Heirloom

Oklahoma Formula Mix Improved

Zinnia elegans

Photo: Ermell · Wikimedia Commons · (CC BY-SA 4.0)

Harvest

75-90d

Days to harvest

📅

Sun

Full sun

☀️

Zones

2–11

USDA hardiness

🗺️

Height

0-3 feet

📏

Planting Timeline

Zone:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Start Indoors

Transplant

Direct Sow

Start Indoors

Transplant

Direct Sow

Showing dates for Oklahoma Formula Mix Improved in USDA Zone 7

All Zone 7 flower →

Zone Map

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Oklahoma Formula Mix Improved · Zones 2–11

What grows well in Zone 7? →

Growing Details

Difficulty

Easy

Spacing12-18 inches

SoilWell-drained loam, moderately fertile

WaterRegular, consistent moisture during growing season

SeasonWarm season annual

ColorMixed colors including pink, red, white, and bi-colors

Size1 1/2-2 1/2"

Zone-by-Zone Planting Calendar

Zone	Indoor Start	Transplant	Direct Sow	Harvest
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	—
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	—

Succession Planting

Direct sow every 2-3 weeks from your last frost date through early July in zone 7, stopping when daytime highs are regularly cracking 90°F — the seeds will still sprout in heat, but plants tend to shoot up fast and throw a single bloom rather than branching into the multi-stem cuts you're after. A late April sow and a mid-June sow usually produce two distinct flush periods without much overlap. If you're starting indoors, sow 4-6 weeks before your transplant date and don't push it earlier than that — zinnias stall hard when they get root-bound, and a 3-week-old transplant will outperform a 6-week-old one that's been sitting in a tray too long.

Complete Growing Guide

This improved mix is an essential component of any cut-flower offering. Prolific double and semidouble blooms are easy to use in bouquets due to their smaller size. The 1 1/2-2 1/2" blooms hold up well to handling compared to larger blooms which can snap at the stem due to the weight of the larger flower heads. Cut-and-come-again flower, yielding multiple cuts over the season. According to Johnny's Selected Seeds, Oklahoma Formula Mix Improved is 75 - 90 days to maturity, annual, open pollinated. Notable features: Grows Well in Containers, Use for Cut Flowers and Bouquets.

Light: Full sun (6 or more hours of direct sunlight a day). Soil: High Organic Matter, Loam (Silt). Soil pH: Acid (<6.0), Alkaline (>8.0), Neutral (6.0-8.0). Drainage: Good Drainage, Occasionally Dry. Height: 0 ft. 6 in. - 3 ft. 0 in.. Spread: 0 ft. 8 in. - 1 ft. 0 in.. Spacing: 12 inches-3 feet. Growth rate: Rapid. Maintenance: Medium. Propagation: Seed. Regions: Coastal, Mountains, Piedmont.

Harvesting

Oklahoma Formula Mix Improved reaches harvest at 75 - 90 days from sowing per Johnny's Selected Seeds. Expect 1 1/2-2 1/2" at peak. As an annual, harvest continues until frost ends the season.

Type: Achene.

Storage & Preservation

For fresh storage, keep cut stems in a clean vase with fresh, cool water (65-72°F) in a cool location away from direct sunlight and ripening fruits. Change water every 2-3 days for optimal longevity; blooms typically last 7-14 days. Preservation methods include air-drying by hanging bundles upside-down in a dark, well-ventilated space for 1-2 weeks; pressing blooms between parchment paper under weight for dried arrangements; or silica gel drying for 3-7 days to retain color and shape. Remove lower foliage before storing to prevent bacterial growth.

History & Origin

Oklahoma Formula Mix Improved is open-pollinated, meaning seed saved from healthy plants will produce true-to-type offspring. Listed in the Johnny's Selected Seeds catalog.

Origin: Mexico

Advantages

+Produces abundant double and semidouble blooms ideal for commercial cut-flower operations
+Smaller 1.5-2.5 inch flowers resist stem snapping from weight and handling
+Cut-and-come-again variety yields multiple harvests throughout the growing season
+Easy to grow with straightforward care requirements for beginners
+Compact bloom size maximizes arrangement versatility and reduces waste per stem

Considerations

-Smaller flowers may command lower prices than premium large-bloom zinnia varieties
-Requires consistent deadheading to maintain prolific blooming throughout season
-Susceptible to powdery mildew in humid or poorly ventilated growing conditions

Companion Plants

Marigolds and sweet alyssum do the most work here — marigolds push back on aphids and whiteflies through both root secretions and foliar compounds, while sweet alyssum draws in hoverflies whose larvae consume aphids in large numbers. Nasturtiums pull double duty as a trap crop, taking aphid pressure off your zinnias by being a more attractive target. Dill nearby recruits parasitic wasps that keep Helicoverpa and other caterpillars in check. Keep zinnias well clear of black walnut trees — juglone moves through the soil from roots and decomposing leaf litter across a wide radius and stalls or kills most annuals, Oklahoma Formula Mix included.

