By David Salman, Founder and Chief Horticulturalist for High Country Gardens
A butterfly garden can be a wonderful part of your landscape, and will make a meaningful difference by creating habitat for butterflies in all of their life stages. Anyone who loves growing plants and flowers can grow a butterfly garden. A garden that's good for butterflies is also good for other pollinators, such as bees and hummingbirds, who often share the same nectar plants and utilize the same habitat.
The Four Basic Elements of a Butterfly Garden
Flowers and food: Plant a mix of flowers that bloom from the start of spring through fall. Make sure to include food plants for caterpillars, such as Milkweed for monarch butterfly larvae.
Shelter: Leave some bare patches of ground or small brush piles (in unused corners of the yard). Leave herbaceous plants, such as grasses, standing over the winter to protect overwintering eggs and caterpillar pupae waiting to emerge.
Water: A mud puddle is ideal for butterflies, providing them with a source of water and salt/minerals. You can create one using a bird bath or submerged pie plate, and add sand, gravel and water.
A Safe, Pesticide-Free Environment: Don't use chemical insecticides (especially systemic ones). Use caution when applying organic pesticides and use herbicides only for a weed emergency.
Butterflies and moths have three stages in their life cycles before becoming the flying adult insects we recognize.
The mother butterfly lays eggs on preferred food plants.
The eggs hatch into caterpillars who feed on their food plants. These caterpillars grow to their full size before going dormant as a chrysalis (butterfly) or a cocoons (moth) in preparation for adulthood.
Then caterpillars go through metamorphosis and emerge as flying adults. Adults mate, lay eggs, feed and die, leaving behind the next generation.
Plant Both Caterpillar and Butterfly Food
Often the flowering plants that feed the adult moths and butterflies are different from the plants that feed caterpillars. For a butterfly garden, the gardener must plant both.
Most flowers that attract butterflies and moths will feed a wide range of species.
When it comes to feeding their caterpillars, butterflies and moths can either have a need for very specific food plants or have a taste for a wider range of plants. This depends on the species of each moth and butterfly as they will have different requirements.
Hardy Plumbago (Ceratostigma plumbaginoides) is one of the most versatile groundcovers for cold climates growing in both sun and shade and most soil types. Plumbago blooms in late summer with deep blue flowers followed by the foliage that turns burgundy red in fall.
Nepeta 'Select Blue' (Select Blue Catmint) is a fantastic xeric perennial with dramatic lavender-blue flowers and handsome gray-green foliage. A recurrent bloomer, the first flush of flowers comes in late spring, and again later in summer. A long-lived, easily grown perennial, this is an excellent plant for beginners.
1" tall x 18" wide. Pink Chintz Thyme (Thymus Pink Chintz) is a tight, low growing creeping thyme with thick stems of woolly green foliage that blooms in mid-spring with a profusion of salmon-pink flowers.
Rudbeckia Goldsturm blooms in mid-to-late summer with an eye-catching display of golden flowers. Black Eyed Susan is very attractive to butterflies and the seed heads provide winter food for seed-eating songbirds as well. Reliable and tough, Rudbeckia tolerates both drought and clay plus easy to maintain.
It is important to not spray indiscriminately in your yard and kill caterpillars. Even organic formulations like BT (Bacillus thuringiensis) that you would spray to kill corn earworms (moth caterpillars), are broad spectrum and will kill all moth and butterfly caterpillars.
It's also essential NOT to use systemic chemical insecticides (absorbed through leaf tissue and distributed through all parts of the plants including flowers). Many of these formulations are Neonicotinoids. Systemically treated plants have toxic flowers which will poison the adult butterflies and moths!
And if you have tomatoes, you'll have "horn worms", the caterpillar of hawk moths. These are the hovering hummingbird-like moths that pollinate flowers at dusk like Evening Primrose (Oenothera) and Hummingbird Mint (Agastache). So plant an extra tomato plant or two and pick off the horn worms, don't spray, leaving some to mature into adults.
The Xerces Society is a nonprofit organization that protects wildlife through the conservation of invertebrates (insects) and their habitat. For over forty years, the Society has been at the forefront of invertebrate protection worldwide, harnessing the knowledge of scientists and the enthusiasm of citizens to implement conservation programs.
The society has just published an excellent new book: "Attracting Native Pollinators: Protecting North America’s Bees and Butterflies" which is available on their website: http://www.xerces.org.
It will give you a lot more specific information on what to plant regionally to support native butterfly populations in your garden and landscape.