Red Flint Ageratum flowers arranged in a white vase on a white background.
A close-up macro view of Red Flint Ageratum flowers.
Overhead detailed view of Red Flint Ageratum on a white background.
A floral arrangement of Red Flint Ageratum in a polka dot pitcher on light blue background.
Detailed close-up micro view of Red Flint Ageratum on a light background.
Red Flint Ageratum growing in the trial gardens at Baker Creek.
Red Flint Ageratum flowers arranged in a white vase on a white background.
A close-up macro view of Red Flint Ageratum flowers.
Overhead detailed view of Red Flint Ageratum on a white background.
A floral arrangement of Red Flint Ageratum in a polka dot pitcher on light blue background.
Detailed close-up micro view of Red Flint Ageratum on a light background.
Red Flint Ageratum growing in the trial gardens at Baker Creek.

Ageratum Seeds,
Red Flint

4.76 ReviewsSKU: #FL359Min. seed count: 100
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Description

(Ageratum houstonianum). A unique spin on a cottage garden favorite with blooms in reddish, berry tones! This taller variety stands about 24 inches in height, and the flowers are a unique shade between boysenberry jam and plum—an exquisite departure from the usual! This breathtaking heirloom pops in arrangements, landscapes, beds, and borders.

Growing Tips: Red Flint is a striking heirloom ageratum that breaks entirely from the typical blue and lavender color range of the species, offering rich, jewel-toned blooms in a distinctive shade between boysenberry and deep plum. Its tall, upright habit at 24 inches makes it an exceptional choice for cutting gardens and the middle to back of the border, where its unusual color creates bold contrast with more conventional summer flowers. Deadhead spent blooms regularly to maintain vigorous, continuous flowering throughout the season. 

Plant Details

Botanical Name
Ageratum houstonianum
Life Cycle
Annual
Sun Requirement
6–8 hr.
Days to Germinate
7–10
Days to Maturity
85–90
Planting Depth
Surface sow
Plant Spacing
9–12 in.
Ideal Temperature
75–80°F
Frost Hardy
No

When to Grow

Start seeds indoors 6 to 8 weeks before the last expected frost date, as ageratum is a warm-season annual that should not be transplanted outdoors until all danger of frost has passed. Seeds require light to germinate and should be surface sown without covering. Maintain warm soil temperatures of 70–75°F during germination for best results. In warm climates, a second sowing in midsummer can extend the season and provide fresh stems for late-season arrangements. If you're not sure how to find your first and last frost dates, consult our blog post Our Experts Answer Questions, Share Resources.

How to Sow and Plant

Surface sow seeds by pressing them lightly into moist, well-drained soil without covering. Ageratum prefers fertile, consistently moist, well-drained soil and does not perform well in dry or compacted conditions. Space transplants or thin seedlings to 9 to 12 inches apart to allow for good airflow around the taller, more upright stems of this variety. Incorporating compost into the planting area before setting out transplants will support the strong stem development needed for cutting and landscape use.

How to Grow

Keep soil consistently moist throughout the growing season, as ageratum is sensitive to drought stress. Mulching around plants helps retain moisture and moderate soil temperatures. Apply a balanced fertilizer every four to six weeks to support continuous flower production and strong stem growth. Deadhead spent flower clusters regularly to keep plants tidy and productive. The tall stems of Red Flint may benefit from light staking or the support of neighboring plants in exposed or windy locations.

How to Save Seeds

Allow a few flower heads to dry fully on the plant at the end of the season. Ageratum produces small seeds within the dried flower clusters; seeds are ready when the heads are fully dry and papery.

  • Cut dried flower heads and place in a paper bag to finish drying and capture any seeds that fall
  • Gently crush or rub dried heads to release seeds, then clean away chaff
  • Allow seeds to dry completely before storing
  • Store in a sealed container in a cool, dry, dark place for up to 2 years

FAQ

What makes Red Flint ageratum unusual compared to other varieties?

Red Flint produces fluffy flower clusters in a deep reddish-plum shade—a dramatic departure from the blue, lavender, and white tones typical of ageratum. Its unusual color and taller habit make it especially striking in arrangements and borders.

Is Red Flint ageratum suitable for use as a cut flower?

Yes—its tall 24-inch stems and richly colored blooms make it an excellent cutting variety. Harvest stems when flower clusters are just fully open and condition in water immediately for the best vase life and longest display.

How tall does Red Flint grow compared to other ageratum varieties?

At 24 inches, Red Flint is considerably taller than dwarf bedding types, which typically reach 6 to 12 inches. Its height makes it better suited to the middle or back of the border and to cutting garden use than to the front of a bed.

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