No, but you can overwinter things like spinach and kale for a very early spring harvest before they go to seed. And, there's lots of veggies you can plant now for a late fall harvest, if you have beds available. I'm guessing you're in southern Ontario (aka what we Prairie folk call the Florida of Canada).

Time to put down a pre-emergent iswhen the forsythia bloom. The AI in most pre-emergents will preclude overseeding for up to 120 days. Spray-on weed killers like Weed B Gone by Ortho are better alternatives than granulars like Weed and Feed by Scotts. Read the instruction on whatever product you choose for proper application and advisories regarding overseeding. When applying early Spring fertilizer, keep the total monthly N application to less than one pound per thousand square feet form all sources (Milorganite, Weed and Feed, pre-emergent etc.)

Did you read my post? Using a preemergent in the late summer when soil temps are above 70 F is a good idea mainly to prevent poa annua germination. Lawn burn is usually caused by the fertilizer portion of weed and feed products, but those are generally post emergent herbicide/fertilizer combinations that need to remain on the lawn for a while without watering in. You should always water in fertilizer and fertilizer/preemergent combinations. There are several preemergents on the market you can buy that don't include fertilizer. Dimension, Barricade, Stonewall, Pendulum, Ronstar, etc. Here's a good site to decide what you want to use. http://turf.unl.edu/pdfctarticles/Marchherbicidedelayswhenseeding.pdf

Caryopteris holds off until August in my garden and attracts butterflies by the hundreds. Mine is planted between two Montauk Daisies (aka Nippon Daisies). The caryopteris is just winding down as the daisies take over. For anyone who's not grown this plant...it's wonderful! It's a sub-shrub (like lavender gaura, Russian sage, etc.) and grows to a 4'x4' globe with thick foliage/stems...almost like a succulent. I prune mine down twice/season and it is always covered with hundreds of 3-4" white daisies Labor Day through Halloween. Also, hardy hibiscus will bloom well into late September...early October here. Sedums have faded by mid-August but still I leave the flower heads standing because I think they're attractive in their own right. I rely heavily on berry producing shrubs, foliage, & ornamental grasses for late season color. By mid-September to early October...my perennials are winding down...and so is their gardener!