Q: I will be starting a new raised garden in the spring. Should I build and fill the garden beds now and cover them until planting in the spring or should I wait until just before planting?
A: I can’t tell you how many times people suddenly wake up to gardening in spring, when it is too late to attend to the structure of a garden. Your farsightedness is commendable. It means, first of all, that you can take your time to get it right, that you don’t have to rush and get stressed about it.
The first thing to consider is whether your planned beds are wide enough. A common mistake is to make them too narrow. Think about that. By giving yourself time, you can back-fill the bed with the native soil mixed liberally with organic matter, then cover it with landscape fabric to keep weeds away and to encourage earthworm activity. You can spend the winter compiling a plant list. You will then find that by spring it has settled a little, giving you an opportunity in early spring to add more good stuff to the bed.
Q: I have access to unlimited amounts of shredded tree stumps and limbs generated when city crews take aging trees down. I assume it makes an excellent mulch for top-covering perennials over winter. What ratio of this material should be mixed with soil to make a good top soil for growing plants in containers next season?
A: Wood chips make a good, if temporary, path layer, and although they do make nitrogen as they break down, there’s no reason not to use them in a compost pile if you can mix large amounts of green material with them: grass clippings, kitchen scraps, the vegetation from the garden. You could start a compost pile now and by next spring, it should be broken down enough to use in containers, but you would want to screen it first to get out most of the lingering woody bits. A pile breaks down more quickly if it is at least a cubic yard in dimension, gets some moisture (but is not sodden) and is turned monthly.
Q: I’ve heard a lot about planting clover and other “green manures” over winter, then turning them into the soil before spring. Does it work if you just toss handfuls of clover onto the soil and till it into the soil in late fall? Or are those rootlets the things that are important?
A: Winter covers are great for beds that otherwise would be fallow for the cold months. Importantly, they prevent the soil from being overrun with winter weeds. Legumes such as clover have the added value of adding nitrogen to the soil, but winter oats and wheat are great as well. Vetch tends to reseed and come back in a way that isn’t always desirable. I like red clover, simply because it is beautiful. Cut it down in late winter, dig it into the soil, and you’re ready to go in the spring with veggies or new ornamentals.