely opposite problem can arise. In the picture below (click to enlarge), the bricks and mortar are so hard that the short aerial roots with which ivy stems grip their support have failed to take hold well. The weight of a rainstorm has pulled the ivy right off the wall.

These situations serve to remind us, on both sides of the Atlantic, that enthusiasm for a plant, and condemnation of it, are not simple black-and-white issues. Nature is nuanced, rarely is a simplistic view justified.
Ivy falling off a brick wall. Image ©GardenPhotos.com (all rights reserved)