Sometimes, 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). There 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.

Birds and plants seem to go together naturally. Birders usually seem to be interested in plants, while gardeners enjoy birds. In the US, there’s even a very popular magazine, Birds & Blooms, that combines the two enthusiasms. But not all bird books appeal to gardeners – they may be too focused or too esoteric – but this one is different.

Tweet Of The Day began as a BBC radio series, a one hundred second daily focus on an individual British bird starting each time with its song (the closest North American equivalent is the two minute BirdNote). The popularity of the series has led to this enticing book in which the bird song of the radio series is replaced by bold and captivating illustrations (click to enlarge). The result is an enjoyable month-by-month guide to birds by two of Britain’s most acclaimed naturalists and one of Britain’s premier wildlife artists.

All the familiar garden birds are included, along with many that we’ll see on our walks and drives around Britain. But rather than provide a detailed description of each one (there are plenty of illustrated field guides, after all) authors Brett Westwood and Stephen Moss concentrate on the birds’ habits, their song, and their jizz – what it’s like to see them and how they behave – all clearly derived from their own long day-to-day experience with the birds. And there’s a tempting sprinkling of intriguing stories as well: find out which bird stays in the air for eighteen months after it leaves its nest and check out the traditional way of cooking baby gannet!

Their style is relaxed, conversational almost, yet they pack in so much information without being heavy-handed about it.

And everything is enlivened by the full page, full colour illustrations from Carry Akroyd (click to enlarge), as well as dramatic endpapers, chapter openers and a neat one-shot black and white cameo of each bird.  Her colour work very effectively sets the birds in their landscape: the pheasant and brambling under an autumn oak, the kestrel hovering above a rural road, the kingfisher streaking over the stream, the grouse on the moor. She has the knack of making us feel familiar with a bird even if we’ve never actually seen it, and even the small black-and-whites give you a snapshot of how they behave.

While it’s the illustarions that first grab you, this is a great book for people who are interested in birds but don’t know very much while seasoned birders will discover details they never knew. You start by dipping into it – and end up forgetting about lunch.

BBC radio's Tweet Of The Day is available as a podcast.

* American readers may not be familiar with the birds but they will surely find the text fascinating and certainly enjoy the illustrations.

Tweet Of The Day by Brett Westwood & Stephen Moss, illustrated by Carry Akroyd, is published by Saltyard Books.

It’s purple loosestrife season here in Pennsylvania. Swamps and other wet habitats are vivid in its purple coloring (above, click to enlarge), in some places it looks as if it’s smothered everything. This colourful European native is generally viewed as a destructive menace and many millions of dollars are spent every year in a futile attempt to eradicate it.

In Britain, by the way, where purple loosestrife (Lythrum salicaria) originated, it’s far less common and is a popular plant for bog gardens with over a dozen named varieties, two of which have been awarded the prestigious Award of Garden Merit by the Royal Horticultural Society.

In North America, purple loosestrife is generally regarded as evil but part of its reputation derives from the simple fact that it’s so colorful, it’s so obvious that it’s there. If it had dull brown flowers no one would notice. Ken Thompson, in his important book that I reviewed here recently, put it this way: “Very tall people with red hair, big tattoos and conspicuous facial scars rarely have successful careers as bank robbers, and purple loosestrife has a similar problem: it’s just too conspicuous for its own good.” He goes on to emphasize: “Recognition of loosestrife as a problem was largely based on anecdotal observations, which are likely to be particularly unreliable in the case of a tall species with such bright, obvious flowers. This is a well known problem that standard textbooks warn against: it’s easy to conclude that an otherwise rather dull wetland has been completely taken over if you look at it when loosestrife is in flower…, even if a more careful examination would reveal no such thing.”

My local experience indicates that it does not necessarily spread once the first plant arrives, and that it can also decrease over time. On the lake where we live, I spotted two plants growing together about ten years ago. I checked the whole lake last week and those two plants are still the only ones present in spite of there being many suitable habitats all along the margins. Native swamp loosestrife, Decodon verticillatus, is far far more aggressive.

And in the swamp where I first saw it flowering colorfully it has declined, as it has elsewhere, and a striking feature is that native shrubs including dogwood (Cornus) and arrowwood (Viburnum) are establishing themselves on individual clumps of purple loosestrife.

