How Many Seeds Per Sunflower? A Closer Look at Sunflower Seed Production

Summary Table of Sunflower Characteristics

Common groundsel
Growth habit	Seed weight (mg)	Seed dormancy at shedding	Factors breaking dormancy	Optimum temperature for germination (F)	Seed mortality in untilled soil (%/year)	Seed mortality in tilled soil (%/year)	Typical emergence season	Optimum emergence depth (inches)
tall, branched	4.3–8.7	Yes	cms	68–77	26–47	–	spring	0–4
Photosynthesis type	Frost tolerance	Drought tolerance	Mycorrhiza	Response to nutrients	Emergence to flowering (weeks)	Flowering to viable seed (weeks)	Pollination	Typical & high seed production (seeds per plant)
C3	high	moderate	yes	variable	9–17	8	cross	na & 5,000

General: The designation “–” signifies that data is not available or the category is not applicable.

The first word in the two-word description tells you the relative height (tall, medium, short, prostrate), and the second word tells you the degree of branching (erect, branching, vining).

Seed weight: Range of reported values in units of “mg per seed.”

If most of the seeds are dormant when they fall off, the answer is “Yes.” If dormancy is very variable, the answer is “No.” If most of the seeds are not dormant, the answer is “Variable.”

Factors breaking dormancy: The principle factors that are reported to break dormancy and facilitate germination. The order of listing does not imply order of importance. Abbreviations are:

scd = seed coat deterioration

cms = a period subjected to cold, moist soil conditions

wst = warm soil temperatures

at = alternating day-night temperatures

Optimum temperature range for germination: Temperature (Fahrenheit) range that provides for optimum germination of non-dormant seeds. Germination at lower percentages can occur outside of this range. The dash refers to temperature range, and the slash refers to alternating day/night temperature amplitudes.

Death rates for buried seeds in tilled soil: range of estimates for death rates (percentage of seeds that die in one year) for buried seeds in tilled soil Values were chosen for seeds that were planted below the species’ emergence depth and not moved until they were evaluated. Mortality primarily represents seed deterioration in soil.

Risk of seed death in tilled soil: range of estimates for seed deaths (as a percentage of all seeds that die in one year) in tilled soil Values were chosen for seeds placed within the tillage depth and subjected to at least annual tillage events. Seed losses are the result of dormancy-breaking cues induced by tillage, germination and deterioration of un-germinated seeds.

The typical emergence season for each weed is the time of year when it grows the most in its normal habitat. Some emergence may occur outside of this range.

Optimum emergence depth: Soil depths (in inches below the soil surface) from which most seedlings emerge. Lower rates of emergence usually will occur at depths just above or just below this range.

Photosynthesis type: Codes “C3” or “C4” refer to the metabolic pathway for fixing carbon dioxide during photosynthesis. In general, C3 plants do better in cooler weather or places, while C4 plants do better in warmer weather or places.

Frost tolerance: Relative tolerance of plants to freezing temperatures (high, moderate, low).

Drought tolerance: Relative tolerance of plants to drought (high, moderate, low).

Mycorrhiza: Presence of mycorrhizal fungi. “Yes” means the weed is present, “no” means it is not present, “unclear” means reports of both presence and absence, and “variable” means the weed can grow with or without it, depending on the soil.

Response to nutrients: How plants grow in relation to the amount of nutrients in the soil, mostly N, P, and K (high, moderate, and low).

Emergence to flowering: The amount of time (in weeks) that plants need to flower after they emerge, based on when plants usually emerge in the area where the event occurs. “Emergence to flowering” refers to the time between a plant species’ first flowering and its return to growth in the spring.

Flowering to viable seed: Length of time (weeks) after flowering for seeds to become viable.

Concerning pollination, “self” describes species that only self-pollinate, “cross” describes species that only cross-pollinate, “self, can cross” describes species that mostly self-pollinate but also cross-pollinate at a low rate, and “both” describes species that do both at about the same rate.

Typical and high seed production potential: The first value is the number of seeds that can be grown on a plant under normal conditions where weeds and crops compete. The second value, high seed production, refers to conditions of low density without crop competition. Numbers are rounded off to a magnitude that is representative of often highly variable reported values.

Alexander, H. M. , C. L. Cummings, L. Kahn and A. A. Snow. 2001. Seed size variation and predation of seeds produced by wild and crop-wild sunflowers. American Journal of Botany 88: 623–627.

Burton, M. G. , D. A. Mortensen, D. B. Marx and J. L. Lindquist. 2004. Factors affecting the realized niche of common sunflower (Helianthus annuus) in ridge-tillage corn. Weed Science 52: 779–787.

Cummings, C. L. and H. M. Alexander. 2002. Population ecology of wild sunflowers: effects of seed density and post-dispersal seed predators. Oecologia 130: 274–280.

