Many years ago I was teaching and looking after a family of small children. I had a 30-minute car journey to school every morning when I hopefully transformed myself from harassed mother into competent teacher. I always tuned into Danny Baker on Five Live then. He had a phrase “riding the ski slopes of life” which still strikes a chord today, both in life and in the garden. I’ve plummeted off the edge many a time, Danny boy.

Late August is a definite dip in the ski run, horticulturally speaking, for most of us, and the dry conditions earlier in the year have wrecked lawns and stressed plants.

However, all is not lost. As we near September, we freewheel into the best gardening month of the year. The light quality sharpens and adds a jewel box richness that’s unique to this mellow month.

Needless to say, I am impatient, but the colour blue is helping me to cope with the dog days of late-summer. This rare colour glows as vividly as the evening star when the nights draw in during the second half of August.

The pots of agapanthus, always admired by walkers who see them from The Macmillan Way on the garden boundary, are at their best now. I could grow many of them in the ground, rather than in pots, because the ones with a deciduous tendency are hardier than you think.

My border ones shrugged off last winter’s frost and snow without a hitch. However, grown in sturdy, wide-bottomed Whichford pots some reach over five feet in height: this makes them much more dramatic.

The deep-blue ‘Northern Star’ and the grey-lilac ‘Windsor Grey’ outshine the other varieties. ‘Northern Star’ was bred by Dick Fulcher, of Pine Cottage Plants, a nursery overlooking the Taw Valley in mid-Devon. The Fulchers hold the Plant Heritage National Collection and also attend all the major flower shows. They also do mail order.

‘Northern Star’ was officially launched in 2009 at Hampton Court and it’s going to be widely available. Individual dark-blue flowers form a reflexed pale-blue star finely edged and striped in much darker blue and the whole plant dazzles. Our plant, growing in a 12in-wide pot, has produced 16 flowers on two-foot high stems. The foliage is neat, with dark attractive markings at the base, and the whole plant is poised and balanced.

‘Windsor Grey’ is a softer lilac-grey agapanthus that is almost twice as tall, but the strong stems support large heads without them flopping and the flowers have a warm hint of pink. ‘Tarka’ (also new) is a similar colour but with later flowers and she’s still in bud. I also rate the tiny foot-high ‘Lilliput’ which sends out wands of cobalt-blue flowers on wiry stems.

Feed them with a nitrogen-based balanced fertiliser in spring and then, once in bud, change to a potash-rich tomato food and apply it once a fortnight. Then your plants will give you a stunning show of especially vibrant flowers courtesy of a pigment called anthocyanin.

However hot the sun, the flowers will never flag or fade and there will always be a hint of shot-silk violet among the blues. Once late-September comes, ease up on the watering and then place the pots somewhere sheltered. Repot and divide every third spring if needed.