You may want to grow plants in copper pots or in brass pots, but are unsure whether it’s safe for the plants. Some plants do just fine and even thrive in copper or brass pots, while others struggle and may die. Here’s what you need to know.
- You can grow plants in copper or brass pots.
- Avoid growing plants that are susceptible to copper toxicity.
- Be careful you don’t overwater the plant or overheat it by placing the pot in direct sunlight.
- Know the symptoms of copper toxicity and remove the plant if you observe problems.
- Ideally, play it safe and just nest a potted plant in a decorative metal container.
Role of Copper in Plants
Both copper and brass pots contain copper, since brass is an alloy of copper and zinc. Copper is an essential micronutrient for plant nutrition. Plants use trace amounts of copper in photosynthesis to make food. It is a key element in enzymes used for lignin synthesis and other biochemical processes. Copper causes the yellow color of onions and deepens flower coloration.
Because soil and water supplies generally contain some copper, copper deficiency is relatively uncommon. When it does occur, lack of copper causes cupping of leaves, chlorosis, pale flowers, and stunted growth. The upper leaves of broadleaf plants turn a characteristic blue-green color. If it’s not addressed, copper deficiency leads to wilting and plant death. Crops suffer copper deficiency more often than house plants. Beets, onions, tomatoes, spinach, sunflower, and lettuce all have relatively high copper requirements.
Copper toxicity occurs when a plant gets too much copper. This can be toxic in its own right or copper absorption can reduce a plant’s absorption of other essential elements. Symptoms of copper toxicity include reduced seed germination, low iron availability, root damage, and weak shoots. Peas, potatoes, mint, broccoli, cabbage, beans, and cucumber generally do not require copper supplementation, so they may be at risk of copper toxicity.
Copper bioavailability depends on soil pH. Plants that grow in neutral or alkaline soils have an easier time absorbing copper, while plants that live in acidic soil may appreciate copper supplementation.
So, putting this together, plants with high copper requirements tend to do better in copper or brass pots. Similarly, plants that love acidic soil often do well in these pots. Acid-loving plants include roses, azaleas, and hibiscus. Edible plants with high copper requirements also do fine in copper pots. Ornamental grasses appreciate copper pots. Annual and perennial flowers may have deeper colors when grown in copper or brass pots.
Advantages of Copper and Brass Pots
Copper and brass pots (or containers re-purposed as planters) offer certain advantages over other materials. If you drop them, they may get dents, but won’t shatter. They are sturdy and fairly lightweight. The metal color contrasts beautifully with greenery and flowers. Reaction between the metal and dissolved compounds in water makes the copper available to the plants. But, the most significant advantage these metals have over other materials is that copper is antimicrobial. It kills bacteria, mold, mildew, and fungi. Copper is toxic to invertebrates, including slugs, worms, and both detrimental and beneficial insects.
Disadvantages of Copper Pots (and Brass)
However, metal pots have some disadvantages, too. They don’t drain unless you drill holes in them. Even then, there is no air exchange with the walls of the pot. So, overwatering poses a real risk. Metal pots heat up significantly in direct sunlight and can burn plants. Of course, this risk does not apply as much to indoor plants or planters kept in shaded areas. Copper and brass react with salts in soils and oxidize. These oxidation products, called verdigris, are either beautiful or hideous, depending on your aesthetic sense. Verdigris stains surfaces, so pots with drill holes are best used with plastic drip trays. The most significant disadvantage of copper and brass pots is that the dissolved copper may be toxic to some plants.
Best Way to Use Copper Pots
It’s worth trying copper and brass pots for your plants. But, if you worry about toxicity, simply keep the plant in its pot and nest this pot within the metal one. You’ll still gain the antimicrobial benefits, but greatly reduce the risk of too much copper.
How to Treat Copper Toxicity
If your plants experience copper toxicity, there is no quick fix. But, if you catch the problem early enough, most plants can be saved.
- Remove the plant from the pot.
- Gently loosen the soil from the roots and then rinse off the soil with water.
- Pot the plant in fresh soil. Choose a pot that is not metal and that has excellent drainage. Eventually, routine watering lowers the copper load.
Do you use copper or brass pots? Share your experiences!
References
- Gadd, Geoffrey Michael (March 2010). “Metals, minerals and microbes: geomicrobiology and bioremediation”. Microbiology. 156 (3): 609–643. doi:10.1099/mic.0.037143-0
- Vest, Katherine E.; Hashemi, Hayaa F.; Cobine, Paul A. (2013). “Chapter 13 The Copper Metallome in Eukaryotic Cells”. In Banci, Lucia (ed.). Metallomics and the Cell. Metal Ions in Life Sciences. Vol. 12. Springer. doi:10.1007/978-94-007-5561-1_13 ISBN 978-94-007-5560-4.