Mammoth Improved Onion - 100 seeds
Mammoth onions are a 'long season' onion therefore sowing should be done during January and February. Sow using a seed tray and a good seedling compost, we favour John Innes No. 1 for sowing, but if you are unable to obtain a good supply, one of the soil-less composts can be used.
Cover the seeds once sown with 0.6cm of the same compost which has been put through a fine sieve. At a temperature of 55F (12.8C) germination should take approximately two weeks. The compost should be kept moist during this period. Avoid germinating the seeds at a higher temperature or other than greenhouse conditions. If you have problems with keeping the temperature in the greenhouse, which during January can be quite difficult, we suggest that you delay sowing to late February.
Once the seedlings are approximately 1.75cm above the soil surface 'crook stage' transplant into a stronger potting compost John Innes No. 2 or soil-less type, pots or boxes can be used but the best results are obtained from single potted plants. This stage is very critical, especially if the weather is dull and dark, watering should be kept to a minimum during these times, a spray with Benlate fungicide after potting can prevent botrytis (damping off).
When to harvest, here again much has been written on this subject, we have done many experiments into this and have found that best results for good store onions is to pull while still a little growth in the tops. This will be from mid August onwards but before second week in September.
For the show bench allow approximately ten days before the show day for the preparation. For kitchen or show take the top off approximately 6in (15cm) above the bulb, cut off the root and any split off decayed skin, wipe the bulbs with a soft damp cloth to remove any soil. Place the onions on a bench in a greenhouse or shed with plenty of ventilation and sunlight. For kitchen use leave on the bench for approximately two weeks to dry, then store in boxes, or string bags in a frost free, cool and dry area.
Exhibitors will, after seven days from harvesting, be able to bend the top of the onion over, this can be secured with a rubber band or raffia.