It won’t be long before the trees put on their spectacular shows of autumn colour and the last summer vegetables present themselves for cutting, but there’s no need to write off the gardening year just yet.
In fact, September is a prime month to sow various hardy annuals ready for a superb display next year.
Putting in seeds while the ground is still warm means that they’ll have a few weeks to get going and make small plants ahead of the onset of winter and, once the weather starts to warm up and the light levels increase in a few months’ time, they’ll have a head start over their springsown equivalents.
Hardy annuals that do well when sown in autumn include pot marigold, Calendula officinalis; love-in-a-mist, Nigella damascena; cornflower, Centaurea cyanus; Californian poppy, Eschscholzia californica; and poached egg plant, Limnanthes douglasii, the latter being great for attracting beneficial insects such as aphid-eating hoverflies.
Other seeds to consider putting in now include green manures, which perform a double role of providing nutrient-rich plant material to replenish depleted soils and preventing soil erosion from winter rains and winds by holding on to the ground with their roots.
Phacelia tanacetifolia is a particularly good example, producing plenty of leaves to dig in. It’s also a great flower to grow in the cutting garden, producing plenty of beautiful purple flowers that are much loved by bees and hoverflies.
Along with seed sowing, a little effort directed towards digging up and splitting perennial flowers will result in borders bursting with blooms the following year.
Doing this job now means crowded groups of plants will have room to breathe and divisions will get the chance to put down roots in their new locations before they die back over winter.
Hardy geraniums, Astrantia, Crocosmia, sea holly ( Eryngium), Euphorbia, Hosta and day lily ( Hemerocallis) can all be dug up, split and re-planted in September ready for a super display the following year.
This month is a good time to dig up and divide bearded irises to ensure flowering and increase stocks, although remember to re-plant them so that a certain amount of their rhizome is above the ground so that they can build themselves up by soaking up the last remaining rays of sun.
Multiplying plants from existing stock isn’t an activity that’s restricted to the flower borders, however.
The fruit garden is another good spot in which to be busy in September, with various plants producing runners for the following year.
This is a good time to transplant young strawberries and dig up emerging summerfruiting raspberry plants and transfer them to fresh ground so they have less competition the following year. Remember to ensure that all divided plants get plenty of water to help them get established.
September is a bitter-sweet month; still warm enough to enjoy the last days of summer but loaded with the prospect of dark, colder days to come.
Spending time in the garden now means there will be plenty to look forward to in the year ahead.