One of my dahlias has pretty bad mildew that keeps returning. I will cut it right back and let it grow some new leaves (to bulk the tuber) until the frost knocks it back.
I think yellowing leaves is nutients returning to the roots. Instant black mush is just that, black mush. It will feed the soil, but it won't be returning anything to the tubers.
location: Surrey Hills, England, ex-woodland acidic sand. "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
Dahlia stems are like hollow tubes. I thought the point of cutting them down after a frost was to wait until the stems seal up, to avoid rain water going down the tube and rotting the tuber.
I leave dahlias in the ground in winter with mulch on them. Most survive. I don't cut anything much down until early spring when I clear it all in time to enjoy the daffodils. Untidy gardening is friendlier to wildlife.
Dordogne and Norfolk. Clay in Dordogne, sandy in Norfolk.
I’ve tended to lift my dahlias out of their pots when the leaves have mostly yellowed and the blooms have all but stopped. This has been before any frosts (but not long before as it turned out), and this hasn’t affected how they perform the following year. However, this year, they are still blooming really well and a lot of the leaves are still quite green, so I’m leaving them for now. This has been the best year for them, actually, with many more blooms and for a longer period. They cheer the garden, so I’m happy to leave them be for a bit longer. I don’t leave them outdoors, because it can get pretty cold and wet up here.
We have well-drained sandy loam and I leave all of the dahlias in situ all year with just a mulch when I get round to it. Any which don't survive are the ones I don't grow in the future...too much effort...but almost all do. I don't cut them down unless the foliage is diseased or we have a frost which turns them to mush. They are tidied up when the weather is milder in the Spring. I have also left Hedychiums and Cannas which have come through despite the cold, so I think this is one way in which we may be able to take advantage of climate change to save time and storage space.
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"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
I leave dahlias in the ground in winter with mulch on them. Most survive. I don't cut anything much down until early spring when I clear it all in time to enjoy the daffodils. Untidy gardening is friendlier to wildlife.
I don’t leave them outdoors, because it can get pretty cold and wet up here.