Copper Deficiency in Cannabis Plants
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.
Importance of Copper
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:
- Enzyme activation. Cannabis plants use copper and other micronutrients to activate enzymes that speed up important processes like the synthesis of certain proteins. Most notably, a lack of copper will make it more difficult for a cannabis plant to synthesize the protein lignin, the main building block for the cell walls of the woody tissues that make up its stems.
- Photosynthesis. More than 50 years ago, researchers discovered that copper plays, as had been hypothesized much earlier, a critical role in photosynthesis for all plants. The chlorophyll-filled organelles called “chloroplasts” within the leafy green cells of a cannabis plant will function with greatly reduced efficiency if copper levels drop too low.
- Cannabis plants use photosynthesis to create sugars that they stockpile and metabolize for energy later on. This requires pulling in the macronutrient oxygen from the surrounding air and combining it with stored sugars to release the energy within them. Copper is needed for this process, so a cannabis plant that lacks it can be deprived of energy it needs to grow or remain viable.
Effects of a Copper Deficiency
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:
- Slower growth. Even a slight copper deficiency will force a marijuana plant to grow more slowly than if it were adequately supplied. That can increase the time to reach maturity and throw off an otherwise ideal schedule.
- Lowered yields.Cannabis plants that do not absorb enough copper will grow, bud, and flower more slowly. The longer a copper deficiency continues, the more the yield from a given plant will be reduced.
- Lessened seed production. Although not always a concern, cannabis plants suffering from copper deficiency will also produce fewer seeds. Growers trying to stockpile seeds for future crops can easily run into this problem.
- Susceptibility to disease. A cannabis plant that lacks access to copper will be weaker and less able to fight off disease and pests. That can even leave a plant dying from disease that would not have troubled it if there was enough copper within its tissues.
Symptoms of a Copper Deficiency
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:
- Pale, yellowing leaf tips and edges. A lack of copper interferes with the ability of a cannabis plant to produce deep green chloroplasts. When a copper deficiency first develops, the tip of a plant’s newest leaves will often start turning paler and yellowing. As the deficiency continues, the paleness will extend further down the perimeters of affected leaves. This will generally resemble the yellowing that is expected to happen after flowering, but it can affect a much younger plant.
- Bluish or purplish tint around leaf veins. While the tips and edges of the leaves of a copper-deficient cannabis plant will become pale, adjacent internal portions will darken and take on an unusual blue or purple tint. This normally becomes apparent only after a copper deficiency has continued for some time, so it is best to remain vigilant in looking for pale, yellowing leaf tips.
- A metallic, shiny look. Finally, a copper deficient cannabis plant’s leaves will often acquire a distinctive metallic sheen. This looks different enough from the more subdued natural shine of healthy leaves that it can be quite striking.
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.
Causes and Solutions for a Copper Deficiency
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:
- Overly high pH. The growing medium that hosts cannabis plants should have a pH of between 6.0 and 7.0 for soil-based cultivation or from 5.5 to 6.5 when a hydroponic approach is used. If pH rises much above these upper limits, a cannabis plant will become less able to draw copper in through its roots. Overly high pH is the most common cause of copper deficiency by far and should be considered the culprit by default. Solution: Restoring the pH of the growing medium by flushing it out with appropriately balanced water will normally be sufficient to overcome copper deficiency.
- A lack of available copper. Water and soil normally contain enough copper to keep cannabis plants Solution: In some relatively rare cases, it might be necessary to add copper to a system to make up for a lack of it. Fungicides containing copper sulfate or chelated copper are often used and can be applied to the leaves of a plant. Cannabis growers can also add copper-rich organic materials like kelp or compost directly to a growing medium that lacks the metal.
- Excesses of other nutrients. Should too much of a nutrient like potassium or phosphorous be available to a cannabis plant, it might have trouble absorbing enough copper. This is a fairly rare problem because nutrient formulations normally take care to rule it out. Solution: Switching to a different type of nutrient will sometimes resolve a copper deficiency that could not be addressed by other means.
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.