Iron Yellow
Matthiola incana
Early single-stem, or column-type stock in a highly uniform series for one-cut harvest. Aptly named for strong, straight, rigid stems. Iron performed well in our spring, early summer, and fall trials. Selectable for doubles and 55% double without selection. Compared to Katz, Iron is slightly later to flower, and has somewhat shorter and thicker stems. Tightly spaced florets on the flower spike make for compact 1 1/2-2", buttercream yellow blooms with a full appearance. NOTE: This variety produces one flowering stem per plant. Pinching is not advisable as it will terminate flowering. Edible Flowers: The peppery, clove-like flavor of the flowers lends itself well to use as a garnish on salads, desserts, and drinks.
Harvest
90-105d
Days to harvest
Sun
Full sun to partial shade
Zones
6–10
USDA hardiness
Height
1-3 feet
Planting Timeline
Showing dates for Iron Yellow in USDA Zone 7
All Zone 7 flower →Zone Map
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Iron Yellow · Zones 6–10
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
Iron Yellow stocks are a one-flush cut flower — each plant blooms once and is done, so succession planting is how you keep stems coming. In zone 7, start seeds indoors under lights around February 15, then again March 1, for two waves of transplants going out in April and early May. You can direct sow a third round in late April or early May, but get it in before daytime highs are consistently hitting 80°F; stocks stall out and produce short, weak spikes once heat sets in, and they won't recover when temperatures drop again.
That gives you roughly three overlapping flushes from late May through early July before the Georgia summer shuts them down. If you want fall stocks, start seeds indoors in late August and transplant in late September — they'll bloom in October and November when nights cool back into the 50s and 60s.
Complete Growing Guide
Early single-stem, or column-type stock in a highly uniform series for one-cut harvest. Aptly named for strong, straight, rigid stems. Iron performed well in our spring, early summer, and fall trials. Selectable for doubles and 55% double without selection. Compared to Katz, Iron is slightly later to flower, and has somewhat shorter and thicker stems. Tightly spaced florets on the flower spike make for compact 1 1/2-2", buttercream yellow blooms with a full appearance. NOTE: This variety produces one flowering stem per plant. Pinching is not advisable as it will terminate flowering. Edible Flowers: The peppery, clove-like flavor of the flowers lends itself well to use as a garnish on salads, desserts, and drinks. According to Johnny's Selected Seeds, Iron Yellow is 90 - 105 days to maturity, annual, open pollinated. Notable features: Use for Cut Flowers and Bouquets, Edible Flowers, Fragrant.
Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: Clay, High Organic Matter, Loam (Silt), Sand. Soil pH: Alkaline (>8.0), Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 1 ft. 0 in. - 3 ft. 0 in.. Spread: 0 ft. 9 in. - 1 ft. 6 in.. Spacing: Less than 12 inches, 12 inches-3 feet. Growth rate: Rapid. Maintenance: Low. Propagation: Seed. Regions: Coastal, Mountains.
Harvesting
Iron Yellow reaches harvest at 90 - 105 days from sowing per Johnny's Selected Seeds. Expect 1 1/2-2" at peak. As an annual, harvest continues until frost ends the season.
Seeds will ripen in August and September.
Harvest time: Fall
Storage & Preservation
Fresh-cut Iron Yellow flowers last 7–10 days in a clean vase with flower food and cool water (60–65°F is ideal). Recut stems every 2–3 days and remove any foliage below the water line to prevent bacterial growth.\n\nFor edible flowers, keep fresh petals in a sealed container in the refrigerator and use within 3–5 days. They lose their delicate peppery flavor quickly once harvested.\n\nTo preserve edible flowers for later use, dry them on screens in a warm, dark, well-ventilated space for 1–2 weeks until papery. Store dried flowers in airtight containers away from light and moisture; they'll keep 6–12 months and intensify in flavor. Alternatively, freeze individual petals in ice cubes with a small amount of water for decorative cocktail use—they retain their color and can be stored for several months.
History & Origin
Iron Yellow is open-pollinated, meaning seed saved from healthy plants will produce true-to-type offspring. Listed in the Johnny's Selected Seeds catalog.
Origin: The Coast of Europe from Spain to Greece.
Advantages
- +Strong, rigid stems ideal for professional cut flower arrangements and shipping.
- +Highly uniform series ensures consistent quality across entire harvest batches.
- +Compact, full 1.5-2 inch blooms with buttercream yellow color and tight florets.
- +Performs reliably in spring, early summer, and fall growing seasons.
- +Edible flowers with peppery, clove-like flavor add value for culinary garnish.
Considerations
- -Produces only one flowering stem per plant, limiting yield compared to pinchable varieties.
