It has really been a strange year so far: an unseasonably cold spring, a late beginning to summer, a few ferociously hot days, stormy downpours, and now blustery and rather chilly. I have lost a few things to the dry spells and my autumn clematis are almost all over already (as are most of my repeat-flowering roses), but Michaelmas daisies look set to be on time or even a bit late, and traditionally late-season perennials like aconitum (monkshood) and helenium (perennial sunflower) are holding up well. A monkshood (aconitum) like “Stainless Steel”, growing to five feet and more, provides a good contrast to the abundance of autumn-flowering daisies. However, do be careful when handling monkshood: all of the plant is deadly poisonous, and some people even react badly to brushing against the leaves. Another “non-daisy” to try is Liatris spicata, which, as its name suggest, has spiky flowers in shades of white, pink and purple during August and September.
Any garden can look a bit tatty by this time of the year, so some cutting back of earlier-flowering plants is a good idea. I have a good clump of a wonderful mullein, Verbascum “Christo’s Yellow Lightning”, which lives up to its name in June and July, but has been looking decidedly the worse for wear during the last couple of weeks. Shortening the stems has left a gap, but I can now get up my front garden path without it attacking me. In general, I am not a “tidier upper” during the autumn, preferring to leave as many plants as possible to develop an interesting skeleton that can look wonderful when rimmed with frost in the depths of the winter to come. Dead stems can also provide useful hibernation places for helpful insects like ladybirds.
In the vegetable garden, I notice that the RHS is advising you to plant out spring cabbage and other early-maturing crops like over-wintering onions, spinach and turnips. Has anyone tried their suggestion to “sow green manures like Italian ryegrass and crimson clover to improve the soil texture and conserve nutrients”? September is also a good time to give greenhouses and cold frames a good clean in anticipation of some plants needing their protection during colder weather.
On that note, the lowest temperature ever recorded in the UK in September was on 26th September 1942, when -6.7 Celsius (about 20 degrees Fahrenheit) occurred at Dalwhinnie in the Scottish Highlands. In our balmier climate, gardeners may be glad to know that an air frost has not been recorded in Oxford in September since 1885.