nitrogenI recently posted this picture on the GardenLine Facebook Fan Page (which you should "like" if you haven't). Working on the assumption that everyone pretty much knows how I feel about black dyed mulch, I mentioned that it was a perfect depiction of the nitrogen immobilization that comes with that type of poor-quality mulch. That prompted a couple of "Then what do I use?" questions.

Looking back, it appears that it's been around four years since I posted a list of approved mulches for this area. So I guess it's about time to do it again. But first, I think it's worth reviewing my 10 Commandments of Mulch!!

I - Thou must understand that "wood chips" don't equal mulch - Mulch isn't shredded wood. Mulch is anything that covers the soil to retain moisture and nutrients and prevent weeds. Wood chips or shredded wooden pallets don't do this. They actually rob the soil of nutrients as they attempt to break down.

II - Thou must never use wood shavings as mulch - Too often, I get questions about how to use wood shavings or sawdust from a freshly cut tree, woodwork projects or a ground-out stump. Fresh wood starves plants. Wood is high in carbon, and carbon seeks out nitrogen as it breaks down into the soil. Fresh wood shavings will immediately deplete the area of nitrogen, and the plants will start turning yellow as in the picture.

III - Thou must keep mulch away from foundations - It's extremely important to keep mulch several inches below the point where the house and the foundation come together. Otherwise, insects or moisture can use the mulch as a conduit to weep holes and thereafter enter the house.

IV - Thou shalt not believe charlatans who claim mulch attracts termites - Yes, termites might use mulch near a weep hole as a path in, but just having mulch doesn't attract termites. This is a crock perpetuated by rubber-mulch purveyors and shady pest-control operators.

V - Thou shalt not make mulch "volcanoes" around trees - In the subdivision where I live, someone recently piled dyed mulch nearly two feet deep around the base of a tree. My head almost exploded! Mulch rings around trees are good, if you use the right kind. But it only needs to be several inches tall at best. (And while I'm on the subject, stop planting flowers in mulch rings.)

VI - Thou must ask one's self, "Would I let my kids play in this?" - This is sort of a trick commandment. While I wouldn't recommend wood mulch (with no compost) for landscapes, I think they're good in playgrounds and on running trails. But as for dyed mulches, just stick your hands in a batch and rub them around. Then, look at your hands and tell me if the residue doesn't look like ashen soot or dye. Really ... would you let your kids play in that? I know kids don't usually play in flower and landscape beds, but look what it does to your gloves, hands and clothes when you spread it out!

VII - Thou shalt not be fooled by "good deals" - You get what you pay for! Good mulch is seldom less than $3 a bag. It's always more cost effective to buy in bulk quantities. But you'll see tons of signs and ads that say "Mulch: 5 Bags for $12!" or "5 Bags for $10!!" That is almost always wood-chipped mulch or dyed wood-chipped mulch. And nothing good can come from that. A recent offer of three bags for $10 at a reputable nursery WAS a good deal for great mulch ... but that's $3.33 per bag.

VIII - Thou must avoid dyed (unnaturally colored) mulch - always - Most dyed mulches are made from questionable wood supplies, like shredded pallets, and nothing else. Plus, no dye is good for the soil, plain and simple ... even if it is supposedly organic. It's still dyed, and the dye will leach into the soil - not good for the soil or the plants in the long run. Other ash-infused mulches are just plain caustic. Nitrogen immobilization is what causes all that yellowing in the picture. That's a result of all the nitrogen being employed to break down the wood mulch. Then, there's no nitrogen left for the plants to keep their leaves green.

IX - Thou must understand that rubber mulch is the worst - Bet you didn't think I could slam anything harder than dyed mulch, did you? But let's defend the use or rubber mulch in a couple areas. I can see the need to recycle old tires. I just don't want them in my landscape. I have seen rubber mulch used successfully in dog runs, hiking trails and kids' playgrounds. However, in the landscape, what leaches from rubber mulch is 10 times worse than the leaching from dyed or ash-infused mulches. It introduces dangerous levels of zinc and other harmful chemicals that can kill root systems. Plus it heats up unmercifully in our summers, also killing roots.

X - Thou must believe there is no better mulch than compost - Dyed mulch has become so dang popular along the Gulf Coast because them-there Yankees done moved here from other states. Seriously, people in northern states like Ohio and Pennsylvania are accustomed to darker soils than ours, and I think this may have been their attempt to get a soil shade to offset the colors of their plants. In truth, those northern soils are not really black, just really dark brown. In fact, black does not occur in nature. You can get that dark color by using really good compost as a mulch. And before you complain that weeds will set up in it, there is lots of research that proves otherwise. I've seen it for myself, and I love the idea of good compost for mulch, mainly because it's feeding the soil, feeding the roots and feeding the plants.

So, what mulches can you use? Here are my top five:

  1. Compost - By far the standard in Houston is Nature's Way Resources' Two-Year-Old Leaf Mold Compost. A close second is the vegan compost from The Ground Up followed by Living Earth's Forest Floor compost.
  2. Shredded and double-shredded hardwood mulches - They will have a bit of compost in them as well. Living Earth's is the best known of these.
  3. Mixed (blended) mulch - These mixes of shredded hardwood and shredded pine bark mulch give you a darker color longer. Black Diamond from Living Earth is a great example, as are almost any native mulch from Nature's Way or The Ground Up.
  4. Texas native mulch - Anything you can certify as "Texas Native" is good. Nature's Way has it. Living Earth has product called "Houston Native."
  5. Pine Straw - Sounds simple, and there's usually plenty of it around. It should be used more often, especially around evergreen shrub beds with such plants as azaleas, gardenias and camellias.