Though I use 1020 trays to start my dahlia collection, I will lend some insight on using milk cartons.

Milk cartons have a waxy coating that will not break down. You need to remove that when transplanting your dahlias into your garden.

You can easily cut off the container without disturbing too much of the root system.

Take all of the soil you can with tubers but do not plant it in the container.

Happy Gardening

Keriann~

thanks for the response!! I can sort of visualize how to do this.
I will remove the wax coating, hopefully without destroying the carton.
Maybe punch a few holes to speed the disintegration after that.

Oh... sorry. I meant remove the whole carton... not just the wax : )

Geeze that would be pretty hard to just try to get the wax off :)

you need to cut the whole carton off, the roots can not grow through the carton walls and the carton will not decompose for you.

Keriann~

ahhh!! maybe this isn't such a good method after all. Wouldn't removing the carton damage the roots?
The cardboard left after removing the wax cover is pretty thin but I guess it will take time to disintegrate.
I got a bunch of hits when I did a search on this, so it is probably used in practice. Surprisingly nothing on gweb.
I guess I will try one tuber in the carton and move the others to newspaper pots. I just put the tubers in the a couple of days ago.

Well yes and no.

I give mine a head start in a 1020 tray so the roots are jostled around much more than in a newspaper pot.

I have tried newspaper pots and in the end, both the ones in the tray and the newspaper pots looked the same 1 week after transplanting them outside.

Sure a few feeder roots snapped off, but it did not stunt my dahlias to the point it was noticeable.

If you are concerned about root damage, newspaper pots are the way to go.

But I encourage you to try the milk carton method once; you might like it in the end.

Keriann~

really appreciate the input!! I like the convenience of the carton and labeling the open flap is nifty too.
I noticed that after removing the wax coating, the cardboard is pretty thin, though thicker than the newspaper.
Do you think if I cut off all the sides and plant the dahlia with the bottom ( sort of like placing the tuber on a flat tray), it might work?
I guess only one way to find out. :)

I love experiments!.. and you are welcome : )

Dahlias are pretty tough flowers, so I donÂt think you will lose any.

Just monitor how much water they are in need of once you transplant them outside. If they are requiring more water than your other plants they may be a sign their roots are tangled and Âballing up on youÂ. In that case you will need to dig them up and get the cardboard out.

Just an FYI, I take my tubers out of the trays before planting them outside. Almost all of the soil falls off so I am planting a 'naked' tuber with quite a bit of top growth, but I water in well and they bounce back within 3-4 days.

Keriann~

There are many very serious dahlia growers who grow their dahlias in pots buried in the ground. Some do so to avoid having the tubers be eaten by gophers. Your milk cartons would not slow down a growing dahlia plant. Even dahlias grown in 6 inch pots do well as long as the pot is buried.

6" pots?

For bedding dahlias right?

That seems way to small (6" container), in my opinion, to grow any dahlias other than bedding dahlias.

I would never risk it.... I do not think they would get enough water and nutrients.

Keriann~

The tubers I have are in the 36'' - 48'' range. The milk carton is half a gallon, so not much soil volume there.
I don't see this working unless of course the roots are able to penetrate the carton into the soil.

The milk carton is just a container to use when you start dahlias indoors to give them a headstart, so you get blooms earlier.

They are not planted in the garden in the milk carton. : )

I don't think the roots could penatrate through both of the wax coatings on the carton (inside and coated outside)

Keriann~

I was speaking hypothetically in response to the poster above.
I already agreed what you wrote earlier ;)

One of the growers of full sized dahlias in pots is commercial, selling cut flowers. One and two gallon pots have weep holes where moisture can drain and roots can sneak out. Teresa Bergman of Cowlitz River dahlias planted a show garden of dahlias that grew four feet and taller in 6 inch and smaller pots. Gordon Leroux of Kenora dahlias planted all of his seedlings in small pots and left all of the pots in the ground. They grew to normal size with normal sized flowers. He planted 2600 of them one year. The milk cartons would work fine if you remove some material on the bottom to let it drain(you probably did that already as you do not want to drown them).

ted, thats some interesting info!!! thanks! I am going to try this on a couple.
I am surprised that there are so many references to this method but not a clear how-to, specially at the transplant step.