Winter is a perfect time to show migrating monarchs some butterfly love.

Monarchs pair—bug talk for mating—over the winter in Mexico and California, and in February they begin their 2,500-mile journey north to Canada. It takes up to seven generations to get there, as each generation breeds and dies along the way.

To help them, you’ll have to get passionate about milkweed.

Milkweed is a perennial wildflower. It’s the only plant monarch butterflies lay eggs on, so it’s needed along their entire migratory path. Its leaves are the only food source their larvae will eat. Eastern Monarch populations have plummeted 90 percent in just the last two decades because of the loss of milkweed, whose habitat has been converted to farms—herbicide-tolerant corn and soybean fields with heavy pesticide use—and roads and other development. Climate change also threatens their migration patterns.

When Brad Grimm took his fiancée to the Monarch Trail at Natural Bridges State Park in California on Valentine’s Day 2013 to show her the thousands of monarchs he’d seen there 20 years earlier, they counted just five. Western monarchs, which traditionally mobbed that part of California in the winter, have declined to the point that the species will likely go extinct in the next few decades if nothing is done.

Monarchs are an indicator species telling us something is wrong with our environment. They share their habitat with birds, bats, bees, and other pollinators responsible for producing a third of our food supply.

Back home in Sparks, Nevada, Grimm wanted to help

the bugs make a comeback by planting milkweed but couldn’t find any at his local nursery. They directed him to a nearby park.

“There are plants growing in the parks, mostly along rivers and streams, even irrigation ditches,” Grimm said. “The next year, ironically, the local nursery had native narrow-leaf milkweed growing by their entrance but didn’t seem know about the plant or its value to the monarchs because they cut the plants back in mid-July, when monarchs need milkweed the most.”

Grimm’s initial difficulty in finding seeds and plants turned into a passion. He started a seed store, Grow Milkweed Plants. In September, he sold 221 packets. He planted the Biggest Little Butterfly Garden in the World, registered by the nonprofit Monarch Watch as Monarch Waystation 8269. All of his profits go to monarch conservation. He hopes to earn enough to buy land for the monarchs.

It’s not hard to make a huge difference in the life of a monarch. Here are five ways.

Grow milkweed

In North America, more than 100 species of milkweed (genus Asclepias) grow, and the first step is finding a kind expert to your area, such as Grow Milkweed Plants or Xerces Society.

Fall and winter are the perfect time to start milkweed from seeds. In general, milkweed seeds need a 30-day cold period to germinate, so planting them outdoors in the cold weather is ideal. You’ll have plants by spring.

Alternatively, you can germinate them indoors by putting them in the refrigerator between damp paper towels in a plastic bag for three to six weeks. Give them a head start before spring by planting the germinated seeds indoors in small pots, then transplant them outdoors before temperatures reach the mid-80s. Water well until the plants are established.

You can also buy potted milkweed to transplant.

Put milkweed in small spaces …

Small yard? No yard? Place pots of milkweed on your patio or porch where you can delight in watching the caterpillars and butterflies. Monarch butterflies need nectar from a variety of plants, so grow other flowers, too.

… And large spaces

Create Monarch Waystations at residences, businesses, parks, zoos, nature centers, and along roadsides or other unused plots of land. Ten milkweed plants, representing at least two varieties, become a monarch hub, with enough milkweed for their ongoing feeding. Now you’re rolling, and you’re ready to launch a community effort.

Don’t use ’cides

Monarchs are insects, and all ’cides—herbicides, fungicides, insecticides—are poisonous, either to insects or the plants they eat. Garden organically to keep pests away without killing beneficial insects. And do what you can to make sure your community doesn’t use these chemicals.

Get community cooperation

Lobby your local representatives to support the Monarch Joint Venture, a partnership of federal agencies, nonprofit organizations, and citizens working to conserve monarch butterfly migration. Because milkweed can be toxic to livestock, many areas target it for eradication. Ask to stop roadside mowing, and ask to allow milkweed and other nectar plants to grow along monarch migratory corridors, in parks, and important monarch breeding grounds.