Insectary Plants

Insectary plants are grown to attract and provide for beneficial insects.

There are many insect parasites and predators that can help control garden pests without the use of chemical pesticides. While they may not eliminate all of the pests, insect parasites have evolved into effective predators of the insects that plague our gardens and landscapes. By installing plants that attract and feed these beneficial insects, the need for more stringent measures is reduced. And, hey, who doesn’t want a garden filled with flowers?

Borage

What makes an insect beneficial?

Insects are called ‘beneficials’ when they help us get what we want. In the case of gardening, beneficial insects may be pollinators, predators, or parasites. Pollinators, such as solitary bees, increase crop yields by transferring pollen to female flowers. If you have a monochrome garden with no flowers other than your cucumber and tomato plants, you won’t get nearly the same production as you would with a diverse color palette and many other flowers besides your vegies. Other beneficials, such as lady beetles, chow down on aphids and many other pests, like they were a bag of potato chips. A third group of beneficials is the parasites. These insects lay their eggs in insect pests, killing them from the inside out. The syrphid wasp, or hoverfly, and many other tiny parasitic wasps, are very efficient killers and, no, they do not sting people.

The problem with buying predatory insects

Some beneficial insects are so well known that you can buy them. Lady beetles (ladybugs), lacewings, and praying mantis are purchased each spring by the millions, It is true, they are voracious feeders and they can put a serious dent in an aphid or other pest population. And they can fly, which means that if your landscape does not give them what they want and need, they will go elsewhere. This is where insectary plants comes in. 

Color, shape, and height

Some insects prefer globe flowers, while other prefer flat landing strips. Most insects see a very limited range of color (even if that range is frequently beyond what we can see). Some insects prefer flowers and foliage that are low to the ground, while others seek out taller flowers with a better view. By planting a wide variety of flower colors, shapes, and heights, you can attract and retain the widest range of beneficial insects to your garden or landscape.

Chives

Plant selection

The trick to attracting and maintaining these beneficial insects is to plan for sequential flowering. Of course, your job will be even easier if you select plants well suited to your microclimate, while you’re at it! The choice of which plants to use depends on the pests commonly found in your garden or landscape. These plants are nearly always a good bet:

• angelica
• basil
• borage
• caraway
• chives
• coriander/cilantro
• cosmos
• dandelion
• dill
• fennel​

• globe lily
• lavender
• mint
• parsley
• Queen Anne’s lace
• rosemary
• sunflowers
• sweet alyssum
• tansy
• yarrow

Cilantro

Where to put insectary plants

Your insectary plants can be used to create hedgerows that surround a garden plot, along a walkway path, or you can simply intersperse these helpers throughout the landscape. Most residential gardens, however, are too small to make this much of a concern, unlike agricultural fields, so you can put them wherever they will thrive and look nice.

Like other plants in the landscape, your insectary plants will need weeding, irrigation, and protection from vertebrate pests to stay healthy. The initial investment of time and effort will make your job as a gardener that much easier, once these plants become established. Be sure to provide your guests with water, while you're at it!