Professional growers attempt to replicate scarification using sulfuric acid while many home growers use vinegar. I’ve never tried either and probably won’t, choosing to buy plants from a nursery instead, but that’s just me.
Stratification is another process that nature uses to prepare seeds for germination. Plant seeds that require layering include speedwell, lavender, phlox, coneflower, delphinium, milkweed (milkweed), and penstemon, among others. The seeds of these plants must go through a period of cold weather before they can germinate successfully. This is why many gardeners harvest the seeds of their milkweeds to store in the refrigerator until spring planting. There are a variety of recommendations for accomplishing the stratification of various plants, but all involve a “chill” period in the refrigerator.
OSU recommends soaking seeds requiring stratification for 12 to 24 hours in room temperature water, then storing them for two to six months in the refrigerator with a damp paper towel. Stratified seeds should be planted as soon as they are taken out of the refrigerator.
In both processes, all we’re doing is mimicking what happens in nature that allows those seeds to germinate.
Fruit plants of various kinds need what is called a cooling period to produce their fruit. The chill period is the number of hours below 45 degrees these plants need to produce fruit in the spring, and different varieties require a different number of chill hours. As you can imagine, relaxation hours vary from state to state. For example, in the Tulsa area, blueberry varieties that succeed here are those that require about 800 hours of chilling per season, while varieties that can be grown in the southern part of the state may only need from 150 to 600 hours of cooling.