Hi, Well you don't really need to plant close and then thin. That advice is generally used for vegetables with small seeds that are hard to space at planting time. Carrots are a good example. It's often easier to sow them thickly and thin them later because the seeds are so tiny AND because germination rates may vary. So, to insure a good solid crop, overseeding has advantages. But, if you want, you can sow thinly and not thin later on. Yet, with some crops, I don't even bother to thin. With some greens such as arugula, looseleaf lettuce, spinach, mustard, etc I just sprinkle seeds in the planting bed and let them go. With a plant like Mammoth sunflowers, they are very easy to plant at any distance you want and since they generally germinate very easily, just plant the seeds at intervals and you won't have to thin at all. Thinning is just a technique to use if you have planted too many seeds or are concerned about germination rates.