Not sure where to start with growing broccoli from seeds? Have you tried growing broccoli before but not been successful?
Growing broccoli from seeds involves planting the seeds, nurturing the seedlings, transplanting and growing through to harvest. Don’t forget seeds just want to grow. There’s no need to be nervous, just give them some attention, look after them a bit and they will likely grow well.
In no time you will be watching your tiny seeds flourish into hearty, green heads. In this guide, we’ll take you through three essential steps to successfully grow broccoli from seeds.
Step 1: Sowing Your Seeds
You will need:
- Seeds (no need to pre-soak the seeds before planting)
- Potting compost (for the best results), ordinary compost also works
- Containers to grow your seeds in (small pots, toilet rolls)
- Watering can or water spray bottle
Fill your pots with compost. Make a small hole around 1cm deep and place a couple of seeds in the hole. Cover the seeds with compost. Water lightly.
I like to cover my germinating seeds with a thin plastic bag to give an extra layer of warmth. As the seeds germinate they release heat and water which collects on the plastic keeping the seeds in a lovely moist warm environment, ideal for germination.
Remove the plastic cover once there is a tiny bit of growth to make sure that the seeds don’t mould. This also gives them room to expand and grow. Broccoli seeds tend to germinate quite quickly within a few days of sowing, as long as it is warm enough for them.
Using a small pot or container for planting seeds means that you don’t need to use very much compost just to get things going. If your seeds don’t germinate for any reason then you haven’t wasted much.
Low Cost DIY Tip 1: You can use old yoghurt pots, just make some holes in the bottom for drainage.
Low Cost DIY Tip 2: You can use old toilet rolls to fill with compost and sow your seeds. The advantage of this is that when it comes to transplanting you can plant them straight into the ground and not disturb the roots. The cardboard will just rot into the earth.
I like to sow seeds every week throughout March to May, this means that I can have a continuous crop later on in the year.
I also choose sprouting broccoli rather than growing varieties that have a single full head. I prefer it in cooking and also find it easier to grow without being attacked by pests.
Common problems with sowing seeds
- If there is insufficient light the growing plants can become ‘leggy’, tall and thin. They are focussing on growing towards the light, rather than filling out and growing roots and leaves. Brassicas are very good at becoming leggy so keep an eye on them. Turn your growing trays regularly to keep light levels as even as possible.
- Sowing seeds at the wrong time of year. It’s best to sow broccoli between March and May, always check the seed packet for the specific variety that you are planting.
If the seeds are sown too late the result is that the harvest will be poor. The maturing plant will be growing when there are lots of caterpillars around to damage the broccoli heads. And it will not be mature enough to fight them off.
- Sowing directly outside. In my experience in the UK, sowing seeds directly outside is rarely successful. Slugs and snails eat the emerging seedlings before they have had time to establish. I always start my plants inside (in the house or in a greenhouse), it massively increases my chance of success.
Step 2: Transplant
When the plants are 10 – 15cm tall it’s time to transplant.
Hardening Off
I grow my seeds inside a greenhouse. Before transplanting they need to be hardened off. Which means making them a bit tougher. In a covered space the plants are not exposed to the wind and rain. Outside they are.
If plants go straight outside into the ground without hardening off they get a shock. This reduces their growth for a bit whilst they adjust. They are weaker plants in this state. And weaker plants are more likely to be attacked by slugs and snails.
Hardening off is usually done by bringing the seedlings outside to get some exposure to the elements during the day and putting them back inside at night. Usually done for 3 – 4 days before planting out.
Pro Tip A DIFFERENT HARDENING OFF METHOD. Brushing your hand lightly over the top of the growing seedlings can also work. No need to move the plants in and out. Just give them a good brush, as if you are the wind.
You will notice that the leaves start to toughen up after a few days. I do this from when the plants are small to encourage them to grow into strong, tough plants which are more likely to survive outside.
Spacing
Follow the guidelines on the seed packet for spacing. Generally space the plants somewhere between 30 and 45cm.
Mulch
Broccoli grow big and require a lot of nutrients from the soil. I provide this by using no dig raised beds that are full of compost and well rotted animal manure.
If you don’t have this then a good 5cm layer of mulch can work just as well. No need to dig it in, that’s what the worms do for you! If you apply the mulch to the bed at the time when the seeds are planted (early/mid spring) then the nutrients will be available to the plants when you transplant them.
The mulch adds structure to the soil, it prevents water loss and protects the soil from erosion, as well as feeding your growing plants.
Pro Tip: Wind
Wind can have a big effect on growing plants. When they are transplanted the plants are particularly vulnerable. Doing what you can to minimise wind through planting wind barriers, using fencing or micro poly tunnels can help to get your plants off to a good start.
Step 3: Harvest
The seed packet will tell you when you should expect a harvest. There are so many varieties, some that harvest in the late summer and autumn, some throughout the winter and some that overwinter for the next spring.
For sprouting broccoli the harvest period happens over a couple of months. You can start harvesting once you see the flower heads mature.
The following tips will help to increase your harvest:
- Mulch. Keep the soil mulched to keep it moist and provide nutrients to the growing plants.
- Water. Keep the soil well watered, if the plant dries out then it will not produce so much.
- Companion planting. A few of my favourite annuals are strong smelling herbs, like dill or basil or veg like onions or shallots, to keep the pests away.
- Companion pollinators. I also like to plant flowers amongst my veggies to attract lots of beneficial insects into the garden. I like calendula and chamomile.
- Perennial companions. I also have perennial plants within my vegetable garden to attract pollinators and deter pests, including lavender and rosemary.
And remember, a weak plant will be attacked first by the pests. If you grow weak plants they won’t produce great harvests. If you do have a plant that is weak, it might be better to eat it as a microgreen and still get lots of health benefits.
FAQ
Is there a difference between broccoli seeds and broccoli sprouting seeds?
There are different types of broccoli seeds, those that form a single large head (sometimes called calabrese or broccoli) and those that form lots of smaller heads (called sprouting broccoli). Check the seed packet for what you have.
How to grow broccoli in pots?
Broccoli can be grown to maturity in pots. Just ensure that the pots are kept watered, that the compost used is full of nutrition. As broccoli requires a lot of nutrients to grow, you may need to add more compost or organic matter to the pot, or a top dressing of seaweed or similar to give an extra boost of nutrition through the growing season.
Can you put seeds straight into the soil?
You can, and the seeds will germinate and grow. However in my experience the slugs will eat the seedlings before they mature. I always start the seeds indoors where things are protected and the plants can establish before they are exposed to the pests and weather outside.
Does broccoli regrow after cutting it?
For sprouting varieties, they will regrow.
Does broccoli regrow every year?
Broccoli that is available from seeds is an annual plant that will not regrow every year. It is possible to get perennial broccoli that does continue to grow year on year. However this is a different plant.
Good luck with growing your broccoli from seeds. Remember a few golden rules, seeds just want to grow. Giving them the right conditions will give them the best chance. And remember growing broccoli from seed is as much about the journey as the end result. Even the process of growing your own veg is good for your body and mind.
I would love to hear how you get on!