Corn seed buying and growing guide

Choose the Right Corn Seeds

Corn is a warm-season crop grown for sweet edible cobs, mature kernels, colourful ornamental ears and specialty production. Varieties differ in sweetness, kernel texture, cob colour, maturity, plant height, pollination requirements and intended use.

Seedmart supplies corn seeds for home gardens, market gardens and commercial production throughout Australia. Choose traditional sweet corn for familiar flavour and broad use, supersweet hybrids for heightened sweetness and longer post-harvest quality, or colourful specialty corn for ornamental cobs and niche production.

The best corn seed will depend on your climate, available space, intended harvest, preferred sweetness and whether the crop will be used fresh, frozen, processed or allowed to mature fully.

Why Grow Corn?

Productive Summer Crop

Healthy corn plants can produce substantial cobs during warm weather with adequate water and fertility.

Freshly Harvested Flavour

Sweet corn provides its best eating quality when harvested at the correct stage and used promptly.

Strong Upright Growth

Corn adds height and structure to vegetable gardens and larger field plantings.

Different Kernel Types

Choose traditional sweet, supersweet, coloured or specialty corn according to the intended use.

Successive Plantings

Plant smaller blocks at intervals to spread pollination and harvest over a longer period.

Packet and Larger Quantities

Select smaller packs for household gardens or larger seed quantities for field and commercial plantings.

Corn Seeds for Different Growing Goals

Some corn varieties are selected for sweetness and fresh eating, while others are grown for processing, traditional flavour, ornamental colour or fully mature kernels.

Growing Goal Recommended Corn Type Why Choose It?
Premium fresh eating SH2 supersweet corn such as Max F1 Produces highly sweet kernels that convert sugar to starch more slowly after harvest.
Traditional sweet corn flavour SU1 sweet corn such as Grampian F1 Provides familiar sweet corn flavour with strong field performance and broad culinary use.
Freezing and preserving Grampian and other uniform sweet corn varieties Produces consistent cobs suited to whole-cob freezing, cut kernels and appropriate preserving methods.
Home vegetable gardens Sweet or supersweet corn Fresh cobs can be harvested close to the ideal eating stage and used immediately.
Market garden production Uniform F1 sweet corn hybrids Consistent maturity, cob shape and eating quality support scheduled fresh-market harvests.
Colourful ornamental cobs Glass Gem Corn Produces multi-coloured mature kernels for decoration, seed displays and specialty uses.
Specialty or traditional corn Jolly Roger and other non-standard types Offers characteristics distinct from mainstream yellow supersweet hybrids.
Commercial field performance Grampian Yellow F1 Selected for vigorous establishment, uniform cobs and dependable production.

Choose Corn by Type

Supersweet

SH2 Sweet Corn

SH2 supersweet corn produces heightened sweetness and retains eating quality longer after harvest than standard sugary corn. It requires warm, well-drained soil for reliable establishment.

Traditional Sweet

SU1 Sweet Corn

Standard sugary corn provides familiar sweet corn flavour and is often selected for field vigour, fresh eating, freezing and processing.

Hybrid

F1 Sweet Corn

F1 hybrids are developed for consistency in plant vigour, maturity, cob shape, kernel quality and yield.

Colourful

Glass Gem Corn

Glass Gem develops mature ears containing translucent kernels in a broad mixture of colours.

Specialty

Traditional Corn Types

Specialty corn may be selected for unusual kernels, mature cobs, cultural use or characteristics not found in mainstream sweet corn.

Fresh Market

Yellow Sweet Corn

Yellow sweet corn remains a familiar choice for home gardens, roadside sales, markets and commercial fresh-cob production.

Sweet Corn vs Supersweet Corn

Traditional sweet corn and supersweet corn are both harvested while the kernels are tender, but they differ in sweetness, seed characteristics and pollination requirements.

