(2) Most species of the Ranunculus-family need lower temperatures during the cooling-period – about –5°C [23°F]. In other respects follow the directions in 1. above. The reason is probably the freezing point of these seeds, which is at –7°C [19°F], while most other seeds freeze at –5°C [23°F].

(1) Cold-germinators are still referred to as frost-germinators, although this isn’t quite correct. The sowing must be kept warm (about +18 to +22°C) [about 64 to 72°F] and moist for the first 2–4 weeks. After this period the sowing must be kept at a cold temperature (between –4 and +4°C) [between 25 and 39°F] for another 4–6 weeks. Colder temperatures of –5°C [23°F] are only advantageous for most species of the Ranunculus family. It is not so important if the temperature is higher or lower during the cooling period, but the cooling period has to be prolonged because the synthesis of the germination inducer, hormon-like acid, slows down or comes to a standstill.
It is beneficial to cover the sowing with snow during the cooling-period. The temperature below it usually keeps in the optimum range of –4 to 0°C [25 to 32°F]. The sowing is kept moist, and the melting snow helps to destroy the shell, which is advantageous for the germinating seedling. After this cooling-period the sowing may not be immediately exposed to high temperatures. The most effective temperatures are between +5 to +12°C [41 to 54°F], even if germination has started. The best location for this sowing, even in March, April and May, is the open field, the cold frame or a cold greenhouse.

(3) These species usually show excellent results if sown soon after the harvest, although most of them only germinate in spring after the effect of winter. For best results please order seeds in time.

(18) See 17. Allow the seed trays to be left for only 2–4 weeks at warm temperatures, then keep at 0°C [32°F] for another 4–6 weeks. It does not matter if the water freezes. After this treatment allow temperature to rise gradually.

(17) Waterplants must be sown in waterproof plastic trays or similar containers containing a nutritious muddy compost. Fill water up to 1 cm over the top of the compost. Keep the trays at warm temperatures of approximately +22°C [72°F].