Looking out through the large picture window at the back of my house, I had a view through a little wood of Japanese oaks, mountain cherries and chestnuts of our small vegetable plot, a lovely wide hay meadow and more woods clothing the foothills of Iizuna mountain that rises on the horizon.

That was in 1983, when I started living in this house in Nagano Prefecture — the first I had both built and owned myself. In late spring, my heart would soar with the high-flying larks as they sang their little hearts out; while at the end of summer, the smell of freshly cut hay winged my memories back to a boyhood in Britain. Then, after winter's white blanket had gone, I could watch kites, crows and the occasional fox foraging in the maze of burrows and runs that mice had made under the snow.

Those lovely seasonal sights lasted for a decade or so as the yen, meanwhile, grew strong and my neighbor figured it was cheaper and easier to buy imported feed from America for his cows than to mow the meadow and make hay while the summer sun shone.

A meadow is a special place, whether it's a wild one grazed by deer, rabbits and other creatures, or one nurtured and cared for by generations of farmers who'd cut the grasses for hay or silage, and grazed their animals on the land. Such use of a meadow encourages not only nutritious grasses, but also wild flowers and butterflies. How well I remember meadows in my boyhood dancing with lambs, prancing with young colts, or all calm and lazy with cows.

Haymaking in those long-ago days in the South Wales hills was a time for hard work with pitchforks under the sun, for dusty throats and fierce thirsts slaked with jugs of cider cooled in a spring. Then came rides high on hay carts hauled by horses, where a lad might flirt with girls all pink-faced from sun and cider — trying with dubious whispered promises to lure them later into a cozy hayloft. Ah, youth flies by so fast, yet lingers in the mind like yesterday!

My neighbor here in Kurohime had never turned out his cows to graze in his meadow, perhaps because that wasn't the local tradition as the field had been pioneered from wild woods just after the war by desperate folk returned from Manchuria. The meadow wasn't fenced or walled, and my neighbor once told me that some folk would complain about cows in a field, because they dropped smelly dung. At the time I shook my head at the stupidity, but commiserated with him over the difficulty of maintaining a strong and high enough fence in a climate that delivers 1 1/2 meters of snow in the winter.

When he stopped cutting the meadow, replacing hay with that imported feed, a tall alien weed was introduced. Local people call it buta kusa (pigweed). Trying to identify it precisely was not that easy because there are so many varieties, but the stuff here seems most likely to be o-buta kusa (Ambrosia trifida, also known as giant ragweed). This plant was first found in Japan in 1952, brought over in animal feed from abroad.

But whatever its correct scientific name, the damn stuff has taken over the entire meadow — and is trying to encroach into my backyard. It grows over the summer into a dense thicket about 3 meters high, and all the grasses, flowers, larks and butterflies have gone.

If the place is ever again to be a productive meadow — or a field for wheat, barley, buckwheat, potatoes, cabbages or whatever — my neigbor will have to go right back to repeated cutting of the thick-stemmed, densely rooted weed, along with a time-demanding regimen of plowing, tilling and hoeing.

It is a tragedy — but one which could have been avoided by cutting the meadow grasses twice a year with a tractor-drawn mower.

Instead, this noxious weed — which is a major cause of respiratory allergies — is spreading all over, running riot in other neglected fields and plots as well. Our pigweed problem reminds me of the rampages of Japanese knotweed (Fallopia japonica), which was introduced into Britain as a garden plant in the 1850s. There, it hybridized with a giant northern species of knotweed, spreading a massive underground network of woody rhizomes that now fuel a small industry of people and pesticides trying to eradicate it.

Invading knotweed takes over fields and hedges, pushes up paving and gravestones and thwarts even the best-laid plans for concrete and tarmac. Indeed, Japanese knotweed is so comprehensively damaging that in Britain it is proscribed by the 1981 Wildlife and Countryside Act. This means that you can be heavily fined, or even imprisoned, for growing it or causing it to grow, and you must have a registered waste controller remove or destroy it.

We have knotweed growing wild in our woods, a gentle plant that reaches about a meter high and has a sour-sweet taste to its hollow stem. In Japan, knotweed (itadori) is a food plant — one that doesn't cause us any trouble at all. Is this essay leaning toward delivering a sinister message about not letting those awful aliens invade, reproduce and take over? Will rightwingers rally to the flag and bang their tin drums?

Wait a minute! It is not only alien invaders who are getting out of control. All over Japan, and especially here in northern Nagano where I live (and therefore where I notice changes most), the native broadleaved, tough-stemmed kudzu vine (Puearia lobata) has got out of control. (This is the same plant that infested the state of Georgia when it was brought into the United States to control erosion).

In my garden and in our Afan Trust woodland, we keep the hairy perennial under control by frequent cutting, but elsewhere the hardy vine is smothering trees, signposts and even buildings. But it's not just unsightly, because when the kudzu vine smothers a tree, its big leaves not only steal the light but it also makes the branches heavy and more vulnerable to snow and other damage. But if you just keep on cutting the vine as it starts to grow, the rest will wither and die. You just have to be diligent — and by the way, I hear that kudzu leaves make excellent feed for goats.

This serious and damaging spread of kudzu here in Japan is mostly due to neglect — I would even go so far as to say laziness — combined with the sad fact that the traditionally wiser and hardworking farming folk are growing old and dying off. The rampant spread of the vine is also likely aided by warming winters. But a huge additional problem is that most people don't even notice, and think simply that "green is green."

It isn't.