When To Sow: March-April (indoors); May-June (direct seed) Harvest: August-October
Germination: 7 to 14 days Full sun.
Brussels sprouts prefer well-drained soil, ideally with a pH between 6.0-7.5. They perform best in soils high in organic matter.
Starting Indoors: Sow in flats or modules from March until early April at a seed depth of ¼”. (6 mm.) deep. Cover lightly and firm. Once the seedlings have at least two true leaves, transplant into individual pots. Harden off gradually in April or early May for transplanting outdoors.
Direct Seed: For a later crop, direct seed outdoors from early May until the first week in June. Thin the seedlings as soon as they appear.
Space rows 3 ft. (91 cm.) apart and plants 18 - 24 in. (46 – 61) cm apart.
Maintenance
Make sure to give them consistent water throughout its growing season. Also make sure the soil is firm around them. Brussels will produce sprouts that are open rather than tight buttons if their roots are in loose soil.
Plant these in an area that’s protected by wind, if your site or garden is open place some stakes around the plant and attach netting to these stakes that will act like a small wind break.
Water well and often. Mulch is great for Brussels sprouts – it not only helps with water retention, it also helps suppress weeds.
Later in the year (early-mid September), add additional compost or soil around the base. Mounding it up well will provide additional support and protection for your plant.
Here in the UK, the wood pigeons love, love, LOVE to eat our brassicas. Make sure you net your plants or you’ll find they beat you to the crop. (Netting also helps protect against the cabbage butterfly.)
Brussels sprouts and other brassicas love their nitrogen. I’ve found it useful to prepare the ground with manure before planting and then work in some blood fish bone later during the growing season. I like to add some chicken pellets during June – July (just keep them away from the base of the plant).
Harvesting
The sprouts will form from the base of the plant upwards and will continue all the way up to the top of the plant. Pick when about walnut size, starting from the bottom up. Twist until they break away from the plant or simply push downwards. As you work your way up the stem, remove the yellowing leaves. This will encourage the plant to continue growing upward, producing more leaves (and more sprouts!). Crispus brussels sprouts hold up remarkably well on their stalks, which means they can be harvested as you need them over a long period in the fall. (There’s no need to harvest them all at once!)
Companion Planting
Brussels grow well with other brassicas (i.e. broccoli, kale, and cabbage). It also likes tomatoes, spinach, and swiss chard. It benefits from being planted with alliums (onions and garlic).