The Mixed Border: An Enduring Garden Style

A mixed border is exactly what its name suggests:  A mixture of perennials, annuals, and shrubs in a garden bed edged on at least one side by a structure, fence, driveway, walkway, wall, or other boundaries. This style of garden bed has been utilized for centuries and with good reason.  It is a very flexible style that can be adapted to showcase preferences for color, texture, and height.  The degree of formal structure in a mixed border is up to the gardener, with some preferring a relaxed casual style while others favor a careful arrangement of plants in lines and shaped groupings.  Mixed borders can be used to soften or accent hardscape features such as fence lines, sidewalks, or garage walls and change their shapes by incorporating curves. When carefully planned, mixed borders can provide beauty for multiple seasons.

Creating a mixed border can seem like a big project but breaking it down into steps such as those described below can make it a little more manageable and more enjoyable.

Site Selection

The first step in creating a mixed border is the selection of a site.  Survey your landscape and decide where you want to place your new mixed border. How much sun does it receive? Is it usually dry or damp?  The conditions of the site will play a big part in determining your plant options, so choose the site carefully.  Use a rope or garden hose to lay out the boundaries, then step back and try to picture the space already planted. Adjust the rope or hose to make it larger or smaller, add curves, or change the shape until you are satisfied with it.

Choosing a Style

Now that you have selected your site, it’s time to decide on the look you want to achieve.  One way to do that is to observe existing gardens. Check out those in your neighborhood and consider what you like and don’t like about them. If possible, visit public or botanical gardens to get ideas.  The Arboretum at Penn State, located in Centre County, has many beds, borders, gardens, and other types of plantings on display and is well worth a trip. Looking through gardening magazines and perusing garden sites on the Internet can help you picture the many possibilities for mixed borders.

Another consideration is the season of interest, which refers to the time or times of the year when your mixed border will brighten your landscape.  Most often summer is the primary season of interest, but you can design your garden to be attractive during other seasons as well. This takes some planning and requires additional space but can be very rewarding. For example, adding spring-blooming bulbs, ephemerals, and flowering shrubs to the mixed border will give it color and interest early in the growing season before most perennials awaken from their winter dormancy. Ephemerals will disappear as perennials begin to take over. Bulbs, such as tulips, daffodils, and hyacinths are a different matter, and their leaves will be present in the beds for several months as they soak up the sun’s energy to enable them to bloom the following year. Wherever possible, plant perennials in front of bulbs so that, as perennials grow and leaf out, they obscure the leaves of the bulbs. Creating a planting diagram can help to document the location of bulbs so they won’t be disturbed when adding plants to the border. Taking photographs with a cell phone camera can help you avoid disturbing bulbs as well. Fall blooming perennials, such as chrysanthemums and native asters can give your garden color through October and sometimes November after the blooms of many other perennials are long gone. Shrubs are a good option for creating winter interest in the mixed border.  Combining evergreen shrubs with shrubs that have berries during winter months adds color and attracts birds.

A mixed border in summer. Photo credit: Debra Burrows

Plant Selection

The characteristics of your site determine which plants can be used.  A location that receives full sun (at least six hours daily) is suitable for plants that will thrive in bright sunlight, not those that prefer shade or partial shade. Matching the plants’ cultural needs with the site is sometimes overlooked, with very disappointing results.  A few years ago, I visited a bright sunny landscape that had been extensively planted with hostas. The hostas, which prefer shade or part shade, were brown, shriveled, and dying. The entire area had to be replanted and a lot of time, money, and effort went to waste.

Another consideration is moisture. A hot, dry site should be planted with selections that do not require consistent moisture and, conversely, sites that remain wet or damp, should be planted with selections that prefer such conditions. One of my favorite shrubs, winterberry holly (Ilex verticillata), which enhances winter landscapes with its bright red berries, prefers moist conditions. It’s a beautiful, reliable native shrub and I often recommend it to friends, but only if they have locations with sufficient moisture.

The USDA Hardiness Zone is an important site characteristic to consider as well. Perennials and shrubs selected for a mixed border should be suited to the zone of the location. While it’s often tempting to try to include an especially appealing plant that is just outside of a zone, doing so can be a recipe for disappointment.

With site characteristics in mind, you can begin creating your plant list. If you have plenty of space, you may want to include annuals, perennials, shrubs, and even small trees in your mixed border. Shrubs and small trees can add height and create a backdrop for lower-growing perennials and annuals.  Their leaves or needless also bring a variety of textures.  Evergreen shrubs will provide a very nice contrast for many shades of flowers.  In this type of mixed border, the small trees and shrubs are usually placed at or near the back of the border, with taller perennials in the middle and shorter perennials or annuals near the front.

Smaller mixed borders may only have room for annuals and perennials, so you may need to limit your selections. If you have favorite “must-have" plants, this is the time to add them to your list. As space allows, include groupings of various heights, textures, and colors. Consider the mature size of each plant and plan accordingly. While a full, lush look is often desirable, an overcrowded one is neither appealing nor healthy for the plants.

Whether your mixed border is large or small, remember the importance of native plants and include them wherever possible. Penn State Extension Master Gardeners can provide you with lists and descriptions of native perennials, shrubs, and trees for your area and there are many from which to choose. In addition to being appealing additions to your borders, they will attract butterflies and bees and provide them with much-needed food and habitat.

The same mixed border in early fall. Photo credit: Debra Burrows

Site Preparation

The site you have laid out for your new mixed border will need to be cleared of unwanted vegetation such as weeds and lawn.  There are several ways to do this, including digging, smothering, and using herbicides. My personal preference is to use a method called sheet composting, which requires more time but much less effort and no chemicals. Sheet composting information is available here: Create New Garden Beds with Sheet Composting and Sheet Mulching. Whichever method you choose, make certain your new bed is weed and grass-free before installing the first plant.

A soil test should also be done before planting and will help to determine if fertilizer or lime should be added.  Soil test kits are available through county offices of Penn State Extension, at garden centers, and from commercial sources. Penn State also offers an online soil test submission form which can be downloaded, completed, and submitted along with payment and soil samples.

Adding organic matter, such as compost, or well-rotted manure, can help to improve soil and increase its ability to hold water and make it readily available to plant roots. It should be added to the bed and worked into the soil prior to planting.

Planting

Now that your site is ready, it’s time to decide on the placements of the plants you plan to add. Mixed borders tend to look best when plants are grouped into clusters of at least three of the same plant, with clusters repeating throughout the bed.  Try to avoid planting just one plant by itself because doing so detracts from the overall appearance of the border, giving it a disjointed quality.

It can be helpful to place your plants, while they are still in their pots, on the soil surface and then step back and observe. Picture the plants as they will appear when they are full grown. Did you leave enough space between them? Are tall plants toward the back and shorter ones in front?  What about the colors? Have you placed plants in locations where their colors will complement each other?  Try to picture the color and texture of the foliage of the plants when they mature. Are plants with similar texture and color too close to each other? Try to consider all the possibilities. If needed, you can do some re-arranging until you are satisfied with your layout. Then it’s time to start planting!