I think that if I had to choose the one plant that has given me the most pleasure throughout August, it would be Hydrangea villosa. I recall first being hypnotised by the magic of this particular shrub on a visit to Kiftsgate Court in Gloucestershire, which had an enormous specimen flanking an entrance. At The Laskett, it has reached about 9ft, which is what the books tell one is its height, pyramidal in form, like an ascending multi-branched candelabrum, its upturned panicles of pale-pink flowers encircling a fuzzy deep-lavenderhued centre. Caught in the golden autumn light of the close of August, it possesses the mystical visionary quality one associates with the artist Samuel Palmer’s Shoreham period.

August has been busy. Jo, our one-day-a-week assistant gardener, has landed another job, so we are short-handed and hedge clipping beckons. I therefore have placed an advert in the local paper and hope. Meanwhile, the builders have finished the alterations to the façade of the house aimed at achieving the fullest interplay between house and garden. The 1920s bays have gone (they were rotten) and new windows reaching to the ground permit that dialogue as never before. I’m entranced by the light flooding into the house and, equally, by the views across the knot garden. The demolished yew hedge, which had concealed that vista, is springing again and I already anticipate clipping it into green clouds upon which this phoney Palladian doll’s house will sit.

The builders have hacked a large hole in the garden-front wall of the large drawing room. This is even more exciting, as light, for the first time, pours in, and plans are made to hack back two yew hedges to frame a second vista, this time down to the two fountains. Within, I intend to fill the redecorated room with flower pictures, including ones I have commissioned of my wife’s favourite fruits: quinces, medlars and crab apples.

At the rear of the house, a new entrance hall already has the large frame ready to receive Richard Shirley Smith’s capriccio of the garden.

All of this creative energy flying around is driven on by the fact that I am now in my eighth decade and, therefore, had better get on with it. I have optimistically re-labelled it as the Great Decade for, with limited time ahead, you must rally yourself to make and carry to reality your final garden statements.

My 70th birthday was celebrated at this time last year, and was marked by two fetes, one of which was a buffet lunch for about 90 in the garden. Where else? Up went a tent over the new topiary garden, its sides open to the new great flower border on one side and to the pleached limes on the other. Round tables covered in green gingham tablecloths and topped with tiny bouquets of sweet peas were scattered near obelisks and nascent topiary peacocks. A friend conjured up garlands of laurel and rosemary for the tent’s pediment, and I used Sellotape and green string to tie more laurel on the tent’s supporting poles. The dress code was casual, although I gave a flower-sprigged 18th-century waistcoat an outing.

I had decided that if I had to be 70?and there was no escaping it?this was one way to do it: a grateful tribute to friends and all those who have helped me make a new life. And to it, of course, came gardeners, among them the Bankses from Hergest Croft, writer Mirabel Osler and photographer Andrew Lawson. Afterwards, everyone wandered through the garden, and I couldn’t help reflecting on this as an immemorial scene, the use of the garden as a setting for festival, and that my birthday took its place in a long descent of revelry through the centuries from Louis XIV’s Versailles down to the annual fête in the big house’s garden.

All around, the purples and golds are romping away, but there’s a late-summer-into-autumn tableau that I relish. It flanks the gate piers into the orchard vista: here are huge banks of purple-headed eupatorium, a robust spreader with leathery leaves that calls for water, or else it flops. But the butterflies love it, and enchantment comes when, bathed in the warmth of the sun, they settle in shades of gold, orange and brown, hung like jewelled pendants across the imperial purple. As anyone who delivers you a plate of anything these days seems to say: ‘Enjoy’.

This article first appeared in COUNTRY LIFE magazine on August 31, 2006