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Understanding, Identifying and Using Cannabis Leaves

The leaves are the most recognisable and well-known part of the cannabis plant. Despite the great degree of variation found naturally in local populations of cannabis, the leaves do not alter greatly in appearance between varieties. Here is the story behind the leaves of three main strains, how to identify them and some ideas on how you can use these leaves.

The leaves of a cannabis plant play a big role in supporting its growth and the overall health of the plant. The stomata on the bottom of the leaves, which are tiny little holes that open and close, take in carbon dioxide and release water and oxygen. This is required for photosynthesis, which would be near impossible without the leaves. They also provide a way for the plant to absorb nutrients (foliar feeding).

Cannabis leaf phyllotaxy

According to the standard phyllotaxy (the arrangement of leaves on a plant stem), cannabis leaves are compound (with multiple leaflets, as opposed to simple, where a single leaf grows from the stem) and opposite decussate rather than alternate.

Opposite leaves emerge in pairs, one each side of the stem, with a clear vertical space between the leaf pairs. Decussate leaves are opposite, but each new leaf pair is at a right-angle to the last pair. Alternate leaves emerge from the stem singly, swapping sides as the vertical height increases.

Although cannabis leaves are usually decussate, as the plant prepares to flower the leaves may begin to emerge in an alternate pattern. Interestingly, rejuvenated cannabis plants demonstrate alternate phyllotaxy.

Experiments with hemp showed that early-planted specimens, which flowered in low light conditions but did not die, began to put out new alternate leaf growth when hours of sunlight increased. The initial new growth was simple rather than compound, and as new growth continued, the number of leaflets gradually increased.

There is some evidence that this phenomenon leads to vegetative growth of greatly increased vigour, although the genetic processes responsible are not fully understood. It is thought that the evolution of opposite-decussate phyllotaxy occurred comparatively recently, from an alternate-leaved ancestor, and that the genes controlling the decussate phyllotaxy ‘switch off’ around the time of inflorescence.

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The leaves can help identify common growing mishaps

The leaves of cannabis plants can be very telling. Here are some tell-tale signs of a mishap in the making that can be seen by merely inspecting the leaves:

  • Blistered, twisted, shiny “wet” looking leaves – This may be an indication of mites, which are too small to see with the naked eye. If this is the case, new leaves may grow in twisted, top leaves can droop.
  • Spotted leaves – Spotty leaves may indicate a deficiency (likely a calcium deficiency). This normally affects new leaves or parts that are actively growing.
  • Edge of leaves fading to pale yellow – This is likely a sign of magnesium deficiency.
  • Edge of leaves change to white or bright yellow – If this is seen along with the inner main part of the leaves turning purplish or dark blue, then there’s probably a copper deficiency. They may also appear shiny or start to turn under. This most often affects leaves directly in the light.
  • Curling, folding, miscolouring leaves – If leaves are too close to light or heat, they can start undergoing heat stress. This can lead to them folding up, curling down under and turning yellow or even plainly getting a burnt look to the edges.
  • New leaves grow in bright yellow – If new leaves are growing in from the get-go with a bright yellow colour, the plant may have an iron deficiency.

Leaf differences between the three main subspecies

Putting aside the eccentricities of cannabis leaf growth for a moment, let us take a look at the differences between the three pure main subspecies of cannabis, which are:

  • C. sativa
  • C. indica
  • C. ruderalis

C. sativa leaves are long and slender, often with pronounced serrations, giving the leaves a jagged, almost spiky appearance. The colour of sativa leaves ranges from bright, lime green to blackish-green at the darkest. The largest leaves can often have up to thirteen leaflets.

C. indica leaves are much wider. The largest leaves usually have fewer leaflets than the largest sativa leaves, with seven to nine leaflets. Indica leaves are commonly deep olive-green; very light green leaves are rare and often a sign of deficiency.

C. ruderalis leaves are generally smaller than the other subspecies’, as the mature plant is much smaller overall. The largest leaves may contain anything from five to thirteen leaflets. Ruderalis leaves are usually closer to the indica in terms of width, although they can be much narrower than any indica leaf would normally be.

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Mutated patterns seen in cannabis leaves

The incredible variation in cannabis morphology throughout the world has led to some very unusual leaf patterns occasionally occurring. Many of these traits are seen as highly desirable due to their visual dissimilarity to “normal” cannabis, as they can serve to disguise a crop from the unwelcome attention of law enforcement in areas where cultivation is illegal.

Webbed leaves are a common mutation, and one which various breeders have attempted to stabilise. Such efforts have unfortunately not prevailed to the point where webbed varieties are now commercially available, though. In the past, however, it was possible to source webbed varieties such as Ducksfoot in seed form.

Whorled phyllotaxy is another common mutation, although this is less desirable as a concealment trait as the plants still definitely resemble cannabis.

However, many growers find the trait desirable for cosmetic purposes, Some believe that such plants yield flowers of higher potency, although this has not been demonstrably proven.

Australian Bastard Cannabis is perhaps the most striking mutation yet seen in cannabis. It is believed that this mutation was first seen in escaped populations around Sydney. Breeders have also attempted to stabilise this trait … again, without commercial success.

This mutation takes the form of hairless, succulent leaflets, usually with no more than five leaflets to a leaf. The individual leaflets usually do not exceed a few centimetres in length.

Despite the allure of cannabis that does not resemble cannabis, most attempts to breed viable strains using these genetics have ended in failure.

Not unsurprisingly, the best results will usually be gained from healthy plants that exhibit normal characteristics. However, the success of breeding ruderalis genetics (which are poor in cannabinoids) with higher-potency varieties indicates that further research may yield improved results.

