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Gardening Tips

Grow-How Tips for September


September! Often the loveliest month of them all, when all the angst of wet July and August BBQs etc. is behind us, and we can enjoy the soft early autumn days calmly and gratefully.  Let’s get on with a few tasks including dividing perennials, creating green manures, and feeding container bedding plants…………….


I could never make head nor tail of these topics in maths at school – much to my sisters’ infinite scorn.  But I know how to do their horticultural versions now all right!  September is a great time to divide up your herbaceous perennial plants to make new ones or rejuvenate an established clump.  Watch my little video to see how to make divisions of two sorts of plants – the ones whose rooted rosettes you can pull apart once you’ve dug them up; Heuchera, Nepeta (catmint), hardy geraniums….. and the ones you have to chop apart Hemerocallis (daylily), Persicaria, Aster, Astilbe, Phlox, etc. You can do this job in spring as well, but I like to do it in autumn if I can, because I can see more clearly where the gaps are in the border, and imagine what the divisions will look like in their new positions.  Don’t divide grasses at this time though – they can sulk and rot in a cold, wet winter so leave these until at least March.


Hairy vetch – a manure???

Now here’s an odd thing – you can sow a load of seed onto a bare patch of soil, and the resulting plants will IMPROVE the fertility of the ground! We are so used to hearing that plants of all kinds strip the soil of its goodies, and we have got to pile on the feed and the fertilizers and the compost to make up for it, but if you sow certain things onto that empty patch in your veg garden that will be lying empty till the spring, then dig the resulting plants into the soil, usually before they flower, they will keep the ground AND add nitrogen (lots of it !!  The charity Garden Organic recently found that growing green manure can reduce the loss of this key nutrient by up to 97% compared with soil left bare!)) to help massively with next year’s crops.  There are  various seeds to use  – any sort of bean or pea, Phacelia (scorpionweed), Limnanthes douglasii (poached egg plant)…but I am very tempted to go for the enchantingly-titled hairy vetch (Vicia villosa) – just for the name really!  I shall sow it quite thickly, cover the seed with half an inch of soil, water them well and stand  back…….


September is the moment to give your hedges their final trim

The hedges get their final trim

before winter.  Tidy up the top, to a line made by a piece of string, if you can.  And remember to make your hedge a little thinner at the top than at the bottom.  This allows the light to reach the lower stems and make them grow more strongly.  You don’t want your hedge to be facing the perils of winter with a fat head loaded with heavy snow, and its legs all bare and chilly!


* It’s still worth staking tall asters, sedums etc. – autumn winds can be strong but with support, they will give colour for several weeks yet as well as prolong the season for all the insects

* If you’re thinking about starting to plant bulbs, begin with the woodlanders – anemones, trilliums and the like, which prefer a longer autumn season than most spring bulbs, to get established

* Do keep feeding and deadheading the container bedding plants once a week – let’s hang on to the summer for as long as we can![jetpack_subscription_form title=”The3Growbags” subscribe_text=”If you’d like to keep up to date with the3growbags gardening chit-chat just pop your email address in here” subscribe_button=”and click!”]

By the3growbags

We're three sisters who love gardening, plants and even the science of horticulture but we're not all experts. We'd love everyone even remotely interested in their gardens to be part of our blogsite.

3 replies on “Grow-How Tips for September”

Dear Growbags, I enjoy your seasonal comments so much – they make me wish I had sisters of my own! I am one half of the daft couple who visited Elaine’s beautiful Normandy garden twice on the wrong day in two years. I have to blame jardinscotecontention for getting it wrong. What wonders you have done during school holidays in the past. All really beautiful but something caught my eye especially in the Cottage garden, a perennial pea (lathyrus latifolius) winding itself through…I can’t remember now quite what but it was perfect. My Normandy garden hasn’t been visited by us so frequently over the years and I can only boast well tended hedges and jolly, self seeded Mexican daisy (Erigeron) though a newly planted rosier now has some beautiful David Austin ‘Lark ascending” shrub roses that have withstood the neglect of the Covid months. Current dilemma in my SE English town garden is the ceratostigma wilmottiana that pops up colourfully, beautifully and faithfully, each year but plays havoc with my attempts at a subtle colour scheme!? Crocosmia too harsh, more of the same or just get rid of it. Any suggestions?

Hi Caroline, Elaine here. Yes, it’s been very difficult to get back to our beloved Normandy gardens in the last two summers, hasn’t it – SO grateful to have made it here. The roses have been especially wonderful this year ‘Lark Ascending’ does look a stunner.All I can say on the ceratostigma/crocosmia question is that I’ve become much more brutal in my old age – if a plant is not doing what you want it to do in your garden, then it must come out! Try not to end up with a garden full of plants you actually feel a bit cross about! So bad for your karma! Good luck.

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