mulch altering ph to dangerous levels?

17 years ago

In the perennial border I have been using pine bark mulch for years. I like the look better than any other mulch. Other than adding some additional nitrogen to counteract any nitrogen depletion due to the pine bark mulch mulch drawing nitrogen in its early stage of decomposition, I have had nothing but great results with pine bark mulch. A gardening friend insists that only cedar bark mulch is to be used as pine bark drastically alters the ph to detremental levels. What do you say on the subject? Do you know of any scientific evidence supporting my friends claim? Thank you.

Sort by:Oldest

Comments (9)

morz8 - Washington Coast
17 years ago
It's working for you and your plants are healthy? That should be answer enough :)

No scientific data at my fingertips just now, but I think the PH of pine bark is a little more acidic than that of cedar. Many, many plants prefer soils that are lower than neutral. Lavender, daphne, delphinium are three exceptions that I grow in my naturally acidic soil...for those, I insert a stick of plain blackboard chalk into the soil near the roots for a slow release of lime.
lindac
17 years ago
Tell your friend "pah!"...Is her garden all that fabulous?? Is your's all that dismal?
I will not go to the bother of looking for documentation....but will say...I have been mulching with pine bark for lots and lots or years.....and things are just fine.
Perhaps your friend is unaware of the buffering action that happens in a well mulched soil?

Linda C
Related Discussions
Help with BER and container mix ph and calcium
Q
Comments (15)
I applied lime as a top dressing and the CDB seem to have hopefully stopped with BER. Can't say if it was just time or lime, haha. Found some BER on the Tasmanian chocolate and a couple of Tims Black Ruffles. The TC could be a washout because I made the mistake of planting it in a 20 gallon pot with Gold Nugget, a determinant cherry which has completely overtaken the space. So far the BW's are BERless but nothing ripe yet. I'm hoping bloody butcher will start to show some blush this week. Temps have definitely cooled down. Let me know how you find the foliar spray works. Carolyn doesn't think it's effective, but I say go for it!
...See More
How can I lower soil pH from 6.5 to 4.5 by Spring?
Q
Comments (47)
If drainage is a problem, you can use sand if you create mounds for the plants using a great deal of sand. A little sand can actually make things worse from research I've seen, but if you use something like a third sand by volume, mixed with a third peat and a third soil and create the mounds with this it should work fine. If you make such a mix without building mounds you may create bath tubs that fill with water and drown roots. You can also grow them in pots mixing 50/50- sand to peat and put them half way into existing soil- or make a mix with ground pine bark that is aged for the purpose (this is harder to find but more often used in blueberry production). If you set up a drip system or water them consistently, blueberries grow very well this way, if you put them in big enough pots. 5 gallon pots would support mature plants pretty well. Is your soil clay? Do you know the texture of your soil? This is something that is not at all obvious and people often are confused about the texture of their soil. This is also where your county cooperative extension can provide better advice than you can get on-line- although there are simple tests using dishwater detergent to get a general reading on your soils composition. Drainage is easier, because you can figure out how long it takes to drain after heavy rains or dig a hole and fill it with water several times. Not sure of the exact procedure but it is an easy search for details.
...See More
Trying to change the PH in soil
Q
Comments (1)
Yes and no :-) Ammonium sulfate and aluminum sulfate are two very different products. While both can help to lower soil pH, that is not their primary intent and one should be careful when applying either. Ammonium sulfate is a high nitrogen fertilizer (21%N). It is often used in association with alkaline soils to reduce pH, but fast acting nitrogen can also encourage a lot of rapid, leafy growth at the expense of flowering. Over application can result in the 'burning' of plant tissue from salts and it has an ability to leach easily into groundwater, contributing to pollution. Aluminum sulfate is sometimes sold as a soil acidifier and of course as 'hydrangea bluing'. It is the aluminum level in the soil that determines if a bigleaf hydrangea will bloom blue or pink. Freely available aluminum will result in blue flowers, unavailable aluminum will result in pinker flowers. And the soil pH will determine how much aluminum is available - acidic soils tend to have a higher available level of aluminum - in more neutral to alkaline soils, the aluminum is chemically bound and not freely available. Over applying aluminum is the issue - it is very easy to build up to toxic levels, even with hydrangeas. And many other acid loving plants - like rhododendrons and azaleas - are very sensitive to aluminum and you should avoid using aluminum sulfate in their vicinity. It is the sulfate or sulfur in both products that have the acidifying effect. Just applying horticultural sulfur will successfully lower soil pH (to a degree) and without any harmful side effects. However, if there is not sufficient aluminum available in the soil, even acidic soils will not produce very blue hydrangea flowers. Other products that will help to acidify soils are cottonseed meal, and peat moss. And most organic mulches will buffer soil conditions to at least bring alkaline soils close to neutral. Chlorosis, or yellowing of the foliage, is very often a result of iron deficiency or lack of availability. This is very common with alkaline soils and chelated iron is an excellent amendment for correcting this problem. Either of these products -- used in moderation -- can be helpful in adjusting soil pH and therefore influencing the flower color of hydrangeas, provided all other soil conditions are appropriate. It is always a good idea to have your soil tested to determine a) the existing soil pH and b) current nutrient levels, including all the trace elements. It is also important to understand that it is extremely difficult to significantly alter soil pH one way or the other and that any adjustments tend to be quite temporary. If you have alkaline soils and/or irrigation water and want to grow very blue hydrangeas, it might make more sense to grow them in raised beds or containers where you can 'design' the soil to your requirements. Same with growing pink or red hydrangeas in very acidic soils.
...See More
Anyway to reduce PH several weeks after transplanting seedlings.
Q
Comments (7)
One week isn't that long in terms of plant growth. They tend to go in spurts, mostly affected by temperatures, though a rough storm can make them sulk as well. And they may not be adding any top growth because they are concentrating on developing roots. Are you using those DIY home soil test kits? Because they are pretty notoriously inaccurate. Honestly, I think you should leave it be. My pH here in raised beds is probably closer to 8, has been for years, and the plants don't seem to mind. 7 seems great to me, in terms of soil chemistry affecting nutrient availability that's about where you want to be. Any fix you try will have to be slow-acting enough to not shock the plants, and thus won't do you much good this season anyway. If you really feel like you can't live with a 7, you might try adding one of the sulfur products this fall after the season is done but read the label like three times because that stuff can be pretty dangerous if misused. PS - adding good compost from a reputable source is often a safe bet, it acts as a pH buffer but isn't strong enough to burn plants. Some people on the forum will top dress with compost that doubles as mulch.
...See More
mad_gallica (z5 Eastern NY)
17 years ago
All compost biodegrades to a neutral pH. That's what the scientists who have watched it work say.
arbo_retum
17 years ago
i remember an article on this subject in hort. mag. or fine gardening mag., sometime in the last 10 yrs! and i believe it said that bark mulches/leaf mulches have minimal effect on the soil ph. why not google "pine bark mulch soil ph" ?
best, mindy
mxk3 z5b_MI
17 years ago
Nah, I wouldn't worry about it.

