Zinnias are easy to start from seeds, indoors or outdoors. The seeds of most of them are a good size, too, so they're a perfect choice for a child to sow in the garden as well. Buying Potted Plants . Select plants with fairly compact growth and good branching. If you can't plant the zinnias the day you bring them home, water them well and set them under a tree or patio cover where they'll be protected from the drying effect of direct sun.
Zinnias grow best in full sun, which means six or more hours of direct sun daily.
Amend the soil by digging in a 2-inch layer of compost or peat moss before planting to ensure good drainage and fertility. The best time to transplant any plant is on a cloudy day or in late afternoon so the plants have a chance to get settled in before they have to contend with the drying effects of the sun. Set zinnias in the ground at the same depth they were growing in the pots. If you're transplanting from flats or six-packs, try to keep as much soil around the roots as possible so they don't dry out. Combine pink double-flowered zinnia with a dwarf of Russian sage.