Onions

Question 1

What are the temperature preferences of onions?

Answer 1

• 13-24C
• Many are frost tolerant and can overwinter outside
• There are two main types, autumn and spring.

Question 2

Explain the soil and site selection for onions.

Answer 2

• Open, sunny site
• Well-drained, fertile soil
• Prepare well in advance, digging over and incorporating plenty of well-rotted organic matter
• Do not like freshly manured ground
• Low nitrogen requirements.

Question 3

What are the two times for sowing and harvesting onions?

Answer 3

• Spring sown are harvest in late summer (take 12-18 weeks to mature)
• Autumn sown are planted in late summer or early autumn, overwinter outside, and take up to 42 weeks to mature.

Question 4

Explain sowing of onion seeds.

Answer 4

• Secondary cultivation of soil two weeks before sowing
• V-shaped drill, 13mm deep
• Rows 30cm apart
• Once germinated, thin to 5cm apart.

Question 5

What are onion sets?

Answer 5

Specially raised small onions ready for planting out.

Question 6

What are the advantages and disadvantages of onions from sets and seeds?

Answer 6

Sets

• Mature before those from seed
• More resistant to mildew and onion fly
• Tend to bolt
• More expensive than seeds.

Seeds

• Take longer to mature than sets
• More susceptible to mildew and onion fly
• Less likely to bolt
• More cultivars to choose from
• Cheaper option than sets.

Question 7

Explain sowing spring-sown onions from sets.

Answer 7

• Plant sets in well-prepared seedbed in April
• Place so nose is just above ground
• Space sets 30cm apart
• Cover with mesh to avoid birds pulling them up
• Weed regularly.

Question 8

Explain the harvesting of onions

Answer 8

• Onions can be harvested at any time once they’re ready.
• If you’re storing them, let the foliage die down naturally.
• Spring sown onions keep better than autumn sown ones.
• Once ripened, lift and dry for storing (plait or place in single layers in wooden boxes and store in a dry shed).

Question 9

Name a pest and a disease of onions, including symptoms and control methods.

Answer 9

Onion Fly

• White burrowing larvae eats bulbs
• Yellowing leaves, tunnels in bulbs, death of plant
• Place collars around plants in May and August; Grow sets instead of seeds; Destroy infected plants; Grow resistant cultivars; fleecing.

Onion White Rot

• Fungal disease that can last in soil for 15 years
• Plants suddenly die, leaves yellow, roots rot off; white cottony-looking fungal growth with black poppy seed-like sclerotia at base and sides of bulb
• Grow from sets rather than seeds; buy from reputable source; use long rotation and avoid infected ground for at least 8 years; grow resistant cultivars; good hygiene.

Question 10

Name:

• 2 autumn seed onions
• 2 autumn sets
• 2 spring seed onions
• 2 spring sets

Answer 10

Autumn Seeds

• ‘Senshu Yellow’
• ‘Keepwell’ F1

Autumn Sets

• ‘Radar’
• ‘Autumn Gold Improved’

Spring Seeds

• ‘Caribo’
• ‘Red Baron’

Spring Sets

• ‘Sturton’
• ‘Stuttgarter Giant’.