Brussels sprouts, a member of the cabbage family, are a cool-weather crop that requires a long growing season. They must be planted early so the small, leafy buds mature during the cooler temperatures of fall and early winter. Starting plants from seed allows the gardener precise control over variety and timing, which is beneficial for a crop that occupies garden space for many months. Sowing the seed requires specific attention to detail to guarantee a robust stand and healthy future plants.
Determining the Ideal Number of Seeds Per Hole
The standard recommendation for directly sowing Brussels sprout seeds is to place two or three seeds into each designated planting spot. This practice acts as an insurance policy against variable seed viability and environmental threats. Since even high-quality seed lots rarely achieve 100% germination, using multiple seeds ensures at least one seedling emerges in every location.
This technique guards against failure from older or improperly stored seeds, or those targeted by soil-borne pathogens or pests. Losing one of three seedlings still leaves a viable plant, while losing the only seed means the planting hole is empty.
Using two or three seeds is efficient because the tiny seeds do not require significant resources to sprout. Planting more than three seeds per hole is unnecessary and leads to a dense cluster of seedlings that compete too aggressively. This excessive crowding makes the subsequent step of thinning more difficult.
The goal of this multi-seed method is to guarantee a single, strong plant in the intended location. Once seedlings emerge, the gardener assesses their health and vigor to select the single best specimen to continue growing. This initial over-seeding sets the stage for a strong, uniform row of plants.
Setting Up the Physical Planting Environment
The physical environment of the seed hole is important for successful germination and initial growth. Brussels sprout seeds should be planted shallowly, covered with only one-quarter to one-half inch of fine soil. Planting too deeply prevents the small sprout from having the energy to push through the soil and reach the necessary light.
The final spacing between adult plants must be substantial due to the Brussels sprout’s tall growth habit and large leaf canopy. The large, paddle-shaped leaves are necessary for the extensive photosynthesis required to produce a long column of sprouts. This means planting holes must be spaced widely, even though the seed itself is small.
Within the planting row, final plants should be spaced between 18 and 24 inches apart, though some varieties benefit from up to 36 inches. Brussels sprouts grow upward, often reaching three feet or more in height, making adequate in-row spacing crucial. This wide distance promotes optimal air circulation around the developing stalk, which helps prevent fungal diseases.
The distance between rows should range from 30 to 36 inches. This generous spacing provides room for the gardener to work and ensures that sunlight can penetrate to the lowest leaves on the plant. Sunlight feeds the entire plant, fueling the development of the sprouts along the stem, which maximizes both the quantity and quality of the finished crop.
Thinning Seedlings After Germination
Thinning the seedlings is the necessary follow-up to the multi-seed planting approach. The process must be executed promptly once the seedlings have established their first set of true leaves and have grown to a height of about four to six inches. True leaves are the second set of leaves to emerge, following the initial seed leaves, known as cotyledons.
Thinning at this stage ensures the remaining plant has minimal competition, allowing it to quickly establish a robust root system. Delaying the thinning allows the multiple seedlings to become root-bound and intertwined, making it harder to remove the extras without damaging the keeper plant. Competition for light, water, and nutrients will quickly stunt the growth of all plants in the cluster.
The correct technique for thinning is to use small, sharp scissors or snips to cut the unwanted seedlings off at the soil line. It is recommended to snip the stem rather than attempting to pull the plants out of the ground. Pulling a seedling can disturb or damage the delicate, shallow roots of the adjacent, intended plant, stressing the survivor.
The gardener must carefully choose the single strongest seedling from the cluster, selecting the one that appears the most vigorous, has the thickest stem, and displays the best color. After snipping the others, only one plant should remain in the planting spot, ensuring it receives all available resources to grow into a large, productive stalk. The discarded seedlings can be left on the soil surface to decompose.