What to plant in August in the UK: vegetables, flowers and monthly garden tasks

At this time of year, we are eating fresh produce from the vegetable garden every day. The only downside is that, if you don’t keep up with the picking, the courgettes turn into marrows, the lettuces go to seed and the beans become overgrown and stringy. Plants that would normally carry on producing slow down and go to seed if you aren’t harvesting from them. So picking little and often when the vegetables are still small and tender is the best approach.

The same goes for the flower borders. Sweet peas need picking regularly; if you leave the flowers on the plant, they will turn into seedpods almost before your eyes, triggering the plant into early dormancy. The way to keep them going longer is to tackle them once every week or 10 days, ensuring you pick every single bloom from as low down the stem as possible, watering the plants at the same time if the weather is dry. I’m also deadheading other perennials obsessively at this time to keep everything going – penstemons, dahlias, heleniums, astrantia and many others benefit from the removal of dead flowerheads, enabling the plant to put its energy back into producing strong growth. This prolongs the flowering season well into autumn – as well as making the plants look neater.

The other task I enjoy doing in August is taking cuttings from salvias, penstemons and pelargoniums, all of which are easy to propagate in this way. Take your cuttings from non-flowering shoots, as they will root more easily, and snip off a shoot about 10-15cm just above a bud. Trim off the lowest leaves and pinch out the growing tip, then dip the end of the cutting in hormone rooting powder before planting three or four around the edge of a 9cm pot, in multipurpose compost mixed with a little grit for drainage. Keep the cuttings protected in a greenhouse or coldframe over winter to plant out the following year.

• Cut back alchemilla and hardy geraniums to encourage more growth
• Water flowers and vegetables if the weather is dry
• Prune wisteria to keep it in shape
• Collect seed from foxgloves and other early-summer perennials
• Feed container plants with high-potash liquid fertiliser to prolong flowering
• Lift and pot up rooted strawberry runners to make new plants

MAY WE SUGGEST: How to grow dahlias

Many of the late-summer-flowering perennials and bulbs we grow in our gardens are from South Africa, such as gladioli, agapanthus and crocosmia. Adapted to tough climatic conditions, most of these plants are very drought tolerant once established, adding welcome colour to the garden towards the end of summer and into autumn.

Recently introduced, this agapanthus has lilac-mauve blooms with darker streaks on the petals. Each generously sized flower head sits on top of a strong stem and is set against bold, arching leaves. Reaching about 1 metre tall, it can be grown in a pot or in a border in an open and sunny spot.

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All about agapanthus and how to grow them

If you are craving hot colours for a late summer pick-me-up, this crocosmia fits the bill perfectly. Its bright orange flowers are splashed with crimson and are larger than is typical for a crocosmia, opening wide to form eye-catching, star-shaped blooms. Tough and drought resistant, it will form large clumps that can be divided.