Garden Q&A: When do butterflies come out?
Q: When can I expect to see butterflies? I know my pollinator plants won’t be flowering yet, but I’m curious when to start looking.
A: The butterfly species that live here year-round or migrate into Maryland appear at different times. Some overwinter here as adults, tucked away in sheltered spots like gaps in rock piles or under loose tree bark. (Sorry, the manufactured “butterfly houses” for sale don’t work except to appeal to invasive paper wasps or other unintended critters.) March is a time we begin to see a few adult butterflies, but even earlier is possible during mild spells.
Mourning cloak butterflies are one of the first species to be seen in woodlands, overwintering as adults. Other species overwinter as eggs, larvae (caterpillars), or pupae (a chrysalis), so they take longer to mature into adults once the weather warms. Migrants like monarch butterflies tend to arrive earlier than people realize since it’s the later generations that have built-up over the summer that are more noticeable.
Have you seen a tree or shrub with yellow-bellied sapsucker holes in its bark? Sap oozing out of those “wells” can be invaluable to wildlife, like these early butterflies and the ruby-throated hummingbird migrants making their way up the continent not long from now. Butterflies like the mourning cloak and its kin don’t often come to flowers for nectar; instead, they use sources of calories and nutrients like sap, fallen fruits/berries, and unappealing items like animal scat.
A pollinator garden can serve lots of insect species (plus birds and other benefactors) and is worth creating, but just be aware that it won’t completely serve all the species that might be in your area. This is why having additional habitat elements like brush piles, leaving dead and dying trees or snags, and growing a diversity of native plant species helps support the butterflies we rarely get to see.
One of the other early-flying butterfly species is non-native but ubiquitous region-wide. Cabbage white, sometimes called imported cabbageworm when labeled a pest on cabbage crops and their relatives, is a mostly white smaller species that flits about among the early spring blooms. I wouldn’t encourage them to set up camp in a butterfly garden, though. They can out-compete native species in their family and don’t need more of a population boost, but realistically they’re not going away at this point and can still be a prominent sign of spring.
Q: Do I control crabgrass when forsythia blooms? Or is it earlier or later than that?
A: Using the behavior (like flowering) of other plants to determine when to take action for certain species is part of a practice called phenology. That is a classic example: using forsythia flowering as an indicator for the application of pre-emergent herbicide for crabgrass. Unfortunately, while a handy memory trick, it’s not always perfectly in sync with the germination window of crabgrass.
The main driver of crabgrass germination timing is soil temperature, and since spots of land that are cooled by shade or warmed by a nearby brick wall are experiencing somewhat different temperatures, the entire germination window for that weed can span way longer than the forsythia shrub’s bloom may last. Plus, winter jasmine can look a lot like forsythia, and you don’t want to confuse one for the other since winter jasmine flowers too early to be associated with crabgrass.
Weed seeds can respond to several environmental cues. Crabgrass germination tends to begin once soil temperatures reach above 55°F for at least 3 consecutive days. Late-bloomer individual crabgrass plants might not germinate until weeks later. In that situation, a second herbicide application can catch that other group, though that will depend on the chemical chosen. As with any pesticide, always consult the entire product label before purchase and use to understand its intended use and restrictions. Some Maryland locations cannot use synthetic herbicides on home lawns, so investigate your local restrictions.
Herbicide should be the last resort for controlling crabgrass since this weed thrives in areas where the desirable lawn grass is struggling. Keep the lawn as healthy, vigorous, and dense as possible and it will do most of the work of out-competing weed seeds so they never get a foothold. This includes yearly overseeding to maintain grass density and to add the most up-to-date varieties for reliable performance.
Fortunately, crabgrass is an annual, so worst-case, a generation sprouting this year will be dead by next winter, and you can start lawn improvement efforts this August through October (if you’re growing tall fescue) to bolster its ability to fend for itself with less intervention.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.