My seeds won't pop. How do I start seeds and keep seedlings alive?

GROWER ANSWER

Usually the seed is fine. A slow seed is most often a cold one, or a wet one that can't breathe. Every seed needs three things held steady around it: warmth, moisture and air. Get those right, start the clock, and keep your hands off. Most seeds that die don't die from neglect. They die from rescue.

A slow seed isn't a dead seed. Read the room first.

Why seeds from the same pack pop on different days

Two crack open in a day and the other three just sit there. That doesn't make the slow ones duds. Each seed sits in its own tiny pocket. One is a little warmer, evenly damp and still getting air. Another, an inch away, is cooler, wetter, or packed in tight where the air can't move. Those small differences alone can stagger them by days.

Usually it's geography, not genetics. Before you blame the seed, make sure the room gives every seed an equal chance.

The three things a seed needs

Steady warmth. Aim for 72 to 80°F, held steady. Below about 70°F germination slows down, and above about 82°F the seed gets stressed. Steady beats strong. A heat mat with no thermostat can roast a seed at noon and chill it at midnight, and that swing hurts germination as much as plain cold.

Damp, not soaked. Seeds need water to wake up, but they need oxygen just as much. A dripping towel or a waterlogged plug pushes the air out and the seed suffocates. Wet also invites mold and rot. Evenly damp is the target.

Air. A paper towel that goes moldy was usually too wet and never aired out, so vent the bag or dome once a day. Seeds don't need light to sprout. Darkness is fine until the sprout breaks the surface.

Paper towel or straight into the mix? The method isn't the magic. Steady warmth, moisture and air are.

Dead or just slow? Read the clock

At the right temperature a healthy seed usually cracks and shows a root tail in 1 to 3 days. Day 7 is the decision line, not day 4. Before day 7, assume it's just behind unless you see rot.

Work through it in this sequence:

1. Read the clock. How many days, and at what temperature?

2. Check the warmth. Is it steady, or riding a roller coaster between day and night?

3. Check damp against air. Moist, not dripping, with air around the seed.

4. Factor in age. Older seeds and hard shells take longer to soak up water. Slow doesn't mean dead.

5. Stabilize and wait. Warm, damp, breathable, left alone.

Signs it rotted: cloudy, funky soak water, a brown or mushy root tail, mold, or a sprout that comes up and collapses. Signs it's just slow: no smell, no mush, no mold, just no crack yet, especially if it's been cool.

What not to do

Don't peel a stuck shell. The sprout is soft tissue, and the shell is often still stuck to the growing tip. Pull it and you can tear the first leaves or snap the stem. If one is stuck, raise the humidity around it a little with a dome, then leave it alone. The shell comes off on its own.

Don't re-soak a planted seed. A short soak before planting, 12 to 24 hours at most, can help an old or hard shelled seed. Past that you're not helping, you're drowning it.

Don't keep checking. Opening the bag every few hours swings the warmth and the moisture, and a fragile root tail snaps easily. Doing nothing isn't quitting. Sometimes it's the most skilled thing you'll do all week.

Once she's up: keeping a seedling alive

The same rules carry on after the sprout. Go gentle.

• Gentle light. Once the sprout breaks the surface it needs light to keep from stretching, but not full flower strength. Around 200 to 300 PPFD at the top of the seedling is plenty.

• Warm, humid air. Keep the air at 72 to 80°F with humidity around 65 to 75%.

• Damp, not wet. Waterlogged mix is how seedlings damp off: fine yesterday, collapsed at the base this morning, because the root rotted in mix with no air left in it. Keep it evenly damp, with air in the mix, and don't drown her in help.

When it's something else

• A seedling drooping and you're not sure about water: see How often should I water, and why is she drooping?

• Humidity you can't seem to hit: see What humidity should I run, and what if I can't hit it?

• Bleached or curling leaves under a strong light: see Tacoing or bleached tops: is my light too close?

• Ready to start shaping her: see Should I top or LST my plant, and when?

Keep going

Watch the episode: Why Seeds Don't Pop the Same: Dead or Just Slow, and How to Tell on MyRemy Live.

Steady warmth, damp not soaked, air, and patience. The whole system for a steady grow is written down in the free Stability Playbook. Get the free Stability Playbook

More answers: all grow guides. Every shelf guide and maker feed chart: Grower Resources.