Compost: Cook some compost. Hot summer weather will break down compost fast. Begin building a new pile now, and it could be ready by fall. Also, don't place currently cooking compost around plantings. It's probably still too hot. Set it aside and allow it to continue composting. Or, use it as an amendment for new planting areas, digging it into soil and allowing it to compost until spring.
Divide irises: Dig and divide irises until midmonth. Dig up rhizomes with a spading fork, and cut or snap each leaf fan so it's free of the main clump and has a 3- to 4-inch-long rhizome attached. Cut leaves to 6 inches. Place the rhizomes in a circle in a shallow basin in soil, with leaves facing out. Bury rhizomes with a shallow soil layer.
Lawns: Raise mower height. You should be letting grass grow taller now to shade roots and cool soil. Aim for a 3-inch height for most Mountain West grasses, including Kentucky bluegrass and tall fescue.
Houseplants: Any indoor plants spending the summer outside need fertilizer during these peak growing weeks. Using liquid fertilizers, give flowering plants a bloom booster product every 10-14 days. Fertilize leafy plants every two weeks with a 20-20-20 liquid fertilizer mixed to full strength.