Master
Gardener: Monarch butterflies depend on milkweed plants
Bill Sevier: Ask a Master Gardener
Saturday, September 12, 2015
Q: I have some milkweed, which has both small eggs and caterpillars of
monarchs. How long does it take for the eggs to hatch and the caterpillar to
become a butterfly? T.W., Tulsa
A: numbers of monarch
butterflies and their dependence on milkweed plants has inspired many people to
become actively involved in their support.
The monarch’s life cycle
and migration are uniquely amazing. There are two groups of monarchs in the
U.S. — Western and Eastern. The Western group remains in California. The larger
group of Eastern monarchs overwinter in Mexico and migrate mostly up through the
Midwest. They may fly over 3000 miles and as far north as Canada.
The monarch’s migration
typically involves four remarkable generations, each of which goes through four
stages of development — egg, larva (caterpillar), pupa (chrysalis) and then
adulthood. The time from when the egg is laid to an adult butterfly is about
four weeks. All of the development times quoted are dependent on the
environment, especially the temperature.
The eastern monarch
populations leave their overwintering area in Mexico in February and March,
flying northward. They soon mate and deposit eggs on milkweed plants. The eggs
hatch in four to five days, and the larvae (caterpillars) eat large amounts of
milkweed leaves and mature in about two weeks. At that time, they turn into a pupa.
The pupa hangs upside
down using a silk attachment, called a chrysalis. Inside the chrysalis, the
caterpillar changes into a mature butterfly, which emerges in about 10 days.
This adult will be ready to mate in a few days.
A second generation of
monarch butterflies is produced on their northward journey in May and June.
This generation lives about two to six weeks. They lay eggs and produce a third
generation in July and August as they continue to feed on flower nectar and
migrate to their summering home in the Midwest or as far north as Canada. This
generation, too, lives about two to six weeks and is responsible for producing
a fourth generation in September and October.
The fourth generation is
unique. They may live for six to eight months. These monarchs migrate back to a
warmer climate in either Mexico or California, where they overwinter until the
following spring. After overwintering, they start northward and serve as the
parents for the next yearly migration cycle in spring.
This is a remarkable story
of these beautiful butterflies, which we often take for granted. We can do
several things to help lessen their decline, one of which is to plant milkweed.
For a list of milkweeds that are native to Oklahoma and the region in the state
where found, go to the Master Gardener website and look for “Monarchs and
Milkweed” under the “Tips and Techniques” section.
Garden tips
It is time to divide and replant
spring-blooming perennials like iris, peonies and daylilies, if needed.
In fall, strawberry plants build
up food reserves and form fruit buds for the next year’s crop. They should be
fertilized between mid-August and mid-September with a nitrogen fertilizer such
as ammonium sulfate at a rate of 1.5 pounds per 100-foot row. Apply 1 inch of
water if no rain is expected.
You have all of September to plant cool-season vegetables like spinach, leaf lettuce, mustard and radishes and until the middle of September to plant rutabagas, Swiss chard, garlic and turnips
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