7 Tips for Flower Gardens in Autumn

Spring and summer flower displays are often eye-catching. The arrival of warm temperatures and reliable rain showers can lead to color throughout the early seasons. You may still find your yard losing color as summer gives way to fall, even if you plant varieties known for their fall-blooming habit. Landscaping and garden plants need a little extra help during late summer to prepare them for fall blooming that provides beauty until the first frost arrives. Boost your fall blooms by gearing up for the end of the gardening season so that you can go out with a bang.

The most useful trick for keeping most landscaping plants blooming into the fall is deadheading. It’s simpler than you might think. All you need to do is snip off the summer blooms as they lose their color and dry up. Most plants that bloom a second time in the fall will simply use that energy instead for making seed pods if you leave dead summer blooms in place. By trimming off summer blossoms as soon as they lose their appeal, you’re ensuring a secondary bloom of fresh flowers when the plant attempts to replace them. If you see seed pods, cut them off as well to ensure the plant receives the signal to keep blooming rather than calling it quits for the year.

Many plants that only begin blooming in late summer or fall put on impressive vertical growth over the summer. If you find your sedums or chrysanthemums are leggy by the time their buds plump up and begin opening, try staking the plants and using natural jute or hemp twine to hold them upright. Cages can also support tall and top-heavy fall plants while adding a decorative touch. If it’s still summer and the plants aren’t near blooming yet, you may be able to cut them shorter and force new growth at a shorter height. Before cutting summer growth, look carefully for developed buds, even in the earliest stages. If you trim off all the growing flower buds, the plant may not have time to replace them all by the fall. You may need to give leggy plants a trim by June or July at the latest to control their height without compromising bud development.

Keep your plants well-watered into the fall if you expect them to put out a good showing of blooms. Aim for two to three inches of water per week for most varieties. The key to fertilizing perennial plants for good fall blooms begins in the spring. Apply a balanced 10-10-10 fertilizer to the plants when they first emerge from the ground, then another dose about one month later. The instructions for fertilizer application depend on the form it’s in. Liquid fertilizers are usually watered in with at least a gallon of water, while slow-release pellet or powder fertilizers are spread on the soil’s surface.

Fertilizer can be applied at any time of the day or night unless the product you’re using has instructions to the contrary. Avoid applying more fertilizer in the summer since it tends to trigger leaf and stem growth rather than blooming. Bloom-booster fertilizers that are high in phosphorus help certain varieties of flowers that require it, but unless it’s recommended for the plants you’re growing, you likely don’t need it. If you do use a nitrogen-dominant fertilizer past the spring, consider diluting it by at least half to ensure you don’t interrupt the blooming cycle.

Aside from annuals like chrysanthemums, most fall-blooming plants are best planted in the spring before you plan to see them blooming. Bulbs and shrubs need at least one summer of steady watering and care to start flowering the following fall.

Try popular fall-blooming perennials like rudbeckia, salvia, cyclamen, agapanthus, and fall-timed hydrangeas. If you have fallen behind in your fall flower planning, try zinnias for a quick burst of color before the frost, even if you’re starting from seed, since many varieties only need six to eight weeks of growth. Chrysanthemums are the classic fall-blooming option. Although many people buy them as short-lived annuals and only plant them in the late summer for a few weeks of color, you can grow them from seed by starting in the spring and may even enjoy perennial growth from them in some areas.

5. Soil & Mulching

As fall approaches, it’s important to focus on soil and mulch management to ensure that your spring summer flowers continue to thrive. The cooler temperatures and increased rainfall of autumn can affect soil conditions, making it essential to refresh and protect your garden bed.

Soil Conditioning: Fall is an excellent time to add compost to your garden soil. This not only replenishes nutrients that may have been depleted during the summer but also improves soil structure. Adding organic material helps the soil retain moisture while also improving drainage, which is crucial as the weather changes more. Enriching the soil helps with strong root development and is important for the cooler months ahead.

Mulching for Protection: Mulch acts as an insulating layer that helps maintain soil temperature and protects roots from sudden cold snaps. It also helps retain soil moisture and reduces the need for frequent watering as the weather cools. Mulch can also suppress weed growth, which is less severe in the fall but still a potential issue.

6. Watering Adjustments

As the temperatures drop in the fall, your watering should be adjusted to meet the changing needs of your garden. While fall often brings more natural rainfall, it’s still important to monitor the moisture levels in your soil to ensure your flowers remain healthy.

With cooler temperatures and shorter days, the evaporation rate of water decreases, meaning your soil will retain moisture for longer periods. However, it's important to keep the soil consistently moist, especially for summer flowers that are trying to extend their bloom into the fall. Water deeply but less frequently to prevent the soil from becoming waterlogged. 

The best time to water your plants in the fall is in the morning. This allows the water to soak into the soil and for the foliage to dry before evening temperatures drop. Watering in the morning reduces the risk of fungal diseases, which can thrive in the cool, damp conditions often found in the fall.

Before the last of fall’s flowers disappear, consider giving your spring flowers a boost. Mulch the areas well where spring bulbs like crocus, snowdrops, and jonquil will emerge. Apply a slow-release fertilizer so the roots can take in a last dose of energy before going dormant for the winter. If necessary, dig up and divide bulbs and clumping plants so they can fill in the landscape next year.

A boisterous fall display of color often includes bright foliage as well as fall-blooming plants. Consider adding some shrubs and trees that display exciting fall colors to bring out the beauty of your home landscape truly.