Mulch Matters

I recently read an article, “The Mulch Matters,” and want to understand more. I would like to plant several Japanese maples and at present have only pine straw. What more can I do to improve soil quality for these trees (since they prefer a more acidic nutrient base) without using fertilizers?

It’s true, mulch does matter, but compost matters more! If you want to improve soil quality for any plant, compost is the way to go. Its many benefits are outlined in the November 2014 newsletter article by Tara Mitchell, “Composting: Turning Garbage into Gold.” It’s a must read.

I’m guessing that you garden in the Mid-Atlantic or the South where pine straw (needles) is used frequently for mulch. It’s interesting to note that research has shown that pine straw (needles) does not acidify the soil, a commonly held myth. Here’s why: Fresh pine needles taken from a tree are only slightly acidic, so have a very limited effect on soil pH. The old needles that are shed are barely acidic and once on the ground they totally lose their acidity in a very short period of time (days). So if the aim is to acidify the soil with the pine straw, this type of mulch isn’t up to the task. Actually one cannot rely on mulch alone to change the pH of the soil significantly.

But first, before we place (actually buy) a plant, we should:

  • Get a soil test done to determine the pH, the amount of organic matter present, and other important information about your soil. The test will also recommend when and what amendments are needed to correct any deficiencies found. It’s a waste of time, money and effort to add materials that are not needed. Additionally, adding amendments that are not needed can be detrimental to a plant and can even limit, or prohibit in some case, its ability to take up the nutrients it needs. The good news for you and your maples (and the bad news for some other species) is that acid rain is a huge contributor to increased soil acidity. Check your pH periodically; you might find that your soil is just right or has become too acidic, which creates other problems.
  • If the test is done by a lab (university extension services sometimes offer these test for a small fee), they will recommend “fixes,” including the amount (critical) and the best time to apply amendments.
  • In addition to soil pH, other factors must be considered to determine if the plant you’re considering is a good candidate for your landscape:
    • Site/Growing Conditions: is the site wet/dry, sunny/shady, windy/sheltered?
    • Plant Requirements: how drought, heat and/or cold tolerant is the plant you’re considering?
  • The U.S. Department of Agriculture’s Plant Hardiness Zone Map and the  American Horticultural Society’s Plant Heat Zone Map (update in 1990) are excellent assessment tools to help you determine the “right plant for the right place”.

Keeping fingers crossed that you’ll find that a Japanese maple is the right plant for you. Good luck.

Kathy Sargent-O’Neill, KSO Fine Garden Design & Care

ELA members have spent hundreds of hours learning the best ecological solutions to problems in the landscape. You can benefit from all that accumulated knowledge by posing a question to our experts. If you are stumped by a problem in your landscape or are looking for a second opinion on a potential solution, ask ELA’s Eco-Pros. Send your question to ela_new@verizon.net, using Eco-Answer in the subject line. And if you need additional help, refer to our listing of ELA Professionals.