Mulch for Azaleas

Schaumburg, IL

What type of mulch is recommended for Azaleas? I put down hardwood bark a year and a half ago and my Bakeri did great. However, I was just reading about this much and a comment was made that this was bad for them. I am new to Azaleas and need some help.

Hurst, TX(Zone 7b)

Azaleas are shallow rooted plants and so, an acidic mulch would be best for them because they prefer to live in quite acidic soil. Hardwood mulch is alklaine and you do not want to make the soil in the top few inches of the ground alkaline. But the thing is, you really need a lot of that mulch to cause a problem because azaleas and rhododendron will tolerate s-o-m-e alkalinity anyway.

Acidic Soil locales: If you apply alkaline mulch to acidic soil and leave the soil unattended for a while, your soil will tend to return to its normal acid level on its own. For example, I did not worry much about the type of mulch I was using when I lived in mostly acidic Georgia and had no problems with iron chlorosis. Over there, I would be more concerned with having enough mulch rather than having acidic mulch.

Alkaline Soil Locales: But if your soil is near neutral or laklaine to start with, hardwood mulch may elicit a response from the azaleas if they deem the soil too alkaline for their taste. To grow azaleas in Illinois where the soil is usually alkaline, you have to amend the soil with products designed to keep the soil acidic. You can use slow acting garden sulphur, iron sulfate, Hollytone; or faster acting liquid iron-chelated compounds sold at nurseries.

Bottom Line: Azaleas will tolerate alkalinity for a while and show no symptoms but, if the soil gets too alkaline, they will protest and develop iron chlorosis. Newly planted azaleas in alkaline soil tend not to show signs of iron chlorosis "quickly" because the roots are still growing in the medium in which they were planted at the nursery (usually acidic soil). Once the roots grow into your garden soil, any alkalinity will start to bother them a little. Then more later on.

When starting a program to alter the soil acidity or alkalinity, it is wise to determine just how acid/alkaline the soil is to begin with. You accomplish this by doing a soil pH test. Cheap soil pH kist can be purchased at nurseries and will give you a general idea. Better tests can be made by giving a soil sample to your soil extension service. Once you know you soil Ph, you determine how much of these acidifying products you need to apply to reach your goal. For azaleas, aim for a soil pH between 4.5 (very acidic) to 6 (acidic).

I keep my shrubs in alkaline Texas around 6 to 7 and they have not complained for the last 7 years. I do mulch them with acidic soil and I do amend the soil once in Spring with garden Sulphur. If your soil pH is borderline and the plant is happy, do nothing other than to monitor it. If it ever "complains" then apply one of these products.

The Cumberland Azalea, also called R. cumberlandense (also called R. bakeri), likes acid soil and generally grows in woody areas centered around Tennessee (AL, GA, NC, VA and NC). Enjoy and post pictures when you can!


For more information on soil acidity, see the following article courtesy of the University of Illinois:

Schaumburg, IL


Thanks for all of the information. I really liked using the hardwood bark mulch because it is supposed to break down faster and add nutrients to the soil. However, I was concerned about the alkalinity. I also have some Japanese Maples which like a more acidic soil.

Attached is a picture of one of the Bakeri that I planted last spring (2nd picture in the next post). This year, I see alot more buds. I just hope they make it through the winter. I am zone 5 and I think that is borderline for these. Excuse the thousands of green seedlings in the picture. I went on vacation and when I came back I had these from my tree. They were easy to get rid of once I stirred up the mulch.

Thumbnail by JAPMAPLE
Schaumburg, IL

2nd picture.

Thumbnail by JAPMAPLE
Christiana, TN(Zone 6b)

I am using pine needles on all my rhodies and azaleas. Well, just about everything else too. So far so good. I've read they are acidic in nature.
One of the good things about pine needles is they take about twice as long to break down as hardwood mulch and, to me, look much better.
Some may say they are too expensive but overall for me they are worth it.

Pink Hill, NC(Zone 8a)

I use coffee & tea grounds.

Hurst, TX(Zone 7b)

I started that with Starbucks coffee grounds about a month ago, downeastgarden. Of course, I just had to have some coffee while I was in the store too. Hee hee hee! Pretty easy to do now since a lot of people consume coffee in winter and the stores put a lot of coffee grounds free for the picking. Do stop adding coffee grounds in July or so though. Doing that helps prevent new tender growth from developing, growth that can then be zapped by early frosts in the Fall.

I write a reminder to stop applying it into a PC application like Outlook but you can add it on a wall calendar as well. That is how I also remember to prune plants in mid-summer because if I do not do that, my brain sleeps thru summer and I do not remember until winter! LOL!

Oh well. I sense the need to "apply some more coffee grounds to the azaleas" now so have a great evening!


Pink Hill, NC(Zone 8a)

Thanks for the advise re to stop adding coffee grounds in July. I think I do anyway cause it is so darn hot and I've long forgotten about spring plants by then. Does anyone have a local restaurant save coffee grounds for them?

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