Plant Together

Cosmos

Support beneficial insects and create natural pest control partnerships

Sweet Alyssum

Ground cover that attracts hover flies and other beneficial predatory insects

Nasturtiums

Act as trap crops for aphids and cucumber beetles, protecting nearby flowers

Lavender

Repels moths, fleas, and mosquitoes while attracting beneficial pollinators

Sunflowers

Provide beneficial insect habitat and can offer wind protection for smaller flowers

Dill

Attracts beneficial wasps and predatory insects that control garden pests

Marigolds

Repel nematodes, aphids, and other harmful insects while attracting beneficial pollinators

Zinnias

Attract beneficial insects and pollinators, complement wildflower displays

Keep Apart

Black Walnut Trees

Release juglone toxin that inhibits growth and can kill many flowering plants

Eucalyptus

Produces allelopathic compounds that suppress germination and growth of nearby plants

Dense Turf Grass

Competes aggressively for nutrients and water, suppressing wildflower establishment

Troubleshooting Oklahoma Formula Mix Improved

What you'll see, why it happens, and what to do about it.

White powdery coating on leaves and stems, usually showing up mid-summer when nights cool down slightly

Likely Causes

Powdery mildew (Erysiphe cichoracearum) — a fungal disease that thrives when humidity is high but foliage stays dry
Crowded spacing under 12 inches that kills airflow between plants

What to Do

1.Thin plants to at least 12 inches apart if you haven't already — airflow is the main lever here
2.Spray affected foliage with a diluted baking soda solution (1 tablespoon per gallon of water) or a neem oil mix on a cloudy morning
3.Remove and trash the worst-affected stems; don't compost them

Seedlings collapse at the soil line, usually within the first 2 weeks after germination

Likely Causes

Damping off — typically Pythium or Rhizoctonia fungi thriving in cold, soggy soil
Overwatering combined with poor drainage in seed trays or beds

What to Do

1.Let the top inch of soil dry out between waterings once seeds have sprouted
2.Start indoor seeds in a sterile seed-starting mix, not garden soil
3.Direct sow outdoors only after soil temps are consistently above 60°F — zinnias germinate in 7-14 days at 70-75°F and rot faster than they sprout in cold ground

Ragged holes chewed in petals and leaves, sometimes flowers disappear overnight

Likely Causes

Japanese beetles (Popillia japonica) — they go straight for the blooms
Caterpillars, particularly corn earworm (Helicoverpa zea), which feed on buds and open flowers

What to Do

1.Hand-pick Japanese beetles in the early morning when they're sluggish and drop them in soapy water
2.For caterpillars, apply Bacillus thuringiensis (Bt) spray directly to affected foliage — it's effective and won't harm bees
3.Check plants every 2-3 days during peak summer; early catch keeps populations from exploding

Stunted plants with distorted, curling new growth and sticky residue on stems and buds

Likely Causes

Aphid infestations (commonly Myzus persicae or Macrosiphum euphorbiae) — they cluster on soft new growth and excrete honeydew
Ant activity nearby, which often means ants are farming the aphids and running interference against natural predators like ladybugs

What to Do

1.Knock aphids off with a firm stream of water from a hose — do this 3 mornings in a row
2.If populations are still there after 5-7 days, apply insecticidal soap directly to the colonies, hitting the undersides of leaves where they hide
3.Trace ant trails back to their source and address the ants separately, or the aphid colonies will rebuild within a week

Frequently Asked Questions

How long do Oklahoma Formula Mix Improved cut flowers last?▼

With proper care, these blooms typically last 7-14 days in a vase. Their smaller size (1.5-2.5 inches) and sturdy stems make them more durable than larger flowers. Change water every 2-3 days, keep them cool, and remove lower foliage to maximize vase life and prevent bacterial growth.

Is Oklahoma Formula Mix Improved good for beginner flower gardeners?▼

Yes, this variety is ideal for beginners. It's classified as easy to grow, requiring only full sun (6+ hours daily) and no specialized care. The prolific blooming habit and cut-and-come-again nature provide quick gratification and multiple harvests throughout the season, making it perfect for learning floristry skills.

Can you grow Oklahoma Formula Mix Improved in containers?▼

Yes, these flowers can be grown in containers with adequate depth (8-12 inches) and drainage. Container growing works well for cut flowers since it allows easy access for harvesting and mobility if needed. Ensure consistent watering and use quality potting soil to support prolific blooming and sturdy stem development.

When should I plant Oklahoma Formula Mix Improved?▼

Plant seeds directly outdoors after the last frost date, or start indoors 6-8 weeks before the last frost for earlier blooms. These flowers prefer full sun and warm soil. Seeds typically germinate in 7-14 days. Succession planting every 2-3 weeks extends your harvest throughout the growing season.

What makes Oklahoma Formula Mix Improved better for cut flowers than other varieties?▼

The 1.5-2.5 inch double and semidouble blooms are ideal for bouquets because their smaller size prevents stem-snapping from weight, unlike larger flower heads. Their cut-and-come-again nature yields multiple harvests per plant, and they're highly prolific, providing abundant blooms with minimal effort throughout the season.

How often can I harvest blooms from Oklahoma Formula Mix Improved?▼

As a cut-and-come-again variety, regular harvesting actually encourages more blooms. Cut flowers in early morning when stems are fully hydrated, removing spent blooms and cutting just above a leaf node. With consistent harvesting and deadheading, expect continuous blooms from 75-90 days until first frost.