The practice of using cremated remains (cremains) in memorial plantings is a growing trend, connecting a loved one’s final resting place with the natural cycle of life. Cremains are not soft wood ash, but pulverized bone fragments resulting from the high-temperature cremation process. Determining their suitability for plants requires understanding their unique physical and chemical makeup.
Understanding the Chemical Composition of Cremation Ashes
Cremated remains are primarily a mineral compound derived from the skeletal system. The substance is overwhelmingly composed of calcium phosphate (often exceeding 98%), which gives bone its rigidity. This high concentration of calcium and phosphate forms the basis of the remains’ chemical profile.
Cremains also contain trace amounts of other minerals, including potassium, magnesium, and sulfur, which are nutrients plants require for growth. However, the cremation process concentrates residual salts present in the body, most notably sodium and chloride. These salts are the source of significant concern for horticulture.
The chemical composition results in a highly alkaline substance, often measuring a pH between 11 and 12.5. Since most natural soils range from pH 5 to 8, this extreme alkalinity, combined with concentrated mineral salts, defines the challenge of using cremains directly in planting.
The Horticultural Impact of Cremains on Plants and Soil
The concentrated mineral content of cremains creates two primary detrimental effects on plant life if applied without modification. The first issue is the highly alkaline pH, which dramatically elevates the soil’s pH level. This shift creates an unsuitable growing environment for most plant species.
When the soil becomes highly alkaline, it initiates a chemical reaction that “locks up” essential micronutrients. Elements like iron and manganese, crucial for chlorophyll production, become chemically bound and inaccessible to the plant’s root system. This nutrient unavailability often results in chlorosis (yellowing of the leaves) and stunted growth, particularly in acid-loving plants.
The second major problem is the high concentration of sodium and chloride salts. These salts are highly water-soluble, creating an environment of high osmotic stress when dissolved in soil moisture. This means the salt concentration outside the roots is higher than the moisture concentration inside the plant roots.
This high salinity draws water out of the plant roots instead of allowing absorption, effectively causing a physiological drought. Symptoms include wilting, browning of leaf tips, and root burn, which can lead to dehydration and eventual death.
Strategies for Safe and Measured Incorporation
To successfully incorporate cremains, the primary chemical challenges—high alkalinity and high salt content—must be mitigated through careful preparation. The most straightforward strategy involves extreme dilution, mixing a small portion of cremains with a significant amount of compost or garden soil to minimize localized impact.
Dilution and Leaching
The most straightforward strategy involves extreme dilution, spreading the concentrated minerals across a much larger volume of soil. A small portion of cremains should be thoroughly mixed with a significant amount of compost or garden soil to minimize localized impact. For a long-term memorial, the mixture should sit for several months before planting. During this time, deep, consistent watering helps leach water-soluble salts out of the mixture, further reducing the risk of osmotic stress.
Buffering Alkalinity
A secondary, and equally important, step is buffering or neutralizing the high pH of the remains before planting. Specialized planting mixtures are commercially available to blend with cremains and adjust the pH toward a neutral range. Alternatively, incorporating acidic soil amendments like peat moss or elemental sulfur can help counteract the alkalinity.
Specialized Planting Methods
Another effective strategy is using specialized biodegradable urns or planting systems that physically separate the concentrated remains from the young plant’s root ball. These systems often include a built-in buffering agent for slow, measured release. When scattering or burying, choose established, salt-tolerant plant varieties, or keep the remains away from the immediate root zone of new saplings.