Q: Last summer an aphid infestation prevented me sitting on my apartment patio. It gets a little sun in late afternoon when surrounding buildings don’t block it. Most plants are in pots, but most of the sun shines on a small patch of dirt that includes peonies, roses, lavender, clematis a tree and some boxwoods. I have tried environmentally friendly things, chemicals and wasted money on ladybugs that flew away after they were full.
I want to be able to enjoy my garden when days get sunny and warm. It’s a lovely spot in the middle of an urban jungle of noise and people.
Virginia Edwards,
Vancouver
A: Surrounded by concrete and asphalt you likely have a major lack of aphid predators.
I wonder what birds (if any) visit your area. Hummingbirds eat aphids but I’m sure there wouldn’t be enough food or flowers to keep birds around for long. A container pond might attract a wide variety of birds — but it could be all you’d get was pigeons.
I think a better tack would be focusing on plants that aphids don’t like.
I wonder if your lavender ever gets aphids. Mine never have, nor my artemesias, rosemaries, santolina nor any of the Mediterranean -type aromatic herbs. Alliums/garlic seemed to be resistant too.
The key to attracting aphids seems to be tender leaves and shoots. Once they’ve found these, they may gradually move to sterner fare if it’s available close by. But aphids seem not to feed on strong-smelling, shrubby plants, though shrubs can be a favourite over-wintering site.
Since high-nitrogen fertilizer encourages excessive tender growth, you would be better to focus on balanced fertilizers (all three numbers the same).
If you have any ant nests in your patch of soil it would be best to try to eliminate them. That’s because ants actually carry aphids up plants in spring so that they can ‘farm’ them for the sweet substance aphids excrete.
There are a gazillion kinds of aphids. I do hope yours are the green ones that can be blasted off by hose. The black ones are so sticky the only resource can be to prune those branches off.
Many aphids overwinter as eggs on shrubs, often in the crevices between buds and the stem. In winter it would be best to examine your shrubs, your tree and especially the boxwoods. Being evergreen, the boxwoods would be a wonderful, warm place for the eggs to shelter — and very hard for you to examine.
It might be best to cut your clematis about a foot (30cm) from ground level after flowering. Clematis handle pruning well. Your rose could handle a good pruning too.
This will make your inspection work easier.
Some aphids overwinter in plant debris in the top inch of soil. Removing this layer in pots and garden and replacing it with fresh soil or compost could help a lot
It’s very sad to give up plants that you love. You may need to decide which matters most to you: fewer aphids or fewer of your favourite plants (boxwoods perhaps).
News Flash: The Point Grey Chrysanthemum Association will sell rooted chrysanthemum cuttings Saturday, April 18, from 9 a.m. to noon at the VanDusen Garden, 37th Avenue and Oak. Information is available at chrysanthemumsvancouver.com
Anne Marrison is happy to answer garden questions via [email protected]. Please add your city or region.
