Written by Spirekassen 24 Feb 2023 14:05

Early sowing of flowers


Take full advantage of your greenhouse in the first months of the new year. March and April used to be months where the greenhouse was empty. The greenhouse would first be used when the tomatoes were ready to be move in the greenhouse in May.

Not long and your greenhouse will bloom of spring. Take advantage of the first spring months to pre-germinate summer flowers in the greenhouse. Climate change has made it possible to utilize the greenhouse much more than we are used to. Normally, summer flowers would be pre-germinated on the windowsills with additional plant light. The space on the windowsills is limited and today’s energy prices can make it an expensive task. There is another way.


Early sowing of flowers

It is actually possible to sow many summer flowers despite them being traditionally cold sensitive. The germination process takes longer, but the plants become more robust than the ones you germinate inside on the windowsills. At the end of February and in the beginning of March, we sow a lot of different summer flowers in our greenhouse, the Juliana Orangeri.

  • Snapdragon (Antirrhinum majus)
  • Flossflower (Ageratum houstonianum)
  • Sweet pea (Lathyrus odoratus)
  • Nigella (Nigella damascena ect)
  • Fewerfew (Tanacetum parthenium)
  • Youth-and-age (Zinnia elegans)
  • China Aster (Callistephus chinensis)
  • Drumsticks (Craspedia globosa)
  • Everlasting (Helichrysum bracteatum monstrosum)
  • Wavyleaf sea lavender (Limonium sinuatum)
  • Hare’s ear (Bupleurum rotundifolium)
  • Bishop’s flower (Ammi majus)
  • Toothpick-plant (Ammi Visnaga)
  • Brompton stock (Matthiola incana)
  • Mourningbride (Scabiosa atropurpurea)


Sowing tips
  • Use a seed tray, that is divided in cells.
  • Fill up the seed tray with sowing and potting soil (soil adapted to germinating seeds).
  • Water the seed tray and make sure the soil is moist.
  • Make a tiny hole (only few millimetres deep).
  • Place one or two seeds in the hole and sprinkle with Vermiculite* or sowing and potting soil.
  • Cover the seed tray with a fibre cloth.
  • Remove the fibre cloth on sunny days, but always cover it with the fibre cloth during the night.

You must think differently than you normally do when you are sowing summer flowers early. The above-mentioned flowers can easily withstand several degrees of frost without much trouble. The important thing is that the small sprouts get used to it from the beginning.

The process of seed germination can take up to 3-4 weeks. In general, always expect the germination process to take little longer when the seeds are not placed on the windowsill. The advantage of early flowers in the greenhouse is that you get more robust plants when they are ready for being planted outside.


(*) Vermiculite

Vermiculite is a mineral that pops like popcorn when heated. Vermiculite achieves a lattice structure containing clay. The structure becomes airy and loose, but at the same time the mineral has the ability to bind water. These abilities are interesting to use in connection with plant cultivation. For starters, vermiculite is completely unique. You use "sow and potting soil’’ as usual but sprinkle a fine layer (a few millimetres) of vermiculite over the newly sown seeds instead of soil. In this way, you prevent fungus while maintaining the humidity. For winter cultivation and for the early sowing of flowers, vermiculite is very suitable. Use the product as described above. Vermiculite has also the great advantage that it retains heat and makes your pre-germination easier at lower temperatures.