How Marijuana Plants Use Sugars
Here is how cannabis plants use sugars in one line: the leaves make them, and every other plant part spends, stores or builds with them. Oregon State Extension (OSU) writes that a plant burns those carbohydrates for energy, stores them, or turns them into more complex compounds such as oils and proteins.
Kind Seed Co starts with the raw materials: sunlight, carbon dioxide drawn from the air and water pulled up from the soil, as OSU describes. For the light side of that story, read how photosynthesis makes cannabis grow.
Where Sugars Are Made
Sugars are made in the green leaves. The work happens inside the leaf, not on its surface.
OSU notes that this food making happens in the mesophyll, the inner layers of the leaf, packed with chloroplasts that hold the green pigment chlorophyll. Its formula is simple to read: six molecules of carbon dioxide plus six of water, powered by light, give one molecule of sugar and six of oxygen. Oxygen leaves the plant as a byproduct.
Carbon dioxide gets into the leaf through tiny pores. According to the NC State handbook, guard cells close those pores when conditions push water loss up, such as high heat or dry air, and they usually close in the dark. When the pores close, less carbon dioxide reaches the leaf, so less sugar can be made. Our page on stomata and how they work covers the pores in more detail.
Looking up carbs for cannabis? The sugars and starches a plant makes are its carbohydrates, as OSU puts it. The plant builds them itself and does not take them in through the roots.
Where Sugars Go in the Plant
Sugars travel from the leaves to every growing part. Some are used at once and some are stored.
The sugars a leaf makes do not stay put for long. The NC State handbook says simple sugars such as glucose are turned into more complex sugars that can move out to stems, roots, flowers and other growing tissue to be used right away. The same handbook names starch as the main storage carbohydrate in plants and adds that sugars also become the building blocks for oils, pigments, proteins and cell walls.
The pathway for that trip is the phloem. NC State describes the vascular tissue of the stem as xylem, which carries water and minerals, and phloem, which carries food. OSU adds that a plant uses its stored products when light is short or sends them to its roots or developing fruits.
So every growing tissue depends on the leaves. New shoots, new roots and, later, flowers all draw on the same supply. The page on how cannabis buds form follows that supply into the flowering stage.
Feeding sugar products to the soil is a different matter. We found no Extension source that supports adding molasses or sugar to cannabis, so we do not recommend it.
Making Sugars vs Using Sugars
Making sugar stores energy and using it releases energy. OSU sets the two side by side.
In OSU’s terms, making food stores energy. Using food, called respiration, releases it. OSU describes respiration as controlled oxidation in a living cell, much like a slow burn, and says that energy goes into cell growth and new tissue.
| Feature | Making sugars | Using sugars (respiration) |
|---|---|---|
| Food | Makes it | Spends it |
| Energy | Locks it away | Frees it |
| Water | Consumed | Given off |
| Carbon dioxide | Taken in | Given off |
| Oxygen | Given off | Taken in |
| Light | Only in light | Day and night |
Based on the comparison table in Oregon State EM 9901.
NC State cautions that respiration is not simply the making process run backward, even though the two equations look like mirror images. A more useful way to picture it is one process that builds carbon compounds and another that breaks them down to release stored energy.
Light and the Daily Light Integral
More light over the day lets the leaves make more sugar. Daily light integral measures that total.
The amount of sugar a leaf can make rises and falls with the light it gets over the whole day. For Iowa State Extension, light quality, intensity and duration together set the DLI. Virginia Cooperative Extension gives the formula as PPFD multiplied by 3,600 and by the hours of light, all divided by 1,000,000. In short, multiply PPFD by the hours of light and then by 0.0036.
| PPFD (micromoles per square meter per second) | DLI at 12 hours | DLI at 18 hours |
|---|---|---|
| 200 | 8.6 | 13.0 |
| 400 | 17.3 | 25.9 |
| 600 | 25.9 | 38.9 |
DLI values are in moles per square meter per day, worked out with the formula from Virginia Cooperative Extension. They show how light level and hours combine and are not cannabis targets.
