Royal Mix
Lathyrus odoratus
Photo: Почта России · Wikimedia Commons · (Public domain)
Royal Mix is a classic heirloom flower variety prized for its vibrant, mixed-color blooms that mature within 90 days. This easy-to-grow cultivar thrives in full sun and produces abundant flowers ideal for cutting and garden displays. The diverse color palette and long flowering season make it a standout choice for gardeners seeking reliable, showy blooms throughout the season.
Harvest
90d
Days to harvest
Sun
Full sun
Zones
2–11
USDA hardiness
Height
3-8 feet
Planting Timeline
Showing dates for Royal Mix in USDA Zone 7
All Zone 7 flower →Zone Map
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Royal Mix · Zones 2–11
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 1 | May – June | July – August | July – September | — |
| Zone 2 | April – May | June – July | June – August | — |
| Zone 11 | January – January | January – February | January – March | — |
| Zone 12 | January – January | January – February | January – March | — |
| Zone 13 | January – January | January – February | January – March | — |
| Zone 3 | April – May | June – July | June – August | — |
| Zone 4 | March – April | June – June | June – July | — |
| Zone 5 | March – April | May – June | May – July | — |
| Zone 6 | March – April | May – June | May – July | — |
| Zone 7 | February – March | April – May | April – June | — |
| Zone 8 | February – March | April – May | April – June | — |
| Zone 9 | January – February | March – April | March – May | — |
| Zone 10 | January – January | February – March | February – April | — |
Succession Planting
Sweet peas bloom in cool weather and shut down when summer arrives, so succession planting has a narrow window and a hard ceiling. In zone 7, start a first batch indoors in late February, then direct-sow a second round in early April — that's about as much staggering as the season allows before daytime highs above 80°F stop flowering entirely. In zones 5–6, you can stretch a third sowing to mid-April. Don't bother after that; you'll get vines but almost no flowers before the plants go down from heat.
Complete Growing Guide
Royal Mix sweet pea seeds should be started indoors four to six weeks before your last spring frost, or direct sown outdoors two to three weeks before that frost date. The seeds have a hard coat and benefit from scarification—gently scratch or file the seed coat before soaking in warm water for 24 hours. This treatment significantly improves germination rates in Royal Mix. If starting indoors, use small pots filled with seed-starting mix and keep soil consistently moist until seedlings emerge in 10 to 14 days. Alternatively, direct sow where you want them to grow once soil is workable in early spring.
Space Royal Mix plants 4 to 6 inches apart in soil that has been amended with compost or well-rotting organic matter. Sweet peas prefer slightly alkaline soil, so add a handful of lime to your planting area if your soil tends toward acidity. Sow seeds about one-half inch deep. Given that Royal Mix plants reach heights of 3 to 8 feet depending on growing conditions, install sturdy trellises or support structures at planting time to avoid damaging roots later.
Water consistently and deeply throughout the growing season, aiming for about one inch per week through rainfall or irrigation. Royal Mix performs best with evenly moist soil, though not waterlogged. Feed with a balanced, low-nitrogen fertilizer every three weeks once plants begin flowering; excessive nitrogen encourages foliage at the expense of the abundant 2-inch blossoms this variety is known for. Deadheading spent flowers extends blooming throughout the season—a critical practice for Royal Mix, which can produce flowers for 90 days or more with regular removal of faded blooms.
Watch for aphids and spider mites, which readily attack sweet pea varieties including Royal Mix. Check the undersides of leaves regularly and address infestations promptly with insecticidal soap or a strong water spray. Powdery mildew can develop in humid conditions, so ensure good air circulation around plants and avoid overhead watering.
Pruning side shoots encourages bushier growth and more prolific flowering in Royal Mix. Pinch out the top of main stems when plants reach about 6 inches tall, and remove lower leaves as plants mature to improve air circulation. Succession planting—sowing new seeds every two weeks through late spring—provides continuous blooms into summer.
Many gardeners overlook one critical need for Royal Mix: full sun with at least six hours of direct daily light. Plants grown in partial shade produce fewer of the vibrant red, purple, mauve, pink, blue, and white flowers this cultivar is celebrated for, and may become leggy or sparse. Position Royal Mix in your brightest garden location for maximum color and fragrance display.
Harvesting
Royal Mix reaches harvest at 90 days from sowing per Johnny's Selected Seeds. Expect 2" at peak. As an annual, harvest continues until frost ends the season.
Type: Legume.
Edibility: Sweet pea fruits are inedible and poisonous to humans.
Storage & Preservation
Royal Mix sweet peas are best kept fresh in a cool environment. Store cut flowers in the refrigerator at 35-40°F with high humidity (80-90%). Change water daily and trim stems every 2-3 days; they typically last 7-10 days in a vase. For preservation, air-dry entire stems in bundles hung upside-down in a dark, well-ventilated space for 2-3 weeks to create dried arrangements. Alternatively, press individual blooms between parchment paper under weight for 1-2 weeks for pressed flower crafts. For longer-term preservation, freeze flowers in water ice blocks or glycerin-treat stems to maintain flexibility and color for dried arrangements.
