How to Grow Broccoli from Seed

We love the flavor of freshly picked broccoli from the garden. Learning how to grow broccoli from seed will give you the skills to grow cauliflower, cabbage, and other brassicas because the practices are much the same. Here are the steps to learn how to grow broccoli from seed.

When to Plant Broccoli Seeds: Plant Broccoli as a Winter Crop in Zones 9 and 10

When learning how to grow broccoli from seed, you must first consider what time of the year you want to enjoy your harvest. What zone you are in and when you want to harvest the broccoli determines when you will plant your seeds. Because broccoli enjoys cool weather and shorter days, you want the plant to be maturing during this time.

In Zones 9 and 10, this can be in the fall, winter, or early spring. In mild climates like Zones 9 and 10, you can plant broccoli seeds in late summer to enjoy broccoli heads during the fall and into the winter. Although it can be difficult to start broccoli seeds during this hot part of the year, the benefit is that your plants will grow while the days are still long, allowing you to avoid the fall effect. The fall effect happens as day lengths get shorter, the sun’s angles are lower, and evenings turn cooler — all factors that cause plant growth to stall. Starting crops in late summer and fall can get you strong starts while the days are longer and increase your yield.

Plant Broccoli as a Fall and Spring Crop in Other Zones

If you are outside of Zones 9 and 10, you have to consider frost when planning when to plant your broccoli seeds. If your summers are mild enough, you can start your seeds in the summer and allow them to mature before your first frost. You can also use season-extending techniques like low tunnels and row cover to gain a few more weeks of growth in the colder winter months. Alternatively, you can start seeds 3–4 weeks before the last frost and plant them out in early spring when the threat of frost is gone.

Planting Broccoli Seeds

When learning how to grow broccoli from seed, you will find that you have a choice of whether you want to direct sow broccoli seeds or plant them in starter pots and transplant them out. Our recommendation is to start your crops in a protected, cool area in starter pots if you are planting seeds during the warm months of summer and fall for a fall or winter crop. Broccoli seeds need to germinate in cool, moist soil, which may be difficult to create when direct seeding during the warm summer and fall months. Broccoli seeds require the same good seed starting practices as any vegetable seed. You can review our pro tips here: Successful Seed Germination.

Once your seedlings have germinated, it’s your responsibility to get them up and growing as quickly as possible. To do so, make sure your seedlings are getting adequate moisture and regular fertilization. Each time you water your seedlings, apply a diluted organic liquid fertilizer like fish emulsion. Once your seedlings have grown to a healthy size of at least 3–4″, you can plant them out in the garden.

Where to Place Broccoli Seedlings

 When learning how to grow broccoli from seed, the other consideration is where to place your seedlings. Because broccoli plants require quite a bit of space, you want to make sure they have adequate spacing to fully mature if you are growing in a small garden or containers.

If you plan to grow broccoli plants in containers, you want to ensure you have a container at least 10 gallons in size to allow for good root development. When growing in containers, keep in mind that you must watch carefully for drying soil and not let your broccoli plants completely dry out. You may have to water more frequently if you are experiencing warm weather. Wherever you place your seedlings in the garden, it’s important to watch them regularly and make sure they have adequate moisture to develop delicious large heads of broccoli.

Harvesting Broccoli

When you are ready to harvest your broccoli, take a sharp knife or a sharp pair of pruners and cut just below the broccoli head you wish to harvest. With most varieties of broccoli, you can harvest the central head and allow for side shoots to continue to grow. Subsequently, you will get smaller harvests of broccoli for several more weeks!

Once the days get longer and the temperature warms up, you will find that your broccoli plants will begin to flower. Nature is signaling that your broccoli has reached its maturity and is now heading into the seed production phase. You can still eat broccoli after the florets have begun to flower, although its flavor will decline. If you have space in the garden, you can leave the broccoli to flower and watch the bees go crazy!

To get the most out of your broccoli, harvest broccoli greens just as you would any dark leafy green.