The rapidly shortening days of fall prompt many garden plants to shut down. Deciduous trees lose their leaves, vegetables stop producing, annual flowers fade. Other plants, fewer in number, thrive in cool weather and shorter days.
There are a few reliable annual ornamentals for extra pops of color in the garden as summer flowers fade, available in garden centers, familiar and dependable. Less familiar is the planting of trees in fall. Counterintuitive to many, fall tree planting is a horticultural secret for success that many nursery professionals wish was not so secret.
Workhorses of the cool season annual color bed, pansies come in a huge selection of colors and sizes from tiny violas to the large-headed ‘Majestic Giant’ series. Some have petal patterns resembling “faces," or can be two-toned, solid, or mottled colors, like the popular 'Imperial Antique Shades.’ In short, there is a pansy to complement almost any color scheme or planting.
Pansies are dependable in cool weather, even light snow, but suffer when temps dip below 26ºF. Plants that are protected or sheltered from the coldest temps and winds, i.e., closely planted to homes, can last well into late fall. Most pansies available are hybrids: Their seed will not perform well if allowed to mature and self-plant. Remove spent flowers before seed develops to redirect the plant’s energy into additional flower production.
There are both annual and perennial chrysanthemums, sometimes creating confusion for gardeners. In fall, most available mums will be perennial (in general, the annual counterparts have much larger flowers and leaves). Mum flowers are of limited benefit to pollinators, but their bright blooms in traditional fall colors — rusts, yellows, oranges, purples — bring great joy to gardeners.
Many mums will rebloom in spring if flower heads are removed after fading. In the past, it has been recommended to cut mums and other perennials to the ground after bloom. Improved understanding of native bee needs suggests we cut off the flower heads but leave the stems of mums (and other hollow-stemmed perennials) to provide native bee nesting sites. Mum bloom is prompted by long nights and short days — but they still need plenty of bright sun during those daylight hours.
Ornamental cabbage and kale
These extremely hardy ornamentals are closely related to the edible versions and are often used as garnishes in food displays. Valued for their white, purple, pink and green ornate leaves, these plants are cold hardier than pansies and may take longer to succumb to snow and freezing.
Ornamental cabbage and kale rise and fall in popularity like hemlines — some years they are found all over, and others not so much. They are sometimes seen in high-end floral arrangements.
For woody material in the landscape, fall color is an important attribute to consider. While most “woodies” bloom in spring or summer, fall color is also achievable — often through colored fruit, or interesting bark that is more visible after leaf drop
Pyracantha comes in many sizes, prostrate and vertical versions, and different berry colors: a great example of woody material with significant fall interest. For most cultivars (named varieties), berries provide color for a lengthy period before they ripen, becoming food for birds. Some types have prolific berries on long, arching stems, providing amazing material for incorporating into holiday floral arrangements.
Almost any tree will benefit from fall planting compared to spring planting, counter to the gardener’s instinct. For trees, there are many reasons to consider fall. While it appears aboveground that little is going on when trees “shut down,” root development and growth are still ongoing underground.
For newly established trees, this root development without competition from canopy growth (leaves) gives the plant an edge the following spring. Fall-planted trees often suffer less drought stress than spring-planted trees due to these more fully developed root systems, sometimes leading to performance so different that some garden centers offer guarantees only on fall-planted trees. Inexperienced gardeners often underestimate the amount and frequency of water needed by trees while they are becoming established in the landscape.
With the range of plant material available, fall is an opportunity for a final blast of garden color and excitement, or a chance to plant woody material for future benefit.