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Seed Germination Requirements

Seedling Started

Seedling StartedMost seeds need only moisture and warmth in order to sprout. But some seeds may have additional requirements.

Check seed packets or planting guides for germination and cultural tips for the seeds you are planting.

Light. Some seeds such as beans need darkness in order to germinate; other seeds such a lettuce need light. Seeds that require darkness should be covered with fine soil or vermiculite to a depth equal to twice the seed’s diameter. Seeds that need light can be just sprinkled with seed-starting mix.

Media. All seed-starting medium whether a soil mix or vermiculite should be loose and smooth. Outdoor seedbeds should be well worked.

Temperature and Moisture. Soil and air temperatures should be near the optimum for the crop and so should the soil moisture.

Temperatures too low or too high can damage or kill seedlings; the optimal soil temperature for germinating most vegetables is between 65° and 70°F.

The same is true for soil moisture; generally a soil mix that is not too dry and not too wet but just moist is best.

Process of Seed Germination Explained:

  • A seed has everything needed to make a new plant; it waits until environmental conditions are met: an ample supply of water, optimum temperature, and situation in well-aerated soil or other medium.
  • Less than 2 percent of a seed’s weight is water;by comparison, 95 percent of a mature herbaceous plant is water. Low water content protects a seed against damage from low temperatures, for example, water in a seed could freeze, expand, and damage the seed.
  • Water absorbed by a seed causes the seed coat or shell to expand and split which in turn allows the seed embryo and cotyledons or seed leaves access to oxygen in the soil. Oxygen is needed for germination chemistry to proceed.
  • Germination chemistry causes food molecules in the seed–starch, protein, and fats–to break down into sugars and amino acids which allow for the construction of new plant cells including a root which anchors the new plant and draws life producing minerals and moisture from the soil. An embryonic shoot grows and pulls the seed leaves or cotyledons through the soil.
  • When the seed leaves reach through the soil to light, photosynthesis begins and produces all the food the plant requires to grow to maturity.
  • Germination ends when the shoot emerges from the soil.

For more on seed starting click on the article titles below:

Simple Seed Starting

Starting Vegetable Seeds Indoors and Out

Seed Failure Troubleshooting

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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