Pruning Hydrangeas: A Step-By-Step Guide For Old And New Wood

To prune or not to prune? This is one of the quintessential gardening questions. Recently, I asked a top landscaper in Virginia to weigh in on the issue. “When is the best time to prune hydrangeas without cutting off next year’s flowers?” I asked. Her reply?

“Never,” she said with a laugh. “But your best shot is after they’ve bloomed.”

It turns out that knowing how and when to prune hydrangeas involves first, identifying what kind of shrubs you own. And it all starts with determining whether they flower on old or new wood. Continue reading

Top Red, White and Blue Flowers For The Summer Garden

For many Americans, Fourth of July is synonymous with fireworks. But for gardeners, the pyrotechnics start early. That’s because by mid June, spring pastels are already giving way to dazzling color as red, white and blue flowers begin lighting up the summer garden. Continue reading

How To Build The Perfect Monarch Butterfly Garden

monarch on pink flowers

Daniel Potter freely admits he’s not an expert on monarchs. But as Professor of Entomology at the University of Kentucky, he and his grad students sure love to run experiments. Recently, they completed a two-year study on the likes and dislikes of the popular orange and black butterfly. Now for the first time ever, there’s a roadmap for building the perfect monarch garden.

WHY WE CARE

If you’re reading this post, you’re probably already a monarch fan. The butterflies’ annual migration from Mexico to Canada is one of the most spectacular events worldwide. All told, the tiny insects fly upwards of 2000 miles roundtrip each spring, stopping four times to breed and lay their eggs. They are the only butterfly species to make such a long, two-way migration.

monarch migration

Over the past 25 years, however, there’s been a sharp decline in monarch populations. Part of this is due to a loss of habitat at the butterflies’ overwintering site in Mexico. Activities such as logging, agriculture and urbanization have all taken their toll on the central highland forests that play host to the insects six months out of every year.

But by far the most significant factor driving the decline is the dwindling supply of a plant called milkweed. The native wildflower is the only plant that monarch caterpillars will eat. And without it, the butterflies cannot complete their life cycle, sustain their migration and ultimately, perpetuate their species.

monarch feeding on milkweed

MONARCH BUTTERFLY GARDENS NEED MILKWEED 

According to the North American Monarch Conservation Plan, we need 1.8 billion milkweed stems to replace those that have been lost to agriculture and urbanization. And these contributions need to come from all land sectors in order to sustain the annual migration. This includes farms, roadsides, schools, zoos, rights of way and yes, suburban and urban gardens located along the butterflies’ migratory corridor.

Luckily, an initiative called the Monarch Waystation Program is starting to make a crucial difference. Established in 2005, it engages citizens in conservation by providing instruction and materials on how to create habitats for monarchs. The guidelines are simple – Plant two or more milkweed species for the caterpillars, some nectar sources for the adults and you become part of a national registry. To date, over 6000 Monarch Waystations in 46 states have become part of the effort. 

WHAT MONARCHS LIKE

And as it happened, the Waystation Program Registry provided the perfect jumping off point for Potter’s research into monarch butterfly gardens. A quick Google Earth search by his team revealed hundreds of habitats scattered along the butterflies’ northward route. What’s more, they represented every kind of landscape.

As Potter put it, ‘Some were non-structured, others ‘wild’, and still others were surrounded by hardscape or located in open rural areas.’ Below are some aerial shots of a few of them. (Photo courtesy Dr. Daniel Potter.)

What Potter and his team wondered was this – with all of this diversity, could there be certain habitats that were more appealing than others? To discover the answer, the group decided to survey 22 citizen-planted Waystations. Below are some key outcomes from their findings. 

1. MONARCHS LIKE STRUCTURE

Like most species, monarchs use visual cues to zero in on what they’re looking for. And in the butterflies’ case, these ‘search images’ are made up exclusively of milkweed. But as the Registry revealed, not all waystations were the same. Did monarchs favor certain monarch butterfly gardens over others?

Monarchs from ‘search images’ for milkweed

To find out, the researchers counted larvae and caterpillars for a year in their target Waystations to see if the type of habitat made any measurable difference.

monarch caterpillar on milkweed leaf

Monarch caterpillar on milkweed leaf

And they discovered that yes, the butterflies had a strong preference. A structured garden, with milkweed set off by mulch, attracted three to five times more monarchs.

