Once finished blooming, annual flowers can easily be coaxed to continue blooming throughout the entire growing season by a simple process called deadheading― pinching off spent flowers.
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.
Simply put, annual plants die in the winter season so you must replant them every year, while perennials come back every year so you only plant them once.
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 “annuals” can be brought inside, even tender plants that need a winter dormancy period. These should ideally come indoors before nighttime temperatures dip below 45°F (7°C).
Your annuals are like a champion boxer – they more you try to knock them down, the tougher they get. If you trim off a quarter of their growth a couple times a year, they come back bigger, stronger, better, and more gorgeous.
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.
CORVALLIS, Ore. – As fall approaches, consider letting some of your annuals go to seed. If the winter isn't too harsh, they may pop up next spring. Annual plants are inherently programmed to set seed and die in one year.
Unlike perennials, annuals do not come back from season to season so there is no reason to leave these in the ground. Pull them up, roots and all, and add them to your compost pile. Remove weeds and leaf debris. These are common places for diseases and pests over winter.
Continue to water annuals until freezing temperatures kill them. If your annuals are in containers, move them into a garage or other protected space when temperatures are forecast to dip into the 40s overnight. You can do this until daytime temperatures no longer rise above that threshold.
Some cool-season annuals can tolerate soil temperatures as low as 45 degrees Fahrenheit; however, most cool-season annuals will grow best in soil temperatures at 65 degrees Fahrenheit or warmer.
The short answer is that annuals don't come back. Plants that flower and die in one season are annuals—although many will drop seeds that you can collect (or leave) to grow new plants in the spring.
One obvious sign of dead floras is mushy and fragile stems plus roots. Once a plant has reached this stage, no home remedies will save it.
Build a cold frame or greenhouse
It is the best solution for keeping your young and tender plants safe and warm in the winter.
Perennial plants regrow every spring, while annual plants live for only one growing season, then die off.
Tender annuals — Tender annuals thrive in warm soil and warm air temperatures. They should only be planted once temperatures reach and stay above 55°F. They can be severely damaged or die if they are exposed to frost or temperatures below 32°F.
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.
Geraniums, marigolds, mums, petunias, and most other annuals benefit from regular deadheading. Even newer hybrids of annuals such as Wave Petunias that are specifically grown to need less deadheading can still benefit from removing the old flowers.
They can get turned into “compost.” Compost is an awesome material we can add back into our garden soils to improve their quality. Pull the dead plants out of your flowerpots. Add all of your dead plants that were healthy at the end of the season to the compost bag.
Avoid placing plants near cold drafts or heat sources. Keep plants several inches away from exterior windows. In cold regions, if windows frost overnight, move plants away from windows at dusk. You can also slip a heavy shade or other insulating material between plants and glass.
An annual, such as a zinnia, completes its life cycle in one year. Annuals are said to go from seed to seed in one year or growing season. During this period, they grow, mature, bloom, produce seeds and die.
Gardeners in Warm Winter Areas
If you live where the winters are mild, you're lucky; you can leave your plants outside year-round. But watch the weather and be prepared to cover them or bring them inside if unusually cold temperatures are forecast.