The White House on Tuesday outlined its strategy to restore the nation’s struggling honeybee and monarch butterfly populations to some semblance of health, mostly by expanding the acreage devoted to the wildflowers and milkweed that are crucial to their survival.

The strategy, devised by a group President Obama appointed last June — which he called the Pollinator Health Task Force — envisions adding or improving wildflower habitat on seven million acres of land, an area slightly larger than Maryland, by 2020.

That effort would focus on the central United States, where about two-thirds of the nation’s managed honeybee colonies spend the summer and where monarchs conduct their annual migrations to and from Mexico. It would include encouraging schools to plant pollinator gardens and turning land around Interstate 35, which runs from Duluth, Minn., to the Mexico border at Laredo, Tex., into a continuous wildflower buffet for migrating monarchs and other pollinating creatures.

Conservation organizations broadly welcomed the initiative. But some environmental advocacy groups called it weak, noting that it offers little in the way of new efforts to address pesticides that many experts regard as a major factor in the population declines.