Preparing the Garden for Fall

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By Andrew Bunting, August 31, 2022

Fall is a great time in the garden. In general, the heat of the summer is waning and many plants with fall flowers, fall color and ornamental fruits provide great ornamental interest for several months. 

Fall for Planting 

Fall is also the ideal time to tackle some tasks in the garden. The tagline “Fall is for planting,” which has been popularized over the last 20 years, rings true. Fall is the perfect time to consider planting perennials, shrubs, and trees, because with the cooler temperatures, it is less stressful for plants and the soil is still warm, even though the air temperatures may be dropping. This combination of cooler air temperatures and warm soils results in good root growth for your newly planted plants, allowing them to head into the winter with a well-developed root system. In temperate parts of the country (USDA zones 4-8), planting can even continue into November and December. 

Cleanup Time for Perennials 

In the perennial garden, I like to selectively “cleanup” the garden. In the temperate parts of the U.S., as we start to get the first frosts, some plants will turn black, brown, or even collapse. Generally, if a plant is still ornamental into the colder weather, I will leave it up for the winter. For example, many ornamental grasses will look great all winter long, and add texture and height to an otherwise blank slate. In my home garden, I have Molinia caerulea subsp. arundinacea ‘Skyracer’ which provides an eye-catching clump of foliage with towering airy seed stalks that are ornamental well into the winter. The same is true for many other ornamental grasses such as the prairie dropseed, Sporobolus heterolepis and the many culitvars of switch grass, Panicum virgatum. Leaving perennials up for the winter also has the benefit of providing a much-needed habitat for overwintering pollinators. Depending on your own ornamental preferences, you can decide on what gets cutback and what remains for the winter. 

Leaf Mulch and Compost 

Don’t throw out those leaves! Leaves are a great source of soil nutrition, can act as a natural mulch for your garden, and are beneficial to wildlife. One strategy to make use of old leaves is to rake them onto your lawn, run over them multiple times with the lawn mower, and then rake back into the perennial and shrub beds. This provides great fall and winter mulch, as well as additional habitat for overwintering pollinators and other insects. If you live in an area where there is a large amount of leaves, they can be put into piles to create leaf compost for the subsequent spring. You can also add organic debris such as cutback perennials, annuals that have been killed by frost, and grass clippings to this compost pile. 

Overwintering 

In areas of the country that have USDA hardiness zones below 6-7, fall is the time to consider bringing your non-hardy tropical plants, which provide beautiful summer interest, inside for winter. Cannas and most elephant ears can survive a few frosts. You can then go into the garden and cut back the foliage of these tropical plants to prepare them for more consistent cold, wintertime temperatures. 

For cannas, it is important to dig up the fleshy roots (rhizomes), and in the case of the elephant ears, dig up the bulb-like roots (tuber). Put these roots in a container for the winter with a layer of compost or mulch and store in a cool, dark room like a root cellar or basement. Make sure you label each container, so you know what the species or cultivar is the next spring. Banana plants can also be frosted and have their leaves removed, leaving a large water-filled trunk. I also overwinter these in the basement in a pot with a layer of mulch to cover the roots. 

Throughout the country many of us take our houseplants out for the summer and use them to decorate our balconies, porches, and patios. Before it gets too cold, these plants should be gathered up and brought back into the house for the winter. However, be mindful that these houseplants could have insect eggs such as white flies, aphids, or spider mites living in their containers after spending the season outdoors. To combat these insects, an insecticidal soap can be applied, but it is important to be diligent in continuing to monitor your plants for outbreaks to help manage the issue. Once your houseplants come back inside, don’t be surprised if you see some leaves turning yellow or some leaf drop- this is likely because plants come from a much more humid environment outside to a dry environment inside, and it takes time for them to re-acclimate. 

Shifting to Autumn Plants 

There are many great annuals available in garden centers to bring autumnal interest to the garden. Combining ornamental cabbages and kales with ornamental peppers and flowering pansies and different salvias can extend the interest in the garden by several months, and these species can withstand colder temperatures typical of fall. With these gardening tips in mind, be sure to check out your local garden center or nursery to get inspired by great ornamental foliage and flowers for the fall season.