Why Grow Sweetcorn
The decision to grow sweetcorn can be complex, as it requires consideration of various factors including taste, health benefits, cost, harvest size, harvest timing, and organic availability. Despite its lower score on this rating system—due to its space requirements and relatively small yield—sweetcorn remains a favourite. The exceptional flavour of freshly harvested sweetcorn is unmatched, and the joy of harvesting it with family adds to its appeal. The sugars in sweetcorn quickly convert to starch, making the immediate consumption of freshly picked cobs a delightful experience.
How Many to Plant
For a main crop variety such as 'Incredible', each plant typically yields 2 cobs, maturing 1-2 weeks apart. To achieve a staggered harvest over approximately 6 weeks, one should plant no more than three successions. Calculate the number of cobs desired during this period and divide by 2 to determine the number of plants needed. Good pollination occurs with a block of plants, ideally arranged in a 3x3 formation, making it essential to grow more than one plant for most families. If sweetcorn is primarily a treat, dedicating 1m² may suffice unless there’s ample space or a desire to freeze surplus.
Suitability for Different Growing Environments
Sweetcorn thrives in well-drained, fertile soil with a pH between 6.0 and 6.8. It prefers a warm, sunny location, requiring full sun exposure for optimal growth. Ensuring the soil is rich in organic matter and drains well is crucial, as sweetcorn is prone to rot in waterlogged conditions.
Lifecycle
Sweetcorn is typically sown in mid to late spring, ideally after the last frost date. Although young plants can withstand light frost, it’s best to plant them when they are more established, about 4 weeks before the last frost date for the first succession. Rapid growth characterises sweetcorn, but young plants are vulnerable to strong winds; thus, a sheltered spot or windbreak is advisable for small plantings.
Male flowers develop at the top of the plants, dropping pollen to fertilise the hairs at the end of the developing cobs, leading to swelling once fertilisation occurs.
Sowing and Harvesting Periods
For a single succession, mixing varieties that ripen at different times is an option, although typically one packet of seeds is used.
First Earlies
Sweetcorn should be sown after the last frost date. Early crops may require protection under cover, with March sowing indoors and transferring to the ground by mid-April. While direct ground sowing is possible, it often competes for space with more valuable crops, making container growing a preferred option.
Options for container growing include:
- Full-term growth in a polytunnel for an early harvest.
- Growth until after pollination in a polytunnel, then moving outdoors.
- Starting in a polytunnel until the last frost, then transitioning outside.
Main Crop
Start the main crop one month before the last frost date. While others may plant earlier, cooler weather and wind can hinder growth, often resulting in lower yields. This timing maximises the likelihood of multiple cobs ripening with good quality.
Late Crop
A later crop can be sown 2-3 weeks after the main crop, but with fewer plants due to increased risks of adverse weather affecting yields.
Recommended Varieties
To minimise the risk of cross-pollination, it’s advisable to avoid planting multiple varieties in the same location. This risk extends to different successions if growing conditions favour the late crop.
How to Sow
Two primary sowing methods exist, although direct sowing in the ground is not recommended by many. Chitting seeds on tissue paper or sowing directly into modules is preferred, with seeds sown 2 cm deep.
Choosing module types depends on confidence in planting young plants after 3-4 weeks. Six-cell trays are effective, allowing for an additional week of growth in case of poor weather. Root trainers provide flexibility, enabling early starts and accommodating weather changes.
How to Prick Out/Pot On
When chitting seeds, create a depression in compost, place the sprouted seed, and lightly cover it without compacting the compost. The orientation of the seed doesn’t need to be a concern.
Where to Plant
Sweetcorn flourishes in bright, sheltered areas with well-drained, organic-rich soil. When interplanting with squash, planting sweetcorn two weeks earlier ensures it grows above the squash by the time they meet.
How Many to Plant
Assuming first early successions yield one cob and main crops yield two, calculate accordingly.
How to Plant and Spacing
Plants should be gradually hardened off unless they are under cover. On sandy soil, spacing of 12-14 inches with clusters of four plants is recommended, ideally interplanted with squash. Clumping aids in pollination, while blocks of plants should not be excessively large for ease of harvesting.
If planting in blocks proves challenging, such as when creating a double row along a bed's edge, acceptable but less than optimal pollination can still be achieved.
Protecting and Supporting Plants
In the event of inclement weather, covering plants with fleece on a frame can offer protection. Established sweetcorn typically requires no support unless in windy areas. Temporary support can be provided using fence pins or bamboo canes.
For additional security, consider planting deeper than soil level or earthing soil around the stems.
How to Feed and Water
Sweetcorn is best planted in beds previously growing field beans, with a mulch of well-rotted horse manure, compost, or mushroom compost applied. Initial watering is necessary until plants are well established. Once established, watering may be required every 1-2 weeks, increasing to twice a week as cobs develop.
Fertilisation may be needed, preferably with a general-purpose high-nitrogen feed, such as chicken manure or tomato fertiliser during cob development.
How to Prune/Manage While Growing
Minimal management is required, aside from providing support and possibly hand-pollination. Side shoots may develop but are typically non-viable and can be ignored or removed.
How and When to Harvest
Harvesting begins when the tassels at the tops of cobs turn brown. Feel the cobs to check their development, peeling back the green sheath for kernel assessment. Cobs should be snapped off and consumed fresh, either raw or lightly boiled. Regular checks are essential due to the short harvest period.
How to Store
Sweetcorn is best enjoyed fresh, with no need for storage.
How to Eat/Cook
Fresh sweetcorn can be eaten raw or lightly boiled.
Dealing with Pests and Disease
Birds and rodents are the primary pests, along with the risk of cobs over-ripening and splitting. To mitigate this, cobs should be harvested promptly once ripe.
When and How to Remove Plants
Plants can be removed and chopped for compost or cut at the roots and left in the ground to decompose. Leaving roots intact enriches the soil, provided they’re well-spaced for subsequent planting.
What to Plant Before
Various crops such as lettuce, spinach, radish, field beans, and most brassicas can be planted and harvested by mid-May.
What to Plant After
Post-harvest options are limited, primarily consisting of alliums (garlic, overwintered onions, salad onions), corn salad, claytonia, or field/broad beans.
What to Interplant With
Sweetcorn pairs well with winter or summer squash and can be underplanted with dwarf French beans, lettuce, or spinach. True interplanting should consider the symbiotic relationships between crops, enhancing growth, pest protection, and nutrient accessibility.
Interplanting should not significantly reduce the primary crop’s density, but the interplanting density may be reduced to maintain balance and optimise benefit.
