Paul Hervey-brookes on the jobs to do in September
With the scent of autumn now on the breeze, make the most of the remaining sunny days in the garden
Rudbeckia, althea, verbena and a host of late season plants keep up the good cheer by bringing burnt oranges and sparkling yellows into the garden. September is the first month you can smell autumn on the breeze but there are plenty of warm sunny days still to be had.
FLOWERS AND CUTTING GARDEN
There’s plenty of deadheading to be done this month to keep annuals and other flowering plants going. This is also the month to stop deadheading certain plants you actively want to let self-seed, or collect the seed to sow later in the autumn or next spring.
Dahlias really are a star performer this month. They will keep flowering until the first hard frost, so deadhead and pick for vases. Pelargoniums and other tender annuals which have been put out for the summer can be given a good deadhead and trim to give them a fresh burst of life for the next few weeks. In cold frames or the greenhouse, begin sowing annuals and short-lived perennials for next year; you will get much bigger, stronger plants this way and ensure lots of flowers. You can also pot up next year’s spring bulbs now – they may not show for a while, but they will start developing roots and make for stronger flowering plants in the spring.
VEGETABLES AND HOME-GROWN
If you are making large-scale changes to your vegetable beds, this is the month to do it – I am making wattle edges to mine and raising the soil level with organic matter. If you are simply clearing your beds, then sow green manures on any beds you are not using over winter; this reduces soil erosion and will enrich the soil for next year.
Beans, peas and any other legumes can now be chopped to ground level, leaving their roots in the soil to be dug in; this is a valuable nitrogenfixing plant and will improve the soil for next year’s crop!
There are still six good weeks ahead of us if you act fast, so spring onions, radish, hardy peas, rocket and broad beans can still be sown for a late season crop, and a fresh bed can be prepared for autumn shallots. Think now about garlic varieties in advance of sowing as the rule of thumb is plant on the shortest day and harvest on the longest! This is also the right time of year to sow coriander; it will reward you with vigorous, tasty leaves for spring next year. Lastly, cut to the ground herbs such as chives, sorrel and, if not being left to seed, lovage – this, with a little feed, will be sowing fresh, new leaves in a couple of weeks.
Unlike the herb vervain (verbena officinalis), the tallgrowing verbena bonariensis is a native to tropical South America which gardeners have increasingly welcomed into the garden. Still in flower into October, these tall, willowy short-lived perennials can reach over 2m in height and are easily grown from seed. So prolific in fact are they that in warmer places they have naturalised themselves. In Washington State, whole fields can now be seen with their square-topped flowers smothered in bees and butterflies. Sown this autumn they will make tall, open flowering plants next year in the garden and are well worth the minimal efforts involved!
SEPTEMBER The countdown to autumn begins with RHS Malvern Autumn Show, and I will be there observing the Floral Marquee judging process before leading an RHS tour to Italy. It will be a busy month as I am also running a series of day courses on garden design at Allomorphic and hosting an exhibition of paintings by Betty Harrison.