Cannabis leaves are so recognizable, they’re basically iconic. But what do you know about them? Learn to identify the leaves and what you can do with them.

Wild hemp identification

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower:

Hemp has both male and female flowers, usually on separate plants but both may be on the same plant. The male flowers are greenish and become cream or pale yellow with maturity, are ½-inch across when fully opened, hanging down with 5 widely spreading narrow petals and 5 creamy-tipped stamens, and loosely clustered on branching stems up to 12 inches long.

The female flowers are green, stalkless, enclosed in gland-dotted bracts, and densely clustered along the stem and at the top of the plant, the pale style mostly erect.

Leaves and stems:

Leaves are in a fan-shaped array, palmately compound in groups of 3 to 9, alternately attached at the stem, though they may be oppositely attached near the base of the plant. Leaflets are linear to narrowly elliptic, tapering to a point at each end, coarsely serrated, with short stiff hairs on the surface. Leaflets in the middle of the fan are longer than those on the end. On a large male plant the middle leaflets may be up to 12 inches long and 1 inch wide. A female plant has smaller leaves, more tightly clustered at the stem but is generally more robust than male plants. Stems are smooth and green, sometimes tinged red.

Fruit:

Fruit is a teardrop shaped capsule containing white or greenish seeds mottled with purple.

Notes:

Hemp is sometimes referred to as “Industrial Hemp” for its uses such as making rope, fabric, and paper, or for its food value. Plants found in the wild are often leftovers from the days when it was a farm crop and do not typically have the “recreational” value of Marijuana, though I did once come upon a secret stash of Marijuana growing in 5-gallon pails at Boot Lake SNA in northern Anoka County. Whoever had placed them there was either very clever or very dumb, as they were located in the middle of a patch of Poison Sumac! Hemp is considered a noxious weed in Koochiching, Murray and Waseca counties of Minnesota, though there are no official records of its existence in those particular counties. It is likely a very under-reported species. There is some debate regarding subspecies, but when recognized, subsp. indica (also known as Cannabis indica) is generally considered a more compact plant with broader leaflets, where subsp. sativa has narrow leaflets. The chemical composition of the two is also rather different with indica apparently the more intoxicating of the two.

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More photos

  • Wild Hemp plants
  • a male and a female plant
  • more plants
  • early growth
  • clusters of male flowers
  • clusters of female flowers
  • subsp. indica leaves

Photos by K. Chayka taken at Long Lake Regional Park, Ramsey County. Other photos courtesy Peter M. Dziuk.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Neighbor found one growing in my ditch, pulled it out. It was fairly large for it’s age, found it in June. It was definitely an indica variety. Now I see more growing around here, all Sativa. I’ve pulled the males so the females won’t produce seeds and spread like crazy next year. The sativa’s growing around here all happen to be where I brought my trailer in the the spring for yard work, which means I unknowingly transplanted seeds all over my property.

Really? I didn’t even know they grew wild here, where are these plants you speak of?

There was a small patch of this growing (or probably will be growing later after it sprouts) along the creek just above Foxborough park. Several years ago some kids tried to harvest it. They had it in black plastic garbage bags which they left behind my neighbor’s house. I was walking and saw it and thought it was someone’s lawn clippings. It got thrown in the yard waste container and I presume it became compost. I’m sure they were disappointed as there is a lot of stinging nettle along the creek where it was.

Minnesota ditch weed is all over the place. When my great grandpa was younger in which he has been gone for 38 years the farmers grew hemp to make rope. There was a hemp factory in this small town. The hemp plant now grows wild in this area.

I find patches of it all over SE Mn when I am out mushroom hunting. It spreads quickly once established. I saw some kids eyeing one patch and 2 weeks later I came back and it was gone. I think they thought they found someone’s stash but if they had taken the time to look around they would have seen it all along the roadside for at least a half mile.

Found a large patch at Holthe SNA. All the way at the end of the road past the gate on the left side. It’s all Hemp. trust me.

Ditch weed grows everywhere here. Especially around train tracks.

We have this growing in our back yard. Not sure which species or variety it is.

Its growing along the railroad tracks, in between HYW 13 and the Minnesota river in Eagan/Mendota Heights

Confirmed ditchweed in Waseca! It’s found near pretty much any agricultural field or ditch near a crop field that has a water source near by, I think the run off fertilizer helps it out. My dad as a teen with his friends used to work the fields in the summer, and they would pick ditchweed to get a free high, no matter the poor quality lol. My neighbors found marijuana in their backyard when they moved it and burned it immediately because they were frightened the cops would reprimand them. I’m not sure if it was feral or if it was my previous neighbor’s grow stash, but the few plants that they burned definitely made the neighborhood hazey for a few hours hahaha

So for this plant to be soooo horrific and invasive does anybody in mn care that it’s able to in “one” mn growing season pull in 10x the co2 an put out 10x the oxygen a tree can in its entire life. Also can be transformed into a bio fuel for cars drive now. well being in 100% compliance with the rules ( just not the laws) like they did with the corn but won’t infringe on our diet, well giving us clean air also beneficial to our lakes and rivers pulling harmful polution from our drinking water. amber

I’ve seen this in people’s yards and by the road. God put it there before it was illegal. If hemp is now legal then there is no reason the entire genus shouldn’t be, not just ruderalis. We have outlawed a part of our culture that made America. Please legalize cannabis.

we smoke ditch weed around here. Yes, I gives a bit of a buzz

Photos and information about Minnesota flora – Hemp: male: loosely clustered ¼-inch pale greenish flowers that may turn cream or pale yellow with age. female: dense clusters of greenish flowers up the main stem and at the top of the plant