What to Know About Monarch Butterflies and Milkweed in Your Garden – Orange County Register
In 2020, around Thanksgiving, a total of fewer than 2,000 monarch butterflies were counted at approximately 250 overwintering sites where they have traditionally been counted in the state of California. A year later, nearly 250,000 wintering monarchs were counted at these same sites. I was curious about this change and wondered if more milkweed, which has been increasingly planted by gardeners in recent years, might have something to do with this 1000% increase in monarch numbers. . Milkweed is the only plant where monarchs lay their eggs.
Looking for a solution to this conundrum, I turned to Ron Vanderhoff, General Manager of Roger’s Gardens in Corona del Mar. Vanderhoff is deeply involved in monarch conservation efforts and personally counts monarchs at their various sites of monarchs. wintering in Orange County.
“Monarch populations can vary wildly from year to year,” he wrote, “due to a variety of factors, nearly all of which cannot be confirmed as determinants in the number of monarchs we see. from year to year.Populations of almost all annual species of short-lived insects are accustomed to wild fluctuations in numbers which are an adaptation to the changing conditions of their environment.If food is plentiful, the weather is ideal , competition is minimal, predators are reduced, or some other “advantage” is present, these creatures are hardwired to rapidly increase their populations in order to exploit this immediate opportunity.
“Conversely, if food is scarce, drought is severe, there are many predators or competitors, or a debilitating disease is present, the species will conserve energy and decline in abundance. It’s sort of a natural way to balance populations of insects or other animals with their environment. Birds of prey are great examples of this and lay more eggs when there are lots of mice and fewer when there are fewer. In the past two years, due to the drought, there have been fewer plants and flowers growing in our wild lands. This means fewer pollinating insects and, with less pollination, fewer seeds are produced. Since seeds make up a large part of a mouse’s diet, fewer seeds mean fewer mice and other small animals to eat for hawks, hawks and eagles. These birds therefore did not lay many eggs. Likewise, tuna will spawn more prolifically when there are plenty of anchovies, grasshoppers will go crazy when plants to their liking are abundantly available, and so on.
“What all of this means is that populations of animals, especially those with short life cycles, will sometimes fluctuate wildly. usually has many factors at play at once, but scientists and ecologists don’t give too much credit to erratic peaks and troughs in populations, paying more attention to longer-term trends that paint a better picture. how the animal is doing. Against this backdrop, the conservation and research community is pleased with last year’s monarch counts, but cautions not to get too optimistic – it’s just ‘a year.
“That being said, 250,000 monarchs in California is much better than 2,000 monarchs. Let’s just hope this trend continues and it’s not a mistake of a year or two. I think the recent commitment to planting native milkweeds in our urban gardens is at least a contributing factor to these better Monarch numbers, although of course I can’t prove it Roger’s Gardens buyers alone have added over 7,000 native milkweeds to our urban landscape last year, and a similar number will likely go this year. The Tree of Life Nursery in San Juan Capistrano is another big contributor of milkweed to urban gardens and has provided a similar amount. Although I don’t think anyone else has come close to the two of us in terms of milkweed numbers, that’s still about 15,000 more native milkweed plants for monarchs and I have to believe that all of those additional plants Basics help one way or another.
“While you may have heard that the monarch butterfly was upgraded to endangered status last month, this statement was made by the International Union for Conservation of Nature, which has a limited influence. In the United States, the US Fish and Wildlife Service designates a species as endangered. When this occurs, funds are made available for protection, research and conservation. However, the ‘USFWS has not yet added the monarch butterfly to its endangered species list and we are pushing for that to happen soon.
It is important to remember that while native species of milkweed are good for monarchs, imported tropical species are not. Yet, some nurseries have tropical milkweeds and exclude native milkweeds from their plant stock. This is likely because tropical milkweed is evergreen with bright orange and yellow flowers, while native milkweed does not bloom as brightly and also goes dormant in the fall, looking completely dead, factors which make it less attractive as nursery fare. (In the garden, if you’re cutting off dead milkweed stems, it’s a good idea to leave the bottom six inches as a marker so you don’t inadvertently dig into this area; new shoots will start growing from the roots. the following spring.)
