It’s that time of year again when we all head out to buy annuals for our containers. And the flowers always start out looking gorgeous. But, in no time the blooms fade and the stems turn long and leggy. As a garden designer, I find this is one of the most frequent questions I am asked: How do I keep my potted plants in shape all summer?
WATER, WATER, THEN WATER AGAIN
The most important thing to remember when caring for flowering potted plants is that they require:
Annuals and tender perennials, which are the flowers most commonly planted in pots, are shallow-rooted. This means they require a regular supply of water in order to survive. In fact, small root systems, which have limited capacity to store water, require water daily. If the top of the soil dries out, these plants are in trouble.
To protect your flowers, water your potted plants at the soil level so that liquid doesn’t accumulate on the leaves (which can lead to leaf scorch or cause fungus to develop.) Then wait until the water seeps out of the drainage holes in the bottom to make sure the potting soil has been thoroughly moistened.
FEED FOR MORE BLOOMS
In addition to lots of water, potted plants need regular feeding to keep on blooming. This is because as the potting mix breaks down, it naturally loses its nutrients as the plants absorb them. I feed my flowers three times during the summer with a water soluble fertilizer. (Miracle Gro All Purpose Plant Food works great.)
However, it’s important not to overdo it. Over-fertilization will produce lots of lush foliage, but fewer blossoms.
GROOM TO KEEP THE SHAPE
Finally, in order to keep your flowering potted plants in shape, you need to groom them. This involves regular deadheading, pinching and pruning. Depending on the size of the stem, you can pinch off spent blooms and leggy branches using your thumb and forefinger. Or you can snip them with scissors or pruning shears. These important tasks help to maintain the form of your plants and stimulate them to keep on blooming.
Here are three popular annuals/tender perennials often grown in pots and how to groom them.
Though grown as an annual in most areas, the common geranium, or Pelargonium x hortorum, is actually a tender perennial, meaning it won’t survive the winter outdoors (though you can overwinter it indoors.) While it’s tempting to buy this beautiful plant as soon as it hits the garden center in early spring, it’s usually best to hold off until around Mother’s Day when there’s less risk of it getting zapped by an overnight frost.
A healthy geranium is comprised of a few central stems and lots of side shoots (which is the optimum structure for a strong plant that will produce lots of flowers.) To keep your geranium looking good, prune back the central stems by about a third a week or two after potting it. This will encourage more side shoots to develop and maintain the plant’s fullness.
As the season progresses, regularly pinch the side branches of your geranium down to the angle where the branches fork. This will prevent the plant from becoming too leggy. And deadhead (pinch at the base) all flower stems as soon as they have faded, which will encourage new flowering.
Petunias can become leggy fast without some prudent intervention. They can also quit blooming almost entirely after an initial colorful flush. No worries, though. With proper watering, feeding and grooming, you can keep your petunias looking good all season.
Petunias need to be regularly deadheaded to encourage new flowering, but unlike geraniums, removing the dead flowers from the plant accomplishes only part of the job. That’s because at the base of the petunia flower stem there is a small, nugget-sized pod that produces seeds. If you leave the pod on the plant, the petunia will stop blooming. As a result, in order to stimulate the plant to produce more flowers, you’ll need to remove the entire flower stem.
Deadheading the flowers (with stems) on a regular basis will keep your petunias looking neat; however, it won’t solve the leggy problem. To control legginess, prune the plant every week, cutting back about a third of the petunia. You can do this by pinching branches selectively or grabbing clumps and shearing them off. Each week cut the plant back by another third. Rejuvenating petunias in this way will encourage new stems and blossoms to sprout from the interior branches.
For a great tutorial on how to keep your petunias looking full and flowering, click here.
These bright-colored specimens require less care than geraniums or petunias, but still need regular pruning to help them maintain their compact shape. The same goes for the indoor varieties, by the way.
To keep your begonias looking their best, prune the outer branches (called canes) harder than the interior ones, pinching back the growing tips of new shoots to encourage new stems to form. Prune the interior canes at varied heights and prune the outer canes at the lowest. This will encourage new growth at the base and prevent the plant from looking bare at the bottom.
If your begonia has lost all its lower leaves, you can cut it back all the way to the soil. This will force the plant to send up new shoots. You can then continue pinching new stems as they grow until you achieve the desired shape and fullness.
A note on begonias, both indoors (as houseplants) and out: They don’t like to be overwatered.
A final note: sterilize your garden shears between uses to prevent diseases from spreading among your flowers. Then, sit back and enjoy your potted plants for the remainder of the season.
This article was updated May 2020.