Mulch

[Hans L]

We have a small area next to the house (in the Cleveland, Ohio, region), where my wife has planted petunias for the second year in a row. It gets sun part of the day. Last year, the flowers lourished and eventually covered the entire surface. However, before they had proliferated, one could see the hardened, dreary-looking soil. So this year, I added mulch. Looks great.

Now, the flowers did not expand at all this year, and a bush in this area died rather quickly at the beginning of the summer. A neighbor and my wife claim that it is the mulch that hampered the growth, and my question is if this could be the case. It needs to be mentioned that we have had a lot of rain this year, that there is no slope in this area, that the humus/soil-cover is rather thin, and that there is clay underneath.

Thanks -- Hans L

[paghat]

If you used something like heavy straw for winter mulch, it has to be removed near winter's end or early spring as it smothers stuff that is trying to grow, & as straw too-slowly decays, it robs the surface soil of nitrogen. In some cases, an uncomposted bark can also rob the soil of nitrogen.

But if you used a completely composted manure topcoating for mulch, that improves the soil & healthful microorganism populations, in addition to protecting roots of things in winter & encouraging worms to work the soil a bit. Manure compost would not have stunted or stopped the growth of anything except seedlings (a pure surface compost tends to be sterile & it is difficult for seedlings to get started through it, which is why compost topcoatings suppresses weeds, but not so good if seeds were surface-sown).

I'd look elsewhere for the cause of problems. Unturned compacted soil with too little organic material in it, plus poorly draining clay soil during a period of heavy rainfall, would predictably stunt plant growth or even kill some of things outright.

-paghat the ratgirl

[Pam - gardengal]

This is entirely correct, however I would also add that the specific type of mulch can make an impact on the plants' performance. Mulches comprised primarily of sawdust or very fine bark can reduce the available nitrogen in the top layer of the soil, which can result in stunted or or less than optimal growth. This is more likely to be a problem with very shallow rooted and herbaceous plants like annuals and most perennials rather than larger and sturdier, woody shrubs and trees with deeper root penetration. Simply providing additional nitrogen rich fertilizer will offset this or use a compost mulch in these areas.

Since you indicate a shrub has died off as well, I'd be more inclined to agree with paggers that too much rainwater combined with the less than ideal drainage of heavy clay soil is most likely the culprit. This can be a fatal combination for the majority of plants.

pam - gardengal

[Hans L]

Hello paghat the ratgirl & pam - gardengal:

Thank you for your insights. I have two followup questions:

- I added bark mulch because the soil, before the plants covered it, became dry and hard as rock, looking aweful. The bark mulch (tinted black in our case) makes the ground look nicer. What else, more beneficial to the soil, could give the same effect?

- Is there any way to drain a flat area as ours? Digging up the clay and mix it with sand? Or ...?

Hans L

[Vox Humana]

surface-sown).

What is the possibility that the mulch was contaminated? I understand that some bagged mulches can contain ground-up shipping pallets that are contaminated with all sorts of chemicals that might have been in containers that they supported.

[remove munged]

Not only contaminated with chemicals, but carrying potential pathogens from overseas!

[Jim Carlock]

Home Depot and Lowes are two companies selling mulch that is treated by CCA. CCA is carcinogenic when exposure to very tiny amounts occurs over a period of a week or longer, and when it gets wet can possibly release arsenic gas. Arsenic gas can is odorless and tasteless and can be extremely poisonous resulting in loss of life, limbs, etc.

What is CCA ? It is sometimes called pressure treated wood.

Home Depot and Lowes are refusing to label bags of CCA mulch as such and once it's in your environment, your property is considered a hazardous waste site by the EPA and you are expected to clean it up.

This mulch is currently being sold in Florida and possibly other states, is banned in multiple countries around the world, is considered toxic waste by the EPA and Home Depot and Lowes are both refusing to label the product as having CCA contained within.

For more information:

want to make sure you are aware. The state of Florida refuses to correct the problem and there's a problem in other states as well involving wooden playsets made by CCA (pressure treated) wood.

Home Depot and Lowes are refusing to mark CCA bags of mulch and are refusing to stop selling such bags. It might be a problem with other places as well and may not be limited to Home Depot and Lowes. The State of Florida supposedly makes these wood chips. If a bolt of lightning were to strike such a pile of mulch, who knows what would happen?

A 2x6 piece of pressure treated wood has enough arsenic in it to kill 100 full grown men.

[Pam - gardengal]

Any form of good composted mulch. You can purchase already prepared bagged compost from most garden supply outfits (including the box stores) or make you own. It really doesn't matter what the compost is comprised of - manures, yard waste, mushroom compost, whatever - as long as it has been thoroughly composted. There is not much better than compost for improving soil quality and properly prepared compost should look dark and rich and have no appreciable odor.

I'd avoid using sand - you will need an awful lot of it get beyond the concrete stage and it will need to be very coarse (large granules) to accomplish improved drainage. The standard recommendation for improving heavy clay soils is to add organic matter (compost) in significant quantities, digging it down and incorporating it into the clay. Usually pretty hard work. An alternative is to raise the beds and fill with enriched soil. Can you use something like landscape timbers or concrete blocks or stone to raise the level of the beds?

pam - gardengal

[Hans L]

Well, I have used it all over, and grass grows pretty well in the bark mulch I have used. Hans L

[Hans L]

Pam, what I think I will do is to

- rake off the soil in the fall

- use a pick and loosen the clay af far down and as much as possible

- use some other tool (what?) to crush the clumps of clay

- mix in compost

- return the soil

- add more soil on top

- add compost on top (or mix in?) -- sorry if I am repetitive, but I want to avoid having the top surface become dry, hard and gray!!!

Hans L