Black Oil Sunflower Seeds (BOSS) are a widely cultivated variety of Helianthus annuus, chosen for their high oil content and thin shells. These characteristics make them a preferred food source for wild birds and a valuable crop for oil production. BOSS seeds are notably denser and richer in fat than common striped sunflower seeds, offering excellent nutrition. Growing BOSS is a straightforward process that rewards the gardener with a high yield, provided the plant’s specific needs are met.
Preparing the Planting Location
Selecting the right environment is the first step toward a healthy black oil sunflower crop. These plants thrive in full sun, requiring a minimum of six, but preferably eight, hours of direct sunlight daily to support robust growth and large seed heads. BOSS plants typically reach heights of five to seven feet. The planting area should offer protection from strong winds or allow for staking to prevent heavy heads from toppling over later in the season.
The soil should be well-draining, ideally loamy, to prevent the deep taproot from sitting in excess moisture. Black oil sunflowers are adaptable, but amending poor soil with a few inches of finished compost or aged manure before planting is beneficial. This organic matter improves soil friability and water infiltration, which is important for the plant’s extensive root system. Avoid high-nitrogen fertilizers at this stage, as too much nitrogen encourages excessive leafy growth rather than seed production.
Sowing the Seeds
Timing the planting correctly is crucial for maximizing seed yield. Sow seeds directly into the garden only after the last danger of frost has passed. The soil temperature should be consistently warmed to at least 50°F, or preferably between 60°F and 70°F. Plant the relatively large seeds at a depth of one to two inches to ensure proper moisture contact and help the emerging seedling shed its tough seed coat.
Proper spacing allows each plant enough room to develop a substantial seed head. Plant seeds eight to twelve inches apart, though wider spacing up to twenty-four inches is used for the largest possible heads. If seeds are planted closer together, thinning the weaker seedlings is necessary once the plants develop a few true leaves. To ensure a continuous supply rather than a single large harvest, stagger planting dates every few weeks throughout the late spring and early summer.
Nurturing Growth and Protection
Once seedlings emerge, care shifts to consistent watering and managing potential threats. Newly germinated plants require regular moisture; water daily or twice daily in hot, dry weather until they are well-established. After the young plants develop a stronger root system, transition to deep, infrequent watering. Aim for about an inch of water per week, especially as the large flower heads begin to form.
Avoid excessive fertilization, as the goal is seed production, not foliage. If a soil test indicates a deficiency, use a low-nitrogen, balanced fertilizer sparingly. Thinning should occur when seedlings have two or three pairs of true leaves, removing the smaller or weaker plants to leave the strongest ones at the final spacing. Tall varieties need staking when they reach about three feet in height to support the heavy mature heads, particularly in windy areas.
Pest management is important, as developing seeds attract common garden pests. Birds, such as finches and sparrows, feast on the seeds as they ripen, and squirrels may attempt to harvest the entire head. Applying physical barriers, like fine mesh bags or netting, over the maturing flower heads is the most effective protection from wildlife. Insect pests like sunflower moths or aphids may appear, managed with a strong jet of water or by introducing beneficial insects.
Harvesting and Storage
Identifying the right time to harvest is essential for collecting viable, plump seeds. The flower heads are ready when the back of the head turns from vibrant green to pale yellow or brown, and the ray petals have dried and dropped. At this stage, the seeds inside should look plump and fully colored, and the head will naturally begin to droop forward.
To prevent premature consumption by birds and squirrels, cover the flower heads with a paper bag or fine mesh netting once the petals begin to fade. When ready, cut the head from the stalk, leaving about a foot of stem attached. The heads must be thoroughly dried before seeds are removed to prevent mold during storage. Hang the heads upside down in a warm, dry, and well-ventilated area for several weeks.
Once fully dry, the seeds can be easily rubbed or brushed out of the head. Store the cleaned seeds in an airtight container, such as a glass jar, in a cool, dry, and dark location. Properly dried and stored seeds maintain their quality and high oil content, ready for use as bird feed or for planting the following season.