Cannabis Nutrient Deficiencies: How to Spot and Fix Every Common Issue

Why Do My Cannabis Leaves Turn Yellow?

Yellowing cannabis leaves are one of the most common signs of a nutrient deficiency. However, before adding anything to your soil or reservoir, check the pH level. Nutrient lockout due to incorrect pH is the most common cause of deficiencies, even if your nutrients are correctly balanced. If your pH is in range and the issue continues, here’s how to diagnose it.

• Older Leaves Yellowing: Likely a nitrogen deficiency.
• New Growth Yellowing: This could be sulfur or iron deficiency.
• Interveinal Yellowing (yellow between green veins): Often magnesium, manganese, or iron.

Look at where the problem starts: top or bottom. Mobile nutrients, such as nitrogen, move from old leaves to new growth. Immobile nutrients like calcium stay in place, so their deficiency shows in newer leaves.

Why Are My Cannabis Leaf Tips Turning Brown or Burnt?

Brown, crispy leaf tips often indicate a potassium deficiency. Potassium controls how cannabis plants move water and handle environmental stress. Without enough of it, the plant can't manage moisture effectively, which dries out the leaf tips and causes that burnt appearance.

You might also notice:

• Yellowing at the leaf edges
• Stunted growth
• Poor bud development

These signs usually appear during mid to late veg or early flowering, especially when the nutrient mix has too much nitrogen and not enough potassium.

Potassium is a mobile nutrient, so signs typically start in older growth.

Why Do My Cannabis Plants Have Purple or Red Stems?

Red or purple stems can be a natural trait of some strains, but if you also notice slow growth or dark, dying leaves—look at phosphorus.

Phosphorus is critical for root strength and flower development. It’s essential during early veg for roots and early flower for bud formation.

Deficiency signs:

• Lower leaves turning dark green, yellow, or getting brown patches
• Red or purple stems
• Yellowing and loss of lower leaves as flowering progresses
• Phosphorus is a mobile nutrient, so symptoms begin in older leaves.

Why Are My New Cannabis Leaves Twisting or Curling Up?

When new growth curls upward, you may be seeing a calcium deficiency. Calcium is immobile, so signs show up in new growth first. This mineral strengthens cell walls and is essential for maintaining a healthy structure.

Signs:

• Browning or spotting on new leaves
• Upward curling edges
• Weak stems or stunted shoots

Calcium issues are common in coco or hydro setups if not appropriately supplemented.

Why Do My Cannabis Leaves Have Yellow Between the Veins?

This symptom is known as interveinal chlorosis and has a few possible causes depending on where it starts:

• Older Leaves: Likely magnesium deficiency (mobile nutrient)
• Newer Leaves: Could be iron or manganese deficiency (both immobile)

Magnesium Deficiency

• Yellowing between veins on older leaves
• Veins stay green
• It can spread to the entire leaf if untreated

Iron Deficiency

• Starts in new leaves
• Yellowing between veins with green veins
• Progresses to a bleached or white look

Manganese Deficiency

• New leaves yellow between veins but with a mottled or speckled pattern
• May develop brown or tan necrotic spots
• Late-stage: curled or distorted leaves

These three all look similar, so location and pattern are key to diagnosis.

Why Are My Cannabis Leaves Pale or Washed Out?

If your plant’s leaves go from green to pale green or light yellow overall, suspect a nitrogen deficiency—especially if it's older growth. Nitrogen is a mobile nutrient used in large amounts during the vegetative stage.

Look for:

• Slowed growth
• Uniform yellowing of older leaves
• Smaller plant size

Reduce nitrogen during the flowering phase to support healthy bud development. Expect some yellowing late in the grow, but if you see it during veg, take it as a warning sign.

Why Are My Cannabis Buds Small or Weak?

If your plant looks healthy but your buds are small, airy, or underdeveloped, check for:

• Potassium deficiency – needed for bud growth and water regulation
• Sulfur deficiency – affects terpene, oil, and resin production
• Copper or Boron deficiency – can affect bud structure and density

Sulfur Deficiency

• Yellow new growth (not old leaves)
• Weak buds and low aroma
• Reduced oil and terpene production

Sulfur is partially mobile so that signs may appear in newer or middle growth.

Copper Deficiency

• Darkened leaves or pale white/yellow tips
• Incomplete bud formation
• It can cause flavor issues later
• Copper is an immobile nutrient, so symptoms show in new growth.

Why Are My Cannabis Leaves Deformed or Miniature?

If your leaves look small, twisted, or oddly narrow, suspect a zinc or boron deficiency. These are micronutrients involved in cell division and growth.

Zinc Deficiency

• Short internodes (tight spacing between branches)
• Small, narrow leaves
• Yellowing in new growth

Zinc is an immobile nutrient, so symptoms appear in newer leaves.

Boron Deficiency

• Brittle stems or distorted new growth
• Poor flowering or fruit set
• Often paired with calcium deficiency

Boron is also immobile, affecting the plant’s newest tissue first.

How Do I Fix Nutrient Deficiencies in Cannabis?

Check pH first. Soil should be 6.0–7.0. Hydro or coco: 5.5–6.5. Outside this range? Nutrient lockout.

Use complete cannabis-specific nutrients. These blends already balance macros, secondaries, and micros.

Follow stage-specific ratios.

• Veg: 3:1:1 (High Nitrogen)
• Early Flower: 1:3:2 (High Phosphorus)
• Late Flower: 0:3:3 (Low N, High P and K)

Flush if overfeeding. Too much of one nutrient can block others.

Use Cal-Mag if growing in coco or RO water. These mediums lack natural calcium and magnesium.

Final Tip

Don’t chase symptoms without checking the root cause. Many deficiencies look alike—and sometimes, it’s not a deficiency at all but a pH issue, poor watering habits, or heat stress. Keep a growth journal, monitor your inputs, and observe your progress.

Want to help diagnose your growth in real-time? Use BudSites to log your growth, upload images, and track nutrients. Our AI-powered assistant helps catch deficiencies before they ruin your yield.