One of the last flowers to bloom in the season, Maximilian’s Sunflower grows to great heights becoming profusely covered with hundreds of bright yellow flowers in the late fall. The lance-shaped gray-green foliage is quite attractive throughout the summer and the flowers make great fresh cut flowers for autumn bouquets. Helianthus maximiliani is a tremendous food source for both birds and butterflies in the late fall.
I. Appearance and Characteristics
Helianthus maximiliani is a North American species of sunflower known by the common name Maximilian sunflower.
This sunflower is named for Prince Maximilian of Wied-Neuwied, who encountered it on his travels in North America.
Helianthus maximiliani is native to the Great Plains in central North America, and naturalized in the eastern and western parts of the continent. It is now found from British Columbia to Maine, south to the Carolinas, Chihuahua, and California. The plant thrives in a number of ecosystems, particularly across the plains in central Canada and the United States. It is also cultivated as an ornamental.
A branching perennial herb, growing from a stout rhizome and reaches heights from 0.5–3.0 m (1+1⁄2–10 ft). The slender, tall, erect stems and alternately-arranged leaves are covered in rough hairs.
The lance-shaped leaves are narrow, pointed, folded down the midvein, and up to 30 cm (12 in) long on large plants.
The flower heads are surrounded at the base by pointed green phyllaries which often stick straight out and curl at the tips. The center is filled with yellow tipped brown disc florets and the circumference is lined with bright yellow ray florets 2–4 cm (1–1+1⁄2 in) long.
The plant reproduces by seed and by vegetative sprouting from the rhizome.
II. How to Grow and Care
Sunlight
The seedlings, leaves, and flower heads of sunflowers all exhibit very strong phototropism. Sufficient sunlight will make the seedlings grow strongly and healthily. During the middle period of their growth stage, sufficient sunlight can promote the growth of stems and leaves and the differentiation of flower buds. If sunflowers receive sufficient sunlight during their entire growth period, the stems and leaves grow healthily and the flowers are vivid and bright. However, if there is continuous rain or they are grown for a long time in a partially shady spot they may grow poorly and become weak. The stems will not be straight, the leaves will be soft and droop in yellow green, and the flower head will be small and irregular.
Temperature
Sunflowers were originally native to North America, where it is cold in the winter and hot in the summer, meaning there is a significant annual variation in temperature. Sunflowers like a warm environment. The most suitable temperature for their growth is 18 to 30 ℃, and they can happily grow as long as the temperature is not lower than 10 ℃. Within this suitable temperature range, the higher the temperature is, the faster sunflowers grow.
At different stages of their growth, sunflowers require different amounts of water, although in general they are drought-resistant. However, their soil should not be too moist since waterlogging soil can kill them. During the budding and flowering period, sunflowers should be regularly watered, to ensure better blooming.
Watering
Sunflowers have different water requirements at different stages of growth. The soil must be moist during sowing and transplanting. The plants need sufficient water, especially during the seedling stage. After that, the soil should be kept moist but not excessively wet. Some drought is beneficial for root growth and to develop a plant’s drought tolerance. In the summer, when the temperature increases and water evaporates more rapidly, the amount of water supplied can be increased as necessary to prevent wilting, which can affect the growth of the plants.
The time from the emergence of flower buds to blooming is the peak period of water demand in sunflowers. During this time, there should not be a lack of water; if the soil becomes too dry, it should be watered. When sunflowers are grown in pots, the plants are often large while the flower pots are small, and there may be just a little soil and insufficient water. Therefore, timely watering is required during the growth period; otherwise, the leaves tend to loss water and wither. The soil should not be too wet, however, otherwise the leaves at the base of the plant tend to turn yellow.
Soil
Sunflowers can grow well in all types of soil. However, the soil they most prefer is sandy loam or loamy soil, with a pH of between 5.8 and 6.5. Good soil drainage is crucial for the growth of sunflowers. If sunflowers are planted in the garden, it is recommended that loose and fertile loam is used, which can be mixed with decomposed compost as a base fertilizer. Quick-acting fertilizer can also be added. Soil should be dug over prior to fertilization and sowing to improve soil structure and drainage.
