How long will cardboard take to break down in a lasagne garden?
I've ordered about 30 bare root roses this year for delivery in late winter (August here in Oz), and the area that I want to plant them in is currently just grass, over heavy clay which is quite compacted and slightly acidic.
I thought I would try the lasagne method to prepare these beds. I was planning to lay down cardboard on top of the grass, then add straw, horse manure, leaf litter and a fairly fine grade mulch. Then at planting time, I thought I'd dig/turn the whole area over before planting, so as to work the compost into the soil. (I'm not going for the lasagne method because I'm worried about the hard work, I just want to have the best soil I can for my roses).
The thing is, I've only got about 3 months until the roses arrive, and I'm wondering if the cardboard will be soggy/decomposed enough by then to be able to turn or dig in? Or will it still be a solid sheet that u will have to cut through?
If it will still be solid, perhaps it would just be better to turn over the grass layer and then add the compost and mulch, without the cardboard?
Thanks in advance!