There are nettles, and there are nettles.

The perennial stinging nettle, Urtica dioica, is often the first British wild plant that kids learn to recognise - because they get stung. The leaves are covered in stinging hairs which contain formic acid, histamine and seratonin. Its annual relation, Urtica urens, actually has a denser concentration of stinging hairs, but the plants are much smaller so the damage to a tumbling child is usually much less.

In the US, two native American subspecies are found as well as the European form which is naturalised over most of the country.

The stings are not dangerous, although a related species in New Zealand is rumoured to have killed horses! But they are not pleasant and come with a red rash – especailly after you’ve scratched it. The cure often grows conveniently alongside – rubbing the stung area with dock leaves, broad-leaved dock, Rumex obtusifolius, for example, takes the edge off the pain.

But also often growing with stinging nettles is white dead nettle, Lamium album (above, click to enlarge) – “dead”, with no sting. When not in flower, stinging nettle and dead nettle look alike with the similarly shaped and sized leaves gathered in pairs along upright stems.

The dead nettle stems tend to be fatter and more obviously square, but when the two-lipped white flowers open the distinction is obvious; nettle flowers come in relatively unobtrusive green tassels. Kids tend not trust the distinction.

Stinging nettles are actually very useful plants; paper can be made from the stems; the foliage is important as food and shelter for many caterpillars; the young shoots can be eaten steamed or made into soup. Nettles have also been used to treat a wide variety of maladies.

And keeping nettles in your pocket is said to protect you from being struck by lightning. Of course, if you misidentified the plant and keep dead nettle in your pocket by mistake – when the lightning strikes, dead is exactly what you’ll be.

Guest post: Canadian garden writer and editor Fiona Gilsenan, relocating to England, visits the Chelsea Flower Show almost as soon as she arrives in Britain.

I didn’t exactly plan my arrival in my new homeland to coincide with the Chelsea Flower Show, but I don’t mind that it did. Fresh off the plane from Canada (after a few days rest in lovely Northamptonshire) I joined the throng of RHS members  hurrying through the streets of SW3 to see Diarmud Gavin’s planty pyramid and find out who got the Gold. Here are a few of my highlights.

Naturalistic plantings. There was lots of mingling and drifting going on in the planting beds, with almost all the big show gardens going for the meadowy look. Capel Manor College (above left, click to enlarge) even had a display entitled ‘Mad about Meadows’, explaining the finer points of Bat Meadows (a new category for me).

 Roundup ready. All this wispy, crowded planting does lead to one inevitable result: weeds. I saw more weeds in the beds than ever before at Chelsea, most looking like an accepted part of the plantings. I was itching to put on my flash new gardening gloves and pull out a few.

Freaky flowers. Under instructions from my 11-year-old son, I looked long and hard for the  ‘weirdest flower there’. A few of the orchids and Nepenthes were among the usual suspects, but I settled on this tarantula-like false bird-of-paradise, Heliconia vellerigera ‘She-Kong’ (left, click to enlarge). I think my son will agree.

Favorite show garden. A toss up between the DMZ Forbidden Garden and Jo Thompson’s Caravan Club. Designed by Jihae Hwang, the DMZ garden (riht, click to enlarge) represents the demilitarized zone between the two Koreas, and is filled with remnants left from the conflict. Above all, it’s a garden with meaning and memory that is powerful and spookily evocative.

New aeoniums. Plant of the Year 2012 was a pretty foxglove (Digitalis ‘Illumination Pink’), but I loved the two aeoniums from Trewidden Nursery, both of which made it onto the shortlist of 20. Aeonium ‘Cornish Tribute’ and A. ‘Logan Rock’ (left, click to enlarge) are compact and container-worthy. Also working in their favour: breeder Claire Batten tells me they are named after her favorite beer and pub, respectively.

Thank you to Fiona Gilsenan, newly arrived in Britain, for this view of Chelsea.

Along a busy road near Hampton Court Palace, King Henry the Eighth’s sixteenth century residence on the southern edge of London, there are some cherry trees. All the way along a wide straight stretch of suburban road, on both sides. But these are not any old cherry trees.

They represent one of the successes of the Roads Beautifying Association which was set up in 1928 to improve the look of the many new roads being built as cars became more popular. Its dedication to roadside planting was the contemporary equivalent of the current enthusiasm for planting wildflowers along new roads. Interestingly, part of their rationale for tree planting along roads was to stop drivers being distracted by looking at the landscape.

It’s years since I’ve been in England at the right time to see them in flower, but it’s obvious that those cherries are now well past their best. I’d say that they were planted in the 1950s so many have already died; cherries are relatively short-lived trees. But trees that have died have been replaced, and it’s clear that the remaining trees are being looked after. I suspect that without the historical connection they would all have been replaced but instead some careful tree surgery has been undertaken and even those with only a few branches remaining have been retained.

