I seem to have left some of the summer flowers right till the last minute and as you read this I will probably have just pulled out this plant from the border edges and tipped them out of the hanging baskets. It is another of the plants that I have unreasonably ignored because it is useful and pretty and easy to grow. And yes, it is another persicaria.
But this is a bit different to most of the others because it is a low, ground covering plant that is easily grown from seed. In climates with only light frosts it can remain almost evergreen and can be invasive but in the UK and Ireland the topgrowth is usually killed in winter and the plants resprout in spring. There will probably be a lot of seedlings around too so you usually only need to sow or plant this once.
This Asian knotweed is a quietly attractive plant with alternate leaves on hairy reddish stems, all marked with the typical chevron. It will hang form baskets of creep along the soil and makes a low but not entirely flat mat. From a very early stage it will flower, producing spherical heads, 1cm or less in diameter, packed with tiny pink flowers that fade to grey/white as they age. The flower heads look a little like clover and they are also popular with bees.
It flowers continuously from early summer to the frosts and although more leaf than flower it is pretty enough for baskets. Like most persicarias it needs a fair bit of moisture so although, visually, it would be perfect around and under lavender and rosemary, it may not be terribly vigorous in such company. It would, however, develop its brightest and richest colouring with rich red foliage under such stressful conditions.
You can easily raise this from seed, sown in gentle heat in spring or you can take cuttings at any time in summer but once you have this in the garden it will probably self seed.
Because it will grow in sun or part shade it can be planted at the front of borders in many situations and might be effective with blue hostas, bright heucheras and a host of hardy geraniums.