Garden Word of the Day
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Fir Bark Mulch
Fir bark mulch is made from the chopped or shredded bark of conifers, such as redwood, pine, and fir.
Fir bark mulch is just one of several different types of mulch you can use to reduce erosion, crusting, and soil compaction. Mulch also helps retain moisture, reduce weeds, and it stabilizes soil temperature. As it breaks down, it even adds nutrients to the soil. Mulch can be straw, grass clippings, compost, wood chips, or fir bark. Fir bark and wood chips last a lot longer than the other mulches.
Which is better for your landscape: wood chips or fir bark?
Fir bark v. wood chips
Wood chips come from the interior of a tree. They can be hardwood, softwood, or a combination of the two. Generally speaking, large wood chip mulches will need to be replaced every 5 to 7 years, while smaller chip mulches need to be replaced every 2 to 3 years. Fir bark, because it is made from plant material that has evolved to provide protection against the elements, lasts 7 to 10 years. Besides durability, there are other factors to consider:
Grades of fir bark mulch
Fir bark mulch comes in a variety of sizes, or grades:
The larger the pieces are, the bigger the spaces between them will be. These spaces allow air and water to flow through. Tiny pieces of mulch will hold more water in the soil, but allow for less gas exchange. Yes, it is a balancing act. The biggest thing to consider with fir bark mulch is the likelihood of flowing water in the area. Fir bark has a waxy coating that prevents it from absorbing water, plus it is very light, so it will simply float away. Wood chips, on the other hand, will absorb the water and are more likely to stay where they are.
To determine the cost of using fir bark, you will first need to calculate the area to be covered, and then deicide the depth of coverage needed. Generally speaking, mulch should be 2” to 4” thick. Newly developed areas should be given 3” to 4” of mulch, while established areas can often do with less. One cubic yard (27 cubic feet) of medium sized fir bark will cover an area of 324 square feet to a depth of 1 inch. Let me say it again:
ONE CUBIC YARD COVERS 324 SQ. FT. ONE INCH DEEP
As an example, let's say you have two areas that are 40 feet long and 3 feet wide, and one area that is 30 feet long and 2 feet wide. Here are the initial calculations:
= [2 (areas) x 40 (feet long) x 3 (feet wide)] + [1 (area) x 30 (feet long) x 2 (feet wide)]
= [2 x 40 x 3] + [30 x 2]
= [80 x 3] + [30 x 2]
= 240 + 60
= 300 square feet
In our example, one cubic yard of medium fir bark would give us a little more than one inch covered, since we only need 300 square feet and cubic yard provides 324 square feet. If we decide to use a 2 inch layer, we would need a little less than two cubic yards of fir bark. If you are a number nerd, like me, you could calculate the exact amount needed for a 2 inch depth (1.85 cubic yards), but that really isn’t necessary because a little extra is fine, or you can use it to top off your container plants.
Cost of fir bark mulch
Currently, in the Bay Area, prices for fir bark mulch average $67 per cubic yard, plus an average delivery fee of $77. A few suppliers will offer free delivery if you buy more than 7 cubic yards, but that is more than most of us will ever use. Some suppliers will also let you pick up fir bark in bags or trucks, so you can save money that way. Of course, it also means you will be picking up all that mulch One More Time. (After moving a full dump truck load of wood chips from my driveway to the back yard using a wheelbarrow, back and forth over 100 times, I can tell you that it feels like an ordeal after a while!)
Nitrogen loss (and gain)
If you use freshly chipped wood mulch of either type, keep in mind that it will, for the first 6 to 8 weeks, pull nitrogen from the soil as is begins to break down. You may need to add a little extra nitrogen during this time. In the long term, as the wood continues to break down, it will add nitrogen to the soil.
Fir bark provides an attractive, durable, and protective covering for your soil, but wood chips are free and less likely to give you splinters.
5/27/2020 02:41:06 pm
If you put a layer of cardboard down first, use drip line for irrigation, will the fir bark mulch still dray nitrogen fro the soil.
5/30/2020 07:10:25 am
7/13/2020 09:51:17 am
Thanks, this is good information, but what I'm most interested in is the acidity and how it impacts the soil. Douglas fir bark is said to be quite acidic - how different are the various types of fir bark from each other? How much do they change the soil and over what time?
7/13/2020 10:16:21 am
2/10/2023 05:02:43 pm
I beg to disagree! Bark is not nutrient laden like wood chips or arborist chips. It is slow to break down, and like armor (it's job on a tree), it tends to link together and block air and water exchange. Wood Chips are HUGELY superior. Not just my opinion....look for vetted university studies comparing bark mulch to wood chips.
2/11/2023 07:43:48 am
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