Traditional Sweet Corn Supersweet Corn
Commonly carries the SU1 standard sugary gene. Commonly carries the SH2 supersweet gene.
Provides familiar, traditional sweet corn flavour. Produces noticeably higher sweetness.
Sugars convert to starch relatively quickly after harvest. Sweetness and tender eating quality persist longer after picking.
Seed generally has greater stored starch and stronger cool-start establishment. Seed is often more sensitive to cold, wet or compacted soil.
Suitable for fresh eating, freezing, canning and processing. Particularly suited to fresh eating and premium market sales.
Can negatively affect nearby SH2 cobs through cross-pollination. Should be isolated from incompatible corn types during flowering.
Sweetness type matters before planting. Standard and supersweet corn should not release pollen at the same time where supersweet eating quality must be maintained.

Grampian Sweet Corn vs Max Supersweet Corn

Grampian and Max are separate yellow F1 hybrids developed for different production priorities.

Feature Grampian Yellow F1 Max Supersweet F1
Sweetness type SU1 standard sugary sweet corn SH2 supersweet corn
Eating style Traditional sweet corn flavour Heightened supersweet flavour
Primary strength Field performance, uniformity and broad harvest use Fresh eating quality and sweetness retention
Post-harvest sweetness Should be chilled or used promptly Converts sugar to starch more slowly
Germination Strong early vigour and good cool-start emergence Best sown into warm, free-draining soil
Suitable uses Fresh cobs, freezing, canning and processing Fresh eating, barbecuing, market sales and freezing

Sweet Corn and Colourful Corn

Sweet corn and colourful mature corn should not be treated as interchangeable crops.

Sweet Corn

Sweet corn is harvested while the kernels are immature, tender and filled with milky juice.

  • Picked at the milk stage
  • Used as a fresh vegetable
  • Boiled, steamed, grilled or frozen
  • Eating quality declines if harvested too late

Glass Gem and Mature Corn

Colourful corn is generally allowed to mature and dry fully on the plant.

  • Harvested after kernels harden
  • Valued for colour and appearance
  • Suitable for ornamental displays
  • Not equivalent to tender supersweet corn
Confirm the intended harvest before choosing seed. Corn selected for ornamental mature ears will not necessarily provide the sweetness or texture expected from fresh sweet corn.

How to Grow Corn in Australia

Corn is a warm-season crop requiring full sun, fertile soil, consistent moisture and effective wind pollination.

Wait for Warm Soil

Plant after frost risk has passed and the soil has warmed sufficiently for reliable germination.

Grow in Full Sun

Choose an open position receiving strong direct sunlight throughout most of the day.

Plant in Blocks

Several short rows pollinate more reliably than one long single row.

Maintain Moisture

Reliable water is particularly important during tasselling, silking, pollination and kernel filling.

Successful corn production depends on pollination. Every silk is connected to an individual kernel, so incomplete pollination produces missing kernels and poorly filled cobs.

When to Plant Corn in Australia

Corn should be planted during warm conditions after frost risk has passed. The most suitable planting period varies with climate and the length of the warm growing season.

Climate Zone General Sowing Period Growing Notes
Cool October to January Wait until the soil has warmed and allow enough frost-free weather for the crop to mature.
Temperate September to January Plant through spring and early summer, with successive sowings where the season is long enough.
Subtropical August to February Plant through the warm season while avoiding periods of severe heat or excessive rainfall where possible.
Tropical March to September Corn is often easiest to manage during the drier period with reliable irrigation.
Arid August to February Provide reliable irrigation and avoid extreme heat during flowering where possible.

These planting periods are general guides. Local frost dates, soil temperature, elevation, rainfall, seasonal heat and irrigation capacity should also be considered.

When to Plant Corn in Australian States and Cities

Regional planting periods should be adjusted according to frost risk, summer heat, rainfall and the maturity of the selected variety.

Location General Planting Guide Key Considerations
Brisbane and South East Queensland August to February Plant through spring and summer, with reliable watering during dry periods and good drainage during heavy rain.
Sydney and coastal New South Wales September to January Wait for warm soil and use staggered plantings to extend the harvest.
Inland New South Wales October to January Plant after frost risk and avoid late crops that cannot mature before autumn cooling.
Melbourne and Victoria October to January Plant once the soil is warm and select varieties capable of maturing within the available season.
Adelaide and South Australia September to January Maintain irrigation and avoid severe moisture stress during tasselling and silking.
Perth and south-west Western Australia September to January Spring and early summer plantings perform well where water is available.
Tasmania November to January Use early or mid-season varieties and plant into the warmest available frost-free period.
Darwin and tropical northern Australia March to August Dry-season production generally offers better disease management and field access.

