Should you plant flowers to attract beneficial insects?
Yes, yes, yes. I’m of the belief that you can’t plant too much. (Too much of one thing, sure – variety is key). Obviously flowers can occur at different times, and offer different things to different insects. So it’s best to provide a variety.
But keep in mind flowers aren’t everything. For example, many parasitoid wasps will feed on flowers’ nectar and pollen, and contribute to pest control, but may need other habitats nearby like an evergreen shrub, bare ground, or a mature tree/bark..etc. A garden primarily grown with flowers will attract a disproportionate variety of arthropods that need only flowers for their lifecycle – which tends to (more often) be pests than predators. So ensure you have a variety of those other areas as well.
Which beneficial insects are you wanting to attract? It might help answering this question first. “Beneficial insects” as an internet term simply means insects you want in your garden. They can vary from the visually-pleasing (butterflies); the well-known and easily seen (ladybugs); the lesser-known-players (lacewings and predatory wasps); and the generally-not-talked-about (flies and mites). As my experience is in biological pest control, I always approach this topic as attracting Beneficial arthropods (to include mites) for the sake of a balanced pest-control in the garden. Because of this, I know it is most important to promote flies and parasitoid wasps which, quite simply, are the most important predators in your garden……. other than spiders. But, I won’t talk about spiders. Spiders are the top predators but they seldom discriminate between eating good and bad bugs. However, they are essential in the grand scheme of balance. But fear-not. Even without directly promoting them, they will arrive when your yard is buzzing with beneficial insects. Similarly, mites are hard to go out of your way to attract. But, they do want food. If you have pests, they will come.
A note on Wasps: All wasps are predators. The ones we hate (yellow jackets…etc) can sting us and so we forget that when it isn’t late summer and they are desperate for protein and simple sugars to prepare for winter (and end up attending your barbecue), they spend the rest of the year eating small and large garden pests – most notably caterpillars.
Avoid getting rid of stinging-wasps nests, unless you’re allergic, they are too close to your house or it is mid summer and they are starting to hang around you patio. The rest of the wasps – which you may never have noticed, despite there being thousands – are parasitoids. Parasitoids lay their eggs inside of a host. The host dies and a new wasp emerges. In many cases those adult wasps feed on similar hosts and parasitize others. They are exceptional predators!
A note on Flies: Flies are simply the least likely to be understood by the average person. Remarkably, most have a larval stage that look nothing like the adult stage and can feed on an entirely different diet. For example, the American Hoverfly (Eupeodes americanus) is considered one of the most effective pollinators as an adult. It only feeds on pollen and nectar. However, it lays its eggs near aphids and the larva are the single greatest natural consumer of aphids compared to all other beneficial insect. Other flies can have aquatic larva, or larva that live in plant material and some flies are even predators in their adult stage (the hunter fly). But the most important advice regarding flies to the home gardener is to come to terms with the fact that flies are responsible for most of the pollination in your garden. They nearly all do it (even mosquitos!) Nectar from flowers is their energy and pollen is their protein. When you plant flowers these foods are just sitting there, easily accessed. So plant flowers and don’t worry so much about what is showing up. More bugs simply means more balance.
Now that you have an idea what to look for, here is a non-exclusive list of some flowers that are known to disproportionately promote beneficial insects:
- Umbellifers: Largely associated with the Apaceae family (Carrots, parsley, parsnip, wild carrot, false queen annes Lace) have clusters of tiny cup like flowers that may be essential for flies who can be heavy, but have short, sucking mouth pieces. They also seem favourable amongst wasps (most of which are parasitoids). It is the “umbrella-like” structure of these flower heads that are so attractive. Larger insects can walk and quickly consume the nectar from multiple shallow flowers.
- Buckwheat: A quick growing plant of the rhubarb family that has few native pests. So it’s easy and carefree, and offers a high nectar flower. Largely associated with promoting beneficial wasps. Flowering can be as short as 4 weeks. It’s great as a filler: throw in some seeds when you’ve removed a plant, or plant some in behind for a taller backdrop.
- Dandelion: Only a weed if you consider it one. Highly nutritious, rich in pollen and nectar. No end to what will feed on it. There will be plenty of pests, but predators are also attracted to the flower, not just the pests on it, so they can be quite lively. No other flower has ever been recorded to host as many different species as dandelions. Most important is that they attract Thrips (a flower pest). However, it’s better to have them on dandelions than in your roses or cucumbers. So allow these thrips to come and attract their predators so thrips predators are lively in your yard.
- Sunflowers: Sunflowers are not alone in having extra-floral nectaries, but they have long been a recognizable native source of them and are easy to spot by insects and birds because of the tall and large flowers. Every part of the plant is beneficial to insects and the leaves are favourable for lacewing and ladybug eggs. Consider it the beacon of the yard. Some native sunflowers attract a parasitic wasp of ants. Each sunflower will have it’s own wasp which controls the ants feeding on the extra-floral nectaries making them available to other insects. (A favourite for butterflies and essential for some native skippers).
- Alyssum: “Snow cloth.” Some alyssum are not suitable in your garden so insure you aren’t growing an invasive species. Alyssum continually flowers in hot and cold weather. It’s a great plant to use as a “green mulch” to shade other plant roots and promote beneficials. Alyssum is extremely high in nectar which attracts many bugs, and being low to the ground helps those that don’t wish to be seen. Similar to umbeliffers and sunflowers, there are many small flowers which allow small insects and those with small mouth pieces to feed.
- Mustards/Canola: Mustards are a great crop because there is a huge variety of leaf textures and colours and they all flower (bolt) quickly. Try growing some for a salad mix. When they bolt, let them flower before hauling them out. The flowers are typically yellow and attract so many insects that I’ve never felt it benefited any one kind. But again, the more bugs the better.
Once again, the above list is not exclusive, nor do those plants need to be planted. They are simply my favourite for attracting and observing predatory insects. So – in the rare case you don’t already – get out there and plant some flowers! If you are a vegetable garden, put some sort of flower in every bed or as close as you can. The benefits are huge.