Germination Testing Seeds: How to Test Viability Before Planting

Testing seed germination before planting takes 5–7 days and prevents the most avoidable of all crop failures: sowing an entire bed with seeds that are 40% viable, then wondering for 3 weeks why only half the plants emerged. A simple rag doll test or seedling tray test on a sample of 20–50 seeds gives you the germination percentage before you commit your season’s planting to old or poorly-stored seeds. If germination is 85%+, use the seeds at normal rate. If 60–85%, sow 30% more seeds than normal. If below 60%, buy fresh seeds — the time and bed space lost to poor germination is worth more than the seed cost.

How Do You Run a Rag Doll Germination Test?

The rag doll test is the simplest and most practical germination test for farm use:

1. Count exactly 20 seeds from your lot
2. Moisten a strip of cloth or paper towel (not dripping wet — just uniformly moist)
3. Lay seeds on one half of the strip at even intervals (seeds should not touch each other)
4. Fold the other half of the strip over the seeds
5. Roll the strip into a loose cylinder (the “rag doll”) — not too tight; air needs to circulate
6. Stand the cylinder upright in a cup with 1–2 cm of water at the base (the cloth wicks moisture up; keeps seeds moist without drowning them)
7. Place in a warm location (25–30°C) — on top of refrigerator, in a warm room
8. Check daily; count seeds that have sprouted (radicle — white root tip — has emerged)
9. Count at day 5 and day 10; record both numbers

Interpreting results:

• Seeds germinated of 20 tested = germination %
• 18 of 20 = 90% germination (excellent — use at normal rate)
• 14 of 20 = 70% germination (sow 30–40% more seeds than normal)
• 10 of 20 = 50% germination (consider buying fresh seeds; if using, sow 100% more)
• Below 8 of 20 = do not use for main crop; buy fresh seeds

What Are the Standard Germination Percentages by Crop?

What Is the Seedling Tray Germination Test?

The seedling tray test is more realistic than the rag doll test because seeds germinate in actual growing medium under actual conditions — useful when you want to test seeds under the specific conditions of your nursery.

Method:

1. Fill 1 row (5–10 cells) of a seedling tray with your standard nursery mix
2. Sow exactly 1 seed per cell; label the variety
3. Water and place in your nursery area under normal conditions
4. Count emerged seedlings at day 7 and day 14
5. Calculate germination % from emerged vs sown

Advantage: Tests how the seed will actually perform in your nursery conditions — not just whether it can germinate under optimal lab conditions.

Disadvantage: Takes longer (14 days vs 7 for rag doll); uses nursery tray space.

How Do You Adjust Seed Rate Based on Germination Test?

Formula: Adjusted seed quantity = Normal seed quantity ÷ (Germination % / 100)

Examples:

• Normal rate: 100 grams for 1 acre; germination test = 85%: use 100 ÷ 0.85 = 118 grams
• Normal rate: 100 grams; germination = 60%: use 100 ÷ 0.60 = 167 grams (67% more seed)
• Normal rate: 100 grams; germination = 95%: use 100 ÷ 0.95 = 105 grams (no meaningful adjustment needed)

Note on very old seeds: If germination test shows 40% or below, simply buy fresh seeds. The cost of patching poor stands, uneven crop, and delayed harvest far exceeds the cost of a fresh seed packet.

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Last updated: March 2026