Pruning Annuals

Around mid-summer you may notice some of your flowering annual plants have become scraggly and leggy. To encourage those plants to bush out and produce a new flush of flowers, most annuals can be pruned back. I realize this strikes fear and trepidation into the hearts of new gardeners but trust me, with most flowering plants, this will work. Of course, there are always exceptions, so that is why it’s important to keep the plant tags from the grower pots. Look up your plants growing and pruning requirements. Make sure your scissors or pruners are very sharp!

Some annuals only require deadheading (removal of dead flowers) to encourage more blooms. The plants themselves keep their shape throughout the season. Many new annual cultivars are self-cleaning, meaning the dead flowers fall off the plant on their own.

Deadhead regularly – Most annual plants can be deadheaded regularly. For example marigolds, tall zinnia, dahlias, annual salvia and zonal geraniums (pelargonium). A geranium flower head can be removed by following the flower stem down to its main stem attachment point. Quickly pinch and turn – it will come off with a quiet snap. You can also trim geranium branches back a bit to shape but most often the plants keep a pleasing form on their own. Thankfully the newest varieties of zonal geraniums are self-cleaning.

Make your early morning foray into the garden the time to deadhead, prune and inspect your flowering plants for leggy branches and lack of flowers. (It is also a great time to check for weeds and unwanted guests!) You can also do all of this on a cool summer day which puts less stress on the plants.

Annuals that are leggy are only flowering on the ends of long leafy branches – think petunias! The plant may also be green (not flowering) and ‘flattened out” in the center. These are plants that should be cut back by about a 1/3 the volume of the plant to encourage bushiness and a second flush of blooms. It also helps to water and fertilize once the plants have been cut back.

When cutting back your flowering annuals, make your cuts just above a leaf node on a stem. This will encourage two new growing tips to form on either side of the node which helps to double the bushiness and flowering potential of the plant.

Here are some popular annuals that benefit from cutting back to restore their health, plant shape and flower power.

Petunias – When your petunia branches begin to jut out at odd angles and flowering has slowed down, cut those stems back by a 1/3 the volume of the plant. Hanging baskets in particular become leggy in summer. Water and fertilize.

Calibrachoa or Million Bells will also benefit from a good trimming in mid- summer. Water and fertilize. Give them a week or two to recover and they will flower into fall.

Cosmos – Cosmos can be lightly trimmed back in late spring to encourage bushiness and lots of blooms. When they are 30 – 45 cm tall, lightly trim the stems back, water and fertilize.   Once each stem is finished blooming, cut back any dying blooms to the next bud on the stem. Dead stems should be cut down to the base of the plant.

Amaranth – Tall varieties of Amaranth can grow very large. To reduce the size of the stems and blooms for arrangements, do cut back the central stem early on to about 45 cm in height.  This encourages the plant to put out more stems and flowers.  Amaranth blooms make striking cut flowers, so deadhead any dying blooms to create more that will last until first frost.

Snapdragons – Snapdragons are an annual favorite and can be used as cut flowers. Cutting them back for this purpose will encourage the plant to bush out, producing more branches.  Flower stalks that have died on the plant; remove by cutting the stalk back to a lateral stem or leaf node. Leave some late flowering blooms to go to seed and they may self-seed next spring in their original planting area.

Sweetpeas – Once the flowers begin to appear, remove stems and flowers for bouquets to encourage more blooms as the season progresses. If you do not do this, they will set seed and the number of new blooms will be greatly reduced.

Nicotiana - Tall and shorter varieties/cultivars of Nicotiana can be cut back in mid- summer by one third of their height.

Coleus flower buds should be pinched off as they appear. If left to set seed, coleus foliage will suffer. Vegetative coleus (those that are started by cuttings) are sterile and will not produce many flower buds as they grow. Trim those back as well.

Zinnias – Some Zinnia varieties will rejuvenate after pruning and some will not. For those that do come back in bloom, cutting a bloom stem back for vase arrangements will encourage more blooms to appear. Do look up the pruning requirements for your particular Zinnia plants.

Pansies - Pansies love cool weather. You will notice that as the temperature goes up, flower power goes down. Cut back leggy branches that have finished flowering. I prefer to grow pansies in containers as they can be cut back and easily moved to a shaded east location in the summer. Lightly fertilize ( ¼ strength) and keep watered. Do not be surprised if they go dormant. It’s a gamble! They are also available for sale in the fall.

Angelonia  - Angelonia is an annual that does well in the heat of our summers. Do lightly trim it back at planting time to encourage bushiness and remove dead flower stems at just above the base of the plant. They do not require deadheading.

Portulaca – Prune out any dead or dying branches near the base of the plant. Leggy stems can be cut back by no more than one third the volume of the plant. If the plant looks overgrown, thin out the branches by pruning a few back to the base of the plant.

Alyssum – Alyssum plants do not like the heat. Don’t be afraid to deadhead regularly and lightly trim off dead or dying blooms and seed heads after the first flush of bloom. Lightly fertilize after trimming.

If you choose, you can leave some annual (and perennial) blooms to go to seed to feed the birds in winter.

The past few years the fall season in Saskatoon has been quite long. This should encourage you to give those annual blooms a second chance. You will be rewarded with beautiful flowers until the first frost!