Gardening With Jennifer: Autumn Leaves: Nuisance or Gold Mine?

By Jennifer Rotermund

Now that we’ve all survived what appears to be the new annual tradition of a couple inches of snow followed by a hard freeze for the Thanksgiving Holiday, I’m reminded of our love-hate relationship with leaves. 

Every year, as I lament the dwindling days of Summer, I’m comforted by the thought of the changing Autumn leaves in all their splendor. The Vine Maples go first, quickly followed by all the others in their genus, with beautiful displays of orange and red, the Raywood Flame Ashes and the Sweet Gum trees seem to redefine the definition of purple into something that would put most Plum trees to shame, and the stately Ginkgo (if you’re a tree lover, like I am, then you probably know of a Ginkgo in your neighborhood and make it a point to admire it on a regular basis) with its sturdy horizontal branches seems to come alive in the Autumn with a display of bright yellow that can only be compared with the sun. 

And if all of that beauty is not enough, these incredibly tinted leaves then fall to the ground temporarily turning our sidewalks, lawns, parks, and favorite wooded trails into a kaleidoscope of luminosity at our feet. What’s not to love!

Ah, but as the weeks pass, and Halloween comes and goes, we’re gradually reminded that this brilliant display served a greater purpose beyond our own delight. The shorter days, the cooler temperatures are sending clear signals to all our beloved trees that its time once again to rein in their activity for the season. The process of photosynthesis slows as energy is pulled back down into the roots, and we face the fact that those luminescent leaf colors are simply the inevitable and wondrous result of leaf senescence. In no time at all the very same leaves we revered are reduced to lumps of dull brown plant matter littering our public spaces and clogging up our gutters. So, out come the rakes and leaf blowers! 

Luckily, we live in a city with a wonderful system that recycles our yard waste into compost, so if all you do is send your leaves through that system, its really ok. But why buy back (in the form of Cedar Grove Compost) what you’re paying to have hauled away? Most leaves break down into a wonderful compost that your garden soil (and beneficial micro-organisms) will reward you for next Spring.

There are just a few tips to keep in mind when thinking about your leaves:

1. Remove leaves from around storm drains - this sounds simple enough, but every year our city experiences flooding on neighborhood streets and intersections caused by leaves clogging the drains. I’ve always made it a point to monitor the storm drains immediately around wherever I’m living for leaf accumulation. Five or ten quick minutes spent raking leaves away from a drain can avoid big headaches later. 

2. Rake up Broadleaf Evergreen leaves - broadleaf evergreen plants, such as Rhododendrons, Azaleas, Camellias, Evergreen Magnolias, etc., have thick waxy leaves that are designed to for “staying power” and don’t break down readily into mulch. If they drop their leaves, I recommend raking them up and sending them on through the city’s yard waste system. I include Oak leaves in this category as well. Even though the Oak tree is deciduous, it dislikes competition and produces a chemical through its leaves that slows the decomposition process. This keeps the leaves around longer and smothers plants underneath.

3. Always rake up the leaves of fruit trees - fruit trees stand in a class of their own and need good hygiene to be maintained in order to avoid (or at least minimize) the pests and diseases they tend to accumulate in the Northwest. Fruit tree leaves left to mulch on the ground around that tree provide a nice winter home for pests or bacteria specific to it. Additionally, fruit trees suffering from any fungal problems - as is common in our Northwest climate - can be continuously re-infected by the fungal spores left to rot on the ground or in the backyard compost. I prefer to send my apple tree leaves through to the city’s yard waste system each fall.

4. Watch out for leaf accumulation on shade INTOLERANT shrubs - you know those shrubs that thrive so much on sun that they shade out their own inner branches? Be it a Nest Spruce or a Ceanothus, you know if you  have a sun-needy shrub or small tree. Make sure to clean leaves off these plants regularly or else you end up with large, unsightly dead patches all over them. I include lawn (and any other sun-loving ground cover) in this category. I would rake deciduous leaves off the lawn and either directly onto the garden bed or into a composting system.

5. Chop up large leaves into smaller pieces - most deciduous leaves make great composting material - especially when they’re fairly small in size. In general, the smaller the leaf, the greater the surface area, and the quicker the decomposition process. If you are graced with a Big Leaf Maple tree on or near your property, and would like to make use of the incredible volume of resulting biomass each Autumn, run the lawn mower over the leaves first, then spread them directly over your garden beds.

Autumn leaf color may be the highlight of the season for us, but once they fall to the ground, those leaves serve a critical role in a nutrient cycle that has cared for the health of the soil and plants we enjoy since before our time on this earth. With a little assistance, that process can continue well beyond our time. I think its the least we can do as a gesture of gratitude in exchange for this annual display of light and color, don’t you?

    

Jennifer Rotermund is the Lead Gardener for Garden of Weedin’ (a local pesticide-free garden maintenance company), owner of Gaiaceous Gardens (an edible landscaping business with a teaching garden/urban farm and certified wildlife habitat located in Shoreline) and a Habitat Steward.

Photos by Jennifer Rotermund