New amenities, including a grand entryway, boardwalks, and water features, will transform Mercer Botanic Gardens over the next decade as part of a plan to expand the gardens and make them more flood resilient.

Mercer approved its master plan, designed by Halff Associates Inc., in 2019, after buying more than 47 neighboring acres outside the special flood hazard area.

Phase 1 of the plan began March 8 and will take six months to complete. Improvements include building three greenhouses on higher ground to replace the Central Garden greenhouses. The extra elevation is expected to keep nursery plants safe from high water and provide a staging area for staff and equipment during disasters like Hurricane Harvey, which caused catastrophic damage at the botanic gardens.

If you're struggling to grow bigger, better plants, the problem may not be you. It could be your ecoregion.

Despite Harris County's typically mild winters and long growing seasons, some plants like peonies, tulips, and lilacs won't thrive outside of their ecoregion. Even bluebonnets, a beloved Texas native, don't grow as well in Harris County as they do in the Hill Country.

Ecoregions are different from U.S. Department of Agriculture hardiness zones, which has long been the gold standard for determining where a plant will grow. Although USDA hardiness zones define temperature ranges for a geographic area, ecoregions can describe much more, including an area's precipitation, geology, and soil type. That's why it's possible to buy a plant for your zone, only to find out it won't grow in your ecoregion.

With 266,807 square miles, Texas consists of 10 different ecoregions that range from forests and prairies to deserts and plains. Harris County falls within three ecoregions: piney woods, gulf coast prairies and marshes, and post oak savannah, each featuring unique conditions suited to a range of plant life.

Here's a snapshot of plants that thrive in each region.

Lantana

Spider lily

Scarlet sage

Gulf Coast penstemon

Turk's cap

American beautyberry

Coral honeysuckle

Coral bean

Pipevine

Halberd-leaved rose mallow

Texas honeysuckle

Autumn sage

Butterfly-weed

Texas bluebonnet

Prairie larkspur

Most of Harris County is in the Gulf Coast prairies and marshes ecoregion, with a small northwest section in post oak savannah, and some of the northeast portion in piney woods. Click to view a map of all Texas ecoregions.

Master Gardeners are community members and Texas A&M AgriLife Extension volunteers trained to bring factual, research-based horticultural information to the public. They provide programs and resources on gardening and home horticulture and enjoy sharing their passion for plants and learning with others. Volunteers complete service hours in exchange for their instruction, receive annual training and education, and provide service hours each year to maintain their certification.

Harris County Master Gardeners offer lectures, online programs, workshops, youth activities, cylinder gardening, demonstration gardens, and more. Those with gardening questions can visit them twice a month and during special events at Mercer Botanic Gardens. They also present a monthly Green Thumb Gardening lecture online here. For more information, visit the Harris County Master Gardener website at hcmga.tamu.edu.

Those who would like to become a master gardener must enroll in an orientation and training course. When applying, please remain patient, as demand is high. Sign up for alerts online at Becoming a Master Gardener.

For gardening questions, contact us at hcmga.tamu.edu/ask-a-question/.

She didn’t have to wait long to find her calling. After just a couple of years working at Mercer, she began planning and designing Mercer’s annual color displays, adding artistic arrangements of pinks, purples, yellows, oranges, and reds throughout the garden.

“Anne skillfully blends all the varieties seasonally into fabulous display areas,” said Suzzanne Chapman, Mercer’s botanical collections curator. “Everyone loves the flowers. Families take multitudes of photos there.”

Each display evokes certain moods and feelings. Clark plants masses of cool purples, whites, and blues to create calm, tranquil spaces; hot colors like reds, yellows, and oranges to excite; and endless combinations of both for contrast.

The task is no small feat. Mercer staff and volunteers grow 80,000 to 100,000 annual plants a year. Clark must plan and manage them all to ensure Mercer stays in bloom. 

In the spring and summer, visitors can view vibrant seasonal plants like angelonias, pentas, coleus, torenia, and more. Easter usually brings a festive display of bunny-face larkspur in the Mercer Herb Garden. This showy plant features tall spikes of pink, purple, and blue blooms topped by white petals resembling rabbits. As a treat, the months leading up to Independence Day yield a patriotic floral display of red, white, and blue. 

The show doesn’t stop in fall and winter. Winter annuals like snapdragons, ornamental mustards, Swiss chard, kale, dianthus, pansies, violas, and wallflowers provide a dazzling display that can withstand average Houston winters. 

Clark’s selections aren’t just beautiful. They can also be useful. Although many gardens dispose of spent annuals, Clark prefers planting ornamental vegetables to harvest and donate to the Houston Food Bank. In the Herb Garden, she’s fond of edible or medicinal plants like purple coneflower, Mexican marigold, sage, and nasturtium. Even roses can be used for their rose hips and violas for their blooms, she said. Ornamental pepper, another favorite, produces edible peppers as bright as any flower.

With spring’s arrival, Clark will once again transform the gardens, trading deep purples and burgundy for pastels. Visitors can see her work on display throughout the Central and Herb gardens this April.

“The annuals are what change every year and what visitors look forward to seeing,” said Clark. “They are the first thing people see when they enter and the last thing they see when they leave.”

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