As with other micronutrients like zinc and molybdenum, cannabis plants only need small amounts of copper to grow, thrive, and mature. Should a marijuana plant’s uptake of copper drop below a certain level, though, serious problems will follow.
Fortunately, most water supplies and soils contain plenty of copper for cannabis plants to absorb, at least under normal, desirable growing conditions. This makes copper deficiency fairly rare, but it is an issue that still arises from time to time.
Learn about the role copper plays in marijuana plant growth and maturation and you will understand why this occasionally overlooked micronutrient is so important. Become able to recognize the symptoms of copper deficiency and the most appropriate solutions, and you will be able to put an end to it before too much damage can arise.
Copper is regarded as “one of eight essential plant micronutrients,” and cannabis plants need it as much as any others. That said, they only require trace quantities of this soft, ductile metal with a distinctive, reddish look.
A healthy, well-fed cannabis plant, for example, will feature concentrations of iron within its tissues around twenty times higher than its copper levels. Given that a cannabis plant’s need for iron is far lower than that for macronutrients like nitrogen, phosphorous, and potassium, it should be clear that the quantities of copper involved are very small.
Despite that, copper is critical to quite a few processes that allow marijuana plants to become established and thrive. A lack of copper will inhibit a cannabis plant’s ability to grow and mature by undermining:
None of these important processes require large amounts of copper, the way that, for example, metabolic respiration does with oxygen. If a cannabis plant is not able to take in enough copper, though, the reduced efficiency of any of these processes can negatively impact its growth and overall health. Some of the concrete problems that are to be expected are:
Fortunately, it is usually a straightforward process to recognize when cannabis plants have developed a copper deficiency. Paying close attention will also make it possible to identify the problem early enough that it can be resolved before it causes too much damage.
Unlike certain other nutrients, copper is relatively immobile within marijuana plants. It gets deposited at the site of new growth and incorporated into cells in quantities sufficient to supply them for life.
When a cannabis plant develops a copper deficiency, the symptoms will normally appear first in new leaves and other younger parts of the plant. Well-established parts of the plant can still appear entirely healthy, since their own copper stockpiles were built up before the deficiency developed. Some of the symptoms of copper deficiency that most often appear first in cannabis plants are:
Being alert for symptoms like these should always make it possible to diagnose a copper deficiency relatively early on. If the problem does not get resolved fairly quickly, an affected plant will start to show even more overt signs of it.
Leaves produced well after a copper deficiency sets in will typically not grow as large as predecessors. They can become obviously stiff or prone to drying up and dying long before harvest time, as well.
The difficulty with synthesizing lignin that copper deficiency causes will also eventually impact the growth and health of stems. Cannabis plants suffering from copper deficiency can take on an unusually compact look, since their stems do not grow as much between leaf nodes. Those stems will also typically be weaker than would be normal for a healthy plant.
One common mistake among inexperienced growers is confusing copper deficiency with nutrient burn, or vice versa. The tips of the new leaves of a plant suffering from nutrient burn will also typically turn yellow at first. They will then acquire a burnt-looking brown cast, however, which is not indicative of early-stage copper deficiency at all.
Fortunately, copper deficiency is both rare and fairly easy to resolve when it appears in cannabis plants. Recognizing and addressing the problem early on will prevent it from inhibiting the growth of an affected plant. The most common causes of copper deficiency in marijuana plants and how to address them are:
In most cases, simply restoring the pH of a plant’s growing medium to an appropriate range will be enough to overcome a copper deficiency. Whether that or another solution ends up being needed, it is important not to worry too much about damage that has already been done.
Since copper does not get moved around readily within cannabis plants, most existing signs of deficiency will persist even when the cause was resolved. Keep tabs on new growth to make sure that common symptoms of deficiency like pale leaf tips are not appearing and you can be confident that the problem has been resolved.