Hybrid

Megaton

Allium porrum

Wikimedia Commons

Early maturing and good field holding of long, thick shanks creates a very high yield potential. Less bulbing and splitting, and easier to peel than open-pollinated varieties. Vigorous and uniform.

Harvest

90d

Days to harvest

📅

Sun

Full sun to partial shade

☀️

Zones

4–9

USDA hardiness

🗺️

Height

1-3 feet

📏

Planting Timeline

Zone:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Direct Sow

Harvest

Direct Sow

Harvest

Showing dates for Megaton in USDA Zone 7

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Zone Map

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Megaton · Zones 4–9

What grows well in Zone 7? →

Growing Details

Difficulty

Easy

Spacing4-6 inches in rows 12-18 inches apart

SoilWell-drained loam, slightly acidic to neutral pH (6.0-7.0)

WaterRegular, consistent moisture throughout growing season

FlavorMild to moderately pungent onion flavor with good storage quality and excellent keeping ability.

ColorYellow-gold

Zone-by-Zone Planting Calendar

Zone	Indoor Start	Transplant	Direct Sow	Harvest
Zone 3	—	—	May – June	August – October
Zone 4	—	—	April – June	July – October
Zone 5	—	—	April – May	July – November
Zone 6	—	—	April – May	July – November
Zone 7	—	—	March – May	June – November
Zone 8	—	—	March – April	June – December
Zone 9	—	—	February – March	May – December
Zone 10	—	—	January – March	April – December
Zone 1	—	—	June – July	September – September
Zone 2	—	—	May – July	August – September
Zone 11	—	—	January – February	March – December
Zone 12	—	—	January – February	March – December
Zone 13	—	—	January – February	March – December

Succession Planting

Megaton runs 90 days from transplant, so a single sowing gives you a fairly tight harvest window. Direct sow every 3 to 4 weeks from March through early May in zone 7; anything started after late May is unlikely to build a decent shank before hard frost arrives. Leeks don't bolt the way lettuce does, but shank growth stalls when daytime highs consistently sit at 90°F or above, so late sowings often stay pencil-thin no matter how long you wait.

Two to three staggered sowings will spread your harvest from June through November. A late-April sowing in zone 7 typically pushes into October and November, when a few light frosts actually improve the flavor.

Complete Growing Guide

Early maturing and good field holding of long, thick shanks creates a very high yield potential. Less bulbing and splitting, and easier to peel than open-pollinated varieties. Vigorous and uniform. According to Johnny's Selected Seeds, Megaton is 90 days to maturity, hybrid (f1). Notable features: Cold Tolerant, Easy Choice.

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: High Organic Matter, Loam (Silt), Sand. Drainage: Good Drainage. Height: 1 ft. 0 in. - 3 ft. 0 in.. Spread: 0 ft. 6 in. - 2 ft. 0 in.. Spacing: Less than 12 inches. Growth rate: Medium. Maintenance: Low. Propagation: Division. Regions: Coastal, Mountains, Piedmont.

Harvesting

Megaton reaches harvest at 90 days from sowing per Johnny's Selected Seeds.

The capsule splits longitudinally and contains small round black seeds.

Type: Capsule.

Storage & Preservation

Megaton leeks store best in a cool, humid environment at 32–40°F with 90–95% relative humidity. Place unwashed stalks upright in a perforated plastic bag or damp sand in the crisper drawer; they'll keep for 3–4 weeks this way. For longer storage, trim roots and tops, wrap individually in damp paper towels, and refrigerate for up to two months.

Fresh use remains optimal within the first two weeks. For preservation, blanch cleaned leek pieces for 3 minutes, cool quickly, and freeze in airtight containers for nine months. Alternatively, slice and dry at 140°F until brittle for concentrated flavor in soups and stocks. Megaton's substantial size makes it particularly suited to slicing and freezing in portion-sized batches, reducing prep work during winter cooking.

History & Origin

Megaton is an F1 hybrid developed through controlled cross-pollination. Listed in the Johnny's Selected Seeds catalog.

Origin: Northern Hemisphere, North America and Eurasia

Advantages

+Early maturity at 90 days enables quick harvests and succession planting
+Excellent field holding prevents splitting and reduces postharvest losses
+Long, thick shanks deliver superior yields compared to traditional varieties
+Easier peeling than open-pollinated types saves significant processing time
+Uniform growth ensures consistent sizing for commercial markets

Considerations

-Hybrid seed cost higher than saving open-pollinated variety seeds
-Requires consistent moisture; drought stress reduces shank thickness
-Less cold hardiness than some winter leek varieties for storage
-Vigor demands rich soil; poor fertility noticeably reduces uniformity

Companion Plants

Carrots are the most practical neighbor for Megaton. The leek's sulfur compounds help disrupt carrot fly (Psila rosae) host-finding, and carrots planted 4–6 inches apart break up the soil in a way that benefits leek shanks pushing downward. Marigolds (Tagetes spp.) nearby pull their weight by repelling thrips through volatile scent compounds and drawing in predatory insects. Brassicas — cabbage, broccoli — share similar fertility and moisture demands and don't crowd leek roots at 12–18 inch row spacing, so they fit well in adjacent rows without much competition.

