Mirabilis jalapa, commonly known as the Four O’Clock flower or Marvel of Peru, is cherished for its colorful, trumpet-shaped blooms and sweet fragrance. The plant earns its common name because its flowers typically unfurl in the late afternoon, remaining open through the night until morning. This vigorous, bushy plant is easily grown from seed and provides a reliable display from mid-summer until the first frost. Although technically a tender perennial, it is most often cultivated as an annual in cooler climates.
Preparing the Seeds for Successful Germination
The large, dark seeds of the Four O’Clock have a hard outer seed coat that can significantly delay or prevent germination. To ensure timely and successful sprouting, employ a two-step pre-treatment process to allow water to penetrate this protective layer. The first step involves scarification, which means physically weakening the seed coat by gently rubbing it with sandpaper or lightly nicking it with a small knife or nail clippers.
The physical abrasion creates an entry point for moisture, which is supplied in the second step: soaking. Place the scarified seeds in lukewarm water to soak overnight, or for up to 24 hours. This hydration signals to the seed embryo that conditions are favorable for growth, accelerating the process.
Determining the Optimal Planting Time
Timing the sowing of Four O’Clock seeds is important for maximizing the growing season, as these plants are highly sensitive to cold temperatures and frost. Gardeners in regions with short growing seasons often start seeds indoors six to eight weeks before the last expected spring frost date. This indoor head start allows tender seedlings to develop in a protected environment, ensuring they are established enough to thrive once transplanted outside.
For direct sowing outdoors, wait until all danger of frost has passed and the soil temperature has warmed sufficiently. The minimum recommended soil temperature for reliable germination is 65°F (18°C), though 70°F to 80°F (21°C–27°C) is ideal. Planting seeds into cold ground results in poor germination rates and stunted early growth, so check your local forecast before sowing.
Specific Planting Depth and Spacing
Once the optimal planting time is determined, sowing the seeds is straightforward. The large size of the seeds means they require a specific depth to anchor properly. Sow the prepared Four O’Clock seeds at a depth of about 1/4 to 1/2 inch in the soil.
The plants develop into bushy, sprawling specimens, requiring generous spacing to reach their full potential. Space the individual seeds or seedlings 8 to 12 inches apart to prevent overcrowding and promote good air circulation. Four O’Clocks perform best in full sun, though they tolerate partial shade, and prefer average, well-dr aining soil.
Post-Planting Expectations and Initial Care
With proper scarification and soaking, prepared seeds should germinate quickly, typically emerging within 7 to 14 days of planting. During this initial period, maintain consistent soil moisture, keeping the seedbed damp but never waterlogged, which could cause the seeds to rot. Once the seedlings appear, they will establish themselves rapidly.
As the young plants mature, reduce the watering frequency but aim for a deep soak whenever the top inch or two of soil becomes dry. The plants are naturally heat and drought-tolerant once established due to their thick taproot. To encourage a continuous flush of blooms throughout the summer and fall, consistently remove the spent flowers through a process called deadheading. This prevents the plant from diverting energy into seed production, prompting it to create more fragrant flowers instead.