Virginia Cooperative Extension also notes that moving lights closer raises intensity but makes light less even across the canopy.
How to Help Your Plants Make and Move Sugars
Give the leaves enough light, a steady temperature, water and room for roots. The steps below tie each one to a source.
- Measure your light. Find the PPFD at canopy height and the hours the lights run, then work out DLI with the formula above.
- Use a full spectrum light. Iowa State notes full spectrum fixtures with a mid range Kelvin value supply both red and blue light.
- Keep the room in a moderate range. OSU reports that sugar production is quickest from 65 to 85 F and drops off when the room is hotter or colder than that.
- Water before the plant droops. NC State says conditions that drive water loss make the leaf pores close, which cuts the carbon dioxide supply.
- Give roots room and air. Compacted soil limits root growth, NC State notes. Read about the role of cannabis roots.
- Leave working leaves in place. OSU places sugar making in the leaf mesophyll, so every green leaf you strip is one less producer.
Troubleshooting
Slow growth often traces to light, temperature or the root zone. Pick the case closest to yours.
Plants look pale and grow slowly under a weak light. Work out the DLI for your lamp and schedule. A low figure means the leaves have little light to work with. Raise the intensity or the hours, keeping the uniformity note from Virginia Cooperative Extension in mind.
Growth slows after a cold night. OSU reports that the making process slows below 65 F. Find the cold spot and steady the temperature before you change the feed.
Leaves droop at midday. Heat and dry air push water loss up, and per NC State that makes the leaf pores close. Check the pot weight and the room temperature, and water if the mix is dry.
Plants stall after moving into a dense mix. Compacted soil limits roots, per NC State. Loosen the mix at the next repot and check that water drains freely.
You added a sugar product and saw no change. That fits what the sources describe. The plant makes its own sugars in the leaves, so focus on light, temperature and water instead.
Sources
- Oregon State University Extension, EM 9901 Plant Growth and Development: https://extension.oregonstate.edu/catalog/em-9901-plant-growth-development
- NC State Extension Gardener Handbook, Chapter 3 Botany: https://content.ces.ncsu.edu/extension-gardener-handbook/3-botany
- Virginia Cooperative Extension, SPES-720 Daily Light Integral for Indoor Growing: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/spes/spes-720/SPES-720.pdf
- Iowa State University Extension and Outreach, Important Considerations for Providing Supplemental Light to Indoor Plants: https://yardandgarden.extension.iastate.edu/how-to/growing-indoor-plants-under-supplemental-lights/important-considerations-providing-supplemental-light-indoor-plants
FAQ
How do cannabis plants make sugar?
In the leaves. Oregon State Extension describes how plants use light energy, carbon dioxide and water drawn up through the roots to form carbohydrates, which are sugars and starches. Oxygen is released as a byproduct. The work happens in the inner leaf layers rich in chlorophyll.
Where do sugars go in a cannabis plant?
Per NC State Extension, sugars move out to stems, roots, flowers and other new tissue to be used right away, or they are stored as starch. They also become building blocks for oils, pigments, proteins and cell walls. The phloem carries them along the plant.
Does a cannabis plant have sugar in it?
Yes. A cannabis plant makes sugars from light, carbon dioxide and water, as other green plants do, and moves them to its growing parts. OSU notes the plant burns some for energy, stores some and builds the rest into other compounds such as oils and proteins.
Do sugar products change how cannabis plants use sugars?
We found no Extension source showing that they do. The plant makes its own sugars in its leaves, so we do not recommend sugar or molasses products. It puts the focus on light, temperature, water and roots, which the sources do tie to sugar making.
Do cannabis plants use sugar at night?
Yes. OSU says respiration needs no light, so it carries on through the night and the day alike. Sugar making stops in the dark, but the plant keeps burning stored sugars for energy around the clock. At night it draws on what it made in the light.