How to Plant Corn Seeds

Corn is generally direct-sown into the garden bed or field where it will mature. The plants develop substantial roots and are easier to establish without transplant disturbance.

  1. Choose a sunny position.
    Select an open area receiving at least six to eight hours of direct sunlight.
  2. Prepare fertile soil.
    Remove weeds and incorporate suitable organic matter or fertiliser according to soil requirements.
  3. Wait for suitable warmth.
    Do not sow into cold, saturated soil, particularly when planting supersweet SH2 seed.
  4. Sow at the correct depth.
    Plant seed approximately 2–4 cm deep, adjusting slightly for soil texture and moisture.
  5. Plant in a block.
    Arrange several short rows beside one another rather than one long row.
  6. Water gently after sowing.
    Maintain moderate moisture without leaving the seedbed waterlogged.
  7. Thin after emergence.
    Retain strong seedlings at the final spacing required for the variety.
  8. Maintain fertility and moisture.
    Support vigorous leaf growth before flowering and reliable kernel fill after pollination.
Do not sow supersweet seed into cold, wet soil. SH2 kernels contain less stored starch and are particularly vulnerable to poor establishment under unsuitable conditions.

How Deep Should Corn Seeds Be Planted?

Plant corn seeds approximately 2–4 cm deep. Sowing depth should be adjusted according to soil texture, temperature and surface moisture.

Heavy or Cool Soil

Use the shallower end of the sowing range to support faster emergence.

  • Sow approximately 2–3 cm deep
  • Avoid compacting the row
  • Do not plant into waterlogged soil
  • Wait for adequate soil warmth

Light or Drying Soil

Slightly deeper sowing can help maintain moisture around the seed.

  • Sow approximately 3–4 cm deep
  • Water thoroughly after planting
  • Monitor surface drying
  • Avoid burying seed excessively deeply

How Long Do Corn Seeds Take to Germinate?

Corn commonly germinates within approximately 6–14 days under suitable warm conditions. Seed may emerge faster in warm soil or take longer where temperatures are low.

Soil Temperature

Warm soil supports faster germination and stronger early growth.

Drainage

Cold, saturated or poorly aerated soil can cause seed to rot before emergence.

Seed Type

Supersweet SH2 seed is generally more sensitive to poor soil conditions than standard sugary corn.

Sowing Depth

Correct planting depth protects the seed while allowing seedlings to reach the surface readily.

How Far Apart Should Corn Be Planted?

Corn requires enough space for root growth, leaf development and airflow while remaining close enough for effective wind pollination.

Planting Situation Approximate Plant Spacing Approximate Row Spacing
Home garden sweet corn 20–30 cm 60–75 cm
Large vigorous varieties 25–35 cm 75–90 cm
Compact intensive blocks 20–25 cm 45–60 cm
Commercial field planting Adjusted to machinery and target population Usually 60–90 cm
Avoid one long row. A square or rectangular block containing at least several short rows generally pollinates more reliably.

Why Should Corn Be Planted in Blocks?

Corn is pollinated primarily by wind. Male tassels release pollen that must land on the silks emerging from each developing cob.

Every individual silk leads to one potential kernel. Where a silk receives no viable pollen, the corresponding kernel may not develop.

Block planting:

  • Places more pollen-producing plants around each cob
  • Improves the likelihood of pollen reaching all silks
  • Produces more complete kernel fill
  • Reduces dependence on one wind direction
  • Works better than a single narrow row

Where only a small number of plants are grown, gentle hand pollination may improve cob fill.

Can Corn Seedlings Be Transplanted?

Corn can be transplanted while seedlings are young, but direct sowing is generally preferred.

The roots grow rapidly and can be disturbed when seedlings are removed from small cells. Transplant shock may delay growth, particularly where the roots have become tangled or pot-bound.

