Benefits of A Chill Before Sowing
Recent information suggests that almost all wildflower seeds will germinate better after a period of 2 – 6 weeks storage in a refrigerator at a temperature of 3C to 5C. This helps to break their Summer dormancy. For some seed species just a few days can do the trick. Store the seeds in sealed containers and keep them dry. Avoid moisture from condensation.
Different methods of pre-treatment may need to be used for different seeds. Read carefully the instructions on the seed packet for reference to any of the methods shown below.
Many wildflower seeds require soaking overnight in water, often in hot water (close to boiling) to soften or break down their hard outer shell and allow water to penetrate to the embryo inside. Seeds of the many Pea varieties are a good example of this. Swollen seed is ready for sowing.
Some of the seeds placed in water will swell sooner than others. Remove the swollen seeds and sow them according to the instructions for that variety. Un-swollen seed can be soaked again to see if they will swell. The scarifying technique can be used before re-soaking. A small percentage of seeds may not swell after scarifying and 2 or 3 soakings and should be discarded as unviable.
Seeds which fail to swell after soaking often respond to a light scratching of the hard outer shell opposite the “eye” from where the shoot will emerge. A small sharp knife, a light nail file, emory board or fine sandpaper can be used to rasp away a tiny piece of the outer shell – don’t overdo it. Those seeds can then be soaked again in hot water until swollen.
I have found it easiest to place the seeds on a sheet of fine sandpaper on a table, place another sheet over the top and gently rub the top sheet over the seeds in a small circular motion for 20 seconds or so. Again – don’t overdo it.
Smoke treatment, smoky water and Seed Starter Granules – some varieties benefit from or even require the smoke from burning bush materials to permeate the soil into which they will be sown – to sponsor their germination when water reaches the seed.
Research has shown that the chemicals in the smoke act as a catalyst to stimulate the germination of the seeds of many Australian native plant species. See Smoke – Magic Ingredient for more information about this.
The burning of a handful of leaves and grass on top of the potting mix, prior to sowing the seeds, will do the trick for some species – but this is often not practical in a home setting.
A recently developed alternative is to briefly soak the seed in Smoky Water or apply some of our Wildflower Seed Starter granules (containing smoky water). The granular form can be added to the hot water when soaking the seeds or spread on top of the potting mix after sowing the seeds and washed in with the first watering to release the germination catalyst called Karrikinolide.
Another commercially available product is Smoked Paper onto which the seeds can be placed and watered instead of sowing into the potting mix. This is said to be effective but less so than smoky water or Seed Starter granules.
A combination of smoke treatments may also be worth a try – but there is no need to overdo it. Usually just a small amount of smoke treatment will trigger germination. See: How Much Seed Starter Should I Use.