Dahlia Tuber Planting ?

I am planting my Dahlia Cactus tubers today , in pots in the greenhouse for planting out late May. Now I have read that the tubers should be planted flat with the "Eye" uppermost. In the first how to video he plants them vertically in a 6" pot . In the second she plants them flat in a very nice container.
I presume vertically is OK , otherwise I will need a large plant pot ?
It also says plant 5" deep , the video shows them just covered ?
TIA

 

The advantage to planting 'flat' would be that there's no chance of an air pocket under the tubers, Harry? And depth would depend on whether there are already shoots showing? They wouldn't like being covered too deeply...

 

Interesting thread Harry

Some of my tubers have eyes on them already. They will be grown in large planters. I do have a greenhouse (unheated) so would it be okay to put them in plastic pots in the greenhouse and transplant them once the last chance of frost has passed?

 

Merle - I asked JWK on another thread , and he said Dahlia tubers will be OK in an unheated greenhouse, around now.

 

Thanks Harry

 

If anything goes wrong , we have John to blame

 

Yes, they MUST be frost free though. A little heat will bring the shoots on, which is helpful if you want to take cuttings to increase your stock.

I plant mine "flat" with the original stalk, from last year, vertical.

Note that the eyes are NOT on the tubers (different to Spuds in that respect) but rather will be on the original stem, and as such you can NOT separate the tubers from the stem, as they are only "energy storage" and will not grow on their own. Apologies if you already know that, just wanted to avert potential disaster

I have a struggle to get them into pots usually, as my home-grown ones tend to have massive tuber clusters, unlike the ones I buy ...

Once crammed into a pot, as best I can, they are only just covered - makes it easier / quicker to get them to the point of having useful material for cuttings - but when I plant them out I do plant them a couple of inches deeper.

 

Hope so, because that is what I have done this week! The only problem will be that the shoots may get quite big before I am ready to plant out and I have to take a lot of care not to break them. No obvious eyes on mine yet, and they've been planted stem upwards.

The tubers, still bagged, have been lying around in my holey and decrepit greenhouse ever since I bought them some weeks ago. They seem absolutely fine despite the sub-zero temps so I wouldn't worry too much about the potted tubers being frosted. Tender shoots wouldn't cope, though.

 

Yes, good point thanks. The tubers, protected by the soil outdoors for example, will survive most winters - it tends to be wet & cold that kills them, and they are unlikely to be wet in a greenhouse but the shoots, when they emerge, will definitely not survive a frost.

 

Just as an aside I too have dozens of huge tubers (about 20 years old),most of which are far too big to practically plant in pots to start them off in the greenhouse. I get a large sheet of polythene and cover that with about 4/5 inches of compost and plant the tubers in that. As long as you don't overdo the watering (usually soak the tubers for about 12 hours before planting if the tubers are looking a bit wizened) it works quite well and is a great deal quicker/easier than as you say "struggle to get them into pots". To plant out I just carefully lift the tubers with a spade taking as much of the new roots as possible and bobs your uncle.

 

I'm going to pot-up my Tubers in the Autumn next year ... doing them in the Spring is just one-more-job when there is so much else going on.

I have some stacking-trays that I use for Cannas / Dahlias that are too big for pots, but in the main mine do fit into pots - some of the pots are pretty beefy though!

 

Thanks Kristen , Silu
all information was new to me as I have not planted dahlias before . They are now planted stalk upwards about 4" deep in plant pots . Even though these are 1st year tubers , they took some pretty big plant pots to pot up in . Your 20 year old ones Silu must be huge !

 

Yes they are Harry! When they get too heavy to lift I split them up carefully as you have to watch for the eyes on the stems as Kristen rightly said. If you damage the tubers they do tend to rot if you aren't careful. I've now got enough to make a Dahlia "hedge" about 40 ft long but because I live in a fairly chilly part of Scotland I can't leave them in the ground over winter more's the pity, so quite a lot of hard work! Watch out for earwigs which are very fond of Dahlias, I use the old method of control, put upturned flowerpots on canes and fill them with hay/ straw/dry grass or similar. The earwigs use the pots as their bedrooms! in the early morning/late evening tip out the flowerpots and squish the menaces but you have to be quick as they can shift! I try very hard not to use insecticides and find this method works pretty well. I don't know if all Dahlias are the same but I leave mine until they have been well and truely frosted (all growth almost black) before lifting them. I cut down all the current seasons growth to about 3/4 ins .Take off as much soil as I can and then store them stem side down (meant to drain better) for a while until they have dried out quite a bit before sticking them on top of a wardrobe for the winter. You've actually done me a favour Harry as it's been so cold I'd sort of forgotten about them and had better get a move on to start them into growth again.

 

I potted my tubers up last week and popped them on the heated propagator base to give them a boost and shoots are already emerging

Interestingly a couple of tubers broke off when I was potting them up and they had small sections of the old stem on them so I potted them up too and they're also shooting

 

*Sigh* I would love a dahlia hedge 40 feet long!