Know Your Nursery: Winter seed treatment

While our pot­ted trees are hap­pi­ly dor­mant under their blan­ket of mulch, the Her­itage Nurs­ery staff is busy indoors prepar­ing our seeds for spring. Most native woody seeds pos­sess a dor­man­cy which, until bro­ken, pre­vents seeds from ger­mi­nat­ing. This built-in insur­ance pol­i­cy pro­tects seeds from ger­mi­nat­ing in the fall, even under con­di­tions that might be con­sid­ered favor­able. In nature, dor­man­cy is bro­ken after a seed spends sev­er­al cold win­ter months lay­ing on the moist for­est floor. After enough time in these con­di­tions, the seed’s embryo is sig­naled that spring has arrived and it is time to emerge. This process is called stratification.

In nature, seed dor­man­cy is reg­u­lat­ed by the chang­ing sea­sons of our cli­mate; how­ev­er, we can also con­trol this process arti­fi­cial­ly. To strat­i­fy the seeds we col­lect­ed in the fall, we store them at 31–41ºF in sealed plas­tic bags of moist ver­mic­u­late, sand, or peat moss for sev­er­al months. When the strat­i­fi­ca­tion peri­od ends, our seeds will be ready for plant­i­ng just as tem­per­a­tures begin to rise in the spring.

Break­ing dor­man­cy is a com­plex and del­i­cate bio­log­i­cal process in both seeds and estab­lished plants. If suf­fi­cient mois­ture, tem­per­a­ture, oxy­gen, light, and even hor­mon­al lev­els are not right, a seed will not ger­mi­nate — mak­ing it one of nature’s most impres­sive feats…one we all look for­ward to each spring!