And it’s not as if purple loosestrife is entirely useless for wildlife. It’s been shown that a number of native species are more likely to grow in habitats containing purple loosestrife and in a study of over 250 plots it was found that there were more birds in those with purple loosestrife than in those without. I’ve seen around thirty individual butterflies on one plant and over sixty insect genera use it, including adult monarchs (left, click to enlarge). Birds even nest in it. Another significant study that looked carefully at this issue found that there was no difference in species richness between plots with and those without purple loosestrife.

Ken Thompson says, as he concludes his discussion of the issue: “Persecuting loosestrife is, and always has been, a waste of time.”

I was tempted to pull out those first two plants that appeared at the far end of our lake but I just left them and kept an eye on the situation. Ten years later they’re doing no harm.

Don’t get me wrong. I’m not saying that anything and everything that could be, and is, invasive should just be left alone. What I am saying is that it’s not as simple as “native good, non-native bad”. Especially when you look at how fast US native swamp loosestrife (Decodon verticillatus) can spread and the monocultures that result.


Monarch butterfly on Purple Loosestrife (Lythrim salicaria). Image © Liz West (http://www.EWestPhotos.com). Used here under Creative Commons Attribution 2.0 Generic License.

The classic British* reference book on trees, shrubs and climbers is The Hillier Manual of Trees and Shrubs. My copy sits with a small and very select group of references just to left of my computer monitor; I probably use it every day.

Now, a new revised edition of this classic has been released by the Royal Horticultural Society, twelve years after the last edition. It has been significantly updated and expanded to include an amazing total of 13,215 individual plants (plus 3,258 cross-references and synonyms) from 706 genera; 1,490 plants have been added to those in the previous edition and this confirms the book’s status as the essential reference on woody plants for British gardeners.

As you can tell, it’s comprehensive. I’ve only failed to find one shrub I’ve looked up over the last few months and believe me I check on some pretty unusual plants. Another thing is that, as with my Encyclopedia of Perennials, the descriptions are written in accessible language – you don’t need to be a professional botanist to understand what’s being said. So no words like “bipinnatifid” and “orbicular” except where absolutely necessary (and of course there’s an easy glossary).

Wherever possible the text notes when species were introduced to western gardens, who discovered them in the wild and who introduced or developed cultivars and other interesting snippets of information. I’m pleased to see that plants which have been awarded the Royal Horticultural Society’s prestigious Award of Garden Merit (AGM) are marked but plants are not given hardiness ratings – not the USDA ratings nor the new RHS ratings. I’m told that the RHS hardiness ratings will added in a future edition.

This medium format book has no colour pictures, and so is priced at under £20 for almost 600 pages of the highest quality information. And it’s worth mentioning that commenters on amazon.co.uk are comparing the book unfavourably with previous editions because there are no colour pictures. But as far as I’m aware the Hillier Manual never had colour pictures; they’re confusing it with the old, extremely outdated and much less useful Hillier Colour Dictionary of Trees and Shrubs and Hillier Gardener's Guide to Trees and Shrubs which included many colour pictures – but covered far far fewer plants.

And, as Roy Lancaster says in his preface: “Even without illustrations, it offers a window on the wonderful world of woody plants to be seen, admired, cherished and ultimately enjoyed.”

But one thing that disappoints me. Bamboos are included, over thirty pages of Rhododendron hybrids are included, there are seven pages of Clematis hybrids – but only ten pages of roses, and none of the huge number of hybrid roses that are so widely available. Considering that in much of the country it’s impossible even to grow rhododendrons (because they need acid soil), to include so many seems perverse when at the same time excluding roses – which anyone anywhere can grow.

The RHS tell me that this is a matter if history - Hillier Nurseries, who developed the original manual in 1971, were never big on roses - and also that modern rose introductions disappear so quickly it would be impossible to keep the book current. My view is that while roses may not have been important to Hillier Nurseries, they're very important to gardeners and including old roses, or AGM roses, at the very least, would have been very helpful.

Finally, let me mention the book’s stout binding (although it’s a paperback it should last like a hardback), its clear typography and layout, and its valuable updated lists of plants for purposes. Excellent.

In all, this is an essential reference, with far more information for your money than any other guide to trees and shrubs.

* I should make clear that, while the book is intended for British gardeners, serious enthusiasts for shrubs in North America and around the world will find plants and information included that are in no other reasonably priced guides – or, in many cases, in any other guides at all.

The Hillier Manual of Trees and Shrubs is published by the Royal Horticultural Society.