63 to 77 days. Sparky Mixture French marigold seeds offer one of the most vibrant and inexpensive blooms available to the home gardener. Sparky Mixture is a familiar alternative to the traditional marigold, quickly maturing to 12 to 14 inches tall boasting unique semi-doubled heads. Marigold seeds are a favorite for kids or novice gardeners because they are a low-maintenance grow tolerant to a variety of difficult gardens. Sparky Mixture marigolds are ideal to grow along walkways, fences, or trimming the back of the garden.