Pine bark is rich in lignin and the lipid suberin. Both resist the efforts of micro-organisms to cleave the hydrocarbon chains the bark is made of. Though heartwood and sapwood contain a fair amount of lignin, they are more cellulose than anything, and break down quickly, which causes N immobilization and a more rapid collapse of soil structure, not a desirable characteristic for bonsai. Other 'forest products' mixed into the bark can also be a problem. Hardwood bark can bring high soluble salts levels and a pH spike during the composting process, so using a product that is as close to 100% pine or fir bark as you can find is to be desired. I have ferreted out multiple sources for bark, so I have lots of options. I grow my short term plantings, like the garden display containers & veggies in a mix of 5 parts partially composted pine bark and one part each of sphagnum peat and perlite. I often find myself adding a little more perlite if the bark is very fine, but most have the opposite problem,. which is finding bark fine enough or bark that is partially composted. It's not necessary that the bark is partially composted; however, I just prefer it for it's water retention. For bonsai and all my long term plantings, I use equal parts by volume of Screened Turface Crushed granite - grower size, or #2 cherrystone and 1/8-1/4" fir or pine bark. Al The 5:1:1 mix I use is in the center here, fir bark at the top, and various other uncomposted pine products at 3,6,& 9: and this just lifted future bonsai is in the 1:1:1 gritty mix: Most people who look at the gritty mixture think you could never grow anything in it, but I guarantee that if you follow a few simple guidelines, that it will outperform (by FAR), peat/coir/compost-based soils. It's great for long term plantings like houseplants, cacti, succulents, trees, shrubs, because it retains it's structure and guarantees aeration indefinitely. The planting being root-bound is a factor long before the thought of soil collapse would even cross your mind. Al

There are pros and cons of each material. By the way, do you mean pine bark chips or the shredded wood that is a by-product of tree companies? (I've never heard of 'shredded' pine bark, is why I ask.) Anyway, there is no question that the wood product lasts much longer....pine bark can last for years without breaking down. Shredded wood decomposes faster than the bark, but will return more elements to the soil as it does so. Many of the tree companies are now using a different kind of chipper that creates very attractive little chips rather than that shredded stuff. Very nice looking. A real plus about the mixed wood chips is that they can often be had for free, as tree companies are very happy to find a place to donate their chips to, rather than pay to have them accepted into a landfill. This is my preferred mulching material, by far. Pine straw deteriorates quite rapidly in hot sun, first losing its color before it turns into dust. Pine straw needs to be obtained when it is fresh or the life span will be shortened even more. Pine straw adds organic compunds to the soil as it degrades, as do all of these materials, but they may be of limited value to the growing plants. Pine straw may need to be refreshed twice a year, which is a pain in the pocket book. Pine BARK lasts longest of all, since it is composed of lignins that even microorganisms can't break down. It maintains its color and consistency for a long time. My personal preferrance, after many years as a professional and now as a (fussy) homeower is the mixed wood chips from tree companies. One good application can last for up to three years before needing a top dressing, in my experience. Probably less in your climate. All three are great at buffering the soil from excessive heat, moisture loss, freezing temperatures, etc.

Thanks for the input! In the past we always ordered the shredded bark mulch, 25 yards or more, in early May. That was really a labor intensive job. This year, being that we waited so long to apply the mulch; the gardens are filling in with ground cover, the Shrubs are larger, the Perenials are larger, at last...the plants are taking over. I remember my Grandma telling me "First year they sleep, second year they creep, third year they leap!" If it is easier (less work) to spread the pine straw then I am all for it. We will be grinding it all up again in the Late Fall, Early Winter with the leaves from 14 large Oak trees...and reapply as winter mulch to enrich the soil. I think we are "Crazy" To work so hard!.........But it seems to be paying off!...........Dianne

Hello Jill: Here in the hot, sunny Sand Hills area of NC, I use pine bark fines (small, shreded pine bark). It is plentiful and not too expensive. It is great for the soil as it breaks down easily and improves the soil. It helps keep the roots cooler in our sometimes 100 degree weather and I think that it discourages visitors such as slugs and sometimes the stinking geese that like to trample through my yard. 'Round here, pine needles are free but I don't like them because of the bugs that consider them home - little red bugs AKA "chiggers" and if you have EVER sat on pine needles, you will NEVER forget it. They are cousins to other unmentionable critters and the red bumps are where they have laid eggs - 'nough said on that! And Larry (sweatin in ga) is right about the nitrogen issue, but the usual application of 18-6-12 granular fertilizer solves that problem. Hope this helps! Renee