Cruciferous plants (Brassicas)
These resilient plants, including various types of cabbage, thrive in cooler climates. They can withstand excessive sunlight and heat, blooming prematurely or halting growth. Depending on our local climate, we can typically plant them in the fall, winter, or early spring. Some varieties, like black cabbage or Brussel sprouts, are even harvested in winter.
Cruciferous vegetables can be categorized based on the parts we consume: the leaves (black cabbage, savoy, kale, arugula), undeveloped flower (cauliflower, broccoli, roman cauliflower), or the bulbs (turnip, kohlrabi).
When we start with brassicas, the best is to start with leafy ones, such as black cabbage. They are easy to grow and can be harvested during the entire growing season. We can also consume and cook with fresh, dry, or frozen leaves.
A common problem that occurs with these plants is pest infestation. Whitefly caterpillars can eat an entire crop in a very short time. That is also why growing them during the colder period when these pests are not yet in the garden is essential. Eventually, plants (already from seedlings) will also be covered with the net.
When buying seedlings, it’s crucial to rinse them properly and check the leaves, as they often come with slimes, caterpillars, or other pests already from the shop. This responsible care from the start sets the tone for a successful brassica garden.
Planting and harvesting brassicas
Planting and propagating
When the weather starts to be warm, brassicas tend to grow taller and develop flowers. We can leave one plant for seeds or wait for an entire crop (leafy cabbage) to bloom and create long, narrow seed pods called siliques. Pods with seeds are ready to collect when the pods have a beige color (dry). We can break them carefully, collect only the seeds, or store the entire dry pod. The seeds will fall out by themselves once the pods break.
Brassicas are easy to grow from seeds. We can pre-grow seedlings and transplant them later (when they are about 20 cm long and strong enough), plant them directly in the ground, or leave them to loose their seeds by themselves.
As a rule, these plants need well-nourished, slightly acidic, moist soil. They need a lot of nitrogen, so I put them as number 2 on the crop rotation list after legumes. Nitrogen provides them with their rich, enormous green leaves.
Spacing and sunlight
When planting brassicas, leaving enough space between plants is essential, especially if we grow plants like savoy cabbage, cauliflower, or broccoli. Leafy brassicas can be planted closer.
Tip: Cauliflower is highly sensitive to extreme heat, so covering the nearly mature head with surrounding leaves is helpful for protection. When harvesting broccoli, cutting off the main head allows the smaller side heads to continue growing, providing additional smaller harvests.
Watering
Cruciferous plants need plenty of water. They can also be watered directly on their leaves, as the water quickly runs off.
Harvesting
Based on the type of brassicas we are growing, harvesting will vary. Leafy brassicas can be harvested leaf by leaf during the whole growing season.
Plants from which we consume undeveloped flower harvest when the head is fully developed and firm – we have to be careful not to wait too long because they could bloom. When harvesting broccoli, cutting off the main head allows the smaller side heads to continue growing, providing additional smaller harvests.
Brassicas that grow as a leafy head can be harvested when the head is fully developed and compacted. They can grow smaller than we are used to from the shop, so even if they are smaller, and we see that outside leaves start to dry, it’s anyway time to harvest.
Other types of brassicas, such as turnip and kohlrabi, are ready to harvest when we see the bulb slightly poking from the ground (it has about 2 – 3 inches across) and the leaves are still green and fresh. When the leaves start to turn color to yellow, it’s the last chance to take them out. Leaving them too long in the ground leads to tough, fibrous, and even bitter fruits.
Companion planting and interplanting with Cruciferous plants:
Cruciferous plants need soil rich in nutrients; therefore, it is not advisable to plant them too close to other plants requiring the same soil composition – they could compete. If we grow a lot of brassicas next to each other, we also invite pests.
When interplanting with brassicas, the approach will vary depending on the type. For example, black cabbage and kale grow tall, leaving plenty of space underneath that can be utilized for other plants. In contrast, cauliflower and cabbage develop large leaves that create significant shade, making it better to plant different crops outside the bed (as a border) and not as interplants.
Cruciferous plants grow well with:
- Umbellifers
- beet greens
- leafy greens
- alliums
Cauliflower is an exception because it doesn’t go well with onions.
Cruciferous plants should not be grown alongside:
- nightshades
- gourds
Planting flowers alongside cruciferous vegetables that attract pollinators and beneficial insects is advisable, as they can help control pests. Additionally, aromatic flowers and herbs can mask the scent of brassicas, deterring pests such as hares and deer.
Suitable companion plants include French marigold, parsley, sage, oregano, thyme, mint, yarrow, dill, fennel, chamomile, and nasturtium.
We can plant annuals between or next to the brassicas. For perennials, however, it’s essential to carefully plan their placement or be prepared to transplant them later. When it comes to mint, it’s best to keep it in a pot (without roots reaching the ground) near the bed, as it can spread rapidly and crowd out other plants.)
Harvest times
Broccoli: 60–100 days from seed; 50–85 days from transplant.
Cauliflower: 70–120 days from seed; 50–85 days from transplant.
Cabbage: 80–180 days from seed; 60–105 days from transplant.
Kale: 50–75 days from seed; 30–40 days for baby greens.
Brussels Sprouts: 90–180 days from seed; 80–100 days from transplant.
Kohlrabi: 55–70 days from seed
Collard Greens: 60–85 days from seed