THE EFFECT OF DIFFERENT TREATMENTS ON THE GERMINATION OF LEWISIA HYBRID SEEDS.

Lewisia cotyledon (S.Wats.) Robins is the most variable of all Lewisia species. Native from California to Oregon (USA) where it grows at altitudes of 500 to 2000 m, this semi-succulent perennial has a rosette from which the very attractive flowers develop.

Usually Lewisia is sold as an alpine or rock garden plant. Seedlings include a wide range of forms and colours and if other lewisias are nearby, new hybrids occur because many species cross easily. Introducing Lewisia as a new flowering potplant, needs therefore an intensive breeding program and a severe selection of the most commercial forms. To improve and speed up the germination two experiments were designed.

In a first experiment the influence of different cold treatments was investigated. A cold treatment (0–5°C) at moist conditions during 3 to 4 weeks gave the highest germination percentage (76 %). Part of the germination occurred during the stratification process itself. An alternating temperature of 5 to 15°C, applied after this process, slightly increased the germination (82 %). Only 16 % of the untreated seeds (at min. temp. of 14°C) were finally germinated.

In a second experiment, using growth regulators, a germination rate of about 55 % was obtained by first soaking the seeds in 10 % solution of NaOCl (10 % Cl) for 30 minutes and then soaked again in 100 mg/l GA₃ or 0.6 ml/l Promalin during 24 hours. Controls showed a germination of 37 %. A higher concentration of GA₃ or Promalin might increase the germination up to the percentage of the stratification treatment.