Robinson, R.G. 1978. Control by tillage and persistence of volunteer sunflower and annual weeds. Agronomy Journal 70: 1053–1056.

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Other common names: sunflower, wild sunflower

Common sunflower vegetative plant

Common sunflower plants in flower Photos by: Anita Dille, Kansas State University

Family: Aster family, Asteraceae

Habit: Tall, upright, branched summer annual herb

Taxonomic note: The species Helianthus annuus has been classified into a cultivated subspecies (ssp. macrocarpus), a wild subspecies (ssp. lenticularis) and a weedy subspecies (ssp. annuus). Weedy populations often have more genetic ties to nearby wild populations than to each other. This makes it hard to believe that weedy forms are a separate taxonomic entity.

Description: Seedling stems below the cotyledons are green to purplish. Cotyledons are oblong, hairless, 0. 5–1. 5 inch long by 0. 25–0. 5 inch wide and fused at the base. The first one to three pairs of true leaves are opposite, and all subsequent leaves are alternate. Early leaves are dull green on top and light green on the bottom. They have teeth on the edges and rough, stiff hairs on both sides. Leaves are oval to lanceolate with a tapered and rounded tip. Mature plants are typically 2–10 feet tall. The stems are erect, branch occasionally towards the top and are densely covered in coarse, spreading white hairs. The leaves are 4–12 inches long, egg shaped to triangular or heart shaped, stalked, toothed and conspicuously three-veined. Both surfaces of the leaves are covered with stiff white hairs. Upper leaves have shorter stalks than lower leaves and may be lanceolate. The root system is a taproot with branching and spreading fibrous roots. One to 12 flower heads occur at the end of stems and branches. The flower heads have long stalks and are 3 to 15 inches wide. They have 20 to 40 yellow ray flowers that look like petals around a lot of red to purple-brown disk flowers. The yellow ray flowers are 0. 6–1. 6 inches long, whereas the disk flowers are 0. 2–0. 3 inch long. Beneath the flower head are two to three rows of overlapping, hairy, green, tapered oval bracts. Seeds are encased in a hard, dry fruit known as an achene. These units (hereafter called seeds) are 0. 13–1 inch long by 0. 1–0. 6 inch wide, oval and flattened, and are tipped with two to four bracts that detach at maturity. The seeds are white, gray, brown or black, and are often mottled or streaked.

Similar species: Several species of Helianthus are similar to common sunflower. Prairie sunflower (H. petiolaris Nutt. ) is an annual species with smaller, 1–2 inch-wide flowers and narrower, 2–6 inch-long by 0. 5–3 inch-wide triangular to lanceolate leaves. The rhizomatous perennial Texas blueweed (H. ciliaris DC. ) is shorter than common sunflower, 28 inches tall and has lanceolate, blue-green leaves. Jerusalem artichoke (H. tuberosus L. ) is a rhizomatous perennial that produces knobby, irregular tubers at the rhizome tips. Jerusalem artichoke leaves are narrower, 1. 6–4. 7 inches wide, than common sunflower, and the flower heads are smaller, 2. 5–3. 5 inches across.

Since sunflowers come up very early in the spring, few seedlings will grow or be a problem if winter wheat is grown next to them. When common sunflowers usually come up, they are slowed down by the thick canopy of winter wheat and spring canola. Also, winter grains are harvested before most sunflower seeds are fully grown, which means that these crops will likely reduce the population. However, it will be up before corn, soybeans, or grain sorghum are planted in no-till summer crops, so it needs to be managed at that time. If not, it will become a big problem for those crops.

For bad infestations, capture the seeds in the combine and separate them from the crop afterward. Common sunflower seed has a high oil content, and captured seed could be a potential fuel source. Alternatively, the seeds can be ground to destroy viablility and fed to livestock. Grazing cattle on infested grain stubble can reduce seed production. It is important to avoid fall tilling when managing common sunflowers because mixing seeds into the soil keeps seed predators away. Large, oily seeds are very appealing to quail and small mammals. During the winter, these animals often eat most of the surface seeds. This greatly reduces the density of seedlings emerging the next spring. Although seeds can potentially survive for many years in the soil, few actually do so. So, using the above methods to drastically cut down on seed bank input for even one year can bring down a serious infestation to levels that can be handled. Hand roguing escaped sunflowers is effective for preventing an increase of low level infestations in row crops.

The seedlings are large, fast growing and can emerge from deep in the soil. Consequently, rotary hoes are relatively ineffective against this weed. Tine weeding should be aimed at breaking or burying the seedlings. If common sunflower plants between rows get large, avoid using shovels on flexible S-shanks. These will tend to walk around the strong taproots and leave the plants in place. Instead, use sharp sweeps fixed at a shallow angle, and run about 1. 5–2 inches deep to sever the shoot from the root. New shoots cannot sprout from root tissue alone. The large nutrient storage in the seeds allows seedlings to penetrate even thick layers of mulch.