Like another mentioned, take a look at your garden - is it healthy? If so, keep doing what you're doing, especially if you like the look.

You know, I have a sister like that - anyone doing it any other way that HER way is wrong. Period. I quit discussing gardening much with her because it is not open to discussion, there's really no open exchange of ideas/thoughts/tips. I have another sister who loves to discuss all things gardening, we discuss tips/tricks/ideas and learn from each other's successes/failures - THAT's what makes a great gardening buddy!

Anyway, keep using the pine mulch if it's doing the job for you. I like how it looks too, prefer it over cedar.
gardengal48 (PNW Z8/9)
17 years ago
There may be some subtle change at the soil surface, but nothing to the extent of "altering pH to dangerous levels". First, nearly all soils have a buffering capacity that resists significant changes in pH and second - as noted above - all organic matter regardless of source will become nearly neutral in pH as it decomposes.

Finally, most plants will tolerate a relatively wide range of pH anyway. My slightly acidic soil (6.3) accommodates all manner of plants with ease, including those that are reputed to prefer more alkaline conditions as well as those that are traditionally more acid loving. As long as you have decent soil conditions with adequate fertility, organic matter and good drainage, you can mulch with whatever you want. I would consider the nitrogen depletion at the soil surface a bit more of an issue, specially with more shallow rooted perennials than with trees and shrubs, but you have already addressed that concern.
ken_adrian Adrian MI cold Z5
17 years ago
its hard to remember everything.. but i seem to recall some extraordinary amounts needed to change pH .....

something like feet upon feet of mulch for decades to have the most negligible effect ...

do you put that much on???.... lol ...

the only lesson you need to learn here .. is to not take everything your friends says too seriously .. which you already knew.. since you came to ask us ...

ken
barrie2m_(6a, central PA)
17 years ago
This is one thread where the snowball of ignorance just keeps rolling down the hill picking up momentum as it rolls.

Rootman, get your soil tested and that will be sufficient scientific evidence. Your soils will typically shift to more acidic pH over time even without added mulch. The danger will be suttle and occur over years, showing up as nutrient deficiency symptoms in plants.

Ironically the condition is the easiest and cheapest to correct, yet most overlooked by gardeners. A few bags of limestone, preferably a mix of Calcitic (high calcium) and Dolomitic (high magnesium) will correct the problem in over the next few years.

Your extension office will handle the soil test kits for the Penn State based service. They will test pH and buffered pH to arrive at lime requirement for your soil. They also routinely test Calcium, Magnesium, Phoshorus and Potassium. In PA if you haven't applied any limestone in the last three years and have been mulching you are in need of help. So far it hasn't come from this group.
rusty_blackhaw
17 years ago
I wouldn't bother with soil testing since you describe great results.

Mildly acidic soil is desirable for a wide range of perennials.

The claim that any wood mulch will "drastically" alter pH is incorrect. This is about as big a wives' tale as the idea that certain foods will significantly alter the pH of the human body.

mulch altering ph to dangerous levels?

Comments (9)

morz8 - Washington Coast

lindac

Related Discussions

mad_gallica (z5 Eastern NY)

arbo_retum

mxk3 z5b_MI

gardengal48 (PNW Z8/9)

ken_adrian Adrian MI cold Z5

barrie2m_(6a, central PA)

rusty_blackhaw

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US