Rose Roots Love Humic Acid

Norma Boswell

Master Rosarian, Tri-City Rose Society

Roses & You, June 2020

In 2020, if you want to place a sweet treat at your roses’ feet, add humic and/or fulvic acid to the soil (and let earthworms create some for you). These acids are not fertilizers. They are wonder-working soil strengtheners that remain after plant matter has decomposed in a special place like a peat bog, your very own compost pile, or the intestines of earthworms. Humic and fulvic acid improve the soil in many ways: strengthening biological activity, increasing water retention, helping chlorophyll synthesis and aiding nutrient uptake. Humic acid can chelate micronutrients. Chelation breaks ionic bonds and increases micronutrients' availability in the soil. Better soil health means better root growth. Better root growth leads to stronger, more beautiful roses.

You can, of course, ask your favorite local nursery whether they sell humic acid. An online source is www.spray-n-grow.com. Their bag of Earthworm Castings is 100% organic and contains 1% nitrogen, 0% phosphate and 0% potash. Spray-N-Grow also sells a kit of ten soil tests for $19.95. These tests reveal pH and status of nitrogen, phosphorus, and potassium.

Last year I was keen on buying bags and boxes containing mycorrhizae and digging them into the dirt. Mycorrhizae are fungi that develop a symbiotic relationship with plant roots. The roots provide mycorrhizae with food, and the long strands of mycelium created by mycorrhizae bring water and nutrients to the plants. At least two problems or doubts have recently come to light about mycorrhizae: (1) the exact kind of mycorrhizae that work best with roses is not clear, and (2) the main nutrient a plant gains from mycorrhizae is phosphorus.

Your rose soil may already have enough phosphorus. When a plant has plenty of phosphorus, its roots won’t encourage mycorrhizal development. If you do a soil test, you can discover your soil’s wealth or scarcity of phosphorus. Phosphorus tends to stay in the dirt for a long time (unlike nitrogen, which depletes quickly and needs to be replaced after the roses have bloomed). If your soil has a wealth of phosphorus, it could be a waste of money and effort to fertilize with more, which tends to cripple the mycorrhizal network. You might want to focus on humic/fulvic acid instead.

My container of Soil Moist Mycorrhizae Container Mix Plus (www.soilmoist.com) adds several species of mycorrhizae fungi and bacteria that grow naturally in undisturbed soils. My box of Whitney Farms’ Life Link Rose & Flower Food from a few years ago contains both ecto and endo mycorrhizae, as well as 4% nitrogen, 6% phosphate and 2% potash. Its fertilizers are derived from dried poultry manure, bone meal, sulfate of potash, alfalfa meal, feather meal and kelp meal.

SOIL TEXTURE IS IMPORTANT

Check the soil for drainage and soil texture. Soil should be “friable” (loose and crumbly). About 50% of the soil should be air and water. Roots grow well in friable soil but not compacted (smashed by foot traffic) or waterlogged (not well drained, drowning rose roots). Healthy soil provides space for many beneficial creatures to flourish, including microbes and earthworms.

A good way to improve soil texture is to add compost. Compost consists of naturally decomposed organic material which adds carbon and nitrogen to the soil. Use your own compost, or buy bags of Dr. Earth compost from Fred Meyer or your favorite local nursery. The best product will be dark brown or black, moist but not soggy, have no recognizable wood, and give off no smell of ammonia or sulfur.

Earthworms will do a lot of texture and soil enrichment work for you. They can travel 3-4 feet in the dirt both vertically and horizontally. They ingest what they find, and excrete humus. The soil is efficiently aerated as they move.

PRODUCTS MUST HELP, NEVER HARM

Protecting our environment is paramount. What we choose to spray on our roses, and incorporate into their soil, must allow creatures that are beneficial to flourish. Read product labels. If contents can harm bees or kill earthworms, don’t use those products. Treat the insects that pollinate our crops, and the creatures that keep our soil workable, with wisdom and kindness. We and those we love will reap the rewards.