It has warmed up enough to get those seeds planted! Cosmos, Zinnias… It is still spring, but it may be starting to feel a bit more like summer. May is the transition month. You are moving from “I can do anything right now I have the power” to “I have exactly two days until the heat kills everything I just planted.” Use the first half of this month wisely to get necessary planting done. You do not have much longer!
Keep your plants mulched and watered. Watering is really the name of the game as we head into summer. However, you want to do it properly in order to stimulate deep root development and drought resistance. Water as deeply and infrequently as you can get away with. Try to see how the plant does without supplemental water. You may be pleasantly surprised or disappointed. Either way, it is less work for you, you have stronger plants, and a lower water bill.
Many spring-blooming wildflowers have gone to seed by now. Collect the seed and dry thoroughly to plant in the fall when such plants begin their lifecycle.
Many plants, from annual to perennial, can still be planted now. But you are running out of time before summer so get to it!
Source, Rebecca Burrow, Master Gardener