Annuals that do well indoors during the winter are limited to Coleus, Impatiens (including New Guinea), Nasturtium, Pansy Petunia, Verbena, Wax Begonia, Lantana, and Geraniums, with Coleus and Geraniums being the easiest. Gardening is about experimenting so try any annual you'd like.
The easiest plants to save seed from are annuals that are open-pollinated and self-pollinated. Beans, lettuce, peas, tomatoes, and peppers are great vegetables for beginning seed savers. Flowers great for seed saving include, marigold, zinnia, morning glory, cleome, nasturtium, poppy, snapdragon, and sunflower.
You can put them in a garage or shed that gets cold but doesn't freeze, ever. They will over-winter as live but semi-dormant plants. Keep the soil just moist, not letting the potting medium shrink and pull away from the pot edges.
Many pests and diseases will persist in the soil and plant debris over winter, if they're given the opportunity. Removing spent annuals and vegetable plants from the garden, improves our chance of eliminating numerous future pest and diseases that would otherwise survive on that dead plant material.
Remove Most Annuals
In general, these plants are easy to spot because after the first hard frost, many of them, including impatiens, begonias, and coleus, have withered and turned brown. If the spent foliage and blossoms on these plants are free of mold and disease, we put them in the compost pile.
If there is no vegetation in the space where you plan on growing wildflowers, your chances of success may be a bit better if you simply toss the seeds onto the ground. However, if you really want to ensure their success, preparing the soil is highly recommended!
If the ground is already prepared — meaning it doesn't have weeds and is already lightly cultivated — Becker said you can just scatter seeds on the damp soil (more about that technique below).
Annual cleanup
Remove all of your summer annual flowers, including their seed heads, from your flower beds. (Throw these in your compost bin.) This does more than save you time next spring. Leaving annuals in your beds over the winter will invite pests and disease as the plants decompose.
Take Special Precautions for Potted Plants
To protect them, you can wrap the pots in an insulating material (think burlap, old blankets, or even bubble wrap), place them close to the foundation of your house, and arrange them close together. You can also put a layer of mulch over them for added protection.
Light freeze - 29° to 32° Fahrenheit will kill tender plants. Moderate freeze - 25° to 28° Fahrenheit is widely destructive to most vegetation.
Wait to prune spring flowering plants right after they bloom. Any of your annuals that are no longer attractive can be either cut off at ground level or pulled out of the ground now. Or you can wait until later in the fall or even next spring. Here is a mix of annuals and perennials in early November.
True annuals and plants that we grow as annuals (considered tender perennials in southern regions) cannot survive cold winter temperatures. But there's no need to say farewell to these plants forever! Many “annuals” can be brought inside, even tender plants that need a winter dormancy period.
You can overwinter potted perennials in an unheated shed or garage. Allow them to naturally go dormant in the fall before moving them inside. Then put them back outside once the weather starts warming back up in late winter or very early spring.
One gardening friend doesn't even bother to prepare her soil—she simply sprinkles seeds wherever she'd like a few zinnias, waters those spots for a couple of days, and lets zinnias' easy-to-grow nature take its course.
Cleome: These are literally toss and grow seeds. These seeds need light to germinate, so you don't even need to rake soil on top of them. The flowers are pink, purple, white and fuchsia. They will self-seed and also resemble their parent plant.
Planting seeds this way is called direct sowing, and it is an easy process that yields great results. Unlike indoor seed starting, direct sowing involves unpredictable elements: weather, wildlife and insects. Even so, many vegetables, annuals, herbs and perennials sprout easily from seed sown directly into garden soil.
On average, it can take around 2 weeks for flower seed to germinate, and around 50-60 days for a flower to, well, flower. However, many factors will determine how long it takes for a seed to germinate, like their growing conditions, where they're sown, what type of seed it is, etc.
Seeds are meant to germinate when they're moist, and hibernate when they're dry. That's why it's important to dry your seeds after you harvest them.
Also, do not cut back hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum). Leave the foliage. It's important to protect the root crowns over winter.
If you can decide, the best way of determining when to transplant is based on the flowering pattern of each plant. If your perennial blooms in the spring or early summer, it should be transplanted in the fall. If your perennial blooms in the late summer or early fall, transplant it in the spring.