I’m sorry to have to raise this issue but it is that time of year again. We are in the last few days of high summer as we slip into a mellow September. (Even though you could be forgiven for thinking October had arrived early judging by all the rain last week). It is a good moment to look back on the triumphs and disasters in our gardens and to make notes, so that we do not make the same mistakes again.

Allow me to share a few of my best mess-ups of 2010.

My first is a mistake I did make last year and forgot about … even though I had written it down. I have a largish group of the musk rose, ‘Penelope’, which flowers beautifully in June. If you leave it it will set some fine hips for the winter but there will be no more flowers. Last year I vowed to deadhead half of it after flowering so that I would get a second flush around now but got distracted and now it is too late. Oh well, there is always next year.

My second mistake was one of omission: there is an area around my pond consisting of a series of long thin borders (I wrote about its birth about a year and a half ago). Some of the beds have worked really well, I think, like this arrangement of Phlomis amazone and Seseli libanotis. The central part, surrounding a pond, has some wonderful grass called Panicum ‘Rehbraun’, planted with Cosmos ‘Dazzler’ and the fabulous Tithonia rotundifolia (pictured, top) that are bushy and wonderful, but I completely forgot to plant anything for spring: no tulips, no alliums, no nothing. As a result I had to live with a big empty space until June. That is not a mistake I will be making again.

My third mistake is due to soft-heartedness. One part of the garden has been colonised by Hesperis matronalis ‘Alba’, the white flowered, scented sweet rocket, which is a beautiful plant in the right place. The thing about white flowers is that they work very well to lift other plants but tend to wash everything away if there is too much. Hesperis has a tendency to self seed and this year there were far too many; I pulled out about half but that was not enough. They smothered the other plants and ruined a whole corner of the garden. This autumn I shall be ruthless and will dig up 90% of the seedlings.

That is probably enough of my garden mistakes otherwise I will completely undermine my own credibility.