Seed Tests Show Increased Dormancy in Peas

Healthy peas on the left have tiny root hairs that hold soil. Chemically damaged pea on the left lacks these.

Dormancy or hard seed counts in peas is not a new phenomenon, but, interestingly, pea germination samples last year and again this year have had higher than usual hard seed counts.

Hard seed is seed that has an impermeable seed coat — the seed is impermeable to water or the exchange of gases that occur during germination. Legumes (clovers) and pulses (peas) are typical examples of physically dormant seeds; they have low moisture content and are prevented from imbibing water through the seed coat. Impermeability is often caused by the outer cell layer or hardened endocarp which occurs during the last stages of development in the plant.
Hard seed is overcome in clovers by chipping or cracking the seed coat to allow water uptake. Laboratories will not usually perform this type of procedure as hard seed is included in the final germination. Hard seed in peas is not included in the germination count. Since it is related to dormancy it is likely that a pre-chill period or cold stress test would alleviate the hard seeds.

The impact is that the final germination may not be as high as you might expect. Again it’s not a huge concern because it’s thought that the action of the soil will break the seed coat over time and full germination will occur. This is particularly true in clovers, but not always in peas.

Dormancy or hard seed should break by itself in the bin after a period of cold storage. If seed tests this fall show a high number of dormant or hard seed counts, I would advise that you retest your germination in the spring to get a more updated assessment of the final germination so that the seeding rate can be set more accurately.