Muscle spasms, which can affect any part of the body, are an involuntary contraction in the muscle tissue. Depending on the muscle's size and location, it might be sharp and painful or nearly imperceptible.
Think of it this way - a seed starting mix kickstarts the seed into accelerated growth mode. How to Choose the Best Seed Starting Mix Lightweight and Hydrated Mix. For your seed to grow into a healthy seedling, the best seeding mix is a lightweight and well-drained soil that has a balanced mixture of organic materials like vermiculite or perlite. The soil mix should also have excellent aeration and water retention properties so that the seed's root can push through and have room to grow.
Potting soil is for established plants not seeds and seedlings. When I start herb seeds I like to fill my decorative herb container with a good potting soil. Then I sprinkle 1 inch of a seed starting medium on top of the potting soil. Then I will sow the herb seeds in the seed starting medium directly in my pot. This way I can avoid the work of transplanting the seedlings.