Sunflower seeds are one of the most popular oilseed crops around the world. Sunflower seeds can be consumed raw, used as birdseed, sprouted for salads and sandwiches, roasted for a snack, or crushed for use in cooking and baking. In addition to their culinary uses, sunflower seeds also offer health benefits due to their high vitamin and mineral content.
When to Harvest Sunflower Seeds
Sunflower seeds are ready to be harvested when the flower heads have turned from green to brown. The best time to harvest sunflower seeds is when the petals have withered and the back of the seed head turns yellow. To ensure a successful harvest, it’s important to wait until most of the seeds on a single plant are ripe before harvesting.
How to Harvest Sunflower Seeds
Harvesting sunflower seeds can be done either by hand or with a mechanical harvester, depending on the size of your crop and desired yield.
When harvesting by hand, wear gloves to protect your hands from any dirt and debris. Cut the stem of each fully mature sunflower head at least four inches below the seed head. The sunflower heads should be free of blemishes and have a golden-brown color when dried. Then, place the cut stems in a bucket or sack for transport.
Once the sunflower heads are harvested, hang them upside down in a warm and dry location to allow for maximum seed drying. After two to three weeks, shake or beat the sunflower heads against a canvas sheet on the ground to release the seeds. The remaining debris can then be removed with a broom.
For larger sunflower crops, a mechanical harvesting system can be used. These machines are designed to separately thresh (or separate) the seeds from the heads. They can also sort out immature seeds and other debris as they harvest.
Seed Preparation for Storage
After harvesting, it’s important to prepare the seeds for storage. This often includes cleaning the seeds, drying them to a moisture content of 5-6%, and sometimes treating them with fungicides to prevent spoilage. Additionally, if seeds are stored for more than one year in a dry state, they should be tested for germination viability prior to planting.
Storage Conditions and Terms
Once the seeds have been prepared, they can be stored. Sunflower seeds are reliably stored only at a humidity of less than 7% and a temperature not exceeding 50°F. At a humidity of 8% and a temperature of 68°F, the maximum storage time is 1.5 months, 50°F – 4.5 months, and at 34°F – more than 6 months. Seeds should never be exposed to sunlight or high temperature for extended periods of time.
How sunflower self-heats
There are four stages of sunflower self-heating;
- The temperature rises to 77°F – the color, smell, and flowability of the seeds do not change.
- Seeds actively breathe, microflora develops intensively, and the temperature rises to 104°F. Seeds are damaged and covered with mold, lose their shine, and acquire an unpleasant odor and bitter taste. Also, the acidity increases, germination deteriorates, and the embankment is compacted.
- When the temperature rises to 131°F, the bitter taste and musty smell of seeds increase, the shells darken, the kernel turns yellow, germination is almost completely lost, and acidity increases significantly.
- Further increase in temperature due to the activity of thermophilic bacteria, acidity doubles from the previous stage, and all seeds are damaged without exception.