History & Origin
Royal Mix is open-pollinated, meaning seed saved from healthy plants will produce true-to-type offspring. Listed in the Johnny's Selected Seeds catalog.
Origin: Southern Italy, Sicily, Crete
Advantages
- +Large 2-inch blossoms in vibrant, clearly distinct colors
- +Exceptional fragrance makes Royal Mix ideal for cut flowers
- +Long blooming period provides continuous color throughout the season
- +Attracts hummingbirds, adding wildlife interest to gardens
- +Easy to grow, suitable for beginning gardeners
Considerations
- -Requires trellising or support structure for optimal growth
- -Prefers cool weather and may struggle in hot climates
- -Susceptible to powdery mildew and root rot in humid conditions
- -Needs consistent moisture; drought stress reduces flowering quality
Companion Plants
Marigolds (especially French types) and nasturtiums are the most practical companions here — both attract aphids away from sweet pea stems and pull in predatory insects like lacewings that clean up the mess. Sweet alyssum works the same angle: its tiny flowers feed parasitic wasps that prey on thrips and whiteflies. Zinnias and cosmos fit well in a cutting bed for practical reasons — similar sun and water needs, no allelopathic conflict, and they fill gaps without competing hard at the root zone. Fennel and black walnut trees are a different story; fennel's volatile oils suppress nearby plants, and walnut roots push juglone through the soil far enough to stunt or kill Lathyrus outright.
Plant Together
Marigolds
Repel aphids, whiteflies, and nematodes while attracting beneficial insects
Sweet Alyssum
Attracts beneficial insects like lacewings and provides ground cover
Nasturtiums
Act as trap crop for aphids and add vibrant complementary colors
Zinnias
Attract butterflies and beneficial pollinators, bloom simultaneously
Cosmos
Provide height variation and attract beneficial insects without competing for nutrients
Lavender
Repels pests with fragrance and attracts pollinators
Catmint
Deters aphids and ants while attracting beneficial pollinators
Sunflowers
Provide beneficial height backdrop and attract pollinators
Keep Apart
Black Walnut Trees
Release juglone toxin that inhibits growth and can cause wilting
Eucalyptus
Produces allelopathic compounds that suppress nearby plant growth
Fennel
Inhibits growth of most garden plants through allelopathy
Troubleshooting Royal Mix
What you'll see, why it happens, and what to do about it.
White powdery coating on leaves and stems, usually showing up once temperatures warm and airflow is poor
Likely Causes
- Powdery mildew (Erysiphe pisi) — a fungal disease that thrives when days are warm and nights are cool with high humidity
- Crowded planting with little air movement between vines
What to Do
- 1.Cut out the worst-affected stems and dispose of them — don't compost
- 2.Thin or retrain vines on the trellis so stems aren't piled on top of each other
- 3.Apply a dilute baking soda spray (1 tablespoon per gallon of water) weekly as a stopgap; it won't cure an established infection but slows spread
Flower buds dropping or failing to open, particularly once daytime highs climb above 75–80°F
Likely Causes
- Heat stress — sweet peas set flowers in cool weather and abort buds when temperatures push past their comfort zone
- Planting too late in spring, leaving no buffer before summer heat arrives
What to Do
- 1.Mulch the root zone with 3 inches of straw to keep soil cooler and hold moisture longer
- 2.Accept that the season is done; pull the plants once buds are consistently dropping and compost them
- 3.Next year, sow indoors 8–10 weeks before your last frost so plants are blooming well before heat sets in
Seedlings emerging then collapsing at soil level, stems pinched and brown at the base
Likely Causes
- Damping off — most often Pythium or Rhizoctonia solani, both soil-borne fungi that hit seedlings in cold, wet, poorly drained starting mix
- Overwatering in the germination tray before seedlings have true leaves
What to Do
- 1.Use fresh, sterile seed-starting mix — never reuse old mix from a previous season for sweet peas
- 2.Water from the bottom of the tray and let the surface dry slightly between waterings
- 3.If you're starting in late winter, run a small fan near the seedlings to keep air moving and surface moisture down
Frequently Asked Questions
How long do Royal Mix sweet pea flowers last in a vase?▼
Are sweet peas good for beginners to grow?▼
Can you grow Royal Mix sweet peas in containers?▼
When should I plant Royal Mix sweet pea seeds?▼
How do you dry Royal Mix sweet peas for crafts?▼
What colors does Royal Mix sweet pea come in?▼
Growing Guides from Wind River Greens
Where to Buy Seeds
Sources & References
External authority sources used in compiling this guide.
- BreederJohnny's Selected Seeds
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.