LESSON 6 | Using Perennials, Annuals and Grasses

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This lesson will cover the use of annuals, perennials and grasses in the landscape. Each one of these subjects could have a lesson of its own, but we are going to show how these three categories of plants can greatly enhance what you have started to put together in your design.

Perennials- Perennials are plants that live longer than 2 years. Herbaceous perennials are plants that die down in the winter but their roots remain alive and send up new growth again in the spring. Herbaceous alone means relating to herbs.

Perennials can be used to make impressive borders that flower from early spring to late fall. Whole gardens can be designed solely with perennials but we are going to focus on how you could add them in and around shrubs and trees to enhance your garden with more flowers, foliage color and texture. (If you’d like to see some examples of perennial garden designs you can click here https://crockernurseries.com/perennial-garden-designs/ where we have some sun and shade designs)

If you are trying to keep your garden low maintenance, then choose perennials that are easy to care for and don’t require a lot of cutting back and also have a long bloom time. These perennials can be tucked in between shrubs or fill in odd spaces in the garden that are too small for shrubs.

A few examples of very low-maintenance perennials for a sunny area are:
Daylilies, Agastache, Silver mound Artemisia, Coreopsis, Dianthus, Gaura, Leucanthemum, Nepeta, Russian sage, Creeping phlox, Salvias, Sedums, and perennial Geraniums
Here is a list of examples for a part shade or shady area:
Hostas, Astilbe, Ferns, Bleeding hearts, Tiarellas, Liriope, Heucherella, Heuchera, Aruncus, Japanese forest grass, Carex and Pulmonaria.

Use of Grasses:

Grasses are a beautiful addition to the landscape. They have an architectural value that gives interest all year round. If you do not cut back your grasses in the early winter, they will keep their seedheads and provide food for your birds and give some dimension to the barren winter landscape. They are also lovely in the fall with their seed heads and fall color.

An exceptional use for them is in a perennial border as a backdrop or intermixed with the perennials. When all the perennials have died back, your grasses will be there moving in the wind, collecting snow and providing food for your feathered friends.

How do you lay out grasses? You can plant them singly in a garden but just like repeating color, it looks much better when you repeat the same grass or similar grasses throughout the bed.  You can also put groups of grasses to make a spectacular showing. It looks better to plant in odd numbers such as 1, 3, 5.

The larger growing grasses with provide a great screen if you are trying to block things from view.

Some of the most popular grasses are:
Miscanthus, Calamagrostis, Panicum and Pennisetums. Within each of these types is a large range of varieties with different heights, foliage color and flower color

Use of annuals

Annuals are plants which only live one growing season. They die back but do not return the following year. This would also include tropical plants which can be used in the garden for the season.

The best usage for annuals is for pots, window boxes and accents in the gardens.

Pots and window boxes are traditional on the Cape and annuals are primarily used in them. The reason for this is that most perennials have a blooming period whether it be late Spring, early Summer or late Summer. When this bloom period goes by, the plants are just left with foliage. In some cases the foliage also disappears. Most people like their seasonal pots to be in flower all through the late Spring and into the Fall. That is why annuals are the preferred plants for this application. They take all their energy and produce flowers all summer long.

The best annuals for pots are compact growing so they don’t get too tall and fall over or grow over the edges and onto the ground. Having compact plants also lessens the amount of maintenance.

Here is a list of annuals for containers.


Annuals can also be a great addition to a garden to have blooms all season long, plus you have many color choices that can complement your shrubs and perennials.  In many cases they are used as a border in a garden bed. Here are some commonly used annuals for borders:

Sun: Spreading Petunias such as Wave Petunias or Supertunias do not need to be deadheaded and will vigorously fill in a space growing up to 4’ across.  New Guinea Impatiens create a nice border with constant blooming and no need to deadhead getting approximately 1’ tall and wide.  Sunpatiens are similar to New Guinea Impatiens and will do very well in full sun and also part shade to shade.  They do create a larger mound, getting to be 2’ tall and wide but have showstopping color all season.  Portulaca is a great low growing option especially for a really sunny, dry, hot spot.

Shade: Impatiens are one of the best plants for shade with continuous color all season and heights that range from 8” to 18” depending on the variety.  They have had issues with a disease called downy mildew, but with new resistant varieties such as Beacon and Imara XDR you can safely plant them again.  Another option is wax begonias which are available in green or bronze foliage with red, white or pink flowers.

There are some other notable annuals and tropicals that you might want to leave a spot for in your garden design that will get quite large over the season.

Annual Salvias: While there are many varieties of salvia some standout ones for the garden are Salvia guaranitica ‘Black and Blue’ or ‘Bodacious Rhythm & Blues’, ‘Roman Red’, ‘Wendy’s Wish’ as well as the Proven Winner Rockin’ Series (blue, purple and fuchsia) which all get to be 3-4’ tall and 2-3’ wide, the size of a small shrub!  They bloom all summer and they are hummingbird magnets. They’ll also take full sun to part shade.

Sunflowers – New varieties of sunflowers such as Suncredible, Sunbelievable and Sunfinity have come out the past few years that offer continuous blooming on large shrub-like plants getting to be 2-3’ tall and wide.
Cleome – Hybrid varieties including Clio Magenta and Pink Lady as well as the Proven Winner Senorita Blanca and Rosalita make a great shrub-like plant getting to be 2-4’ tall and about 2’ wide with blooms that go from early summer into the fall.  They are also deer and rabbit resistant which is a plus!

Coleus, Caladium and Elephant Ears – Great for a shade or part shade spot (though some varieties will take full sun) these all have a variety of colorful leaves that will give you all season color without having to worry about blooms. Varieties can range from 15” tall to over 4’.

Tropical Plants – There are some great tropical plants that can add color and interest to your garden. Because they love the heat they can sometimes be overlooked by shoppers in May as they won’t start flowering well until June/July.  Canna lilies can add height and color with bright colorful foliage and intense colored blooms and can be 3-6’ tall.  Flowering hibiscus are available in bush form (getting about 3-4’ tall) or as a standard (getting about 4-6’ tall) with colorful flowers that really take off in summer.  Banana trees are fast growing and add unique foliage and height. Mandevilla is a fast growing vine that loves the sun and heat and can grow up a trellis, fence or deck railing as a nice backdrop to your garden.  Bougainvillea and Plumbago are also options that come in bush form and tree form.

These are some suggestions on how to use these plants in your garden. Hopefully by now you have started to lay out the bones in your landscape and you can now enhance them using annuals, perennial and grasses. This is like redesigning a room in your house- first you fix any structural defects, then you paint the walls and woodwork and then you add your fabrics and pillows for pops of color. Annuals and perennials are the pillows and I have to admit they really add a great deal to the finished product.

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  1. Pingback: Landscape Design Basics – Mini Course – Crocker Nurseries

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