Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
Tall? Bright orange flowers? Attracts butterflies? Deer resistant? You must be talking about tithonia, one of my favorite garden flowers.
What is Tithonia?
Tithonia (Tithonia diversifolia) is a perennial flower that is native to Central America, the West Indies and the tropical parts of the US. It is only hardy through zone 10. North of there, it is grown as an annual. Thanks to its origins in Central America, the plants are often called Mexican sunflowers. They are not sunflowers which are the genus Helianthus. Mexican sunflowers are the genus Tithonia.
The plants are quite tall, growing up to 6 feet. The commonly grown cultivars are “Torch” which was chosen as an AAS award winner in 1951. It has the characteristic orange flowers. “Yellow Torch” has yellow flowers. There are shorter cultivars suitable for smaller gardens. “Fiesta del Sol” grows to 3 feet and was selected as an AAS award winner in 2000. “Goldfinger is even shorter only growing 2 to 2 ½ feet tall.
Torch is the one that I love to grow. The plants are majestic and covered with bright orange flowers. I haven’t grown “Fiesta del Sol” but I’ve seen it growing in botanical gardens. It looks kind of ordinary and doesn’t grab me the way that the taller “Torch” does.
Tithonia leaves are fuzzy, especially on the undersides. Deer don’t care for plants with fuzzy leaves, so they leave tithonia alone unless there is nothing else to eat. If you have a deer problem, this is a good plant to add to your garden. The flowers are orange or yellow depending on the cultivar. They grow on hollow stems which are fragile and easily bent, especially by birds. Bloom time is mid-summer until the first frost. The flowers also attract lots of butterflies, especially monarchs. It is a nectar flower for them. If you have space in your butterfly garden, you will want to add a tithonia or two to the back of it or grow one of the shorter cultivars if you don’t have space for larger plants. Be sure to deadhead (remove spent flowers) your tithonia regularly to keep it blooming until frost.
How to Grow Tithonia
Tithonia require full sun, 6 to 8 hours minimum per day, and well-drained soil. Because they are so large, it is best to plant them in the back of your garden. You can also use them as a privacy hedge.
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Plants should be spaced 2 feet apart to allow for good air circulation to prevent disease. Crowding your plants blocks air from circulating between the plants and encourages the growth of molds, viruses and fungi on the leaves. You will also want to stake your young plants until their stems are strong enough to stand on their own.
Tithonia do not require a lot of water. 1 inch of rain a week is sufficient. Be sure to water your plants if your area is experiencing a drought. A thick layer of mulch is helpful in retaining moisture in the soil. Mulch will also help keep down weeds which compete with your plants for water and nutrients.
No fertilizer is required. Tithonia prefer poor soils.
How to Grow Tithonia From Seed
Tithonia are easy to grow from seed. You can direct sow the seeds in your garden in the spring after your last frost when the soil has warmed to 70⁰F. The seeds of tropical plants won't germinate in cold soil. In my NJ zone 6 garden, I wait until the end of May to ensure that the soil has warmed, to sow my tropical seeds.
Sow the seed on the surface of the soil. Do not cover them. They need light to germinate. Keep the soil evenly moist. Germination should occur in 1 to 2 weeks. When the seedlings are at least 1 inch tall, you can thin them to 24 inches apart.
You can also start seed indoors 6 to 8 weeks before your last frost. Surface sow the seeds. Do not cover them. They need light to germinate. Using a heat mat, maintain a soil temperature of 70⁰F. Keep the soil evenly moist. Germination should occur in 1 to 2 weeks. You can transplant your seedlings into your garden after your last frost when nighttime temperatures are above 50⁰F. Space them 2 feet apart.
Questions & Answers
Question: i just planted my Mexican sunflowers on July 1st. Is this too late?
Answer: July 1 is not too late. Your seeds will germinate and the plants will grow. They will just bloom later than usual. If tithonia normally blooms in July in your area, I would expect that the late-sown seeds would bloom in August. You don't need to worry about the flowers. Tithonias bloom until frost. The past few years, we have had exceptionally warm autumns with very late frosts so you will have plenty of time to the flowers.
© 2019 Caren White