In the spring, when the soil dries, these cuttings are planted outside in transplant beds. Here, they are grown for one season to put on size and acclimatize to outside conditions. In the winter, they are dug, graded, then held in cold storage preceding spring field planting. Tissue culture allows for rapid build up of new releases. We do not have our own lab, but instead buy plantlets from several commercial suppliers.
Tissue culture is a viable option for elms, but has produced some unique challenges.
Plants in tissue culture often sustain minor and temporary morphological changes. I have observed this across a broad range of species. In Ulmus parvifolia , this phase change is particularly striking and noticeable. Tissue culture grown plants are bushier, with more fine branching and more numerous but smaller leaves. As they grow older, they eventually change to the adult morphology and have all expected characteristics.