Beans and peas don't belong in the same bed. The sulfur compounds leeks produce interfere with the Rhizobium bacteria that legumes rely on to fix nitrogen, which costs the legumes without giving the leeks anything back. Asparagus is a different problem — both crops run long seasons and put down territorial root systems, and they'll fight for the same ground for years.

Plant Together

Tomatoes

Alliums repel aphids, hornworms, and other pests that damage tomatoes

Carrots

Alliums deter carrot fly while carrots help break up soil for allium bulbs

Brassicas (Cabbage/Broccoli)

Alliums repel cabbage worms, aphids, and flea beetles that attack brassicas

Lettuce

Alliums provide pest protection while lettuce acts as living mulch

Roses

Alliums deter aphids, thrips, and may reduce black spot disease

Peppers

Alliums repel aphids and other soft-bodied insects that damage pepper plants

Strawberries

Alliums deter slugs, aphids, and nematodes that harm strawberry plants

Marigolds

Both repel similar pests creating enhanced protection against nematodes and aphids

Keep Apart

Beans

Alliums can inhibit nitrogen fixation by rhizobia bacteria in legume root nodules

Peas

Allium compounds interfere with nitrogen-fixing bacteria essential for pea growth

Asparagus

Alliums can stunt asparagus growth through allelopathic compounds in soil

Nutrition Facts

Calories

40kcal(2%)

Protein

1.1g(2%)

Fiber

1.7g(6%)

Carbs

9.34g(3%)

Fat

0.1g(0%)

Vitamin C

7.4mg(8%)

Vitamin A

0mcg(0%)

Vitamin K

0.4mcg(0%)

Iron

0.21mg(1%)

Calcium

23mg(2%)

Potassium

146mg(3%)

Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #170000)

Pests & Disease Resistance

Common Pests

Onion maggots, thrips, cutworms, wireworms

Diseases

Fusarium basal rot, pink root, downy mildew, white rot

Troubleshooting Megaton

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

Seedlings collapsing at soil level or failing to emerge, especially in cool, wet spring conditions

Likely Causes

Onion maggot (Delia antiqua) — larvae tunnel through the base and roots just below the soil surface
Cutworms (Agrotis spp.) severing stems at night

What to Do

1.Use floating row cover from germination through the first 6 weeks to block adult flies from laying eggs
2.Place cardboard or foil collars around transplant stems at planting to deter cutworms
3.If you've had maggot pressure before, work beneficial nematodes (Steinernema feltiae) into the top 3 inches of soil before sowing

Leaves showing silver-white streaking or stippling, sometimes with tiny black frass specks along the leaf surface

Likely Causes

Thrips (Thrips tabaci) — they rasp the leaf surface and feed in the tight inner leaf folds where sprays don't reach well

What to Do

1.Knock populations down with spinosad-based spray early in the morning, targeting the base of the plant where thrips congregate
2.Remove and trash any heavily infested outer leaves — don't compost them
3.Keep irrigation consistent; drought-stressed leeks draw thrips faster than well-watered ones

Shaft base turning brown and mushy at or just below soil level, with a sour smell, plants pulling up with almost no resistance

Likely Causes

Fusarium basal rot (Fusarium oxysporum f. sp. cepae) — a soil-borne fungus that persists for years in infected beds
White rot (Sclerotium cepivorum) — produces small black sclerotia that can survive in dry soil for a decade or more

What to Do

1.Pull and bag affected plants immediately — don't compost anything that smells like rot
2.Rotate alliums out of that bed for at least 3 years; white rot pushes that closer to 8–10 years
3.Amend for drainage before next season — both pathogens accelerate in waterlogged, compacted soil

Frequently Asked Questions

How long does Megaton allium take to mature?▼

Megaton is an early-maturing variety that reaches harvest in approximately 90 days from transplanting. This quick maturity makes it ideal for growers looking for fast turnover and earlier market availability compared to standard onion varieties.

Is Megaton a good variety for beginners?▼

Yes, Megaton is excellent for beginners. It's a vigorous, uniform hybrid with easy peeling and less splitting than open-pollinated varieties. Its robust nature and straightforward care requirements make it one of the most reliable and forgiving onion varieties to grow.

What kind of sunlight does Megaton need?▼

Megaton performs well in full sun to partial shade, requiring a minimum of 4-6 hours of sunlight daily. While it can tolerate some afternoon shade in hot climates, full sun exposure will maximize bulb development and yield potential.

Why is Megaton known for high yield potential?▼

Megaton produces long, thick shanks with excellent field holding ability, meaning bulbs remain firm and in harvestable condition longer in the field. The hybrid vigor, combined with reduced splitting and bulbing issues, creates exceptional yield per acre compared to traditional varieties.

How should I space Megaton plants?▼

Proper spacing is crucial for developing quality bulbs. Megaton should be spaced 4-6 inches apart in rows that are 12-18 inches apart, allowing adequate air circulation and room for bulb expansion during the growing season.

What makes Megaton easier to peel than other varieties?▼

Megaton's hybrid genetics and bulb structure produce thinner, more manageable skin layers that separate cleanly from the flesh. This characteristic, combined with its reduced tendency to split, makes post-harvest processing and peeling significantly faster and more efficient.