What is a node on a cannabis plant?

Q: What is a node on a cannabis plant?

A node on a cannabis plant is the point on a stem where a leaf and its axillary bud attach; branches, flowers, preflowers and clone roots all start there. The stem between two nodes is the internode. Count nodes upward from the cotyledons, which are not counted. Topping is usually done above the 3rd to 5th node, and preflowers often appear around the 4th to 7th.

Short answer

A node is the point on a cannabis stem where a leaf attaches, with an axillary bud tucked in the angle between leaf stalk and stem. Branches, flowers and clone roots all start at nodes. The stem between two nodes is the internode. Established botany.

Why

Each node is a growth point. A cannabis node carries a leaf on its petiole, an axillary bud that can become a branch, and a pair of small stipules ^[1]^[3]. Remove the tip and the buds at the nodes below take over, which is how topping works.

Nodes are where the first flowers appear. Single flowers form at the nodes once the plant matures; in one cultivar the first pair appeared at the 7th node, whatever the day length ^[2]. In flower, every node on a productive branch becomes a bud site ^[1].

Node pattern shows maturity. Young plants grow opposite nodes; mature and flowering shoots shift towards alternate nodes ^[1].

Internode length shows growing conditions. Short internodes mean compact plants and stacked buds; long ones mean weak light or the post-flip stretch.

The numbers

Item	Typical value
Counting start	First true leaves = node 1 (cotyledons not counted)
Topping height	Above the 3rd–5th node
First preflowers	~4th–7th node
Internode, compact plant	~2–5 cm (1–2 in)
Internode, stretchy plant	10 cm (4 in) or more
Clone cutting	2–3 nodes, one buried or just above the cut

What to do

Find node 1 at the first true leaves and count up the main stem.
Top or start LST once there are 4–6 nodes.
Check the upper nodes with a loupe for preflowers from about week 4.
Take clone cuts with 2–3 nodes; roots form best near a node.
If internodes are long and gappy, check light intensity first.

Common mistakes

Counting the cotyledons as node 1.
Mistaking stipules at a node for preflowers.
Blaming genetics for long internodes under a weak light.

Full article: Cannabis plant biology
Answers: recovery after topping · fan leaves vs sugar leaves
Article: Topping
Terms: node · internode · axillary bud

Follow-up questions

How do I count nodes on a cannabis plant?

Count cannabis nodes from the bottom up, starting with the first pair of true leaves as node 1. The round seed leaves, the cotyledons, aren't usually counted. Each place where a pair of leaves, or later a single leaf, joins the stem is the next node. Count only the main stem when someone says 'top above the 5th node'.

What is an internode?

An internode is the length of stem between two adjacent nodes. Short internodes, about 2–5 cm on compact plants, mean tight bud stacking; long ones, 10 cm or more, mean stretch. Low light, a high far-red share and warmer days than nights lengthen them; stronger light and training keep them short. Most cultivars' internodes lengthen in the first weeks after the flip.

Why do nodes switch from opposite to alternate?

Young cannabis grows opposite nodes, with two leaves facing each other at each node. As the plant matures, new nodes switch to alternate, one leaf per node in a staggered pattern. The switch is a sign the plant has reached its adult stage, when preflowers appear and it can respond to long nights by flowering.

Sources

Spitzer-Rimon B, Duchin S, Bernstein N, Kamenetsky R. 2019. Architecture and florogenesis in female Cannabis sativa plants. Frontiers in Plant Science 10:350. doi.org/10.3389/fpls.2019.00350

Spitzer-Rimon B, Shafran-Tomer H, Gottlieb GH, et al. 2022. Non-photoperiodic transition of female cannabis seedlings from juvenile to adult reproductive stage. Plant Reproduction 35(4):265-277. doi.org/10.1007/s00497-022-00449-0

Small E. 2015. Evolution and classification of Cannabis sativa (marijuana, hemp) in relation to human utilization. Botanical Review 81:189-294. doi.org/10.1007/s12229-015-9157-3