Whorled leaves, cresting, and variegation are just some of the strange abnormalities that can be found in a cannabis crop. The larger your garden, the more likely you are to observe these abnormal characteristics in your cannabis plants.
Below we will discuss some of the main genetic abnormalities that can occur in cannabis leaves, the causes of some of these phenomena, and how to determine whether the symptoms are caused by genetic mutations or external pathogens:
1- Whorled leaves
In the early vegetative stage cannabis leaves generally emerge in pairs, on opposite sides of the stem on each node. During maturity, and when it blooms, it is common for plants to develop an alternate leaf arrangement, with only one leaf on each node, although the leaves may continue to appear in pairs. A spiral leaf arrangement (or spiral phyllotaxis), where more than one pair of leaves appears on different parallel planes, is much less common.
Thus the spirals can have three, four or more leaves on each node. This is not symptomatic of any infectious disease, and could actually increase plant yields. Unfortunately, although it allows the plant to absorb more light energy, it generates a very high number of males. The cause of leaf overproduction appears to lie in the mutation of one or more of the genes that control the plants growth, and that appear to have "evolved" to create individuals with a larger surface area to absorb the sun's rays.
2- Leaf buds
Leaf buds are small buds that form at the junction of a petiole and the blades of a cannabis leaf. Some might see this anomaly and think, "Great yields!" But, while these outbreaks could make a small contribution to bolstering yields, it's likely to be pretty negligible. They do not group many calyces, nor do they form very large flowers. But, it is undeniable that, behind their appearance there could be a new way of understanding flowering. The problem with these mini buds is that they commonly contain hermaphrodite flowers that can pollinate your plants. Regularly inspect the leaves for male flowers, and carefully prune them if you see anything suspicious.
3- Fasciation/ crestation
Fasciation is a plant growth mutation in which the apical meristem (or vegetative cone, the end of the stems), which is normally concentrated around a single point, and produces more or less cylindrical tissue, lengthens perpendicularly in the direction of growth. This produces flattened, tapered, crested, or sinuous tissues.
Fasciation, also known as crestation or polyploidism, is a genetic mutation that creates plants with hyper-vigorous zones (such as buds, for example), turning these plants into true "green monsters". It is an anomaly that occurs when plants have more chromosome chains than the two that are characteristic of their species. Hence the polyploid (many chains), as opposed to the diploid structure (two chains) of cannabis The mutation is usually caused by a bacterial infection, attacks by insects or parasites, or chemical or mechanical damage.
Some plants inherit this mutation, since it does not represent fatal damage to the plant, although the weight and volume of the tissue in question usually increase irregularly, causing the formation of hollow and flexible stems, such that they tend to bend in strong winds. These misshapen and motley buds are also prone to catching fungal infections, like botrytis.
4- Variegation and albinism
Variegation is an alteration of colour, creating multi-coloured leaves or flowers or with different hues. It is caused by a differential gene expression or infection by some virus. In differential gene expression, the location of a cell on a plant determines which of the genes are active, creating differences in colouration. A familiar example is the streaking on watermelon rinds, or the purple rings on the leaves of some geraniums.
Cells within the striped areas or the purple rings have the same total set of genes as the rest of the plant, but they have active genes that cause their different colour, which are genes latent in the rest of the cells. In cannabis, this differential gene expression is responsible for the purple or bluish leaves and buds seen in some varieties. Cold temperatures or bright light increase the expression of these genes.
In some extreme cases the genes that control chlorophyll production can be deactivated and the plant will be completely albino. However, plants that require photosynthesis to live cannot survive and reach full maturity if they are albinos, since chlorophyll is required for the photosynthesis reaction.
5- "Duck foot" leaves
"Duck foot" leaves are made of fused blades that resemble the webbed feet of these birds. This trait can be, intentionally, found in varieties marketed for discreet outdoor cultivation, as they are less recognisable than normal cannabis plants, although they look quite similar in the advanced stages of flowering, when they are full of buds.
This is a hereditary genetic trait not caused by pathogens. In fact, it is a genetic alteration of the classic cannabis genome, which almost always occurs in Sativa plants, and that is of a recessive nature, which means that, if it occurs, it can be conserved and reproduced in the plant's offspring.
An example of this type of plant is the Frisian Duck, a variety whose objective was clear: to create a high-yield plant for outdoor crops. The Dutch seed bank Dutch Passion has been working on it for years, although, right from the first generations of seeds it received rave reviews, because, thanks to the natural camouflage afforded by the unusual shape of the leaves, people could pass right by the plants without realising what they really were.