Sunflowers - will this work?

[Stephanie314]

I live in central PA and have a plot of grass about 300 sq feet that is isolated by concrete from the rest of our property, and we have two boys, 9 and 12. We want to turn it into a small sunflower ‘forest’ this summer, with very tall sunflowers (mammoth and others). Our idea is to start the sunflowers in pots and transfer directly to the grassy plot in about four weeks. We are counting on the flowers growing quickly and shading the grass, we are trying to avoid a big soil prep. We will mow everything down in the fall and re-plant grass. So the real question is can we avoid the tilling?

 

[Oliver Buckle]

So the real question is can we avoid the tilling?

Can't say for certain without knowing what's under the grass, but probably not.
Sunflowers put something into the soil that stops other things growing, I don't know if that would apply to grass.

 

[Meadowlark]

Yes, but expect some reduction in plant size as a result of the competition if you don't remove any grass. Sunflowers contain chemical compounds that inhibit the germination and growth of other seedlings in the growing area.

To give your seedlings a boost maybe you might make a little small clear circle for each plant and let them go from there.

These are my mammoth sunflowers now and they will be 10 ft giants in another month. I don't worry about weeding and just give them a little clear space to get started.

 

[Mr_Yan]

Is there anything to lose if this doesn't work perfectly??? I say go for it. In theory there are allelopathic compounds excreted by sunflowers but it's not too bad or long lasting. I have self re-sowing sunflowers volunteering all over my garden and I always allow a few to grow. Look at Meadowlark's pic above, those sunflowers can't be more than a meter from very valuable tomatoes.

If you can get the sod away from the transplant it should work well enough. And tilling is one of the worst things you can do to soil - I'm firmly in the no-till camp.

Few things I may add though:

• Mix in a few types of sun flowers not just the mammoth sky scraper. This will help get blooms at different times and with some different yellows and oranges.
• Something like a post hole digger or even a bulb planter will help punch a circular hole through the sod to transplant into.
• Don't grow these in the peat pots that supposedly deteriorate into the soil. They don't. The roots may grow through them but the pot will still be there in the spring.
• The root balls at the end of the year may give you some grief if you want to go back to a flat lawn. I let my sunflowers stay standing over the winter for birds and squirrels to feast on then deal with them in the spring. It ends up something like picking up a soccer ball size chunk of soil at the end of a baseball bat.