Discover the Life Stages of the Broccoli Plant (and Calabrese), What Each Stage Entails, and the Factors that Disrupt the Growth of Brassicas.
Calabrese Broccoli
The Bottom Line
From sow to harvest, the broccoli plants’ growing stages are
- Seed germination
- Seedling formation
- The vegetative growth stage
- Flowering phase (harvest time)
- The end phase, formerly known as the senescence stage
Carry on reading for an In-depth insight to the Broccoli plants growing stages.
In-depth Insight to the Broccoli Plants Growing Stages
Stage 1: Seed Germination
It all begins with a single seed.
What’s in a seed?
Energy.
In the form of starch, oil, and protein.
Hopefully, it’s all healthy. Because you can get good and bad seeds.
Some diseases can be carried in a seed that can send your broccoli plant directly to the senescence stage – game over!
Despite your best efforts, some seeds will fail to germinate, too.
You’d need to be really unlucky though because it’s estimated that Broccoli Calabrese seeds have a 96% success rate.
Here’s how to stand the best chance of your broccoli seeds germinating…
- Start with a modular seed starting tray. You don’t want to crowd these plants close together.
- Fill each of the trays with seed compost. These aren’t fussy. You can use a seed starting mix if you like, but regular multipurpose soil will do the trick just the same.
- Poke a hole in the soil about 2cm deep
- Sow two seeds per module
- Backfill and water until the soil is moist.
When watering, rather than using a watering can, use a plastic bottle with holes pierced in the bottle top. It’ll give a softer watering, preventing the seed from being buried farther down in the soil mix.
The deeper it’s buried, the harder it’ll be for light to reach it, and for the tiny seedling to poke its way up through the soil.
If you’re wondering about why you should plant two seeds per cell, it’s just in case you have any bad seeds in your batch.
Incase the worst happens and one fails to germinate, you’ll still get one seedling that’ll grow into a broccoli plant.
If both germinate, thinning seedlings is done simply by removing one.
Don’t grow two seedlings in the same cell. They’ll compete for nutrients.
It’s also worth noting that broccoli seeds can be sowed directly in garden soil. Slightly acidic soil works best – in the region of a pH of 6 to 7.
Sowing directly in the garden bed will take longer.
It’s faster to sow indoors or in the greenhouse and then transplant the seedlings.
How fast does broccoli grow?
From sow to harvest directly in the veg patch, it can take upwards of 80 days.
Sowing indoors, and then transplanting in the garden, you can shorten the growing time to as little as 60 days to 80 days. It does depend heavily on the climate and nothing sinister harming your crops, be it diseases or pests.
If you are sowing the seeds indoors, keep in mind that broccoli is a cool-season crop.
A lot of seed starting kits include a heat mat. You can use one to spur the germination phase along, but they aren’t needed.
Stage 2: Seedling Formation
There’s more to seedlings than meets the eye.
As soon as the seeds germinate, a radicle is formed. The purpose of that is to anchor the seed in the soil, holding the plant upright.
Following that, cotyledons emerge. These are known as the seed leaves.
Following that, you get the true leaves.
So, from germination to seedlings, there are already several stages.
- Radicle forms
- Cotyledons emerge
- True leaves start to grow
The cotyledons do fall off when the true leaves form.
That’s a stage you want to watch for because you shouldn’t fertilize before the young seed leaves drop.
That early in the growing stage, adding fertilizer is likely to burn the delicate roots.
As for the type of fertilizer to use, you want something low in all nutrients, but slightly higher in nitrogen.
A 6-4-4 fertilizer is ample as that’s slightly higher in nitrogen, but it still contains enough of a supplement of phosphorus and potassium to support strong root development.
Whichever type you use, be sure to follow the instructions on the label. Most need to be diluted to either a half strength or a quarter strength.
Transplanting Seedlings
Once your seedlings have about 4 to 6 inches of height, it’s time to get them ready for their final growing zone.
When you sow seeds indoors to transplant them outdoors, they need a little hardening off.
All that means is that instead of instantly transplanting them in a spot where they go from being in the heat indoors, to being in full sun for at least six hours daily, you gradually acclimate them to the new grow zone.
Place them outdoors for a few hours over a few days.
Increase it to four hours the next few days, and again for 5 to 6 hours, then finally transplant them in the garden bed, or grow bag where they’ll be left to grow for the rest of the season.
After a couple of weeks of acclimation, they’ll be ready for the growing season outdoors.
When transplanting, you don’t want to bury them too deep.
Aim to have roughly the same depth they had in their plugs or seed starting cells.
Aim to space your plants with around 18” of spacing. This helps with air circulation and prevents your veg patch from becoming crowded to the point of plants competing for nutrients. None will win that battle.
Once they’re in the soil, water them in thoroughly to help the roots anchor into the soil bed.
It’s also a good idea to add a 1 to 2-inch layer of mulch on top of the soil.
Organic material works best. Untreated grass clippings, shredded leaves, or straw are ideal.
Why?
Because mulch helps keep the soil cool and retain moisture. It’s also handy at keeping weeds from popping up, stealing the nutrients you need your broccoli plants to get.
It’s also worth pointing out at this point that there are many an insect that will jump or land on a chance to feed on the juicy leaves of your broccoli plants.
To protect against garden critters, consider covering the plants with mesh netting, or grow under a cloche or tunnel.
