My balcony garden’s ongoing war with aphids


I love petunias and their gorgeous colours but what I DON’T love are the Aphids!!!! Every single summer, I buy petunias that look stunning up until August and then, the aphids ring the dinner bell and my lush beauties become scrawny and stunted and all the colour is sucked out of the leaves and worse…blooms. I have tried EVERYTHING from using a mist of weak dish soap to buying live Ladybugs and NOTHING HAS WORKED!!! Every year, they come back so not wanting to again just throw away $$$$$ on plants that won’t last the whole summer, I am asking – what can I put on an East facing balcony that will give me some COLOUR?!!!
Thanks! Appreciate it!


A: I hear you!  Paradise lost….The best way to minimize the aphid problem includes continuing to fight the good fight against the pests, and also to ensure that you select plants that suit your balcony’s light/wind conditions.  It is important to take care to keep your plants as healthy as possible so that they are more resistant to infestations.  Include plants in your garden that you love, as well as those that either attract beneficial (aphid-eating insects) or that aphids don’t love so much.  Here are some suggestions:

Continue to be vigilant – Check to make sure that none of the plants you purchase has aphids — prior to planting them.  Keep them in their original containers for a few days before adding them to your container garden.  Also, thoroughly clean and scrub the containers you use for your plants.

Check the undersides of plant leaves and on new growth for the critters.  Watch for stunted plant growth, yellowing or browning or the plants, and curling or wilting of the leaves – signs that aphids are setting up house.  If there are ants in the balcony garden – get rid of them, as the ants like to have aphids around so that they can feed on the honeydew the little suckers produce.

Keep your plants healthy – Balconies offer special challenges to gardeners – often the soil dries out quickly, wind can be an issue, excessive heat can bake plants, etc.  Aphids and other pests tend to attack stressed plants.  It makes sense that the healthier the plants, the less likely they are to be bothered by aphids (or other pests).   Consider the following:

  • What is the “climate” on your balcony? Will the plants get full/partial sun?  Is it baking-hot up there on warm days?  Does wind dry out the soil quickly? Is the balcony sheltered from wind?
  • Choose the right plants. Are the plants you select well-suited to your balcony’s climate?
  • And the right containers. Note too that some plant containers can heat up the soil excessively, affecting the plant roots.  This won’t sustain healthy plant growth.
  • Use nutrient-rich soil.  Fertilize as needed. Too much nitrogen in a fertilizer will encourage vegetative growth, which aphids prefer.
  • Don’t plant your plants too close together. Avoid over-crowding (thin the plants as needed) to ensure adequate airflow
  • Remove plants or plant parts that are heavily infested with aphids or those that appear unhealthy. Less vigourous plants will attract aphids and other pests.
  • Remove debris from around plants. Keep the area around your plants clean.  Discard fallen leaves and other debris that collect on the soil in your plant containers.

You mention that your petunias become infested each year in August.  July and August are generally the hottest months in the GTA – perhaps tending to your plants more vigilantly during these months – ensuring they are well-watered, fertilized and aren’t growing out of control (such that airflow is impeded) – would do the trick.  You might wish to purchase petunias again this year, as you enjoy them so much.  Also buy a variety of different annuals.  Take special care to try and fight off the August aphid army invasion.

Introduce/attract & keep beneficial insects – Ladybugs, which are aphid predators, should work, in particular if you introduce them to your garden early in the season, when the aphids are just starting to colonize your plants.  If you do decide to bring ladybugs into your balcony garden, release them at dusk, after you’ve sprayed your plants with a fine spray of water, which may help convince them to hang around.  And release them onto plants that they love!

Some plants that actually attract ladybugs.  For example, herbs that ladybugs love (but aphids tend to avoid) include caraway, chives, cilantro and dill.  Ladybugs are also attracted to flowers, like marigolds and sweet alyssum – the latter annuals are quite small, with clusters of tiny aromatic flowers and come in several colours — they look terrific in containers. Alyssums prefer full sun but can do well in partial shade locations.

Keep the ladybugs happy – they need a good source of water – balconies can be awfully dry. They will also want to have lots of food nearby (i.e., insects) in order to stick around.

Keeping aphids at bay with water & insecticidal soap – You’ve already tried to get rid of aphids with soapy water – this didn’t work, but was this because you only tried this once or twice?

Spray aphid-infested plants with a strong jet of water from your hose (if you’ve got one on your balcony) or from a spray bottle, to help get rid of the adults (knock ‘em into a bucket of soapy water), then squish any remaining aphids you find on the leaves and stems – a lot of work, but worth it.  Ensure that the water pressure isn’t too high as this could damage your plants.

These efforts should be combined with repeated application of an insecticidal soap to make sure you’ve caught the critters at the (earlier) nymph stage.   Ensure that you cover both the tops and undersides of the leaves, and all areas of the plant, as well as the soil.  The soaps should not kill beneficial insects like ladybugs.  If possible, isolate the affected plant a few metres away from healthy plants for a few days.

A few responses to earlier questions will also be of interest to you:

All the best with your lovely balcony garden!  Please get back to us to tell us how you fared with controlling the aphids later this summer.