I asked Vanderhoff about the tropical milkweed problem.
“Most scientific research agrees that tropical milkweed does indeed interfere with the migration patterns of monarchs,” Vanderhoff noted. “This is due to the propensity of tropical species to provide forage (leaves) all year round, including the winter months.
“The historical ecology of the Western monarch butterfly is to migrate to the immediate California coast in the fall as an adult, not breed for the next three or four months, then to leave again at the end of the season. winter to start a new migration, mainly in search of mates and milkweeds.
“This strategy has evolved over a long period of time and is reinforced by a historical absence of milkweed in coastal California during the monarchs’ winter sojourn as well as during the start of their migration the following year. All of our native milkweeds grow in summer and are completely leafless and dormant from fall to early spring. Edible foliage starts to appear again on our native milkweed species no earlier than April and often not until May.
“No food plants for monarch larvae means there is no reason for monarchs to stay in the area and lay their eggs; therefore, they migrate. However, when a larval food plant (tropical milkweed) is available year-round, including winter and early spring, monarchs continue to breed and lay eggs throughout the year and do not don’t need to migrate.
“Migration promotes insect fitness (migratory butterflies are much stronger than sedentary butterflies), population genetic diversity (the basis for adaptation to changing conditions), and resilience to catastrophic environmental pressures (local disease outbreaks , forest fires, droughts, predators) Tropical milkweed, by preventing migration, is an example of an “ecological trap”, poor quality habitat which, when available, can attract an animal to a habitat of high quality. ”
Vanderhoff also mentioned a protozoan (OE) parasite that lives on tropical milkweed and is eaten by monarch larvae (caterpillars). An OE spore carried by an adult monarch may rub off onto an eggshell or a tropical milkweed leaf. If a monarch larva consumes this eggshell (and the larva often eats the eggshell that covered it before it hatches) or this leaf, it will become infected with EO. The adult that this larva eventually becomes will have a shorter lifespan than a healthy monarch, will be impaired in its ability to fly, and will spread EO through the local monarch population.
Most California native nurseries carry native milkweed plants and seeds, and of course, you can always acquire the seeds, at least, from online vendors.
The monarch butterfly is believed to have been named for a monarch, English King William III (1650-1702). It could only have been named after an English king after the colonization of America began since monarch butterflies are not native to Europe, with one species native to North America, one to America from the South and one from the Caribbean. Incidentally, King William was also known as William of Orange, so there was also a connection between this color and the name of the royal butterfly.
California native of the week:
Narrow-leaved milkweed (Asclepias fasciculatus) is the milkweed of choice for the greater Los Angeles area and everywhere else in California, for that matter. It is simply the best host plant for monarch butterflies. However, it is also visited by the Painted Lady, Doghead, and Acmon Blue Butterflies, as well as Tiger Butterflies. Although Narrow-leaved Milkweed grows in the shade, it blooms more profusely in the sun. It has a reputation for tolerating a wider range of garden conditions than other native milkweeds and has been found growing in clay and saline soils. Narrow-leaved milkweed tolerates drought well and, according to the advice given to laspilitas.comthe best website for detailed information on California natives, we should “mulch heavily or, better yet, plant next to a rock, water well the first month and ignore”.
Although Narrow-leaved Milkweed has its charms, it may look dull to some. Surround it with natives whose bright flowers are also rich in nectar and so they will also help attract monarchs. A list of these plants is provided by the California Native Plant Society at calflora.org and includes: Indian Mallow (Abutilon palmeri), Ceanothus spp., California fuchsia (Epilobium canum), buckwheat (Eriogonum spp.), mint (Monardella spp.), monkeyflower (Mimulus spp.), Penstemon spp., sage (Salvia spp.) and purple apricot (Sphaeralcea ambigua). The following non-native plants recommended by Roger’s Gardens will also attract monarchs to your garden: lantana, butterfly (Budleja davidii), yarrow (Achillea millefolium) and mossy verbena (Verbena tenuisecta).
You are welcome to send your questions, comments and photos to [email protected].