Zinnias range in size from tiny 6-to-8-inch dwarf varieties to towering 3-foot plants. Available in fiery reds, yellows, orange and pink, zinnias grow quickly, making them an ideal flower for beginning gardeners. These delightful single- and double-blooming flowers originated in Mexico and are grown as annuals throughout the United States. Dwarf varieties make excellent borders along walkways and provide a splash of color tucked into small corners. Larger varieties make a striking backdrop for flowerbeds.
Prepare a bed for zinnias that receives full sun, defined as six to eight hours of direct sunlight per day. Till the soil to a depth of eight inches and add well-composted manure or compost to increase aeration and improve drainage.
Plant zinnias within four weeks prior to the last expected frost. Sow two seeds per pot in moist seed starter. Set in a warm location such as the top of a water heater or the TV to provide bottom heat to speed germination. Seedlings emerge in three to five days depending on the temperature of the soil. Once seedlings have emerged and have developed the second set of leaves, thin to one plant per pot. Transplant to a permanent location after the soil has warmed and all danger of frost has passed. Zinnias are finicky and do not like their roots disturbed, use caution when transplanting.
Sow seeds directly in their permanent location in late spring after the soil has warmed and frost has passed. Space plants 9 to 12 inches apart. Larger varieties may require more room. Always follow the planting and spacing guide for your particular variety. Commercial packaging generally provides adequate instructions for planting and spacing on the back of the seed packet. Cover lightly with soil and keep evenly moist until seeds germinate.
Water regularly until the plants are established. Although they do not generally require watering and survive nicely under normal weather conditions, additional water may be needed during dry periods. Monitor for signs of excessively dry soil or wilting of leaves. Harvest zinnias before the flower is completely open for an impressive cut flower that holds well in a vase.