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STOP! Don't forget to cut these plants back in September

Walking Talking Gardeners

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September is a crucial month for garden maintenance and your last best opportunity to prune and tidy many garden plants before winter sets in! In this video, we cover the essential plants you need to cut back right now in September—from tackling fungal and mildew risks to last-chance shaping and deadheading for extended autumn blooms.

Learn the right pruning techniques for herbaceous perennials, herbs, topiary, and hedges, plus the common pruning mistakes you must avoid to protect your garden from frost damage.

🌿 Plants covered in this video:

Fungal & Mildew Control: Hypericum (St. John's wort), Lupins, Delphiniums, Monarda, and Phlox
Hard Cutbacks & Containment: Ivy
Last Chance Pruning & Shaping: Lavender (how to prune properly without cutting into old wood), Rosemary, and Thyme
Hedge & Topiary Trimming: Box (Buxus), Bay, Yew, and Cherry Laurel
Foliage Tidy-Up: Hostas and Arum Lilies (Zantedeschia aethiopica)
Deadheading for More Blooms: Buddleja (Butterfly Bush), Alstroemeria, Nicotiana sylvestris, Dahlias, Marigolds, and Cosmos

⏱️ Timestamps / Chapters:
0:00 - Introduction: Why September Pruning Matters
1:23 - Pruning for Fungal & Mildew Control (Hypericum, Lupins, Delphiniums, Phlox)
3:28 - Ivy: The Only Plant for a Hard Cut Now
4:49 - Last Chance Pruning: Lavender, Rosemary & Thyme
9:10 - Autumn Trimming for Box, Bay, Yew & Laurel Hedges
12:17 - Foliage Care: Hostas & Arum Lilies
15:22 - September Deadheading for Extended Autumn Blooms
18:57 - Summary & Community Tips

💬 Join the Discussion: What plants are you pruning or deadheading this month? Let us know in the comments below, along with your growing region or country!

👍 Don't forget to Like, Subscribe, and hit the notification bell for more practical UK gardening tips and plant care advice from Walking Talking Gardeners.

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20 Comments

@walkingtalkinggardeners Creator 3 weeks ago Pinned

September always feels like that tricky transition month where you're not quite sure what to prune and what to leave alone! ✂ Are there any specific plants in your garden you're hesitant to cut back? Were there certain plants that you have already cut back by accident? Drop them below and let us know! 👇Lots of love, Simon and Lorna XXX

@kenegelly3546 2 weeks ago

Pruning advice always most welcome. In the midst of ‘life’ it’s all too easy to forget the must do’s when it comes to this housekeeping chore. Thanks for the timely reminders!

@arthurscott8583 1 day ago

Ivy berries are a really important food source for blackbirds and other thrushes late in the winter and going into spring. Going in hard on Ivy now will be hitting those birds in your garden hard as well.

@AnnJackman-rc7sg 2 weeks ago

if you have the space it is great to leave ivy to flower as it provides lots of food for bees when there is little else for them, and it is awe inspiring how many bees you see on a sunny day.... and berries for birds too.

@TickityBoo70 2 weeks ago

Hyped, liked and subscribed because your content is just fab and I really enjoy your personality! Plus, I’ve gleaned some invaluable knowledge throughout the past 6 months. Thank you very much 💚 from a novice gardener who’s getting her proverbial finger out and getting it green.

@carolewynn-jones9517 3 weeks ago

Good video as always. Thank you.

@infraterrestrial 3 weeks ago

I always leave ivy until spring, for the critters

@MartaMcGillivray 2 weeks ago

Will really miss Monty Don but so glad I've discovered your programmes - just need you to get a dog!

