Douglas fir needles and cones

Asked July 12, 2019, 2:19 PM EDT

Hi there, I recently moved into a home that has about a dozen Douglas Fir trees, very old. The previous homeowners used the space under the trees as a bit of a dump and apparently never removed the cones and needles that fell from the trees. We would like to clean it out. I would also like to get rid of some of the lawn in the front yard by creating a berm that I can plant with things like Lavender, possibly blueberries, rosemary, and other useful, lower maintenance (as opposed to grass) plants. I’m writing to see A; will it hurt the Douglas Firs if we remove the old needles and cones from beneath them (since in a forest this material would just stay where it falls and perhaps provide some insulation?) and B: I was wondering if mixing the needles and cones with soil would be alright as filler for the berm I’d like to create. Obviously I would add soil and hopefully some rock to make up the berm. And a final question; is there a local resource to get rocks economically other than buying them from a landscaping company? The house is from 1947 and needs quite a bit of updating, so our budget is rather small. Many thanks in advance for your help.

Hood River County Oregon

1 Response

It shouldn't hurt to remove accumulated Douglas-fir needle and cone litter that is not decomposing or full of live roots. When you get to the older layers in the forest floor that are decomposing and being incorporated in topsoil, then you might want to leave those to protect roots. Tree roots get a lot of their moisture and nutrients from the top few inches of soil and decomposing litter, so keeping that intact is best. In general, the accumulating needle litter does act as a mulch. But in home landscapes near buildings, it can also be a fire hazard, so most folks keep it raked.

Mixing the needles and cones in the filler soil for your berm should be good as it adds organic matter. But if you want it to decompose faster and provide better nutrition, you might need to add fertilizer to help the organic matter breakdown and not tie up other soil nutrients. Lots of high-carbon tree undecomposed litter mixed in the soil will use up nitrogen as it decomposes.

As for sources of rock, the big landscape suppliers usually have a decent price by the yard or ton when you haul it by the pickup truck or larger truck load, rather than smaller quantities.You get a much lower price per yard on the rocks if you order a bigger dumptruck load (~5-10 yards), but then you have the delivery cost. Estimate how much you really want by measuring depth * surface area = volume. Call around to get quotes on material and delivery cost - do the math to get delivered cost per yard vs DIY loads and see what works for you.