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Communications July 24, 2019

Plant Seeds in the Fall for Springtime Blooms

Bluebonnets, larkspur, or a wildflower mix — what will you choose?

Several types of native and non-native seeds are now packaged and ready to give away during the September 7 Tropicals, Cacti, and Succulent Plant Sale and the October 5 Pollinator Festival.

Attend these events to pick up a complimentary packet of seeds to plant in the fall and enjoy in the spring.

Check out a listing of available seed varieties below.

Native – Texas Bluebonnets

Bluebonnets typically thrive in the rocky, alkaline soils of the Hill Country, but they can also grow in rocky and sandy areas around Harris County. Bluebonnets also require a little “tough love” to germinate, said Mercer Greenhouse Manager Jacob Martin. “Put a handful of seeds in a small container with sand and small rocks, and then shake,” he said. “You can also rub the seeds between pieces of sandpaper. Before you plant them in early October, soak your seeds in warm water until they double in size. Be sure to change the water daily. One of the best tricks we have learned is to throw seeds out just before a rain.”

Bluebonnet seeds will grow throughout the winter. You can expect to see blooms around the end of March through mid-May. After blooming, green seedpods will form and change to yellow. When they are brown with a fuzzy surface, start collecting the seeds. “We collect seeds at Mercer to share, but leave enough to reseed the area for blooms next year,” said Martin.

Native – Honey Bee and Wildflower Blends

The assortment of annual and perennial seeds in the honey bee blend help keep honey bees healthy throughout the season. Gardeners can expect to find Siberian wallflower, California poppy, and a few other pleasant surprises in their garden after planting this seed mix.

The wildflower blend has a mixture of annual and perennial seeds that will blanket a field or flowerbed in gaillardia, purple coneflower, dwarf evening primrose, lemon mint, and blue sage.

Both blends should be planted one-quarter to one-half inch deep prior to mid-November. Water well and keep the soil moist for the first few weeks until they germinate. These seeds were donated by Bamert Seed Company.

Non-Native – Larkspur

Grandma always said you could see a bunny face in a larkspur bloom. This beautiful reseeding winter annual is easy to grow. Full sun is best, but larkspur can grow in some partial shade. Plant seeds in the fall after temperatures cool to about 60 degrees. Sow at one-quarter inch deep and space seeds or seedlings 12 inches apart in each direction. Although beautiful, the seeds and leaves of the larkspur are toxic if ingested.

Non-Native – Delphinium “Belladonna”

The brilliant blue “Belladonna” is one of many types of delphiniums, a type of larkspur, that stunned Mercer visitors this spring. The flowers are long-lived, sturdy, bushy perennials that grow to be about four feet tall and bloom spring and summer. They prefer moderate heat in areas of full sun, well-drained soil, and a pH that ranges from neutral to slightly acidic. These easily grown seeds should be planted in pots or flats in July or August. Transplant them in October for late spring or early summer blooms. Harvest seeds in the spring when stalks become dark brown and the bunny faces resemble skeletons. Delphiniums are a toxic plant, so avoid planting where pets or children can access them.

Non-Native – Carnation Poppy

Mercer’s carnation poppies achieve heights of up to four feet with full, frilly blooms in a pinkish or coral color. They are self-seeding, so if blossoms go to pod they will sprout next spring. They do best in full sun with good drainage and fertile soil. They require regular watering and deadheading to ensure continued blooms. Sow seeds in late fall, eight inches apart in clusters or rows and cover with one-quarter inch of soil. Water until evenly moist. Seeds should start to germinate in about one week. When seedlings emerge, keep the soil moist with frequent light watering. Gradually reduce watering to once a week with approximately one to two inches of water at a time. When plants are six inches tall, apply a one-inch layer of organic mulch to preserve soil moisture and keep the roots cool.   Source:

How to Store Your Seeds

Remember, seeds do not last indefinitely. To maintain your seeds, follow the tips below:

  • Dry seeds for about two weeks.
  • Store in an envelope or paper bag, do not use plastic bags.
  • Make sure to label your seeds.
  • Store out of direct sunlight in a cool, dry, and dark location away from pests.
  • Plant annuals in spring and perennials in fall.

As a reminder, Mercer asks visitors to not harvest seeds from the gardens. Mercer staff collects these seeds to plant for the next year and to swap with other botanic gardens. Some seeds are also left in place to sprout the next year. For more information on native and non-native seeds, visit Mercer’s Pollinator Festival on Oct. 5. Visitors will receive one seed packet of each variety while supplies last.