Sunflowers are extremely fast growers, have amazing flowers that follow the sun, and are fun to harvest and roast. Sunflowers have a functional role in building great soil, as they produce a long taproot that will help loosen your soil several feet below the surface. This action also works to pull nutrients back to the surface that have leached deep into the soil.  When you compost the plant, you will be able to recycle and replenish these lost nutrients back to the soil surface. This was my favorite snack growing up, and love growing these and sharing the experience with my kids.

The Basics: This guide is specific to the Mammoth Variety, but is consistent for other sunflower seed producing varieties.

Sun: Full

At SeedingPotassium
1 Month After Seeding – General fertilizer, such as Compost
3 Months After Seeding Nitrogen such as blood meal
At Flower Head FormationPhosphorus such as bone meal

Favorite Soil: Loamy, Sandy (mine did alright in clay) Sunflowers have a long taproot that will help loosen your soil in the long term.
Favorite pH: 6.0 to 7.5
Planting: Plant in March. Soak seeds in water overnight before planting. Plant 1 inch deep 18 inches apart, with rows spaced 2.5 ft. Plant directly in the soil, the taproot does not like to be transplanted.
Other needs: May need staking or support if in a windy area
Watering Needs: Water deeply, keep moist but not soggy. Below is a description of the root behavior which can help you setup the best irrigation plan.

  • Root Size: The majority of the roots will form a 3ft wide radius around the plant, and 3ft. deep. Sunflowers have an extremely long taproot extending down beneath the plant. The taproot will extend in the best conditions to around 9ft deep.
  • Root Zone Shape: The majority of the roots form a half-sphere with radius of 3ft. Extending from this root zone is one long taproot extending down into the soil around 9ft., also the sunflower will shoot out a few laterals around 5.5ft. in various directions around the plant.

Pest Control:

Seeding through Month 1 – Use Sluggo or your favorite slug and snail control.
Year Round  – Use a proactive ant control system, like this one that I described in a previous blog, to make sure the aphid population does not get out of control (I did not the first time I grew these, and it was a mistake).
As Needed – Use water jets and neem oil to control Aphid populations. Some friendly neighborhood ladybugs also helped.

Harvest: August (When the petals dry and fall off, and the back of the head of the sunflower turns yellow or brown. The seeds should be black with white stripes.) Cut off the head and scrape the seeds off with your hand or spoon or other item. You can also set the heads aside in a paper bag to dry out more and make seed removal easier. You can then go through by hand and remove small seeds, stems, etc.

Preparing & Salting the sunflower seeds:

To prepare the seeds for roasting, soak the seeds in salt water overnight. Mix 1/2 cup of salt for every 2 quarts of water, and add your sunflower seeds. Warm water works best to dissolve the salt and penetrate the seeds. Stir the seeds at least once so that the seeds on top get a chance to be fully submerged in the salt water bath. After they have soaked overnight, drain the salt water and spread the seeds out on a paper towel. (You can save some of the salt water to spray the seeds during cooking)

This is our cute daughter mixing the seeds in a salt water bath.


Cooking the sunflower seeds:

Preheat the oven to 300 °F, while you spread the wet seeds out on a cookie sheet. Cook the seeds for approximately 30 minutes, and stir them once after 15 – 20 minutes. If you like your seeds on the salty side, you can spray or brush some salt water onto the seeds a couple minutes before you plan to take them out of the oven. Remove the seeds once they dry and/or they start to brown. Burnt sunflower seeds taste terrible, so be careful not to overcook them. Pull the seeds out of the oven and let them cool. Store the seeds in an airtight container once they’ve cooled.

Sunflower Gallery