@aparkins8142 3 weeks ago

Thanks in advance 👍

@davidw3567 2 weeks ago (edited)

I live in Amman, Jordan, where we have a loooong growing season. We have two types of lavender in the garden: a Lavandula agustifolia, or English Lavender, and several Lavandula multifida, or Fern leaf Lavender. The English Lavender, in its second season, produced on schedule, starting to bloom in May, and, with deadheading produced another bloom later in the season, ending in late July. After that, I followed the 8/8/8 rule. It's actually looking a bit peaked, but there are plenty of tiny little new buds waiting to burst forth next spring. The Fern leaf is quite another story. Two seasons ago, we bought a row of them at a nursery, not because I especially liked the look of them, in fact, they looked tired even then, but because that was the only variety he had. They all died. But, lo and behold, before popping off, they had reseeded themselves, came back last spring, and now we have, let's call it, half a row. Those things have been flowering all summer (I deadheaded them mid-season, too), and they are continuing to flower into mid September. I still haven't cut them back, and I'm not sure when I should. They basically have no woody growth yet. I've grown to love them, certainly because of their long-lasting display. But also because I saw a mature stand of them at an old house, which formed a lovely gauzy cloud of foliage topped off by those persistent blooms. I'm hoping ours will reseed again and start growing our own gauzy cloud!

@ocn14s 3 weeks ago

With the greatest respect Simon, I'm not prepared to trim or prune my two lavender plants yet while they are still in their prime , my blooms are still a beautiful lush bright purple with no hint of woodiness or fade and they are still being pollinated by the bees - I have done a bit of googling about lavender and it says that in its first year (mine was only planted in the bed at the end of May) it does not need trimming or pruning - unless it dramatically fades between now and the end of the month - Im prepared to take my chances and wait until next Spring - if I turn out to be wrong I will admit it - all my other plants are and have been deadheaded regularly - plus I have asked a couple of other gardeners who have seen the plants who think the plants should not be trimmed or pruned yet

@northwalescoast7911 3 weeks ago

👍

@nwenban 2 weeks ago

Thanks Simon occasionally in my gardening work there are jobs that I am very reluctant to do but nevertheless need to be done. Last week I had to prune hard one side of a long Holly hedge laden with berries which had not been pruned for several years & had encroached several feet over a private path making life very prickly for the family, postmen, couriers, etc. The hedge is over 10ft tall, I pruned up to 6ft (still too short for you 🙂) so the top half is still laden with berries & I will advise the owner to get tree surgeons to cut the top half in early Spring before nesting season. Anyway your slacking mate sort out that blasted Bindweed growing through your Arum Lily 🙂 cheers Steve

@DGardenlover5-i7w 2 weeks ago

I don't prune the flower stalks off my lavender until spring because they still have lots of blooms and because the flower stalks help protect the plant from heavy snow and the cold of winters in zone 5 in Southern Ontario Canada. I prune in spring as I often have to remove some winter damage.

@SilkFeathers 3 weeks ago

thanks for all of the advice Simon! I'm only getting into outdoor gardening this year, with last year being my introduction to indoor plants... this is eye opening and very informative! Also love the funny quips, and the lack of AI generated content. Loving it overall - new subscriber now!
also - any advice for rose cuttings coming up to the colder September nights? I am worried they won't survive, though I am overall just over-anxious of my propagations' overall well-being.... again, being inexperienced and all. Located in Ireland!

@StuartFrost-v8d 3 weeks ago

When is the best time to trim and tidy up my magnolia Stella Star and red robin. Thanks

@nettie8376 3 weeks ago (edited)

thanks, useful advice, can I do a tidy trim on my myrtle that is still flowering? In West Wales

@hlederer3938 2 weeks ago

My sambucas nigra black lace is too big. Can I do some heavy pruning now, so that new growth this year will produce flowers next year ?

@paulettestancil5986 2 weeks ago

Hahahaha Lorna it’s your garden too 😂

@redlantern3371 2 weeks ago

@18:31 I love that combination color of plants! The yellow/reddish dahlia, the blue salvia, and bronze/red/yellow of that 3rd plant. What is the name of that one? All together they are so pretty! Thanks for all the great instruction Simon. Excellent video! 💚