Oh the joys of waking up to temperatures in the upper 40s and days in the mid 70s — it is officially fall in Missouri.

Oh the joys of waking up to temperatures in the upper 40s and days in the mid 70s — it is officially fall in Missouri.
It has been an absolutely beautiful weekend. With the much needed rain at the end of last week, the surrounding countryside looks refreshed and ready for autumn.
This is a great time of year to collect seeds from late summer and early fall blooming wildflower plants growing in your garden.
Although collection of seeds can be tricky in and of itself, getting wildflower seeds to germinate presents its own sets of problems due to germination requirements of many of our native wildflowers.
Whether you are collecting seed in October off the beautiful New England aster (Aster novae-angliae) or the bold and tall saw-tooth sunflower (Helianthus grosseserratus), which are both vigorous early fall blooming natives, be sure to be good stewards of the environment and collect only a very small percentage of the seeds produced by a single plant to allow the plants to naturally spread themselves.
Wildflower seeds can be easily purchased from multiple wildflower nurseries throughout the state, and these seeds also must go under certain germination requirements prior to sprouting.
The following is information regarding some but not all common seed germination requirements:
Stratification: Often seeds of trees, shrubs and herbaceous plants native or cultivated need to undergo certain environment conditions prior to germination (going from a state of dormancy to a state of growth).
Some seeds require a period of cold moist stratification, that is, they require a long period of time in moist storage at temperatures below 40 degrees Fahrenheit. This requirement mimics the winter season and can be achieved by sowing seeds in a cold frame outdoors or storing them in moistened sand for small seeds and moistened vermiculite for large seeds in a refrigerator kept above freezing but below 40 degrees F.
Other seeds which have other stratification requirements might require warm moist stratification, and others require a cycling of the two.  
Scarification: Another type of germination requirement is scarification, which means that the seed has such a hard seed coat (outer protective layer) that water cannot penetrate the embryo to induce germination.
Often plants in the legume family, such as Lupines, require their seed coat to be “damaged” to allow water to penetrate the seed before germinating.
As a home gardener, this can be accomplished by using sandpaper to slightly damage the seed coat layer of larger seeds, soaking seeds in a hot water treatment to soften the seed coat, placing the seeds briefly in a rock tumbler with coarse sand or sowing the seeds outdoors allowing the natural environmental weather changes to work on the seed coat over time.
Chemical inhibitors: Many times a seed is covered with a fruit or pulp which contains chemicals which prevent the seeds from germinating. The southern magnolia (Magnolia grandiflora) is an example of a plant whose seeds are covered in a reddish pulp which prevents it from germinating.
For best results, this pulp must be thoroughly washed from the seed surface before they are sown.
To make germinating seeds easier, the different germination requirements are often broken down into letter codes, for example A, B, C.
If a seed requires both scarification and stratification, it would be listed in plant propagation information sources according to both letters representing that requirement.
If you are interested in propagating wildflower seeds purchased from a nursery or collected from your home garden plants, the “New England Wild Flower Society: Guide to Growing and Propagating Wildflowers of the United States and Canada” by William Cullina is a great resource.