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Growing broccoli from seed can be a bit challenging for beginners, but it’s not difficult. In this post, I will give you all the information you need, and show you exactly how to grow broccoli seeds, step-by-step.
Broccoli plants are definitely a staple in my garden every year. Not only does it taste amazing fresh from the garden, but it’s super healthy too!
Many newbies think that growing broccoli from seed is going to be very difficult, but it’s actually quite simple when you know how.
In this complete guide to growing broccoli seeds, I will cover everything you need to know from start to finish. Including the best sowing methods to use and when to start them.
I’ll also give you detailed step-by-step planting instructions, the expected germination time, broccoli seedling identification, care and transplanting to your garden.
Plus I’ll show you how to fix common problems, answers to your FAQs, and much more!
Table of Contents
Growing Broccoli From Seed
Even though it’s pretty darn easy, successfully growing broccoli from seed does require some knowledge.
But the good news is that you can follow these instructions for any variety you want to plant, the steps are the same for all!
Types Of Broccoli Seeds To Grow
You might be surprised to learn that there are a several different varieties of broccoli seeds that you can plant.
Some types have larger heads, while others are small, but more prolific. There are varieties that are fast to mature, while others take longer, and some even get purple heads!
A few of my favorites are Di Cicco (classic heirloom), Early Heading (early to mature), Long Harvest (blend of early and late), Summer Purple (larger heads), Santee F1 Purple (small, but abundant).
What Do Broccoli Seeds Look Like?
Broccoli seeds are smaller than you might expect. I don’t know why, but the first time I saw them, I was surprised that such a large plant produced tiny seeds.
The best way to describe them is that they are black or dark brown, and rounded. Some are a little more oval shaped than others, and you can usually see a tiny white dot on one side (that’s where the seedling comes out).
Recommended Methods For Sowing Broccoli Seeds
The method you use for growing broccoli from seed will depend on where you live. If you’re in a cold climate with short summers like I am, then it’s best to start them indoors.
For those who live in a warmer climate, you can sow them directly into the garden, or you could try winter sowing them.
Related Post:3 Seed Starting Methods That Every Gardener Should Try
Planting Broccoli Seeds
You don’t need to do anything special to prepare the seeds for planting. There’s no cold stratification or nicking necessary.
However, there are a few steps you can take that will ensure they will germinate, and maybe even speed things up a bit. Below I’ll talk about preparing the seeds, and also give you the steps for how to plant them.
When To Plant Broccoli Seeds
For those of us who are in cold climates, you should start them indoors 4-6 weeks before your average last frost date.
If you live in a warmer region, then you can sow them as soon as the soil is workable in your garden in early spring. They are cold hardy, and the seedlings won’t be harmed by a late frost.
But, as I mentioned above, some varieties will mature faster than others. So it’s best to always check the recommended planting dates on the seed packet.
Soaking Broccoli Seeds
It’s certainly not required to soak them first, and the seeds will grow just fine without doing this.
But, soaking broccoli seeds in warm water for 12-24 hours will give them a good head start, and can even speed up germination.
How To Plant Broccoli Seeds Step-By-Step
Though you will need a few things to start broccoli seeds indoors, you don’t need to buy a ton of fancy equipment. If you already grow other seeds, then you should have everything you need on hand.
Supplies Needed:
- Seedling flat with a lid
- Pre-moistened seed starting soil or peat pellets
- Seeds
- Water
- Heat mat (optional)
Step 1: Fill the seed trays – Fill your seedling tray with a high quality seed starting mix, or use pre-moistened peat pellets if you prefer.
Step 2: Decide how many seeds to plant – If you’re using brand new seeds, then you can just plant one per hole. Otherwise, if they are old, then you may want to plant 2-3 per hole.
Step 3: Plant your seeds – You can either make a shallow hole in the soil, and drop the seed into it. Or place the seed on top, and then gently press it into the soil. I find it easier to make the holes first.
Step 4: Cover the seeds – Lightly cover the seeds, and gently press the soil down to ensure it comes into contact with the seeds. Since they are so small, broccoli seeds should only be planted about 1/8″ – 1/4″ deep.
Step 5: Add water – It’s best to water your trays from the bottom, so you don’t disturb the soil or displace the seeds. Simply pour water into the tray, and allow the soil to soak it up from the bottom. Dump out any that hasn’t be absorbed after 20 minutes.
Step 6: Cover the tray – Place the plastic lid on the top of the tray to ensure the soil doesn’t dry out during germination. Then place it in a warm location, or put it on top of a heat mat.
Broccoli Germination Time
For the most part, growing broccoli from seed is fairly quick. It takes about 5-10 days for the seedlings to start popping out of the soil, depending on how warm it is.
If you planted them indoors, and you want them to germinate faster, put the trays on a heat mat to speed things up.
What Do Broccoli Seedlings Look Like?
