Hello,
I have probably a hundred milk weed plants that have popped up in my garden. I did want them but they have taken over the garden. I did remove several early in the season but I also wanted to have some flower. It is now July and they have flowered. can I remove some of the plants? How can I tell if there is a butterfly egg on the plant so I can choose to leave it in the garden. Thanks.
It is terrific that you are growing milkweed and concerned about the butterflies! But with over 100 plants it is understandable that you want to exert some control.
Monarch butterflies mainly lay their eggs on the undersides of the leaves of milkweed plants; although they may also be found on the stems or flower buds. The eggs are very tiny! The are small, ribbed and slightly transparent. Below, is a link to information on the Save Our Monarch website which contains helpful pictures of the eggs and information on how to tell if a monarch is using a particular milkweed plant:
https://www.saveourmonarchs.org/blog/how-to-find-monarch-eggs-and-caterpillars
Once the eggs have hatched the monarch butterfly caterpillars live on and consume the milkweed leaves. However, as there are successive generations of monarchs over the course of a summer, in order to provide each generation with access to milkweed the plants should not be cut back too soon.
There are a number of steps that you can take to control the milkweed in your garden:
- Examine individual plants at this time for monarch eggs and caterpillars and cut back only those which do not appear to be hosting monarchs.
- Reduce the spread of milkweed in your garden by deadheading the flowers to curtail seed production.
- As monarchs hatching from the middle of September on are unlikely to successfully make the flight to their winter nesting grounds, cut the milkweed plants back at that time.
- Next year reduce the number of milkweed plants in your garden by cutting the plants back to a manageable number as they emerge in the spring.
- In future grow consider planting swamp milkweed Asclepias incarnata, which is less aggressive in the garden than common milkweed Asclepias syriaca as swamp milkweed does not spread by underground rhizome in addition to seeds.
Below is a link to the response to a previous question posted to Toronto Master Gardeners which contains more information and links to other information on the life cycle of monarch butterflies and milkweed.
https://www.torontomastergardeners.ca/askagardener/when-is-it-okay-to-cut-down-remove-milkweed/