Direct-Sowing Corn in Alberta: Honest Expectations & How to Succeed

Pick the right variety

The single most important decision is variety selection. Long-season corn (90+ days) won’t finish in Alberta in most years — you’ll get tall stalks and immature ears. Look for varieties under 75 days to maturity. Even 65-day varieties give you margin for cool weather slowing things down.

• Polka F1 (66 days): Sugary-enhanced, holds sweetness post-harvest. Excellent Alberta choice.
• Sugar Buns F1 (70 days): Sweeter than older heritage varieties, reliable in cool weather.
• Earlivee (66 days): Open-pollinated heritage. Less sweet than modern hybrids but you can save seed.
• Honey Select F1 (~79 days): Triple-sweet, holds sugar 7–10 days post-harvest. At the edge for Alberta — only worth trying in a sheltered south-facing spot in southern AB or central AB with reflected wall heat.

When and where to plant

Wait for soil at 15°C — usually third or fourth week of May. Corn seed in cold soil rots faster than beans. Pick the warmest, sunniest spot you have, ideally against a south-facing fence or building wall to capture reflected heat. Avoid low spots where frost settles. Wind-sheltered locations help — tall corn topples in summer thunderstorms.

Block planting (the pollination rule)

Corn is wind-pollinated. Pollen falls from the tassels at the top of the plant and needs to land on the silks emerging from each ear. A single long row pollinates poorly — pollen blows away on the wind without hitting silks. The result: ears with scattered missing kernels.

Plant in a block of at least 4 rows by 4 plants per row (16 plants minimum). A 6×6 or 8×8 block pollinates better still. If you only have space for a single row, hand-pollinate by shaking tassels over silks each morning when pollen is shedding.

How to plant

• Plant 2.5 cm deep, 25 cm apart in rows 75 cm apart.
• Sow 2 seeds per spot and thin to the strongest after emergence.
• Keep varieties separated — if you grow two types in the same block, they’ll cross-pollinate and the kernels can be starchy and odd-coloured. Plant 75 metres apart, or stagger planting dates by 14 days, or grow only one variety per year.
• Don’t mix sweet corn with field corn or popcorn at all — cross-pollination ruins the sweet corn.

Watering and feeding

Corn is a heavy feeder and a thirsty crop. Side-dress with compost or fish emulsion when plants are knee-high (about 6 weeks after sowing) and again at tasseling. Water deeply — 2.5–4 cm per week — especially during silking and ear development. Drought stress at silking is the difference between a full ear and a row of half-empty ears.

Knowing when to harvest

Watch the silks. About 18–24 days after silks first appear, ears are ready. Silks turn brown and dry at the tips. Peel back a small section of husk and press a kernel with your thumbnail — if the liquid that comes out is milky-white, the corn is ready. If it’s clear, it’s too early. If there’s no liquid, it’s too late and starchy.

Pick early in the morning, then eat or process the same day. Sugars start converting to starch the moment the ear comes off the stalk — modern sugary-enhanced varieties hold their sweetness 7–10 days, but heritage varieties can lose half their sweetness in 24 hours.