When they first sprout, baby broccoli seedlings will have only two leaves. Those are called “seed leaves”, and they look like two fat hearts on either side of the stem.
All of the ones that grow after that are called the “true leaves”, and those look like tiny broccoli leaves. They usually start to form within a few days after the seed leaves have opened.
Broccoli Seedling Care Tips
Once you’re done planting your seeds, you might wonder “now what?!”. Well if you ask me, this is where the fun of growing broccoli from seed really begins!
I love the anticipation of seeing tiny bits of green emerging from the soil. But that excitement can quickly ware off when you realize you have to keep those seedlings alive. Yikes!
Don’t worry, you’ve got this. To help you out, below I have included some detailed broccoli seedling care tips. You can also learn more about general seedling care here.
Light
Broccoli seedlings growing indoors need a lot of light, or they will stretch and grow leggy. So be sure to add a grow light as soon as they begin to emerge from the soil.
The light should hang a few inches above your seedlings at all times (move the light up as they grow taller). It should be kept on for 14-16 hours per day.
You can buy a nice lighting system to make it easy, or make your own. I made my own seed starting lights using an inexpensive fluorescent light fixture and plant grow light bulbs.
Whatever you decide to use, I definitely recommend getting yourself an inexpensive outlet timer to control the lights for you, it’s so much easier than relying on your memory.
Related Post: A Beginner’s Guide To Grow Lights For Seedlings
Water
From the moment you plant broccoli seeds, you should always be sure to keep the soil evenly moist. Never allow it to dry out completely, but it should’t be soggy either.
The seedlings won’t grow well if the soil is too dry or too wet, and improper watering can lead to problems down the road.
So check the moisture level at least once a day, and water as necessary to keep it moist. A soil moisture gauge can come in handy to help you get it perfect.
It’s also a good idea to water the trays from the bottom, rather than pouring it over the top. That way you won’t accidentally damage the delicate seedlings.
Air Circulation
After most of the seeds in the tray have germinated, it’s a good idea to start giving them some fresh air. This will help prevent mold growth, and strengthen the seedlings.
Start by propping the lids open for a few days, then eventually removing it all together. Once the seedlings have their first true leaves, you can run an oscillating fan on low, so it gently blows in them.
Just be mindful that once the lids are off, the soil will dry out much faster (especially with the fan). So check on them a few times a day to make sure they aren’t drying out too much.
Fertilizer
Broccoli plants are heavy feeders, and fertilizing them is very important. So give your seedlings a good start in life by feeding them as soon as they begin to grow their first true leaves.
Start with a weak dose of liquid fertilizer, and gradually bump it up to full strength as the seedlings mature.
I recommend using an organic compost fertilizer indoors, which you can get in liquid form, or buy tea bags and brew your own.
Once I move them outside, I switch to using fish emulsion or liquid kelp. Broccoli seedlings absolutely love these, but they can get a little stinky when you use them indoors.
Thinning
If you plant more than one seed per cell or pellet, or sowed them close together outside, then you’ll need to thin the seedlings once they start to grow.
If they’re too close together, it will stunt their growth, and you don’t want that. So, once your broccoli seedling get to be a few inches tall, choose the strongest one, and thin the rest.
Don’t pull them out though, or you could damage the tender roots of the one you want to keep. Instead, use a sharp pair of micro-tip snips or bonsai shears to cut them off at the soil level.
Repotting Broccoli Seedlings
If your seedlings get tall enough indoors to outgrow the trays, then you should pot them up into larger containers. That way they will have plenty of room to grow larger.
You’ll know they need repotting if the seedlings are taller than the height of the cells, or roots are coming out of the bottom.
I like to use plantable pots to make transplanting them easier, and so that I don’t have to disturb the roots more than once.
Peat pots work great. But if you’d like to try something more sustainable, then coco coir or cow pots work great too.
Of course, you could always use small plastic nursery pots instead of the plantable ones. They are reusable, which is nice.
Transplanting Broccoli Seedlings Into Your Garden
If you direct sowed broccoli seeds into your garden, then you can skip this section. But, if you started them indoors, then make sure you read these tips for transplanting.
It can be a delicate process, and you don’t want all of the hard work you put into growing broccoli from seed to go to waste if you do something wrong. So don’t skip these important steps.
When To Transplant
Broccoli is frost hardy, so you can be plant the seedlings in your garden 2-4 weeks before your average last frost date in the spring. If that makes you nervous, then there’s no problem with waiting until after your last frost.
Regardless, you should always wait until the seedlings have their first few sets of true leaves before planting them out into your garden. Learn about the timing for when to transplant seedlings here.
Hardening Off
But wait! Before you get busy transplanting your broccoli seedlings, they must be hardened first. Since they’re accustomed to living in a cushy indoor environment, they’ll need to get used to the harsh elements outdoors.
So make sure you do not skip this critical step, or your pampered seedlings could die as soon as you plant them outside.
