Tips for Achieving Uniform Flowering in Durian – The C/N Ratio

To help durian trees flower uniformly, at the right time, and achieve high yield, growers must understand the relationship between Carbon (C) and Nitrogen (N) inside the plant. These two elements determine whether the tree is “growing leaves” or “growing flowers.”
In other words, the C/N ratio is the key indicator that tells us whether the tree is ready to flower, allowing farmers to adjust cultivation practices accordingly.

Understanding Carbon (C) and Nitrogen (N)
C (Carbon)

Carbon is created through photosynthesis and converted into sugars, which are then stored in the stems, branches, and leaves. These sugars play an essential role in stimulating flowering.
When the tree accumulates enough Carbon, this stored energy is used to form flowers and fruits.

N (Nitrogen)

Nitrogen is absorbed mainly from nitrogen fertilizers.
It helps the tree develop stems, branches, and foliage — meaning it promotes vegetative growth rather than flowering.

How the C/N Ratio Affects Flowering

C/N ratio = the balance between Carbon and Nitrogen in the tree

When C < N → The tree grows shoots, leaves, stems (vegetative growth).

When C > N → The tree tends toward flowering and fruiting (reproductive growth).

For durian, the ideal C/N ratio for flowering is around 18:1, meaning the tree must accumulate sufficient Carbon while Nitrogen levels must not be too high.

How to Adjust the C/N Ratio to Trigger Flowering
1. Reduce Nitrogen (N) Fertilization

Reduce or stop applying fertilizers with high N content.
Switch to low-N formulas to help the tree accumulate more Carbon → increasing the C/N ratio, allowing flowering to begin.

2. Increase Phosphorus (P) and Potassium (K)

P and K promote flower bud differentiation and improve fruit set.

3. Adjust Irrigation

Before flower induction, farmers may reduce or stop watering for several weeks.
This helps:

accelerate leaf maturation

reduce nitrogen absorption

increase carbohydrate accumulation in stems and branches
→ preparing the tree for flowering.

4. Observe Leaf Condition

Mature leaves will turn dark green, thick, shiny, and no new flushes appear.
This indicates:

the tree has accumulated enough nutrients

C/N ratio is optimal

ready for flower induction

Summary

The C/N ratio is a critical indicator for actively managing the flowering phase in durian:

Low C/N → the tree “runs leaves,” making it difficult to flower

High and balanced C/N → the tree “runs flowers,” leading to high yield and good fruit quality

Farmers should regularly monitor tree physiology, adjust fertilizer programs, and manage irrigation properly to ensure strong trees, uniform flowering, and a successful harvest.

Technical Department – Sitto Vietnam Co., Ltd.

See also:
Tips for Inducing Flowering in Durian Trees | Understand the Principle – Take Control of the Process