Four o’clock seeds germinate quickly when planted after the soil has warmed in late spring. Knowing exactly when to plant four o clock seeds is the key to getting a vibrant display of these fragrant, evening-blooming flowers. These seeds are easy to grow, but timing matters for strong germination and healthy plants.
If you plant too early, cold soil can rot the seeds. If you wait too long, you shorten the blooming season. This guide covers everything you need to know about the best planting window, soil conditions, and step-by-step methods.
When To Plant Four O Clock Seeds
The best time to plant four o’clock seeds is after the last spring frost date has passed and the soil temperature is consistently above 60°F (16°C). In most regions, this falls between late April and early June. You can also start seeds indoors 4-6 weeks before your last frost for a head start.
Four o’clocks (Mirabilis jalapa) are tender perennials grown as annuals in colder climates. They love warmth and will sulk in cold, wet ground. The seeds have a hard outer coat, so they benefit from warm soil to soften and sprout.
Checking Soil Temperature
Use a soil thermometer to check the temperature at a depth of 2 inches. Wait until it reads 60°F or higher for three consecutive mornings. Cold soil below 50°F will cause seeds to rot or germinate very slowly.
- Ideal soil temp: 65°F to 75°F (18°C to 24°C)
- Minimum temp: 60°F (16°C)
- Too cold: Below 50°F (10°C) – seeds may rot
Regional Planting Windows
Your location determines the exact calendar date. Here are general guidelines for different USDA hardiness zones:
- Zones 3-5 (Cold winters): Plant outdoors from late May to early June, after the soil has warmed. Start indoors in mid-April.
- Zones 6-7 (Moderate winters): Plant outdoors from mid-April to mid-May. Soil warms faster here.
- Zones 8-10 (Mild winters): Plant outdoors from March to April. You can also plant in fall for winter blooms in frost-free areas.
Starting Seeds Indoors
Starting four o’clock seeds indoors gives you a longer growing season and stronger plants. This is especially helpful in short-summer regions. The process is simple and takes about 4-6 weeks before transplanting.
Step-By-Step Indoor Sowing
- Soak seeds overnight: Four o’clock seeds have a hard seed coat. Soaking them in warm water for 12-24 hours softens the coat and speeds up germination.
- Use seed-starting mix: Fill small pots or trays with a light, well-draining mix. Moisten it before planting.
- Plant seeds 1/4 inch deep: Press one seed per pot or space them 2 inches apart in trays. Cover lightly with soil.
- Keep warm and moist: Place pots in a warm spot (70°F to 75°F). Cover with plastic wrap or a humidity dome to retain moisture.
- Provide light after sprouting: Once seedlings emerge (7-14 days), remove the cover and place them under bright light or in a sunny window.
- Harden off before transplanting: About a week before planting outdoors, gradually expose seedlings to outdoor conditions for a few hours each day.
When To Start Indoors
Count backward from your last frost date. For example, if your last frost is May 15, start seeds indoors around April 1-7. This gives the seedlings 4-6 weeks to grow before transplanting after the soil warms.
Direct Sowing Outdoors
Direct sowing is the easiest method if you have warm soil and a long growing season. Four o’clocks grow quickly from seeds planted directly in the garden. Wait until all frost danger has passed and the soil is warm.
Step-By-Step Outdoor Sowing
- Prepare the soil: Choose a sunny spot with well-draining soil. Loosen the top 6-8 inches and remove weeds. Mix in compost if the soil is poor.
- Soak seeds (optional but helpful): Soak seeds in warm water overnight to speed germination. This step is not required but can cut germination time by a few days.
- Sow seeds 1/4 to 1/2 inch deep: Plant seeds about 12-18 inches apart, as mature plants can spread 2-3 feet wide. Drop 2-3 seeds per hole and thin later.
- Water gently: Keep the soil consistently moist but not soggy until seedlings appear. This usually takes 7-14 days.
- Thin seedlings: Once seedlings have two sets of true leaves, thin to the strongest plant per spot, spacing them 12-18 inches apart.
Ideal Outdoor Planting Dates
Here are more specific dates based on common regions:
- Northeast (New York, Boston): Late May to early June
- Midwest (Chicago, Detroit): Mid-May to late May
- South (Atlanta, Dallas): Early April to early May
- Pacific Northwest (Seattle, Portland): Late April to mid-May
- Southwest (Phoenix, Las Vegas): March to April (avoid summer heat)
- California coast: March to May
Factors That Affect Planting Time
Several factors can shift your ideal planting window. Pay attention to these to avoid common mistakes.
Soil Moisture
Four o’clock seeds need consistent moisture to germinate, but they rot in waterlogged soil. If your spring is rainy, wait until the soil drains well. Raised beds can help in wet areas.
Frost Dates
Know your area’s average last spring frost date. You can find this from local extension offices or online gardening calendars. Do not plant outdoors until 1-2 weeks after this date to be safe.
