My new growth is pale. Is that a deficiency?

The short answer

Look at the veins.

If the veins are pale along with the leaf tissue — the whole leaf a uniform light green — you’re almost certainly looking at normal young growth. If the veins stay green while the tissue between them goes pale, so the leaf looks like a green net over a yellow background, that’s chlorosis and it’s worth chasing.

Why the test works

Pale new growth at the top of a plant is one of the most common things a grower panics about, and it is very often nothing. Actively growing tissue simply hasn’t finished building its chlorophyll yet. It comes in light and darkens over a few days.

Chlorosis is a different process. When chlorophyll is lost or never forms in established tissue, the veins hold their colour considerably longer than the tissue between them. That mismatch is the signature. It’s the same reason experienced growers describe interveinal chlorosis as “netting” or “marbling” — the pattern is the diagnosis.

What you’re seeing	Veins	Tissue between them	Pattern
New growth	Pale	Pale	Uniform
Chlorosis	Green	Pale	Contrast

Why this beats comparing photos

The instinct is to photograph the plant today and hold it against last week’s picture. That’s a worse test than it looks, and I learned it the tedious way building a camera into a tent.

Any camera with automatic exposure adjusts to the scene. Change the light, change the angle, change how much of the frame the plant fills, and the camera quietly re-adjusts to suit — so the same leaf photographs at a different brightness on two different days with nothing wrong with the leaf. The plain colour of a leaf from one day to the next is not something you can trust, unless you have gone to real trouble to pin down the exposure, the white balance and where the camera sits.

The vein test sidesteps all of that, because it compares two things inside a single frame. If the exposure shifts, the veins and the tissue shift together. The contrast between them survives. One photograph, taken however you like, is enough.

How to actually look

• Pick a leaf that is fully expanded, not one still unfolding.
• Get close. Fill the frame with the leaf, or hold it up and look with your eyes — a wide tent shot is far too coarse for this and a small magnified look beats any measurement here.
• Ask one question: are the veins a different colour from the tissue beside them, or the same?
• Check where on the plant it is. Uniform pallor confined to the growing tips is the reassuring case. The same pallor on older, established leaves is not.

If it’s genuinely chlorosis

Then you have a starting point, not an answer. That netting pattern has several possible causes, and the honest next step is to narrow it down — where on the plant it appears, whether it started at the tips or the base, what your root-zone pH has been doing. How much of each nutrient the roots can actually take up depends on pH, so a lockout looks identical to running short of something you have plenty of.

I’m not going to give you a mineral name from a paragraph of text. Anyone who does, from a photograph, is guessing with more confidence than the picture supports.

What my device does with this

Croplock photographs the canopy on a schedule and flags leaves worth a second look, then walks you through narrowing the cause with questions rather than announcing a verdict. It shows you the source behind whatever it suggests. The vein test above is a technique I use myself and it’s the direction I’m taking the on-device version — but as I write this it is my eyes doing it, not the software, and I’d rather say that than imply otherwise.

Sources

Unlike the other pages here, this one isn’t built on published studies, and I’d rather say so than dress it up:

• The vein test is my own observation, from my own plants, checked against a real chlorosis episode in one of them in July 2026. It is consistent with how interveinal chlorosis is described generally, but I have not found a paper that states the discriminator in these terms — if you know of one, I’d like to read it.
• The auto-exposure problem is a first-party finding from building a scheduled camera into a tent, not a citation.
• That nutrient availability varies with root-zone pH — so a lockout can look exactly like a shortage — is standard horticultural ground and not specific to cannabis.

Treat this page as a technique that works for me and is cheap for you to check, not as a settled result. That distinction is the whole reason these pages exist.

More of these at Answers. The device is at croplock.com.