The takeaway? If you want more monarchs, make it easy for them to find the milkweed to lay their eggs on. Plant it apart from other plants. Even better, surround it with a mulch circle. But make sure to provide other nectar producing plants nearby for the returning adult butterflies to feed on.

2. MONARCHS PREFER A NORTH-SOUTH ACCESS

Interestingly, the researchers found that gardens with unimpeded north-south access recruited more monarchs. This makes sense since it coincides with the butterflies’ migratory route.

monarch migration map

Monarchs prefer gardens with a north-south access

3. THE TALLER THE BETTER

While all milkweed species are suitable for food, not all are equally favored by monarchs. To find the answer why, the group compared 8 species of milkweed all grown in Kentucky and native to the area. They evaluated them as to their suitability for egg-laying as well as their usability as food for monarch caterpillars. And there was a clear preference.

Where they had a choice, monarchs preferred the taller varieties, Swamp, Common and Showy over the smaller varieties like Butterfly weed

The takeaway? If you want to attract more egg-laying monarchs to your monarch butterfly garden, plant the tall, broadleaf milkweed species.

4. MILKWEED CULTIVARS ARE EQUALLY TASTY

But what about all of the new milkweed cultivars, you ask? As it has grown in popularity (mainly due to monarchs), milkweed now comes in many cultivars boasting unusual colors and sizes.

Asclepias Gay Butterflies Mix/White Flower Farm

Not to worry. Potter and his students discovered that monarchs find these cultivars just as attractive as the straight species. But again, go with the bigger varieties if you want more monarchs.

5. DON’T LET YOUR MONARCH BUTTERFLY GARDEN BECOME AN ECOLOGICAL TRAP

Finally, there’s the case of tropical milkweed, a non-native plant that has exploded in popularity over the past decade. Both gardeners and monarchs love it. But buyer beware. Tropical milkweed is not ‘bad’, per se, but when planted in warm areas of the U.S. it encourages monarchs to stick around longer and even enables them to winter-breed.

tropical milkweed

Tropical milkweed, Asclepias curassavica

Research shows, however, that monarchs breeding on tropical milkweed throughout the winter (rather than returning to Mexico) have higher levels of protozoan infection compared to monarchs in the normal migratory cycles. It turns out that migration is key to outrunning these pathogens.

The takeaway? Stick to the tried and true native milkweed species in your monarch butterfly garden and help the insects keep to their schedule.

To learn more about Daniel Potter and his research into monarchs and other insects, click here for the Dr. Daniel A. Potter Laboratory.

This article was update January 2021.

Top Annuals for the All-Season Cutting Garden

Annuals for the cutting garden/Photo: Julie Hove Anderson Photography

As a landscape designer, I’m well versed in perennials and the kind of annuals you buy from a nursery. But when it comes to growing annuals from seeds, my experience lies mainly with zinnias. So recently, I was delighted to attend a webinar hosted by ButterBee Farm owner Laura Beth Resnick on the top annuals she grows for her cutting gardens. Continue reading

Identify Plants In A Snap With These 6 Top Apps

 What's That Flower app

Now that we’re all spending more time at home, it doesn’t hurt to know what’s blooming. And finding the answer is easier than ever with one of the dozens of plant identification apps available. But which ones work best and provide the fastest, most reliable material? I decided to do a comparison. Continue reading

Finally, A ‘Phenomenal’ Lavender That Looks Good All Winter

They said it couldn’t be done, but finally, there’s a new kind of lavender that looks good all winter. Appropriately dubbed ‘Phenomenal’, it’s so good, in fact, that it’s now being used for municipal plantings. To understand the hype, I bought three plants last year to carry out a trial run. What I discovered was nothing short of, well, phenomenal. Continue reading

Meet Stevia Rebaudiana: The Plant Behind the Hype

stevia rebaudiana

Stevia rebaudiana

Last week, I was vacationing in Canada when an interesting commercial popped up on the television. It was an ad for the sweetener, stevia, and it featured enthusiastic users growing plants at home. Needless to say, it caught my attention. I had heard that stevia extract came from a ‘natural’ source. But I’d never stopped to consider what that meant from a gardening perspective.

I decided to dig deeper. Continue reading

Chesapeake Bay Wildflowers: July’s Top 10 Bloomers

IMG_0118

‘There are always flowers for those who want to see them’ – Henri Matisse

For most of my life, I’ve been more attracted to ornamentals than to wildflowers. Even though I’ve noticed many beautiful species in the landscape, I’ve never really taken the time to observe them. You might say, I’ve been wildflower blind. Continue reading