Yes, it definitely time to think about mulching and possibly strulching your dahlias.
If you listened to my first ever podcast episode, you’ll know I talked about the sheer insanity of leaving your dahlias in the ground over winter. However, if you’re the reckless type who fancies their chances against the vagaries of winter, you will definitely need to choose your preferred dahlia mulch and have it to hand.
Here in East Sussex, the first frosts will probably come in the next few weeks, although it’s tough to predict for sure given the odd weather we’ve had the past few years. When the frost hits your dahlias they’ll turn into a mushy pile of dead foliage. It might take a hard frost or a few milder ones before this happens but when it does, I would clear away the mushy foliage from around the crown of the plant. Then I’d stick a label somewhere in the vicinity to remind myself the tuber was there and I’d heap on a good layer of mulch – probably as thick as 15cm-20cm.
If I had to choose a mulch to put on to protect dahlias, I might go for Strulch. If you haven’t used Strulch before, it’s slightly bizarre stuff. It looks and smells like horse feed - the smell is really quite strong but not unpleasant. It feels as if it might blow away in an instant as it’s light to handle but in practice, it stays put where you apply it. It’s certified organic and doesn’t contain any animal products or by-products. It comes in bags made from recyclable plastic but if you’re ordering the large bags, I can confirm they make the most amazing mini-composters if you’re pushed for space. A few years back, I had lots of the large bags left over after a job. I took them home and filled them with a mixture of garden rubbish, rolled the tops over to close them and left them at the side of my greenhouse. Within a matter of months, the contents had rotted down into lovely compost.
According to the Strulch website, the surface of the Strulch mulch dries out quickly and this property, along with the combination of added minerals present in it, make it an inhospitable surface for slugs and snails. The website claims Strulch doesn’t cause any harm to gastropods, it simply deters them. I can’t honestly say I’ve ever used Strulch for this reason but there appears to be plenty of anecdotal evidence on the website supporting the claims. Young dahlia shoots are top of a gastropod’s culinary hitlist, so any help you can get dissuading them from eating new growth has to be a good thing.
My reservation is that, as I understand it, it’s processed purely for the purposes of becoming mulch, which seems a little unnecessary. There are other things you can use for mulch that are the by-products of other processes, such as coffee grounds or spent hops, if you can get hold of them. Probably the best mulches are natural ones, especially if you want to increase the population of earthworms in your soil (as explained here in the Worms episode of the podcast). However, a plus point to using a processed and therefore ‘clean’ mulch is that it shouldn’t harbour any unwanted things like plant disease pathogens or slug’s eggs.
I wanted to give Strulch a review as I’ve previously worked with it and I do know people who swear by it. I think it would be a decent product for mulching your dahlia tubers, it’s a nice product to work with, it looks as if it would provide good insulation for the tubers due to its physical construction and it looks decorative. Would I mulch a whole border with it? Probably not as it works out fairly expensive compared with other mulches. Does it deter slugs? I don’t know. I’m aware of a slight ache in my backside, I think it’s from sitting on this fence. As with all things, It depends what you’re looking for. If you haven’t tried it before, I’d give Strulch a go around your dahlias to start with, you may love it.