Where transplanting is necessary:

  • Use individual deep cells
  • Transplant while seedlings are small
  • Keep the root ball intact
  • Harden plants gradually
  • Water immediately after planting
Direct sowing usually produces the most efficient establishment. Transplanting is mainly useful where the outdoor season is short or early seedling protection is required.

Can Corn Be Grown in Pots?

Corn can be grown in large containers, but it requires substantial soil volume, water, nutrients and enough neighbouring plants for pollination.

A single corn plant in a small pot is unlikely to produce a well-filled cob.

Container Requirements

Use a broad, stable container that can hold several plants together.

  • Choose at least 40–50 cm of soil depth
  • Provide substantial total soil volume
  • Use unrestricted drainage holes
  • Position the container in full sun

Container Management

Container-grown corn dries quickly and requires close fertility management.

  • Plant several corn plants together
  • Water deeply and frequently
  • Support tall plants in windy locations
  • Hand-pollinate where plant numbers are low

How Long Does Corn Take to Grow?

Corn commonly requires approximately 70–110 days from sowing to harvest, depending on variety and growing conditions.

Corn Group Typical Period General Characteristics
Early sweet corn Approximately 65–80 days Selected for relatively quick maturity in short growing seasons.
Mid-season sweet corn Approximately 80–95 days Common maturity range for many garden and market varieties.
Late sweet corn Approximately 95–110 days Requires a longer period of sustained warm weather.
Ornamental or dry corn Often 100 days or longer Allowed to remain on the plant until kernels and husks mature fully.

Maturity varies with soil temperature, air temperature, sunlight, irrigation, fertility, plant population and the stage at which the crop is harvested.

Watering and Feeding Corn

Corn develops tall plants and substantial leaf area, making reliable water and fertility important throughout the crop.

The most critical watering periods are:

  • During germination and seedling establishment
  • During rapid stem and leaf development
  • When tassels and silks are forming
  • During pollen release and pollination
  • While kernels and cobs are filling

Water deeply enough to moisten the active root zone. Shallow watering encourages surface roots and may leave plants vulnerable during hot weather.

Corn generally responds to adequate nitrogen during early growth, followed by balanced nutrition as flowering and cob development begin.

Water stress during pollination can permanently reduce cob fill. Once silks have dried without receiving pollen, missing kernels cannot be restored later.

How to Tell When Corn Is Ready to Harvest

Sweet corn is harvested at the milk stage, when the kernels are plump and release a milky liquid when pressed.

Signs that sweet corn is ready include:

  • The silks have turned brown and dry
  • The cob feels full through the husk
  • The tip has filled with developed kernels
  • The kernels are plump and brightly coloured
  • A pierced kernel releases milky liquid

Clear liquid generally indicates an immature cob. Thick or doughy contents indicate that the kernels have passed the ideal fresh-eating stage.

Check one cob before harvesting the full block. Maturity can vary between plants, planting dates and positions within the crop.

When to Harvest Sweet Corn

Sweet corn is usually ready approximately two to three weeks after the silks first appear, although temperature and variety affect the exact period.

Harvest during the cooler part of the day where possible. Hold the cob firmly, pull it downward and twist it away from the stalk.

Standard sugary corn should be used or chilled promptly because sugar begins converting to starch after harvest. Supersweet corn retains sweetness longer but still provides its best quality when freshly picked and cooled quickly.

When to Harvest Glass Gem and Dry Corn

Corn intended for mature kernels should remain on the plant until the husks become dry and papery and the kernels are hard.

Harvest before prolonged wet weather where mature ears could develop mould or begin deteriorating.

After picking:

  • Remove or loosen the outer husks where appropriate
  • Dry the cobs in a protected, well-ventilated location
  • Prevent access by rodents and insects
  • Confirm kernels are fully dry before storage

How Many Cobs Does a Corn Plant Produce?

Many sweet corn varieties produce one main cob per plant, while vigorous plants may produce a second smaller cob under favourable conditions.

Cob number depends on:

  • Variety
  • Plant spacing
  • Soil fertility
  • Water availability
  • Sunlight
  • Pollination
  • Overall plant health

A smaller number of well-filled cobs is generally more valuable than several poorly developed ears.

Can Different Corn Varieties Be Grown Together?

