Bounty from the tree canopy

This week a bewildered neighbor walking her dog saw me out raking the gutter across the street from home and asked whether I was cleaning up the neighborhood. “No,” I said, “It’s for compost. Biomass.” 

Why waste organic material?

     Oak blossoms, called catkins, had piled up on sidewalks and in the gutters. Just about every surface was sprinkled with those lacy brown chains of tiny flowers that had chosen the previous week to drop from the trees en masse. 

They're everywhere

To many, they looked like litter for the street sweeper to deal with. To me, they offered a great opportunity to add some organic material to the compost piles.

    Oaks, like many tall trees, depend on wind for pollination. That’s why they don’t bother making showy, colorful flowers and why they produce so much pollen. 

Strings of male oak flowers, like beads on a chain

The wind carries the yellow dust everywhere, to the chagrin of allergy sufferers and everyone who has to clear it from a windshield. Once their work is done, the catkins drop from the trees. I find the sheer mass of them awe-inspiring. What a vast amount of tree energy went into producing that huge volume of flowers!

     If I swept the oak catkins up and threw them into the yard waste, I’d be interrupting the soil cycle. In the forest, leaves, branches, and tree flowers fall to the ground and decompose there, becoming part of the soil that in turn nourishes the trees. 

Every part of a tree is recycled in the forest

    If those oak catkins were carted off my property to the distant industrial composting site that receives the city’s yard waste, then what my big oak tree drew from the soil to make those flowers wouldn’t be replenished. I’d be sending away nutrients and photosynthetic energy that could be here powering the garden ecosystem. 

Headed for the yard waste composting site

    Of all the compostable materials I cart to the piles in the course of the year, these oak blossoms are a favorite. They’re light and easy to gather with a rake or broom. Loading them into the wheelbarrow is a cinch. And they decompose really fast.

    Bigger pieces of plant tissue that are defended against decomposition, such as tough, leathery oak leaves, take a full two years to decompose in my compost bins. I don’t even try to compost twigs, because it would take too long. I could speed up the process by turning the piles, but I’ve got other priorities for limited gardening time. Tiny, fluffy oak catkins break down much faster, because they’ve got lots of surface area relative to their size. If I dug through the piles this fall, I’d find that soil organisms had already blended the catkins into the half-made compost.

Oak catkins break down fast into usable compost

    Another thing I appreciate about oak flowers is that they don’t come with seeds. Maples drop a bounty of organic material in spring too, those winged samaras that twirl to the ground, each carrying two seeds. I don’t compost those because so many germinate in the piles. Acorns won’t be viable until fall, so I can compost oak catkins and not worry about inadvertently planting trees.

Maple seeds-best kept out of the compost