Dragonfly Habitat
The first and last word in attracting dragonflies to the garden is water, and lots of it. Dragonflies lay their eggs either near or in water, which hatch into nymphs that spend the first few months of their life cycle as aquatic organisms.
Insect Ecosystems
Now, standing water also brings with it numerous other creatures with a similar life cycle, including mosquitoes: these two live in a predator-prey symbiosis, so it’s impossible to have one without the other. However, while mosquitoes—with their shorter life cycle—can reproduce from egg, to larva, to pupa, to adult within less than twenty days, dragonflies can need up to six months to make similar metamorphoses, during which time they feed on aquatic mosquito larvae. This means that mosquitoes can reproduce in a rain barrel, pot of water, or puddle, and dragonflies need a more fixed aquatic environment, like a pond or water feature.
Accordingly, there is often a predator-prey imbalance in garden ecosystems without a constant water supply, which beyond merely sustaining dragonflies can sustain other mosquito predators like frogs, toads, and fish. Compared to impermanent sources of standing water like bird baths and puddles (which in terms of aquatic and insect life more or less serve exclusively as mosquito breeding grounds), permanent water features like ponds facilitate a much more balanced ecology.
Beyond merely consuming mosquitoes—considered by most to be the most obvious insect foe of humans—dragonflies also consume ten to fifteen percent of their own body weight daily eating pests as diverse as blackflies, deerflies, horseflies, termites, and midges.
Dragonfly Ponds
As far as the sorts of bodies of water to which dragonflies are attracted, there are a few key features that will maximize the chances of getting a population started.
Firstly, the pond needn’t be filtered, but it should be sheltered from wind, and situated in a “full-sun” (5-6 hours of exposure a day) location. Shallower vegetated ponds are best: a maximum depth of about 2-3 feet with shallow edges, full of plants that simultaneously provide shelter for aquatic organisms and oxygenate the water will provide an ideal place for dragonfly nymphs to flourish.
Secondly, dragonflies are known to be extremely territorial about breeding and hunting ranges, and like many predators, prefer to lounge on a high vantage point from which they can survey their environs. Accordingly, fences, rocks, stakes, trees, and higher-growing herbaceous plants provide a space on which adults will be more inclined to roost.
Backyard Conservation
In North America, 37 species of dragonfly and damselfly—eight percent of all species surveyed by the IUCN—are categorized as threatened. Creating an aquatic habitat in your yard, or working for wetland and freshwater conservation in your local area, can go a long ways towards conservation of your local dragonfly species.