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.
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.
Shape and reduce the size of overgrown and bulky plants by cutting unwanted stems to the base of the plant or where stems meet. Typically, it is good to remove up to one-third of the stems, especially in overcrowded areas where the foliage is beginning to discolor or die.
How to Overwinter Annuals by Taking Cuttings. Another way to overwinter annuals—and the only viable method for true annuals—is to take cuttings from your existing plants. This can also be the best method for tender perennials that don't adapt well to transplanting, such as coleus and begonia.
It's important to cut back foliage in the fall to protect flowering plants from disease and give them a clean start for regrowth as winter starts to turn into spring. However, there are some plants you can keep around through the winter since they benefit wildlife and still offer visual interest for your home.
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.
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.
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.
Go through your garden, beds, and planters and simply rip the annuals out, roots and all, shake as much soil from them as you can, and make your way to the composting bin. Though the process of composting slows in the winter, it doesn't cease entirely if you do your part.
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.
Some perennials, like hostas, peonies and daylilies, need to be pruned in fall to avoid winter damage. Plants like these should be pruned after the first few frosts in late fall or early winter. Other perennials like mums and coneflowers are better off being pruned in spring just before new growth comes in.
HOW FAR CAN YOU CUT BACK PETUNIAS? Petunias don't benefit from a hard pruning, so be sure to have a light touch as your prune, only removing long stems—especially the ones that are beginning to look leggy. Don't prune back more than one-third of the plant's stems.
Perennials to prune in early summer: joe-pye weed (Eutrochium), tall coneflower (Rudbeckia 'Herbstonne'), bee balm (Monarda), catmint (Nepeta), yarrow (Achillea), balloon flower (Platycodon), Culver's root (Veronicastrum), Veronica and garden phlox (Phlox paniculata).
Many gardeners cut back their perennials much too soon. There are nuances specific to certain perennials that dictate whether it is better to cut them back in fall or spring, but the general rule I like to follow is to only cut back perennials that start looking bad in fall.
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.
Remove Most Annuals
If the spent foliage and blossoms on these plants are free of mold and disease, we put them in the compost pile. If we see traces of powdery mildew (zinnias are often afflicted), downy mildew or other diseases, the plants are put into trash that's hauled off the property.
Frost and Freeze Protection in the Spring
Vegetables, annuals, and tropical plants planted outdoors early in the season are the most important plants to protect during a late frost or freeze event in spring. Protecting emerging spring bulbs and perennials is not necessary.
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.
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.
Q: When is the best time to cut back in the fall? A: “When they start to look too ratty for you and before the fresh new growth begins,” says Sarah. For plants that are frost-sensitive, wait until after the plants have gone through several hard frosts to ensure they're dormant before cutting back.
Cut the plants down to within three to five inches of the soil line. Leaving the plant slightly above the ground has several advantages. First, the remaining foliage helps provide a bit of insulation for the plant through winter.