- -Slightly later to flower than competitor variety Katz, extending production timeline.
- -Shorter stems than some alternatives may limit options for certain arrangement designs.
- -Pinching terminates flowering, removing any flexibility for crop management adjustments.
Companion Plants
Marigolds — French marigolds (Tagetes patula) specifically — are the most useful neighbor here. Their root secretions suppress soil nematodes, and their scent disrupts aphids scouting for soft new growth on your flower stems. Nasturtiums pull a different trick: they act as a trap crop, drawing aphids onto themselves before those aphids find the stocks you're actually cutting. Sweet Alyssum is worth tucking in at the bed's edge too; its small blooms run almost continuously and draw in parasitic wasps that target cabbage moth larvae.
Black Walnut is the one to stay clear of — its roots release juglone, a compound that inhibits cellular respiration in sensitive plants, and Matthiola incana is sensitive enough that you'll see stunted, yellowing stems before the plant gives out entirely. In our zone 7 Georgia gardens, dense shade trees are a more everyday hazard than walnut; stocks need at least 4-6 hours of direct sun to push up the tall, full spikes that make them worth growing, and a shady spot will get you short, sparse stems no matter what else you do right.
Plant Together
Marigolds
Natural pest deterrent, repels nematodes and aphids while attracting beneficial insects
Nasturtiums
Acts as trap crop for aphids and cucumber beetles, attracts predatory insects
Sweet Alyssum
Attracts beneficial insects like lacewings and hoverflies that control pests
Zinnia
Attracts butterflies and beneficial pollinators, similar growing requirements
Cosmos
Attracts beneficial insects and provides complementary height and texture
Celosia
Similar sun and water requirements, attracts pollinators and beneficial insects
Sunflowers
Provides beneficial shade and attracts pest-eating birds and beneficial insects
Lavender
Repels pests like moths and flies while attracting beneficial pollinators
Keep Apart
Black Walnut
Produces juglone which is toxic to many flowering plants and inhibits growth
Eucalyptus
Allelopathic properties suppress growth of nearby plants
Dense Shade Trees
Blocks essential sunlight needed for proper flowering and growth
Pests & Disease Resistance
Common Pests
Cabbage moth, flea beetles, spider mites
Diseases
Downy mildew, root rot, Fusarium wilt
Troubleshooting Iron Yellow
What you'll see, why it happens, and what to do about it.
White-gray powdery coating on lower leaves and stems, spreading upward — usually appears after a stretch of cool, humid nights
Likely Causes
- Downy mildew (Peronospora matthiolae) — thrives when nights drop below 65°F and humidity stays high
- Crowded spacing that traps moisture against the foliage
What to Do
- 1.Pull and bag any heavily affected leaves — don't compost them
- 2.Thin plants to at least 12 inches apart so air can move between them
- 3.Apply a copper-based fungicide at first sign; reapply every 7-10 days if wet weather continues
Plant wilts suddenly and doesn't recover after watering — roots look brown and water-soaked when you pull it
Likely Causes
- Root rot (Pythium spp.) or Fusarium wilt (Fusarium oxysporum) — both triggered by poorly drained soil and overwatering
- Planting into beds that stay wet after heavy rain
What to Do
- 1.Pull the affected plant — it won't recover; check whether nearby plants show the same basal discoloration
- 2.Amend the bed with perlite or coarse compost before replanting; aim for soil that drains within 30 minutes of a heavy soak
- 3.Rotate stocks out of that bed for at least two seasons and avoid planting other Brassica-family crops there in the meantime
Small irregular holes punched through young leaves, mostly on seedlings within the first 3 weeks after transplant
Likely Causes
- Flea beetles (Phyllotreta spp.) — tiny, fast-jumping, worst when transplants are stressed or soil is dry
- Cabbage moth (Mamestra brassicae) larvae feeding at night on older seedlings
What to Do
- 1.Cover transplants with row cover (Agribon AG-19 or similar) immediately after planting and leave it on for the first 2-3 weeks
- 2.If flea beetles are confirmed, a perimeter of diatomaceous earth around the bed slows them down — reapply after rain
- 3.Check the undersides of leaves at dusk for cabbage moth caterpillars; hand-pick and drop in soapy water
Frequently Asked Questions
How long does Iron Yellow stock take to grow from seed to flower?▼
Can you grow Iron Yellow stock in containers or pots?▼
What's the difference between Iron Yellow and Katz stock?▼
Do you need to pinch Iron Yellow stock plants?▼
Is Iron Yellow stock good for beginners?▼
What do Iron Yellow stock flowers taste like, and how do you use them in cooking?▼
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.