To protect against any larvae that hatch from insect eggs laid on the leaves, you can place collars around the base of the stems to stop any larvae, caterpillars, or grubs from burying beneath the soil to eat on the roots of your broccoli plants.
Stage 3: The vegetative growth phase
During this stage, you’re really only paying attention to the leaf formation. Mature leaves grow bigger as the plant matures. The bigger the leaves get, the better the plants able to photosynthesize.
If you don’t know, the green pigments on plant leaves contain chlorophyll. That absorbs the sun’s rays, captures the energy, and transforms it into sugars the plant can use for energy to grow.
Or in the case of broccoli, to produce flowers.
You do know that the head of broccoli is really just a large clump of immature flower buds? If you don’t harvest broccoli at the right time, they will go to flower and put out seeds, then die. You’ll miss your edible crops.
To get to that point though, it takes a good few weeks for the initial flower bud to form in the center of the plant, then mature.
During this time, keep an eye on the leaves for pests, diseases, and any fungal growth on either the soil or the mulch.
Known pests to impact broccoli crops
- The cabbage root fly
- Cabbage looper
- Aphids
Birds can also be persistent pests to the big leaves on broccoli plants, tearing parts from the leaves, or pecking holes through them.
Anything that damages the leaves, hinders the plants’ ability to photosynthesize. That will result in a loss of yield at best, and at worst, in the case of rabid pest infestations, kill your broccoli plants completely.
Known diseases to watch for
- Clubroot
This is a soil-borne disease that causes the roots of broccoli plants to swell. Symptoms include the leaves turning a purplish shade, growth gets stunted and the leaves wilt. It’s usually only a problem in the peak of summer when downpours tend to less regular, but more heavy when it does rain.
- Downy mildew
This is a fungal infection that causes a yellow to gray mottling on the underside of the leaves. The cause is leaves staying wet for too long. Usually because of overcrowding, or the lower leaves resting on the topsoil or mulch. When leaves begin to contact the soil surface or mulch, best practice is to remove them to prevent any fungal spores from getting onto the leaf surface.
- Black rot
This is a bacterial infection that causes yellow and brown patches to appear on the leaves. Warm and humid conditions are when this is most active. Leaves turn yellow while the veins of the leaves darken. Once the bacteria gets a foothold, the plant rarely survives. The bacteria can, even when composted so be sure that if you do suspect this you only use hot composting to dispose of the plant, or just discard it.
- Alternaria leaf spot
This is a fungal disease that causes dark spots to appear on leaves. Sometimes, you’ll see these spots with a yellow halo. The odd spotting isn’t a concern. It becomes a problem when the fungal spores get spread through splashing when it rains or by overhead irrigation. This is one of the diseases that can be carried in the seed, so if your seeds were harvested from an infected crop last season.
Stage 4: The Flowering Phase (Harvest Time)
As the plant matures, the main flower emerges in the center of the Calabrese plant. For sprouting broccoli cultivars, you’ll get multiple smaller florets sprouting on different leaves. The process is the same though.
The only difference between sprouting broccoli and calabrese broccoli is the size of the main flower head.
Calabrese broccoli produces on large cluster of flower buds in the center.
Sprouting broccoli produces multiple clusters of flower buds across multiple stems. They’re just smaller.
For both types, timing when to harvest is crucial. The right time is when the main floret is a good size and the flower buds are compacted and tightly formed.
Without harvesting before flower buds open, you’ll get yellow flowers sprouting. That’s great for attracting pollinators, but not so for the veg you want to eat.
Harvest the broccoli before it flowers.
Using a pair of sharp secateurs or a straight-bladed knife, cut the stalk a few inches below the main floret and cut at an angle.
The reason to angle the cut is to allow for any rainwater to run off.
Without being angled, water would rest on the stalk paving the way for rot, disease, and numerous problems.
Don’t uproot it and call it a day yet though because once you cut away the main head of broccoli, it encourages the plant to put out side shoots.
The heads from the side shoots won’t be nearly as big, but it’s more broccoli you wouldn’t have if you take one head of broccoli florets and call it a day.
There’s likely to be several more weeks of smaller broccoli heads to emerge from the shoots.
These are how you can get an extended harvest from each of your broccoli plants.
Stage 5: The Senescence Stage
Calabrese plants sprouting broccoli are best grown as annuals because they need loads of energy to produce all those masses of flower buds.
Fresh seeds are best.
The senescence phase is the last stage in a plant’s life when it begins to dwindle and die. It marks the end of the growing season.
Leaves yellow from the bottom up, then turn brown marking the end of the plants’ growth stages.
Postharvest senescence is normal and will happen a few weeks after the main head has been harvested and several side shoots have developed florets too.
As the plant naturally ages, the lower leaves discolor and the plant loses its vigor. It’s done! Uproot and compost it.
When to worry is when you spot early signs of the senescence stage as that’s indicative of something stressing the plant.
These don’t cope with stress well. It usually goes one of two ways.
Kickstart the reproduction process by causing bolting (premature flowering), or if something is seriously disruptive, it can kill the plant early on.
Armed with the knowledge of the Broccoli plant growing stages, what’s your plans? Drop your comments or feedback below, or start a forum thread to get answers to any questions you have about growing calabrese or broccoli plants.
