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From The Professor's Greenhouse: Late Summer Gardening Part II, Annuals

I addressed growing vegetables in Part I, but a few comments are warranted on those plants that bring us beauty rather than bounty in July and going into August as well.

Annuals, They're Not Just For Spring

Annuals are plants that complete their lifespan in one growing season. They start as seeds and, at the end of the season, leave seeds and die. These include cosmos, calendulas, zinnias, impatiens, and many others, even sunflowers. As such, they are often past their prime blooming time by high summer or soon will be. The bloom season on these can be extended by several practices.

Cosmos are among annuals that can be enjoyed through the hot summer months.

Tricks to Extending Your Bedding Plants' Blooming Season

The first is to take care that the plants are as stress-free as possible. Stressful growing conditions will accelerate aging, moving the plant to seed production and shortening the time of blooming. By keeping the soil moist, feeding, and keeping competing weeds away from them, they will provide blooms and a pleasing appearance farther into the season. Providing a mulching cover on the soil around the base of these plants will accomplish all of these. In feeding, water-soluble fertilizer is excellent for this.

A trick I learned in growing orchids for many years that works well with annuals is to feed a more diluted solution but do it more often: ‘weakly – weekly.’ Mix the fertilizer at ¼ strength and use it weekly.

The second is to cut off spent blooms. This process is called ‘deadheading’ and will often either keep the plant producing blooms or stimulate a second and often a third flush of blooms. The process is simple, cut blooms past their prime off of the plant. Remove a spent blossom with a snip below the flower but above a set of leaves below it. There are often new buds waiting at the angle between the stem and leaf, and removing the spent bloom stimulates the plant to develop this new flower.

And there are other things to mention on the topic of ‘deadheading.’ First, cutting those blooms for arrangements in the home (if your cat does not eat them like mine) or to share with others will have the same effect as deadheading; often, it results in more blooms later. Also, removing the first buds produced by many annuals (and perennials) will result in a fuller and bushier plant with many blooms later. And some annuals are grown for their foliage. Removing the flowers as soon as they develop will prolong the beauty of these. Good examples are Coleus and Basil.

"Deadheading" spent blooms will keep your ornamentals producings all summer. Photo Credit: Karen Jackson

The third ‘trick’ is to plant new seedlings, if you can find them, or sow seeds. Our long growing season allows seeds of many annuals planted in July to develop beautiful flowers before the frosts of November or December. Planting the seeds of flowering annuals around the base of the annuals they are destined to replace will often provide a continuous display of pleasing beauty in the border or flower bed. The older plants will shade the new plants, and the older plants can be removed as the new ones mature. One note here: cut the old plant off at the base, rather than pull it out by the roots to avoid disturbing the new one.

Container Garden Care

For those pots, hanging baskets, and window boxes, keeping the soil from drying is the most important factor. As the days get hot, especially those beautiful days when the humidity is low (it happens), the potting media loses moisture quickly. There are a few tricks that can prevent drying.

Water the plants frequently. This may be daily, or less, and only you can determine this as so many factors are involved. Smaller containers dry faster than larger ones. Larger or many plants in a container will need more water than smaller plantings. The weather plays a large factor, as well as location. Plants in full sun will dry much faster than plants in shady locations.

A good practice is to water the container until water runs freely out of the bottom of the pot.

Sometimes the potting media does dry and contract allowing the water to drain around the roots of the plants without wetting them. Submerging the pot in a bucket of water for a few minutes will re-wet the potting media.

Another trick especially useful for those pots too big to easily move is to poke several holes in the soil around the base of these plants with a pencil or similar object and then water several times over the next few hours.

Incorporating a water-retaining gel in the potting mix will extend the time between waterings of containers with the added benefit of providing the plants preventing over and underwatering plants. Think of it as a time-release water supply.

Yet another trick for watering containers makes use of those plastic bottles being thrown away. Fill one with water, leave the top off, and stick the open end in the soil so the water slowly seeps out into the soil.

Feeding plants in containers is perhaps the next most important consideration to extend the beauty of the plants. A slow-release fertilizer is convenient. But it is often easy to over-fertilize plants in containers with this method. Overfeeding can do more harm than underfeeding! Another method is to use a water-soluble fertilizer with the ‘weakly-weekly’ method. A note here: don’t fertilize stressed plants. A thorough watering before feeding, even with a water-soluble fertilizer, and feeding in the cooler morning are the best plans.

Add plants to keep the container with a ‘full, lush’ appearance. As one plant fades, remove it and add something new. This can be with seeds (those fast-growing summer annuals), seedlings (if you can find them or start your own), or even cuttings (coleus and many sages are almost too easy to start this way).

A mixed container of annuals provides blooming and foliage interest all summer long. Photo Credit: Kevin Jones

With care to keep the container from drying, many plants can be started from cuttings right in the container planting.

Yes, the temperatures are getting up there, and the sun beckons to other activities, but a few minutes in the cool morning in July and August can keep those flower gardens looking beautiful into the fall.


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