Trees in the Garden: Leaves of Life

It's heartbreaking to see people throw away or burn their best source of nutrients and fertility in the name of tidiness.
If you have leaves, lucky you.
If you can get your neighbor's leaves, do it.

How to use them? If they fall on perennial beds, bulbs, shrubs orchards, or beneath trees, you don't have to do anything except feel smug about the fertility they are adding.

If they are on grass or pavement or other places where they are not convenient, rake them up and put them

• as a mulch on vegetable or perennial beds
• in the compost
• in their own pile to make leaf mold and potting soil
• through the shredder if you have one so they will rot down faster

Leaves add all-important carbon to the soil, but have enough nitrogen so that they don't cause nitrogen loss when used in the garden. They are full of minerals the tree brings up from deep layers of the soil. They host beneficial fungal networks and mycelium. They make the best potting compost for starting seeds because they contain gibberellic acid, which spurs germination.

Traditional English gardeners kept leaves in their own compost area, and used the crumbly dark  humus from under the pile for seed starting mix. You can mix 3 parts leaf mold with 2 parts garden soil and one part coarse sand, perlite, vermiculite, rice hulls, or other  drainage-promoting ingredient.

Want to make a new vegetable bed out of lawn or a weedy area? I do this:
1)Mark out your new bed. Find and wet some pieces of cardboard (any cardboard box is good, as long as it is not shiny and doesn't have colored inks--brown cardboard and black ink are fine.) Remove the plastic tape, if any. Overlap the edges and any holes, so weeds can't grow through. Let the cardboard extend a foot outside the edge of the future bed, to prevent weeds from coming in.
2)Pile on leaves, straw, grass clippings, and other garden "waste"
3) Keep moist and protected from wind. A tarp or sheet can be used if necessary. Or another layer of cardboard and a rock.
4) uncover in spring and plant squash, tomatoes, or potatoes. None of those object to a few lumps and leaves. Keep mulched all season with more leaves, straw, etc.
5) By the next year, you have good garden soil and can plant anything.

Leaves to avoid
Most deciduous tree leaves are great for your garden. Pine and especially spruce needles are not so good for vegetables and should be left under their mother tree or used on forest plants that can deal with the oils in them. I am not so worried about acidity, but spruce and cedar do have natural herbicides to prevent the germination of other plants, so leave them in place where they will prevent weeds.

Oak, elm, cottonwood, fruit trees, maple, and other broadleaf trees are all good. Avoid black walnut and eucalyptus. They have poisons in that not only prevent germination, but can kill adult plants of sensitive species.

If you, like me, have a black walnut, you can find lists online of common landscape plants sensitive to juglone, the chemical that walnuts produce. Under my black walnut, a few adapted plants thrive--grass, miner's lettuce, currants, crampbark, filberts, & elder. Vegetables that tolerate juglone include corn, squash, beans, peas, carrots, parsnips, and onions. (NOT brassicas, spinach, chard, or tomatoes.) Since the roots exude juglone as well as the leaves and nuts, don't site sensitive plants near a walnut. Half my garden is in the "walnut zone" and I grow only tolerant plants in that part.

If you rake up walnut leaves, they can still be composted and make fertile soil, but if there are a lot of them, keep them in their own pile. You can use it on the many plants that don't have sensitivity.

Another great tree-based resource is ramial wood chip. More on that in another post.

(The photo at the top is looking toward our garden from the river. Boats are drawn up for the winter. For scale, the greenhouse in the photo is 15 feet tall. The giant oaks are matriarchs that nourish all forms of life here.)