Many annuals will reseed themselves back, and come back every year. Some examples are Four 'o clocks. They will grow to about 3-4 feet high, and bloom all summer up to frost. You can collect the seeds and plant in other locations, also, but what drops to the ground will grow the next year. They come in various colors. I have "hot pink", but have seen them also in yellow and white. Portulaca is another self seeding annual. It also goes by the name Rose Moss. They spread out to fill in the bed and bloom all summer up to frost. Flower colors may vary, reds and yellows. Yet another is Periwinkle. They are usually white or pink. They are small plants and when they reproduce in the spring, may come in very thick and you can then thin and plant in other locations.
We live in a zone 3 here in southern Manitoba. I hate it when I go to the local Canadian Tire, Walmart or Home Depot and they are selling zone 5 plants to unsuspecting customers. A new gardener would think that they, themselves, did something wrong when they planted it or watered it wrong, when the perennial does not come up next year, just as I did when I started to garden with perennials years ago. So, know your zone and ask about the perennial before you spend the money on it. How easy it is to grow, is it an invasive perennial, does it require a lot of water or sun, etc.
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