Easy Summer Annuals That Beat the Heat

Excerpted from the May/June 2009 issue of Washington Gardener Magazine.

Annuals vs Perennials


For those who confuse the terms, annuals are those plants that last only one year or growing season. Usually, they last from the last frost in spring to the first killing frost in late fall. In the Washington area, that can be from April 15 to December 15. I’ve had impatiens last until January in some years and lost coleus in early October in other years. On average, you’ll get at least six months of enjoyment from your annuals. It is a gamble as to exactly how long they will last, but a worthwhile one. There is no faster and easier way to fill your landscape with colorful plants and flowers than to put in annuals.

Some experienced gardeners shun annuals as “fluff” or “too easy.” They take pride in only filling their beds with perennials, shrubs, and trees. For those of us though who want our gardens to have a look of fullness throughout the growing season and who can’t spend hours every day out in our planting beds, annuals are the perfect solution. They fill in any holes as we await our slow-growing perennials and shrubs to fill in and fill out. They add instant color in those in-between times, such as when the early spring bulbs start dying back or when the August heat intensifies. Finally, annuals allows us to experiment with instant color and texture for very little investment. We can try out combinations in containers and in borders and not have spent too much or dug huge holes for massive root balls.
Caring for Annuals

It is so tempting to buy and plant annuals too early in the spring. For our region, wait until at least April 15 to do so and then keep a close eye on the local weather forecasts for any frost alerts so that you can protect your annuals should a cold front move in.

When shopping for annuals, look for plants that are healthy and vigorous with thick branching stems, dark green foliage (in most cases), and flower buds just starting to show a bit of color. Avoid plants that are either spindly or have yellowing/browning leaves that can be a sign of stress, disease, or pests. Pop them out of their packs and check the root systems make sure they are not dried out, rotting, or too crowded.

As with all plants, it is imperative that they be placed in the right place for them to thrive. That means if they are labeled for full sun and good drainage, site them accordingly and place them with plants of similar needs if grouping in containers to minimize your maintenance efforts.

Because annuals only thrive for one growing season, they consume a good deal of resources. Whether you plant them in the ground or in containers, add in a slow-release fertilizer (such as Osmocote) and water storing granules (such as Soil Moist). This gives them a good head start and helps them get over the transplant shock quicker. It also helps you have to water a bit less frequently. You may still want to add a liquid fertilizer every week or two to annuals that are in containers as they quickly run through the nutrients in the limited amount of soil they are in.

Some annuals, such as cosmos, require deadheading (snipping or pinching off the spent blooms) to keep up their fast rate of blooming. To get full enjoyment from my annuals, I cut the flowers frequently enough to bring in for vases and to share with others, so that I only have to deadhead infrequently, if at all.

Top Annual Plant Picks for the DC Heat

The following area annuals that have proven to survive and even thrive in our region’s intense summer heat and humidity. We urge you to try out a few new ones this year to give your garden instant pizzazz.


Ageratum
Angelonia
Begonia (Begonia x tuberhybrida)
Canna
Celosia
Coleus
Cosmos
Dusty Miller
Geranium
Globe Amaranth
Lantana
Marigolds
Nasturtium
New Guinea Impatiens
Nicotonia
Ornamental Pepper
Persian Shield
Petunia
Portulaca
Salvia
Spiderflower (Cleome)
Sunflowers
Verbena
Zinnias
 
BONUS CONTEST: If you are the first one who can name the annual plants used in the pattern planting AND the specific location where the above picture was reaken, I will give you a year's subscription to Washington Gardener Magazine. Put your answers in the blog comments field. You have until August 1 to answer.

UPDATE: I've uploaded photos of my summer containers here. Most are full of annual trial plants and are doing very well. They are loving the recent heat though I did have to give them more water than usual during those 100+ degree days.