Begin by moving them outside in a protected, shady spot for a couple hours. Then leave them outside a little longer every day, slowly exposing them to more sunlight.
They’ll be ready to go into the garden once they’re used to being outside in full sun all day. Learn exactly how to harden seedlings before transplanting here.
Where To Plant
Though there are dwarf varieties that can grow well in pots, broccoli does best when planting in the garden where it has plenty of space.
It also needs rich, fertile soil in order to produce large, beautiful heads. So you’ll need to amend poor quality soil with compost, well composted manure, or worm castings.
I recommend mixing a high-nitrogen fertilizer into the soil at planting time. You can either use slow-release granules, or root-zone feeder packs.
Spacing
Broccoli plants need ample room, so do not overcrowd them. Overcrowding will stunt their growth, which means smaller heads (or none at all!).
For best results, space the seedlings (or direct sow the seeds) 12-24 inches apart. Be sure to read the seed packets for exact spacing recommendations for each variety.
It will look funny when the seedlings are still small, and you might think you left too much room. But trust me, once the plants grow to full size, they will fill in the space nicely.
Planting Depth
Take care not to plant broccoli seedlings too deep. They should be planted at the same depth as they were growing in the seed tray or pot. Just be sure that all the roots are covered.
Broccoli From Seed To Harvest Time
Many types of broccoli need a fairly long growing season in order to mature, but some are much faster. Depending on the variety, it can take anywhere from 50-90 days from seed to harvest.
That is a wide range, so it’s bet to check the seed packet so you know what to expect from the types you’ve planted. Regularly fertilizing them will speed things up, and result in a much more prolific harvest.
Troubleshooting Common Problems
The most frustrating thing about growing broccoli from seed is when you run into problems, and have no idea how to fix them.
So below I have listed some of the most common problems you may have. You can read even more about fixing seedling problems here.
Broccoli Seeds Never Germinated
When the seeds fail to germinate, it can be caused by a few things. Either they were old and no longer viable, or the soil was too wet or too dry.
They germinate best in soil that is 40-80F degrees, so use a soil thermometer if you’re unsure.
Leggy Seedlings
As I mentioned above, broccoli seedlings will grow tall and leggy when they don’t get enough light. Be sure to add a grow light as soon as they begin to emerge.
Seedlings Falling Over
If broccoli seedlings fall over and die, that is caused by something called seedling blight (aka: damping off).
Unfortunately, there’s no way to save the ones that have already flopped over. The only thing you can do is clean and disinfect the trays before reusing them.
Seedlings Aren’t Growing
The main cause of this is usually overcrowding. You never want broccoli seedlings to be crowded, so pot them up.
They also need regular fertilizer and consistently moist soil in order to grow their best.
FAQs About Growing Broccoli Seeds
In this section, I’ll answer some of the most frequently asked questions about growing broccoli from seed. If you can’t find an answer here, ask your question in the comments section below.
How many broccoli seeds per hole?
If the seeds are brand new, or have a high viability rate, then you can just plant one per hole. Otherwise, if they’re old, then I recommend planting 2-3 per hole and thinning them later.
How deep do you plant broccoli seeds?
The general rule of thumb for seed planting depth is twice as deep as it is wide. The seeds are pretty tiny, so plant them only about 1/8″ – 1/4″ deep.
Do you soak broccoli seeds before planting?
While soaking broccoli seeds before planting is certainly not required, it can help them germinate faster and more reliably. If you want to try it, simply soak them in warm water overnight before sowing them.
How can I germinate broccoli seeds faster?
Indoors, adding bottom heat is a great way to speed up germination. Simply place the trays on top of a heat mat, and monitor the temperature with a soil thermometer. Ideally it should be kept between 60-80F degrees for the quickest germination time.
Do broccoli seeds need light to germinate?
No, broccoli seeds do not need light in order to germinate. Just take care that you don’t plant the seeds too deep.
Can I direct sow broccoli seeds?
Yes, if you live in a warm enough climate you can direct sow them. However, if your summers are short like ours are here in Minnesota, then you’ll need to start them inside.
Growing broccoli from seed is so rewarding, and super fun too! Once you get the hang of it, it’s also very easy. Plus, you can grow some pretty cool varieties when you buy seeds rather than seedlings.
If you need more help, and want to learn how to grow all of your garden plants from seed using any method you want, check out my online Seed Starting Course. This comprehensive, self-paced, step-by-step online course is specifically designed to teach beginners how to grow all types of seeds. Sign up and start today!
Otherwise, if you’re just looking for a refresher, or a quick-start guide for growing seeds inside, then grab a copy of my Starting Seeds Indoors eBook.
More Posts About Growing Seeds
- How To Grow Parsley From Seed: Step-By-Step
- How To Grow An Avocado Tree From Seed
- How To Grow Basil From Seed: Complete Guide
- How To Grow Tomatillos From Seed & When To Plant
Share your best tips for growing broccoli from seed in the comments section below.
