Gardening Q&A: Do marigolds have properties that repel pests?
QI’ve noticed that the sparrows and towhees in my yard love to dive bomb into my Mexican marigold. I wonder if this aromatic plant has insecticidal properties.
Sometimes it looks like a high wind hit it, but no, just the birds shaking the branches. It’s fun to see them all lined up on the fence taking turns diving into the foliage.
A— Ann Foster, Santa Rosa
All varieties of marigolds are rumored to have magical insect repelling properties, which makes them a popular plant to grow among your vegetables and ornamental plants.
Like most things supposed to have magic properties, there is no scientific evidence this is the case. However, there is evidence that instead of repelling pests, marigolds might attract insects, keeping your other plants relatively pestfree.
The birds love marigolds because they seem to have a nice supply of insects for them to eat. They might also be after the seeds the marigolds produce.
It’s my favorite flower to plant around and between my tomatoes, peppers, squash and cucumbers, but I grow them to help attract pollinators to my garden, and because the marigolds thrive in the beds.
Q
I have large galvanized buckets filled with geraniums. When do you prune these in my area? How much do you cut back? — Nancy Newton, Napa
A
It depends on if you have geraniums or pelargoniums.
Pelargoniums are from South Africa; geraniums are a Mediterranean plant. They are related and the confusion began when plant fanciers centuries ago mistook pelargoniums as geraniums. Even though we now know the difference, we still mostly just call them all geraniums because it seems simpler — and in our mild climate we can grow both as perennials.
Pelargonium flowers have five petals, with the two upper petals a different shape and size from the lower ones. Pelargoniums are not frost hardy and can die in cold weather.
Geranium flowers also have five petals, but theirs are symmetrical. The plants produce a seed pod that looks something like a crane’s bill, giving them another popular name, cranesbill. They are frost hardy, going dormant in the winter and returning to vigor in the spring. They tend to have a compact form.
Geraniums generally should be pruned in September, cutting back as much as two-thirds to remove old growth and weak branches and to shape the plant, but you must leave some green showing.
Pelargoniums are tip pruned in September, which spurs new growth at the bottom of the plant, and then given a more rigorous, shaping pruning in late November.