You are right that the training is science-based and not based on the marketing of products, old wives’ tales, or internet memes. Unfortunately, many gardening products are sold through marketing to people who don’t really know what they are doing. For instance, because of advertising in the spring, many tons of grub-control and weed-control products are applied to lawns that have neither problem.
As for grass seed, it is sold in the spring because most people think that is when it should be planted. They look at their lawn just after the snow melts, and they see bare spots and dormant grass. They don’t like what they see, even if it is normal for that time of year. In a couple of months, the grass will look fine, even if they do nothing.
The stores stock grass seed in the spring because they stock all their other gardening plants and hardgoods in the spring. In the fall, when it is the best time to plant grass seed, the stores are stocking Halloween and Christmas items. There are not enough trained people like you that are asking for grass seed at the proper time of year for the stores to change their ways.
For northern lawns, grass seed is best planted in the fall because you are planting cool-season grass that is then going to go through three consecutive cool seasons before the heat of next summer. If you plant cool-season grass in the spring, it immediately goes into the hot, dry dormant season without a strong root system to get water from the ground. If you water it and try to keep it growing, the hot weather works against you and the plant. You will spend too much time and money trying to keep the grass growing when it wants to go dormant in the heat.
In the spring there are a lot of weeds, and they will last all summer. Fall planting invites many fewer weeds. The weeds that do come up are mostly annuals that will die as the weather turns cold without any weed-control efforts. The weeds won’t last long enough to produce any seeds. The fall-planted grass will need a lot less water to keep it growing.
If you can find any grass seed for sale, it will probably be OK if it was stored in a cool, dry location this summer. Each label will tell you in which planting year that package was meant to be sold and installed. Grass seed can last for several years if it is stored properly. Remember: cool and dry. If it was left outside in a hot storage area or if it was in high humidity where the bag became damp, don’t buy it.
The grass will grow best if it is planted a month or two before your area’s first killing freeze. The later it is planted, the smaller the root system and the less chance of surviving a dry winter that dries out the soil.
