I read with interest your reply to a previous question here: https://www.torontomastergardeners.ca/askagardener/plants-that-will-survive-sunflower-seed-hulls-toxicity/. I planted sunflowers in a part of my vegetable garden and was not able to use it this year. Are there any vegetables that will grow after a year of sunflowers? What do you think about always planting sunflowers in the same garden; might the soil get depleted? Or perhaps it would be possible to interseed it with a clover? Any advice you have would be much appreciated. Thank you.
Thank you for contacting the Toronto Master Gardeners with your inquiry.
Most varieties of sunflowers are drought and heat resistant making them ideal for hot summers. The only difficulties that surround growing sunflowers is their depletion of soil nutrients. Sunflowers deplete nutrients from the soil much more rapidly compared to other plants, which may cause some problems if planted in a garden or flower bed. Keeping the soil nutrient-rich is a must. A yearly addition of organic compost to the garden bed will aid in replenishing the soil nutrients.
As you already know sunflowers (Helianthus spp.) produce natural plant chemicals called sesquiterpene lactones that are fairly effective at helping this species fend off competitors trying to weasel into its growing territory. This natural plant-to-plant defence is referred to as “allelopathy”. That being said, it is possible to grow some vegetables along side sunflowers.
The sturdy stalks of the sunflower can act as a natural trellis which is perfect for growing cucumbers, beans, peas cucumbers and squash. A fully grown sunflower can provide enough shade for growing lettuce. Sunflower roots dig deep channels, which can help corn roots grow deep in the following year if planted in the same spot. Chives also make a good companion plant for sunflowers, repelling the aphids that the flowers attract.
There are a number of useful websites which provide additional information on how to grow sunflowers in a vegetable garden: