Have you every bought a packet of seeds that recommended nicking the seeds or soaking them overnight in water before sowing? Morning glory, moon vine, and lupine seed need this kind of treatment to germinate because they have a hard seed coat that is impervious to water. Under natural conditions, a thick seed coat would be broken down by freezing and thawing, abrasion against rocks, microbial action, the chewing of animals, or passage through the intestinal tract of birds. This process is called scarification. When you buy a pack of seeds with hard seed coats you have to act like mother nature and break through the seed coat just enough that water can enter but not enough to damage the embryo inside.
Here are a some easy household methods for scarifying seeds.
Hot Water Treatment
1. Boil enough water to very generously cover the seeds.
2. Take the water off the heat and let cool for a few minutes (to 190o F.)
3. Add the seeds and let them soak over night.
N.B. Soaking the seeds for 4-48 hours in hot water works well too but is a slower method
If the seeds are large you can gently nick them with a knife or run a nail file over them.
If the seeds are small, put them on a piece of medium grade sandpaper in a shallow pan, rub the seeds gently with another piece of medium grade sandpaper wrapped around a block of wood.
The idea is to weaken the coat not destroy it. A gentle touch will do the job and leave the embryo intact, ready to grow. Once you have scarified the seeds you need to plant them promptly so that microbes do not penetrate the weakened seed coat.
How do you know if seeds need to be scarified? If you buy seeds in a packet the planting directions on the packet will tell you; if you collect seeds from plants, you can suspect they will need scarification if the seeds have a hard or thick coat. Members of several families, including Legumaceae (like beans and Baptisia), Malvaceae (like hibiscus and mallow), Convolvulaceae (like morning glory and moon vine) and Chenopodiaceae (like beets and chard), profit from scarification.
N.B. Scarification should not be confused with stratification, the chilling of seeds to break dormancy of seeds.