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Nutrition

Feeding seedlings without burning them

Most seedlings die from too much love. Here's when and how to actually feed them.

3 min read2026-05-2910 views

The first feeding is the most-asked question in cannabis growing. The honest answer: most seedlings don't need feeding for the first 14-21 days. They live off the seed's stored energy plus whatever's in the starter medium. Feeding too early is one of the most common ways to stunt a young plant — and once stunted, the plant rarely fully recovers.

Why seedlings can't handle adult feed

Seedling roots are tiny and thin-walled. They absorb water and nutrients by osmosis. When the surrounding solution has too high a concentration of dissolved salts (EC), the plant can't absorb water — the gradient runs the wrong way. The result: leaf tips burn, growth stops, and the plant can take 2 weeks to recover.

Adult veg EC

1.2-1.6

Light feed

Seedling EC

0.4-0.8

Quarter strength max

First-feed timing

Day 14-21

When first true leaves are big

Daily increase

10-20%

Gradual EC ramp

Watch the cotyledons — they tell you when to start

Cotyledons are the round embryonic leaves the seed pushes out first. They're full of stored energy. While they're still bright green and full, the plant is feeding itself. When cotyledons start to fade — yellow tinge, lose plumpness — the stored energy is depleted. That's the cue.

1
Day 0-7: water only
Plain water, pH-adjusted to 6.0-6.5 for soil, 5.6-6.0 for coco.
2
Day 7-14: very light feed if needed
Only if your starter medium is unfertilized (peat plugs, plain perlite). Use 1/8 to 1/4 strength veg feed.
3
Day 14-21: first true feed
1/4 strength veg nutes, watching for any leaf tip burn.
4
Day 21+: increase 10% per feeding
Build to full veg strength by week 4-5.

Reading early burn signs

Burn vs. deficiency on seedlings

Nutrient burn (overfeeding)

Leaf tips brown, dry, curl down
Burn starts at the outer edges of newer leaves
Crusty white/yellow buildup on soil surface
Fix: water with plain pH-adjusted water 3× to flush

Deficiency (underfeeding)

Cotyledons fading too fast (before day 14)
Leaves pale green or yellowish
Slow stunted growth
Fix: begin gentle feed at 1/8 strength

Common starter media and what they give you

Rapid Rooters / peat plugs — lightly fertilized; first feed often unnecessary in week 1.
Coco coir (washed) — no built-in nutrients; needs feeding from day 1 at quarter strength.
Pre-mixed organic soil (FFOF, Roots Organic) — usually pre-charged for 3-4 weeks; just water.
Pure perlite or rockwool — sterile; feed from day 1 at very low EC.

Common mistakes

Using full-strength bloom nutes on a 14-day seedling.
Mixing veg + bloom + cal-mag + bloom booster on a 2-week-old plant 'just in case'.
Foliar feeding seedlings — leaf tissue is too thin and easily damaged.
Topping off with pH-unadjusted tap water that brings EC down but leaves pH wrong.

My seed is in pre-charged soil — when can I feed?+

Wait until the soil's pre-charge is depleted (usually 3-4 weeks for FFOF). Sign: lower leaves start fading.

Should I use cal-mag from the start?+

If you're in coco — yes, 1/4 strength. If you're in pre-charged soil — no, save it for week 4+.

Can I overwater a seedling that gets feed?+

Yes. Overwatering is the second-biggest seedling killer after overfeeding. Both at once is fatal.

Connect this to CannaForge

Open the [Lineage Atlas](/lineage) to see how strains relate to one another.
Switch to the [Genetics Map](/lineage?tab=map) to visualize parent → child trees.
Use the [Trait Matrix](/lineage?tab=matrix) to filter by family, terpene, or classification.
Browse verified [Breeders](/breeders) and the [Available Genetics](/shop) directory.

Common seedling mistakes

Overwatering, weak lighting, premature feeding, and burying too deep account for 90% of failed seedlings.

pH, EC, and runoff: the only three numbers that matter

Master these and 80% of nutrient issues disappear.

Your first grow: an honest 90-day roadmap

Week by week, what to expect and what to actually focus on.

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