Different corn varieties can cross-pollinate because their pollen is carried by wind.

Cross-pollination is particularly important when growing supersweet corn. Pollen from standard sweet, ornamental, popcorn or field corn can reduce the tenderness and sweetness of SH2 kernels during the same season.

Isolation options include:

  • Growing only one corn type at a time
  • Separating varieties by sufficient distance
  • Staggering planting dates so flowering does not overlap
  • Using large physical separation where available

Using Fresh Sweet Corn

Sweet corn may be prepared in a wide range of fresh and cooked dishes.

Boiled

Whole Sweet Corn Cobs

Cook fresh cobs briefly in boiling water until the kernels reach the preferred tenderness.

Steamed

Tender Corn Kernels

Steam cobs gently to retain fresh flavour and texture.

Grilled

Barbecued Corn

Grill cobs in or out of the husk for browned kernels and a deeper flavour.

Roasted

Oven-Roasted Cobs

Roast whole cobs or cut sections with butter, herbs and seasonings.

Fresh Kernels

Salads and Salsas

Cut kernels from cooked or suitably prepared cobs for salads, salsas and mixed dishes.

Frozen

Whole Cobs or Kernels

Blanch and freeze corn using an appropriate recognised food-preservation method.

Common Corn Growing Problems

Poor Germination

Cold soil, waterlogging, deep sowing and compacted beds can cause seed to rot or emerge unevenly.

Missing Kernels

Incomplete pollination commonly causes irregular gaps along the cob.

Small Cobs

Crowding, low fertility, moisture stress and insufficient sunlight can limit cob size.

Weak or Falling Plants

Shallow roots, wind exposure, waterlogging or severe drought can reduce plant stability.

Damaged Cob Tips

Caterpillars and other corn-feeding pests may enter through the silks and damage kernels.

Dry or Tough Kernels

Sweet corn becomes starchy and firm when harvested after the ideal milk stage.

Packet and Bulk Corn Seeds

Home and Small-Scale Growers

Smaller seed quantities are suitable for household gardens and growers comparing several corn types.

  • Trial traditional and supersweet corn
  • Grow colourful specialty cobs
  • Use small blocks for effective pollination
  • Make successive sowings where space permits

Market Gardens and Commercial Growers

Larger quantities can be more economical for growers producing scheduled crops for markets, retailers, processing or farm-gate sales.

  • Suitable for repeated field sowings
  • Larger quantities available across selected varieties
  • Useful for fresh-market and processing production
  • Compare maturity, cob uniformity and saleable yield
Compare seed value by the finished crop. Germination, plant population, pollination, cob uniformity, harvest labour and saleable yield all influence the true cost of corn production.

Important Considerations for Commercial Growers

Commercial corn production requires varieties suited to the planting season, market specification, harvest system and required sweetness type.

Emergence and Vigour

Uniform establishment supports consistent flowering, pollination and cob maturity.

Sweetness Type

Traditional sugary and supersweet varieties require different handling and isolation strategies.

Cob Uniformity

Consistent length, diameter, kernel rows and tip fill improve packing and market presentation.

Harvest Window

Varieties that hold quality in the field provide more flexibility during large harvests.

Post-Harvest Handling

Rapid cooling helps retain sweetness, tenderness and shelf quality after picking.

Market Demand

Select standard sweet, supersweet, coloured or processing types according to established customer requirements.

Conduct local production trials before large sowings. Germination, maturity, plant height, cob number, sweetness and disease response can vary with planting date, soil, irrigation and climate.

Frequently Asked Questions

Is corn easy to grow?

Corn is relatively straightforward where warm soil, full sun, fertile ground and reliable water are available. Effective block planting and pollination are essential for well-filled cobs.

How do you grow corn from seed?

Direct sow corn approximately 2–4 cm deep into warm, prepared soil. Plant several short rows together, maintain moisture and support vigorous growth with adequate fertility.

When should corn be planted in Australia?

Corn is generally planted from spring through early summer after frost risk has passed. Tropical growers often plant during the drier months.

When should corn be planted in Victoria?

Corn is generally planted in Victoria from October to January after the soil has warmed and frost risk has passed.

When should corn be planted in Melbourne?

