These can help if fertilizer is needed. Often, in a good garden soil, cosmos and many other annual flowers will prosper with a balanced fertilizer when planted, a compost mulch, and no additional fertilizer during the growing season. Plants in pots need fertilizing more often than plants in garden soil. Fertilizing more often isn't necessary and may actually reduce flowering. It's quite possible to love or coddle plants too much, and adding too much nitrogen fertilizer is one way to do that.
Plants establish well for summer bloom if planted in fall.
Some of the great lilies of the 20th century originated in the Northwest, including the Jan de Graff hybrids developed in Oregon. And provide ample organic material such as aged compost dug into the area before planting. Lilies are also available in spring and can be planted then, but fall-planting gives a longer establishment time. These regal plants contribute spectacular interest to summer perennial gardens and can do well tucked into shrub borders. Preparing roses for winter in the milder sections of the maritime Northwest means getting ready for the unknown.