How To Grow Hydroponic Broccoli

Broccoli can be a tad tricky to grow hydroponically, like its cousins kale, spinach, peas and Brussels sprouts it is a cold weather crop that does not fare well in higher temperatures.

Following germination, the temperature should be 50 – 60°F. maximum. The broccoli will still grow at higher temperatures, but sadly you’ll discover that it is bitter and useless for anything other than seed or the compost heap.

Brocolli hydroponic grow room

Also be aware that prolonged temperature extremes, either too cold or too hot will result in bolting. Once the plant bolts to seed it is no longer palatable – it tastes nasty.

I like to drop the temperature down to around 30 – 40°F in the week prior to harvest to help concentrate the flavor. Broccoli as I said is very cold hardy and will withstand light chills.

Broccoli can be started from seeds or plant starts available at many nurseries or even online. If starting from cuttings it is best to harvest them from mature plants.

Hydroponic Broccoli Growing Requirements

  • Nutrient pH 6.0 – 6.8
  • PPM – 1960-2450
  • EC – 2.8-3.5

Seed Starting

Starting from seed is the best choice in my opinion.

Seeds become less viable as they age, germination rates decline incredibly. Be sure to use seed that is packaged for the current growing season.

Once again, being a cold weather crop – cold stratification is a helpful trick used by some growers – it is not absolutely necessary – but is helpful. Keep your seeds in the refrigerator [not the freezer] for a few weeks before using them.

Broccoli Seeds germinate best at temperatures between 45°F to 80°F but will also germinate at temperatures as low as 40°F., with a lower germination success rate. They will also germinate at higher temperatures – ditto for germination success rate.

Be sure to reduce the temperature once the plants have emerged. This of course refers to air temperature.

Broccoli seeds can be started conventionally, in cell packs with potting soil and transferred to the hydroponic setup when they sprout, or they can also be started in Oasis Cubes. They take 4 to 7 days to germinate .

If started conventionally, in soil, you’ll want to take care to remove the soil clinging to the young roots without compromising the root system. Once the soil has been delicately tapped and washed off the young roots, I like to dust the roots with Mycorrhizae, a beneficial fungus that penetrates the root systems of most plants in nature.

They are helpful in providing improved uptake of water and nutrients from the growing media. This is, of course, optional but it does lead to healthier more robust plants.

Seed Starting in Cubes

Oasis Cubes and similar products are also suitable for starting brocolli seeds. Oasis Cubes are manufactured from water absorbent foam, Phenolic foam, also known as Floral Foam. Also known as Oasis Root Cubes, they offer a good starting environment for seedlings and plant cuttings, not as a full growing medium.

  1. Moisten the starter cubes.
  2. Insert the seeds into the cube’s holes. You.ll need roughly 3 -4 seeds per cube, anticipating that some will not germinate and weaker ones can be weeded out later.
  3. They should be placed on a tray and watered daily with 1/4 strength nutrient solution till the seeds germinate and sprout which should only be a few days. After sprouting use 1/2 strength solution.
  4. Once the seedlings are growing, thin out the extra seedlings leaving only one of the fittest looking specimens in each cube. Some of the thinned out plants may be suitable for transplant elsewhere.

    When roots begin to show and seedlings reach a few inches tall they are ready to leave the nest and enter into the setup.
  5. Broccoli plantings should be staggered at roughly 3 – 4-week intervals in order to ensure a continuous harvest.

Nutrients and pH

Alkalinity and Acidity, also known as pH is extremely important in Hydroponic gardening. The requirements of Soil ph is not the requirements of Hydroponics ph ,do not confuse the two. Optimal pH for a nutrient solution is 5.6 (between 5.5-6.0), although most plants can still survive in an environment with a pH of between 5.0 and 7.5.

Broccoli does best in a range of 6.0-6.8, expect it to dip and spike periodically but so long as you maintain within acceptable parameters there really shouldn’t be an issue. pH problems can generally be averted by following the instructions of the nutrient line that you select and keeping an eye on your plants for any signs that may indicate deficiencies or excesses.

Use nitrogen sparingly, excess nitrogen produces hollow stems.

Nutrients should be added to the reservoir twice daily. Some people like to add Vitamin B , although there is no proof that it actually helps the plants, it doesn’t hurt.

The vitamin B is thought to contribute to rapid growth and enhances the vitamin mineral content of the finished product.

Light Requirements of Brocolli

In a 24-hour cycle, broccoli should receive a bare minimum of 10 – 12 hours of light. If you are using a less intense light such as fluorescent jack that up to 16 hours per day cycle followed by 8 hours of darkness.

The light source should be at least 1/2 foot away from the plant. Inadequate light or too much shade can delay maturation.


Broccoli plants in nature do not fare well with excess water, that’s in soil based agriculture.

Broccoli that receives excessive water is prone to rot. In hydroponic agriculture, the roots are immersed in water for quite some time each day, which leads to a quagmire of sorts – how to minimize excess water exposure in a hydroponic scenario. Aeration of the Solution and Good airflow is absolutely essential to avoid rots and fungus.

Aeration methods vary a tad depending on the hydroponic grow system employed. Deep Water Culture in particular requires adequate oxygenation of the submerged root zone.

Floating beds, NFT, drip, and similar systems also demand oxygenation of the solution, but at a lower ratio in order to yield optimal or even acceptable results.