Planting blowsy Japanese cherries along new roads would be frowned upon now. But the Roads Beautifying Association began convinced people that roads needed beautifying, did the job and even produced a book called Roadside Planting.

One final interesting point. The Roads Beautifying Association, which finally ceased to exist in 1963, was founded by a dermatologist called Wilfrid Fox. He also founded and planted one of the finest arboretums in Britain, at Winkworth in Sussex. And my dad and I used to fish for trout in the lake at the arboretum before I was ever interested in plants.

Not 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.

A surprise driving away from London’s Heathrow airport the other day. There’s a huge intersection where the road from Heathrow joins the M25, London’s 117 mile, six and eight and ten lane, orbital motorway. At one point there’s a traffic light and there, by the side of the road, spilling out through the fence, were three huge euphorbia plants, Euphorbia characias.

So, I drove - carefully - all the way round again, extracting my camera from the bag on the seat alongside me as I went. I manoevred across into the lane alongside the euphorbias and – the lights had changed. I came to a halt in just the right spot, snapped three quick pictures out of the window before the lights changed to green, and I was on my way home. One picture was sharp –ish (above, click to enlarge).

This is not a British native plant, it’s from the Mediterranean, but I’ve always grown it. But on a roundabout on the M25? There are no gardens for miles. I bet some mischievous passing gardener threw a few seeds out of the car window. I'll be keeping an eye on them from now on.

I was surprised by this book: I was simply not prepared for it be almost entirely pictures. And of course, being a writer, I find this slightly shocking!

Beth Chatto herself begins with a foreward in which explains how Rachel Warne’s pictures showed her new truths about the garden she’s been developing since the 1960s. The scene is then set by a biographical introduction from Great Dixter’s Fergus Garrett, who also contributes short introductions to the four seasonal collections of photographs.

Intermixing broad views of the garden with galleries of portraits of its plants, the familiarity of the planting style re-inforces Ferus Garrett’s view that “Beth has changed the way the world thinks about gardening… She has made gardeners look at plants in a different way, so broadening our horizons and widening our palette.” The fact that the style is so unsurprising is testament to her huge influence.

Rachel Warne is of the Gardens Illustrated school of photographers for whom atmosphere and softness is crucial but at times her images are let down by rather harsh reproduction. She shows the garden off well, we see all the main features across the seasons, but I would have liked to see more associations of two or three plants – a stage in between the broad views and the plant portraits. And the short winter section is all snow and no flowers.

• Interesting pictorial presentation of the richness of Beth Chatto’s gardens and her influence
• Expansive views put the planting in context
• Plant portraits are unusually illuminating
• Commentary from Fergus on why the planting works so well would have been valuable
• Valuble if you’ve not visited the gardens – and if you have

A Year in The Life of Beth Chatto’s Gardens by Rachel Warne, with introductions by Fergus Garrett and a foreward by Beth Chatto, is published by Frances Lincoln.

Not long after we moved to Pennsylvania, I planted two plants at the edge of the little creek that flows through the corner of our property. It was all a bit bare, and I thought some quietly colourful plants would brighten things up.

One that I planted was Lysichiton camtschatcensis. This is the white flowered Russian version of the yellow flowered American native Lysichiton americanum. As the name indicates, it comes from the Kamchatka Peninsula, just across the narrow Bering Strait from Alaska. Sarah Palin must have had a good view.

For the first few years, all that happened was that the plant slowly - very slowly - became larger. Then it produced a single white flower, and as far as I could tell the seed head was eaten by deer. Then there were two flowers, then, ten years after planting, this year three lovely white flowers appeared. But the point is that a few yards farther down the stream a second plant flowered this year, as you can see in the background in the picture (click to enlarge).

So it’s started to spread down the stream. Some seed must have escaped the deer and germinated and the resulting plant has now reached flowering size. I have to say that I was very pleased to see that some seed had escaped the deer.

But. So. Here’s the thing. Should I rip them all out to ensure that this non-native plant does not continue its spread downstream? Should I watch and wait and see what happens? Or should I just not worry about it, and simply admire them? I’m planning to watch and wait but not tear them out – does that make me a bad person? Should I play safe, and just dig it all out?

Oh, yes, the other plant I put alongside the stream was Darmera peltata ‘Nana’, the dwarf form of what used to be called Peltiphyllum peltatum, with clusters of pink flowers in spring and wine red fall foliage. It grew well for the first half of the first season - then the deer ate it and I never saw it again. So no chance of that spreading.