The garden in September

By

Lee Bestall
9th August 2018

The year is drawing closer to its end and while the September light can be splendid, it’s also softer and cooler. Autumn is kicking in and, while plenty of plants still offer up their best now, others are slipping into dormancy.

This makes the season one of the best times to reposition plants: soil warmth encourages new rooting before winter, but reduced air temperatures reduce the risk of dehydration. Shrubs, trees and herbaceous perennials will thank you for moving them now, in their own silent way.

Plant of the month: Miscanthus sinensis ‘Gracillimus’

Our September specimen is this spectacular grass, hailing from East Asia. It does require room to do its thing – up to 1.5m spread is possible – but its fine foliage, waving in the September breeze, is worth the space. Its flowerheads are an even more appealing element this month, the white tassles shimmering in the gentle light. 

The flower garden 

  • Fork out and divide congested clumps of herbaceous perennials or alpine plants
  • Plant spring-flowerers like wallflowers and foxgloves, sown earlier in the summer, in their final growing position for next year
  • Sow sweet pea seeds now, and they’ll overwinter in a cool covered place, providing earlier blooms next summer
  • Consider bringing tender perennials like gazanias indoors now, especially in harsher areas, ahead of frost-damage; tuberous plants like dahlias are still flowering and will cope until the first frosts blacken their foliage
  • Weedkiller applications to perennial weeds is generally more effective at this time of year

The edible garden

  • Check if apples and pears are ready for harvest: any windfalls under the trees? Does the fruit twist off the stem more easily? How does one taste and feel?
  • Keep winter squashes and pumpkins well-watered – they’re thirsty plants!
  • Seed sowing is coming to an end this month – make sure to sow any hardier veg you plan to overwinter soon, and plant your overwintering onion sets now also
  • Plant out and protect spring cabbages sown in summer
  • Grab a pair of secateurs to prune blackcurrants at the end of September, leaving younger wood

Project of the month: Making leafmould

Earlier this year we urged you to create a compost bin; now we’re extolling the virtues of homemade leafmould. This fantastic free organic matter has several uses. It can be used as a mulch. Use it as sowing medium when very fine. It improves both heavy and sandy soils, loosening the former but binding the latter. It’s a longer process, as it depends on fungi rather than bacteria and heat, but it’s worth the wait.

By far the easiest method of production is to collect fallen leaves using your rake which you can then chop or mow to a finer consistency, before placing in plastic bin bags. Water the contents thoroughly, then fasten the top of the bags. Pop air and drainage holes in the sides and leave somewhere darker and damp to decompose. It’ll take around 12 months, or two years for a finer outcome.

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The Author

Lee Bestall

Lee Bestall

As a horticulturalist and garden designer, I'll be guiding you through the seasons ahead, sharing tips, successes and failures and exploring some of the new and inventive products on the market.

Join me to see what jobs I recommend you should be doing in the garden each month.