What Should I Feed Brussels Sprouts and When?

Brussels sprouts are heavy feeders with a growing season that can last seven to nine months from sowing to final harvest — one of the longest of any vegetable crop. During this time they have a substantial need for nutrients, particularly nitrogen to support their large leaf and stem growth. Getting the feeding programme right produces bigger plants with more well-formed sprouts; under-feeding produces small, unproductive plants while the right balance of nitrogen, phosphorus, and potassium gives both good plant bulk and tight, flavourful sprouts.

Soil preparation before planting

The foundation of a good feeding programme is well-prepared soil. Dig in a generous amount of well-rotted garden compost or manure in autumn or winter before the brassica bed is to be used in spring. This slow-release organic matter provides a steady background supply of nutrients throughout the season. Brassicas generally prefer a firm seedbed — do not over-cultivate after incorporating organic matter; firm the ground well before planting.

Basal fertiliser at planting time

Rake in a balanced granular fertiliser (such as growmore or a brassica-specific feed) at the rate recommended on the packet just before transplanting. This provides a ready supply of phosphorus and potassium for root establishment alongside some nitrogen for initial growth. If you have already incorporated good compost, a light application of balanced fertiliser is sufficient at this stage.

Nitrogen top-dressing in midsummer

Apply a nitrogen-rich top-dressing around the base of each plant in late June or July. High-nitrogen fertilisers such as sulphate of ammonia, dried blood, or a liquid high-nitrogen feed used at the higher end of the recommended rate work well. This boost promotes the substantial vegetative growth the plant needs to carry a good crop of sprouts in autumn and winter. Scatter granular fertilisers around the plants and hoe in or water in well.

Avoiding over-feeding in late summer

Stop applying nitrogen-rich feeds by mid-August. Feeding nitrogen late in the season promotes soft, leafy growth at the expense of tight sprout formation — late nitrogen feeds are one of the causes of loose, open sprouts. If the plant looks healthy and well-grown in August, no further feeding is normally needed. If plants look pale or stressed, a light balanced feed (not high-nitrogen) in August can help without causing the loose-sprout problem.