Zinnias are an adaptable annual that grow successfully in an array of soil conditions. A soil pH anywhere between 5.5 and 7.5 is suitable. While most popular in outdoor flower gardens, you can also grow these bright blooms indoors in a greenhouse or under fluorescent grow lights. Soil should be rich in organic matter, which means compost is key. Kitchen scraps, shredded twigs, and dried leaves will boost growth in any zinnia garden. For most varieties, you'll see seedlings sprout in just four to seven days.

Zinnias should be planted anywhere from four to 24 inches apart, depending on which variety you choose. The most common types only require six inches of spacing between seeds. Once your plants reach three inches in height, trim and thin them down to boost air circulation. When seedlings get growing, thin them to six to 18 inches apart to reduce the risk of disease.

For best results, always grow zinnias in full sun. Not only does this aid growth, but it improves flowering too, resulting in bigger, bolder blooms. While part shade is tolerable, it's not ideal for your zinnia plants. This species requires significant sunlight, so too much afternoon shade makes them more susceptible to damage.

Moist soil is a must-have for zinnias, so stay on top of your watering schedule. Young plants should be watered deeply three times a week to ensure the soil stays moist. Wet the soil down to the six-inch mark, but avoid overwatering. Once plants are established, water them every five to seven days, checking the moisture depth so that it remains at that six-inch mark. This results in a deeper root network, improving strength and appearance once flowers start blooming.

Bright blossoms are natural targets, so be on the lookout for caterpillars, worms, and mites. Each of these intruders destroys leaves, stems, and petals, chewing away to create visible holes and tears. Rolled or webbed leaves are another sign of intruders, and caterpillars love leaving behind eggs and excrement. If you spot any bugs, treat the issue with insecticide or neem oil. Mealybugs suck the sap right out of your zinnias, weakening them to the point of no return. If you spot any, rub down the leaves and stems with a washcloth soaked in rubbing alcohol. Don't leave any area untouched; wipe between leaf joints and folds, too.

Powdery mildew is the most devastating disease facing zinnia plants. This fungal infection drifts into your garden via spores, which rapidly make their way onto flowers. While it primarily affects the tops of leaves, symptoms can spring up on the undersides and stems as well. You'll notice dusty leaves that appear flour-covered, but it starts with smaller, circular white spots. The disease is hard to control once plants are infected, so minimize spreading by destroying any infected parts. If your garden is on its last legs, search for organic fungicides high in potassium bicarbonate, neem oil, and sulfur.

Zinnias are relatively low-maintenance, so they don't require any hard-to-find nutrients. Instead, focus on quality care. Experienced gardeners rely on deadheading, the process of cutting off old flowers, to encourage the formation of new ones. Likewise, it's helpful to let last season's flowers reach full maturity before reseeding. Sow a round of seeds every week for several weeks, and flowers will continue to bloom weeks past their usual end date.

Propagation from cuttings is an easy and convenient way to achieve new plants. Wait until your plants have about 10 to 12 inches of stem with multiple leaf layers, but are not in the process of flowering. Cut diagonally at the stem's base, below the lowest set of leaves. Remove these leaves, then place the cutting in warm water, submerging the bottom two inches. Keep your cutting warm and watered, and you'll notice root growth within five to 10 days.

Zinnias are top-notch pollinators, attracting bees to your garden from late spring into mid-fall. They also draw the attention of hummingbirds, Japanese beetles, and ladybugs, making them a much-loved flower for any home gardener. Those Japanese beetles offer benefits too; they protect plants from infestation — a mutually beneficial relationship. Every time they crawl closer, they're helping ward off future invaders.

Zinnias come in single, semidouble, and double varieties that flower in an assortment of colors, shapes, and sizes. Single-flower zinnias have one row of petals with visible centers, while double-flowered varieties have many rows, with centers that are harder to spot. Semi-double zinnias fall somewhere in the middle. The Dreamland variety offers a rainbow of bright colors and flowerheads that extend up to four inches across. With the Thumbelina series, you'll spot tiny single or semi-double petals for a diameter of only 1-¼ inches, while the State Fairy Series can grow to an impressive 30 inches in height.