Seed Soaking: Why, When, and How Long
Why Soak Seeds?
Soaking softens the seed coat and triggers the biochemical processes that lead to germination. For microgreens, this translates to faster, more uniform sprouting — which means an even canopy and a consistent harvest.
Without soaking, seeds germinate at different rates. You end up with some sprouts ready to harvest while others are still catching up. That unevenness is the main reason first-time growers get disappointing results.
Soaking Times by Variety
Not all seeds need the same treatment:
| Variety | Soak Time | Notes |
|---|---|---|
| Radish | 4–6 hours | Small seeds, don't over-soak |
| Arugula | 2–4 hours | Minimal soaking needed |
| Broccoli | 6–8 hours | Change water halfway through |
| Pea Shoots | 12–24 hours | Large seeds, change water every 8 hours |
| Sunflower | 8–12 hours | Remove hulls if possible first |
| Kale | 4–6 hours | Standard soak |
The Right Way to Soak
- Use clean, room-temperature water — filtered or distilled is ideal
- Cover seeds by at least an inch of water — seeds swell as they absorb
- Place in a dark spot at room temperature (65–75°F)
- Change water for long soaks — stagnant water breeds bacteria
- Drain and rinse before planting — seeds should feel plump, not slimy
Common Soaking Mistakes
Over-soaking small seeds: Arugula, broccoli, and kale seeds are tiny. More than 8 hours and they can start to decompose rather than germinate. If you forget and soak overnight, plant immediately and hope for the best.
Using hot water: This isn't tea. Hot water damages the seed embryo. Always use cool or room-temperature water.
Skipping the rinse: After soaking, seeds develop a mucilaginous coating. A quick rinse ensures they don't clump together when you plant them.
Not accounting for expansion: Pea and sunflower seeds absorb a lot of water and can double in size. Use a container with plenty of room.
When to Skip Soaking
Some very small seeds — like basil and chia — form a gel coating when wet that makes them nearly impossible to handle. These are better planted dry and misted heavily after sowing.
Mucilaginous seeds are the exception, not the rule. For the six core varieties in our growing guides (radish, arugula, broccoli, pea, sunflower, kale), soaking is always recommended.