Around Melbourne, corn is usually planted from October through January. Early and mid-season varieties are useful where the warm season is limited.

When should corn be planted in New South Wales?

Coastal New South Wales growers commonly plant from September to January. Inland growers should wait until frost risk has passed.

How deep should corn seeds be planted?

Plant corn approximately 2–4 cm deep. Use shallower planting in cool or heavy soil and slightly deeper sowing where the surface dries quickly.

How long do corn seeds take to germinate?

Corn commonly germinates within approximately 6–14 days. Warm soil supports faster emergence, while cold or saturated conditions can cause poor establishment.

Should corn seeds be soaked before planting?

Soaking is generally unnecessary. Sow dry seed into suitably warm, moist soil and avoid waterlogging.

How far apart should corn be planted?

Space most sweet corn plants approximately 20–30 cm apart, with 60–75 cm between rows. Larger varieties may require additional room.

Why should corn be planted in blocks?

Corn is wind pollinated. Blocks of several short rows allow pollen to move between plants more effectively than one long row.

Can corn seedlings be transplanted?

Yes, but direct sowing is generally preferred. Transplant young seedlings before they become root-bound and keep the root ball intact.

Can corn be grown in pots?

Yes, but corn requires very large containers, substantial soil volume and several neighbouring plants for pollination. Hand pollination may be needed.

How long does corn take to grow?

Most corn requires approximately 70–110 days from sowing to harvest. Early varieties mature sooner, while ornamental and dry corn generally requires longer.

How many cobs does one corn plant produce?

Many varieties produce one main cob, while vigorous plants may form a second smaller cob. Variety, spacing, water and fertility influence cob number.

How do you know when sweet corn is ready to harvest?

The silks should be brown and dry, the cob should feel full and a pressed kernel should release milky liquid.

When should sweet corn be picked?

Pick sweet corn at the milk stage, usually around two to three weeks after the silks first appear. Check a kernel before harvesting the complete crop.

Can corn be harvested more than once?

Individual plants may produce more than one cob, but the plant does not regrow a new crop after all ears mature. Successive sowings provide a longer harvest season.

What is the difference between sweet corn and supersweet corn?

Traditional sweet corn generally carries the SU1 sugary gene, while supersweet corn commonly carries the SH2 gene and produces sweeter kernels that retain quality longer after harvest.

Is Grampian corn the same as Max supersweet corn?

No. Grampian is an SU1 traditional sweet corn hybrid, while Max is an SH2 supersweet hybrid developed for greater sweetness and longer post-harvest eating quality.

Is Grampian corn the same as Golden Bantam?

No. Both provide traditional sweet corn characteristics, but Grampian is a modern F1 hybrid and Golden Bantam is an open-pollinated heirloom variety.

Can Grampian and Max corn be planted together?

They should not flower at the same time. Pollen from Grampian can reduce the sweetness and tenderness of Max supersweet kernels.

Can Glass Gem corn be eaten as sweet corn?

Glass Gem is generally grown to full maturity for its colourful hard kernels rather than harvested as tender supersweet corn.

Can sweet corn be frozen?

Yes. Sweet corn may be frozen as whole cobs or cut kernels. Use an appropriate blanching, cooling and freezing method.

Can corn seed be saved?

Seed may be saved from suitable open-pollinated corn where cross-pollination is controlled. Seed collected from F1 hybrids will not reliably reproduce the original variety.

Are all corn seeds untreated?

No. Corn seed may be treated or untreated depending on the product and seed lot. Review the individual product specifications before ordering.

Can treated corn seed be eaten or used for sprouts?

No. Chemically treated planting seed must not be eaten, fed to animals or used for sprouts or microgreens. The mature corn crop is grown for its normal intended harvest.

Corn seeds for Australian growers

Grow Corn in Packet or Larger Quantities

Seedmart supplies corn seed for household vegetable gardens, market gardens and commercial field production. Choose traditional yellow sweet corn, premium supersweet hybrids and colourful specialty corn according to the required flavour, maturity and harvest use.

Review the individual product pages for available pack sizes, sweetness type, seed treatment, planting guidance and variety-specific information before ordering.