Lifting & Storing Dahlias
Dahlias are easily my favourite flower of all time but they do tend swing back and forth on the fashion pendulum. Back in the 1800's they were known as Georginas and were frightfully expensive. They were a real status symbol costing one hundred pounds a tuber. Wealthy families would plant large borders full of them and invite guests round for afternoon tea to show them off. By the 1950's they had come down in price and in the drab era of brown and beige lost their attraction. They were considered showy and vulgar and many of them were lost.
Every year gardens up and down the country report that their Dahlias are slow through the summer or that they have short stems. I assure you this is normal! Dahlias are at their best in the early autumn, in the UK this is September time. They originate from equatorial regions such as Mexico, Columbia and Central America, where the days and nights are equal lengths. So the autumn equinox which falls on the 23rd September is the time they love the most. Not too hot, not too cold and not too much sunshine. The tubers have developed and the stems grow much longer.
This summer was exceptionally hot and it took a lot of watering to get them growing nicely, Ours started in late June but really took off at the end of August / beginning of September and were blooming away uncontrollably with fresh pickings every few days. However at the beginning of Sep this year we suffered an early and unexpected frost which wiped them all out in the field in addition to our Zinnias.
In my last Dahlia blog "growing Dahlias" I gave a general overview of all aspects of Dahlia growing and propagation . This time I will focus on what you need to do NOW to store your Dahlias for the winter and ensure that you can re use as many of them as possible next season.
In areas which do not suffer too much from a hard frost lifting is not necessary but for those in the UK it may be wise to lift and store them to secure your tubers for the following year, or if you have wet clay soil/poor drainage which will rot the tubers through winter.
Some do experiment with leaving a few in the ground to see if they do make it through the winter and have has some success. We do find that on our field that they do much better lifted and will bloom much earlier.
Dahlias need to be lifted out of the ground just after the first frosts. You can wait for the second frost before lifting as this will give the tubers more time to maure which will help them through the winter time.
This is usually towrds the end of October or into November where I live in the South of England. You will know instantly when you have had a frost as the leaves will all be turned black. You will then need to cut down all of the stems & leaves, leaving just 10cm or so of a main stem to help lifting.
Using a garden fork loosen the soil around each dahlia and lift the whole tuber out of the ground. Try to do this on a dry ish day so that the excess soil can be easily brushed off. You don’t need to be too thorough when doing this as the remaining soil should have enough moisture in to keep the tubers hydrated for the next few months. It is not necessary to wash the tubers at this stage as they will need to be kept hydrated throughout the winter anyway .
Once lifted ensure that you label each Dahlia. Hopefully your Dahlias still have your labels on them from when you planted out?! My biggest issue last year was the birds pulling them out of the ground so I have been much more thorough this year year and attached extra labels to the stems. Darn those birds!!!
Drying/short term Storage
Once all of your Dahlias are lifted its time to think about some short term storage until you can prep them properly for the winter. Dahlias can be stored in clumps of tubers – there is no need to split or wash them at this stage as the soil will give them enough moisture for a good few weeks. You are essentially removing them from the ground to ensure that the frost does not damage them. I store mine in plastic crates in my garage but any cool dark place – frost free will do such as a basement or shed and ideally the temperature should be 5-10 ℃.
For longer term storage it’s good to ensure that they have an adequate level of moisture and heat to get them through the dark winter months which is just like a hibernation period for them. This can be done in whole clumps but there will be a lot of wasted space with gaps and unviable tubers so to cut down on the space which they take up we divide our tubers and get rid of the unviable ones before storing the rest. If you are only storing a handful then space is not so much of an issue but splitting is good as it ensures that all of the mud gets washed off and they are less likely to rot once they have been cleaned up.
Once you are ready to store your tubers for the winter you will need to give them a good wash with some clean water. You can do this with your hozepipe outside. It's a dirty job and the power from your regular kitchen tap will not be strong enoght to clean the tubers well. You can see from the picture how clean the tubers get. This is essential to ensure any creatures and soil are washed off ready for hibernation.
