A media mix for topiary forms is 1 part peat moss to 1 part potting soil surrounded by sheet moss. English ivy and creeping thyme work well for this. A child's first garden should include sunflowers from seeds. The large seeds sprout quickly and dependably, and the strong seedlings can push their way through crusted soil. If you are shooting for record sunflowers, your plants will need to top 20 feet in height with seed-head diameters of 2 feet to be in the running.
Mulches can change the soil temperature.
Black plastic warms the soil and should be applied before planting. Organic materials delay the sun's penetration thereby keeping the soil cooler. Apply organic mulches after plants are 3 to 4 inches tall and the soil is warm. Cover old stumps with soil to hasten decay. Turn the compost pile and add manure.