If sunflowers are grown in pots, their soil should be made up of peat, vermiculite, and sand in the ratio 2: 1: 1; organic fertilizers can be mixed in at the same time. Please note that sunflowers should not be continuously planted in the same soil or in soil where other plants of the same family have been planted, otherwise they will grow poorly. It is recommended that the soil is replaced once a year, or that sunflowers are grown in a different area.
Fertilizing
When sunflowers are grown in pots, liquid fertilizer or compound fertilizer should be applied once every 7 to 10 days. During the growth of seedlings, nitrogen fertilizer should be applied to promote the luxuriant growth of stems and leaves. When budding begins, more phosphate-potassium fertilizer should be applied, which will provide sufficient nutrients to promote robust growth of the buds and facilitate blooming.
If sunflowers are planted in the garden, no fertilizer is required if the soil is already fertile. However, if the soil is relatively poor, nitrogen fertilizer should be applied during the early stages of growth and phosphorus and potassium fertilizers should be applied during the late stages, similar to that carried out for potted plants. They can be fertilized once every 20 days during the growth period, with an additional two or three applications of thin phosphate-potassium fertilizer provided before blooming.
Planting Instructions
Sunflowers are generally sown in late winter or spring and will bloom 60 to 70 days after sowing. The seeds should be sown directly into the soil, with spacing between the seeds of at least 12 cm. After sowing, a 2 cm layer of fine soil should be used to cover the seeds. Then, the seeds should be watered before being covered with a layer of mulch.
If sunflowers are sown in seed trays, deep seed trays should be used. First, place the compost into the seed tray, thoroughly water it, and wait for the excess water to drain before sowing. Sow each seed in a hole, cover it with a thin layer of soil, place the tray in a shady place, and wait for the young seedlings to appear.
Once the seedlings appear, ventilate them well, reduce the humidity and temperature, and gradually expose the seedlings to sunlight. Two weeks after sowing, the seedlings will grow to about 5 cm. At this time, the seedlings can be transplanted into a 10 cm pot and cared for until planting out. The optimum soil temperature for planting sunflowers is 15 ℃.
Pruning
To ensure the robust growth of the main stem, the lateral buds of sunflowers should be removed so as not to distribute nutrients too widely and affect the growth of flowers on the main stem. If planted in a border, the top bud of the main stem can be picked off, so that branching occurs to give 4-5 blooms and the plant remains quite short and bushy.
For sunflowers planted to provide cut flowers, the apical bud should be removed to facilitate the growth of lateral stems. After such treatment, several stems will be produced, and 7-10 flowers can be harvested from one plant. For sunflowers grown in pots, it is recommended to keep the primary stem and remove the lateral buds, since in this case it is better to have just one flower.
Propagation
Sunflowers are usually propagated by sowing seeds. It is a cross-pollinated plant that can be naturally pollinated by insects and bees, although artificial pollination can also be carried out when sunflowers are in bloom, which can improve the seed setting rate and produce more seeds.
III. Uses and Benefits
- Ornamental uses
Maximilian sunflower is a perennial sunflower species valued ornamentally for its bright yellow blooms. It is planted in country gardens, perennial gardens, and wildflower meadows. This species is considered easy to grow and attracts bees and butterflies. Maximilian sunflower isn’t suited for planting on perennial borders because it requires room to spread for proper growth.
- Other uses
The thick rhizome is edible and provided a food similar to the Jerusalem artichoke for Native American groups such as the Sioux. The flower heads are attractive to insects and the fruits are eaten by birds. Livestock eat portions of the plant, and the seeds are eaten by various wildlife.
The Land Institute, a perennial agriculture research center located in Salina, Kansas, run by Wes Jackson is experimenting with this species to create a perennial oilseed grain crop that does not necessitate replanting each season.
IV. Harvesting and Storage
For sunflowers planted to be used for cut flowers, they can be harvested when the outermost ligulate flowers bloom. It is best to harvest them in the early morning when the temperature is low; they should not be harvested at midday or in the afternoon, when the temperature is high. Gardening scissors should be used to cut the inflorescences obliquely at the bottom of the stem; this can increase the area for water absorption.
The cut inflorescences should be placed in a container of clean water as soon as possible to avoid water loss. If the flower cannot be placed into water immediately, the bottom of the stem should be cut again before it is placed in water to ensure sufficient water absorption. The vase life of sunflowers is 6 to 8 days in the summer and 10 to 15 days in the winter.
