Dahlias

watlingg

This is the first year I have grown dahlias and with much success; they look absolutely glorious and I feel if the weather is kind (I live in Norfolk), they may well flower through to November. My neighbour leaves hers in the ground over winter and just mulches which proves successful and I plan to do the same. My question is, once flowering is over, should I let the stems and leaves die back or do I cut them down. Furthermore, does the mulch have to be removed in the spring/early summer to allow for growth? thanks for your help.

Hortum-cretae

Let the stems blacken, which they will at the first frost, then remove the old growth and do the mulch thing (or lift the tubers and store them). If your neighbour's plants are surviving well with just a mulch for protection, then I'd go with that. No, the mulch can stay - it'll just rot down and become a nutrient release for the plants. However, don't rely on that for food. They will benefit from a top dressing of good compost in spring (not too rich, that can cause yellowing and weak growth) and a high potash feed when buds start to show.

H-C 

watlingg

Thanks for all your advice.

Kelly39

Can I please jump on the back of this post and ask if it would be ok to leave Dahlias in the ground in Surrey/ Greater London?

I'm assuming so but thought I might check.

Thanks 

Kelly39

Also some of mine have grown at an angle. Is it the way I planted the bulb or lack of support structure?

Thanks

Kelly

sooty5

Woud I be able to leave them in , I'm near Bristol on the coast , so not freezing , thanks , 

Fairygirl

Hi Kelly  - I'd have thought you might be ok leaving them in the ground, but they benefit from a mulch if you tend to get frosts. That will help give them some protection. 

As to the angled stems - it could simply be a lack of support. If they're in a border, other planting can help provide that, but they may need staking too. If they're in too much shade, they might be leaning to get more light, so you may just need to site them in a better location. 

Hi sooty - You might be ok with them too. It's cold, wet, heavy ground that is no use for them as they just rot. Frost is fine if you keep them mulched as mentioned, but do it well before you're likely to get any severe weather. Once they get a frost which affects the plant noticeably, that's the time to cut them down and you can mulch then. If you get no proper frost, you can tidy them after the flowers are done or past their best, and mulch then.   As with so many plants, you might find them better in some years than others.  

sooty5

Thanks for the advice Fairygirl. hoping they will continue flowering for a few weeks , what star performers!

willbara

Dahlias really need to be supported from when they are quite small,

directly after i plant mine i put three stakes round each plant and then twine round the outside of the stakes, as they grow up i continue to put the twine round the stakes at intervals until they reach their full height, sounds a lot of work but it is not and it is much easier than waiting until the stems are straggling all over the place.

personally i would be against leaving the tubers in the ground even in the milder areas of the country as tubers left in the ground are inclined to be badly attacked by slugs and in some cases  ruined.   as has been said whatever you do wait until the frost kills the flowers and stems before you cut them back, i personally put all the top in my runner trench, they make wonderful open compost for runner roots to get into the following year.

 

Kelly39

Thanks Fairygirl and willbara