They can immediately be split for winter storage!
Dahlia Anatomy & Splitting
Each plant consists of a stumpy stem or stems and will have several swollen parts attached. They are really not the prettiest things to look at ! These are called tubers and to grow into a successful plant each Dahlia needs a tuber with at least one eye. The section where all of the tubers and stems meet is called the crown. Dahlia stems will grow from buds or eyes on this crown. Look very closely all around the crown of the tubers for the eyes and you will be able to see small freckle like spots, Some tubers will have lots and others just a a few.
Remember the tubers are not roots – they are a food store for the plant. If a tuber does not have an eye then it will not grow no matter how much care and attention you give it.
It can be difficult to know where to start but if you begin by splitting a tuber in half across the old main stem you are half way there already. Try splitting between the tubers so that you get less wastage, but inevitably you will end up with a few which have been sliced through. Make sure that you throw these - they will just rot in storage and put the rest of your stock at risk. You can then split both of these halves again so you end up with four quarters if your tuber is really big.
Now it’s easier to look at each tuber and decide if it’s viable or not. Carefully check the crown of each tuber looking for at least one eye. Some will have none – these can be discarded but others may have many. Then simply cut this tuber away from the rest taking care to cut it away with the eye and some crown. Repeat this for each tuber in turn.
If you have any tubers which are a bit wobbly and broken remove these and do not store them - they may rot. At the same time you can also trim off all of the fine roots as these will not be needed for winter and new ones will be produced next season.
Once you have discarded all the parts without an eye and done your trimming you will be left with a bunch of nice neat looking tubers. From that one clump which you planted in springtime you can get as many as 10+ viable tubers which will in turn make a huge clump of tubers for you to divide next year!
There are a few different ways to store Tubers but the below method is long tried and tested and I have used it for a number of years.
You will need a container to store them in such as a lined bulb crate or a plastic box/bin, and a medium to cover them. There are so many mediums to store tubers but the most important thing is to keep them hydrated and frost free. You can use vermiculite, peat moss, spent compost, wood shavings etc. Last year we used wood shavings - the kind you can buy from the pet shop for rabbits.
Simply take your container and put a layer of your medium in the bottom. Place each tuber onto the medium and ensure that they are not touching then cover the tubers with another layer of your medium. The label which you used for short term storage can then be placed inside the container. You can apply a fine mist of water to the medium... but really only a fine mist - it should not even feel damp to the touch as too much dampness will rot the tubers.
If you only have a few tubers and you want to store them all inside the same container then you can just write on each tuber with a marker pen. Sharpies are very good for this.
Once you have done this store then away in the frost free place at 5-10 ℃
It’s a good idea to check up then once a month until spring time. If the tubers are looking shriveled then a light misting with some water will help to keep them going. They should not be left to dry out too much or be left wet or they will rot.
We then check ours after 2 weeks - yes every single one unpacked from storage checked and then packed back again - this is to remove any rotting ones as otherwise the rotting ,may spread throughout the crate all winter long. We then check them monthly/bi monthly after this and remove any rotting tubers. After the first check it is rare to find many rooting ones but its best to be safe. If you suffer from rodent attacks it is also wise to ensure you use something with a lid ! Just ensure that the lid does not seal in too much moisture and rot the tubers.
We have experimented using shrink wrapping film instead of af storing in a medium but it rotted all of the tubers by sealing in the dampness. They really do need to be done dry when storing like this and we havent managed to get it right as yet so we will continue with the woodshavings for now.
Small numbers of tubers
If you only have a handful of tubers then its not necessarily worth the effort splitting them at the end of the season. They can be stored unwashed in your choice of medium for the winter - you still need to keep them hydrated by misting if needed and check them regularly for signs of rotting. This way you can wait for sprintime to divide them when the eyes have started to form a little more .... they are much easier to see in spring time than in Autumn!