Thursday, November 13, 2014

Save those leaves!

More good advice from WA Dept. of Fish and Wildlife about getting your garden ready for winter.

November 2014
Photo: Vine maple with fall colors
Leaving those leaves helps your garden and wildlife
By Jamie Bails, WDFW Habitat Biologist

A few autumns ago, after watching a neighbor rake and bag fallen leaves, I asked him if I could spread the leaves around my perennial beds as mulch. He hesitatingly agreed and watched suspiciously as I quickly loaded up eight bags into the wheelbarrow and giddily spread the leaves around my flower beds.

Like many people, my neighbor narrowly understood the value of leaf litter. Leaves were simply raked, bagged and taken to the dump -- not my idea of natural gardening. The next year, they cut down the trees, reducing my leaf supply. For now, a 100-year-old big leaf maple and other native trees I’ve planted will provide a healthy supply of leaves, saving me truckloads of soil composted from other people’s yards.

Using those leaves for mulch also helps the wildlife that visit my yard. They provide a food source for insects which in turn are eaten by many birds, reptiles and amphibians. Leaves also indirectly support wildlife habitat in general by improving overall soil and plant health.

As leaves are falling and you’re raking them up this month, think about these Top Ten Reasons to use those leaves as mulch:

Provides food source for beneficial insects which improve the health of the soil and in turn are eaten by wildlife
Improves and adds nutrients to the soil
Increases and strengthens plant root growth
Regulates the temperature of the soil, keeping it cooler in summer and warmer in winter
Reduces weeds, as long as the mulch is weed free and deep enough to prevent weed germination or smother existing weeds
Prevents the surface of the soil from cracking or eroding by retaining moisture
Prevents rain water from running off the soil and disappearing down a storm water drain
Prevents water from splashing up onto plants which slows the spread of soil-borne diseases
Prevents the soil from crusting or compacting
Creates a natural forest floor environment
Without leaf litter on the soil, rain will release clay and silt particles, increasing sedimentation, reducing the soil’s capacity to absorb water, and accelerating soil erosion. Leaf litter also reduces wind erosion by preventing soil from losing moisture and providing cover.

Leaves are valuable soil amendments because they’re the dominant pathway for nutrients to return to the soil, especially nitrogen (N) and phosphorus (P). These nutrients accumulate in the top layer of soil until leaves decompose, by rainfall and organisms, and leach or release the nutrients into the soil below.

A wide range of organisms takes part in the decomposition process, most relatively inconspicuous, unglamorous and, from a conventional human perspective, even undesirable. This detritivore community includes beetles and their larvae, flies and maggots (the larvae of flies), woodlice, fungi, slime molds, bacteria, slugs and snails, millipedes, springtails and earthworms. This community works out of sight and gradually, over months or years. Cumulatively, they are the unsung heroes who convert all dead plant and animal material into forms that are useable for growth.

There are several ways you can use leaves as mulch:

Slow-Compost Method: Rake the leaves off the lawn (assuming you still have lawn) and pile on flower beds to make the rich hummus and leaf mold that you would find in a mature forest. The leaf nutrients will leach out while the remainder of the dried leaf will slowly compost over the winter, putting nutrients directly back into the soil with the aid of the detritivores. This is a great method for soils that are clay, compacted or dry, and it won’t smother or burn plants.

Lawn-mower Method: Run your lawnmower over the leaves and then rake onto plant beds. This is a great alternative to purchasing beauty bark or wood chips. When spreading the leaves, be careful not to cover the plant crowns. Shred large leafs like big leaf maple to break down more quickly. Large, leathery, evergreen leaves like madrona, laurel and photinia need to be shredded unless they can be allowed to decompose over several years in a back corner. Evergreen leaves can be added to a hot compost pile to accelerate decomposition.

Both of these methods are excellent ways to encourage beneficial insects in your yard. Beetles, spiders, and centipedes readily crawl under leaves for protection through the winter, as well as deposit eggs in the soil or leaf litter.

Compost Pile Method: Store leaves in feed sacks and add to compost pile as brown material over winter. An abundance of leaves can be in a wire cage for decomposition over the winter. By spring, the compost is ready to spread on beds or can be added to the food waste compost bin.

Livestock Method: If you keep poultry or livestock, use your supply of leaves for litter or bedding along with straw or hay. Leaf mold thus enriched with extra nitrogen may later be mixed directly with soil or added to the compost pile or spread throughout the garden.

If you don’t have enough leaves from trees on your own property, ask a neighbor if you can rake their leaves onto your yard. They may think you are crazy, but you’ll be walking away with valuable free soil amendments and a boost for your backyard wildlife.