Seed Quality
Fresh seeds germinate faster and more reliably. If you saved seeds from last year, test a few by soaking them. Viable seeds will swell and feel firm. Old or dried-out seeds may take longer or fail.
Weather Patterns
Unseasonably cold or wet springs can delay planting. Watch the 10-day forecast. If a cold snap is coming, hold off. You can cover newly planted seeds with row covers if a light frost threatens.
How To Plant Four O Clock Seeds: Full Guide
Once you know when to plant, follow these steps for best results. Four o’clocks are low-maintenance but appreciate good preparation.
Choosing A Location
- Sunlight: Full sun to partial shade. They bloom best with at least 6 hours of direct sun daily.
- Soil: Average, well-draining soil. They tolerate poor soil but prefer loamy or sandy mixes.
- Space: Allow 12-18 inches between plants. They can spread 2-3 feet wide and 2-4 feet tall.
- Containers: Grow in pots at least 12 inches deep with drainage holes.
Soil Preparation
- Remove weeds and rocks from the planting area.
- Loosen soil to 8 inches deep using a trowel or garden fork.
- Mix in 1-2 inches of compost or aged manure for nutrients.
- Rake the surface smooth for even planting.
Planting Depth And Spacing
Sow seeds 1/4 to 1/2 inch deep. If you plant too deep, they may not emerge. Space seeds 12 inches apart for smaller varieties, 18 inches for larger ones. You can also broadcast seeds and thin later.
Watering After Planting
Keep the soil evenly moist but not soaked. Water gently with a spray nozzle to avoid washing away seeds. Once seedlings are 2-3 inches tall, water deeply once a week unless rainfall is abundant.
Mulching
Apply a thin layer of straw or shredded leaves around seedlings after they emerge. Mulch keeps soil moist, suppresses weeds, and regulates temperature. Keep mulch 2 inches away from stems.
Caring For Four O Clock Seedlings
After germination, your young plants need basic care to thrive. They are tough once established but need attention in the first few weeks.
Thinning
If you planted multiple seeds per hole, thin to the strongest seedling when they have 2-3 true leaves. Use scissors to cut extras at soil level to avoid disturbing roots.
Fertilizing
Four o’clocks are light feeders. Apply a balanced, slow-release fertilizer (10-10-10) at planting time. Avoid high-nitrogen fertilizers, which promote leaves over flowers.
Staking
Tall varieties may flop over. Insert a small stake or cage when plants are 6 inches tall. Tie stems loosely with soft garden twine.
Pest And Disease Watch
Four o’clocks are generally pest-resistant. Watch for aphids, spider mites, or whiteflies. Spray with insecticidal soap if needed. Avoid overhead watering to prevent fungal diseases.
Common Mistakes To Avoid
Even experienced gardeners can make errors with four o’clock seeds. Here are pitfalls to skip.
- Planting too early: Cold soil kills seeds. Wait for warmth.
- Overwatering: Soggy soil causes rot. Water only when top inch is dry.
- Planting too deep: Seeds need light to germinate. Keep depth shallow.
- Ignoring spacing: Crowded plants compete for nutrients and bloom less.
- Forgetting to soak: Hard seed coats delay germination. Soaking helps.
Frequently Asked Questions
Can I Plant Four O’clock Seeds In Fall?
In frost-free zones (USDA 9-10), you can plant in fall for winter blooms. In colder zones, fall planting is risky because seeds may rot or freeze. Stick to spring planting in most areas.
How Long Does It Take For Four O’clock Seeds To Germinate?
With warm soil (65°F+), seeds germinate in 7-14 days. Soaked seeds may sprout in 5-7 days. Cold soil can delay germination to 3 weeks or more.
Do Four O’clock Seeds Need Light To Germinate?
They need some light, so plant them shallowly (1/4 inch deep). Covering them completely with soil can reduce germination. A light dusting of soil is enough.
Can I Direct Sow Four O’clock Seeds In Pots?
Yes, you can sow seeds directly in outdoor containers after the last frost. Use a pot at least 12 inches deep with drainage holes. Follow the same planting depth and spacing guidelines.
What Happens If I Plant Four O’clock Seeds Too Late?
Late planting (mid-summer) still works, but the blooming period will be shorter. Plants may not reach full size before frost. In warm climates, you can still get flowers until fall.
Final Tips For Success
Four o’clocks are forgiving plants once established. The key is patience with the timing. Wait for warm soil, soak your seeds, and keep the soil moist but not wet. You’ll be rewarded with fragrant flowers that open in the late afternoon and attract hummingbirds and moths.
Remember that these plants can self-seed if you let the flowers go to seed. You might find volunteers popping up next year in unexpected places. That’s part of the fun.
If you miss the spring window, you can still start seeds indoors in summer for a fall bloom in warm climates. Or simply save the seeds for next year. Four o’clock seeds store well in a cool, dry place.
Now you know exactly when to plant four o clock seeds for the best results. Mark your calendar, check your soil temperature, and get ready for a beautiful evening garden.