The common sunflower can freely hybridize with the domesticated sunflower, which means that genes for disease and insect resistance from cultivars could be introduced. This may increase survival, reproduction and competitive ability of the weed.

Origin and distribution: Common sunflower is native to western North America. It now occurs throughout the United States, including Hawaii and Alaska, and in much of Canada and Mexico. It has been introduced into the Caribbean, South America the Middle East and parts of southern Asia.

Seed weight: Mean seed weights for North American populations range from 6. 5–8. 7 mg, although seeds produced late in the season (October) can average as little as 4. 3 mg.

Dormancy and germination: The viability of common sunflower seeds can be as low as 2072% and as high as 2094%E2%80%9399%. Seeds are dormant when mature. Many seeds can germinate after a few months of being buried in cold, wet soil after they have been ripe or dried out. However, some seeds may still be dormant even after this long. Shallow burial of the seeds over the winter greatly increases germination the following spring. Some seeds will germinate at 39°F, but germination is quicker and more complete at 68–77°F. Light is not required for germination. It doesn’t matter if the pH is 4 or 10, seeds will still grow. Some seeds will even grow in water with 10,000 parts per million salt.

Seed longevity: A few seeds survived at least 17 years when buried at 8 inches and left undisturbed. Soil burial in the autumn after seed dispersal greatly facilitates formation of a persistent seed bank. Seed mortality rates vary greatly from year to year. Average mortality rates for seeds buried for two to four years range from 26–47% per year. During the first winter, few seeds die in the soil, but most seeds on the soil surface die that winter, and only a few seeds stay on the soil surface for more than two years.

The seedlings in the northern Great Plains come up from late April to early June, with most of them coming up in May. In Kansas they emerge from late March through early May. Some seeds from a population in Kansas were tested at different locations in the Midwest. They grew the most in a two-week period, with the most growth from late March to early May. When plants came up depended on the temperature and moisture of the soil, and it changed a lot from year to year at the same site. Warmer winters prolong the period over which seedlings emerge relative to cooler winters.

Emergence depth: Seedlings can emerge from depths of at least 4 inches.

Photosynthetic pathway: C3

Frost tolerance: seedlings in the cotyledon stage can live in temperatures as low as 23°F, and full-grown plants can live in temperatures as low as 28°F.

Drought tolerance: Common sunflower is moderately drought tolerant. The main taproot can go down 10 feet, which lets established plants get water from deep in the ground where not many other plant roots can reach.

Mycorrhiza: Wild common sunflower has high mycorrhizal infection rates. In domestic sunflower, high mycorrhizal infection improves P uptake and growth. Canola and other non-mycorrhizal crops can make domestic sunflower production go down, and the weed may do the same.

Response to fertility: The USDA says that the common sunflower doesn’t need much fertility, but in Argentina, it can only grow on soils that are fertile and high in organic matter and available phosphorus. It grows on soils with a pH between 5. 5–7. 8. Domesticated sunflower responds very well to nitrogen. Yields often keep going up even when more than 161 pounds of nitrogen are applied per acre.

Soil physical requirements: Common sunflower can grow on soil of fine, medium and coarse textures. It can survive in poor soil, shallow soil over limestone and mild waterlogging. It has medium tolerance to salinity.

Response to shade: Common sunflower is intolerant of shade.

Sensitivity to disturbance: No information available.

Time between emergence and reproduction: Flowering starts nine to seventeen weeks after emergence and lasts for four to thirteen weeks, depending on the population. In the central Great Plains, the common sunflower blooms from July to October and mostly spreads its seeds from September to October, though some may keep spreading all winter.

Pollination: Sunflowers are self-incompatible and are insect pollinated.

Three groups that didn’t have to compete with crops had an average of 38 heads per plant, 136 viable seeds per head, and 5,300 seeds per plant. In another study, a normal plant that didn’t have much competition made 7,200 seeds, but some of them weren’t fully grown and some had already broken. A type of Argentine sunflower grown next to domestic sunflower had 34 heads per plant, 190 seeds per head, and 6,500 seeds per plant on average.

Dispersal: The seeds are dispersed locally by birds and small mammals. They also disperse in surface irrigation water. Combined harvesters help common sunflower patches grow and may sometimes move seeds to fields that haven’t been planted with them yet. The species grows along roadsides, and seeds are likely moved to new spots when dirt is dug out of ditches. Seeds probably also move in soil clinging to tires and machinery.

Common natural enemies: Insects, birds and small mammals eat many sunflower seeds. In one study, 42% of seeds left on the soil surface were eaten in the first 10 days. Red sunflower seed weevil (Smicronyx fuivus), gray sunflower seed weevil (S. Some common sunflower populations in Kansas were hurt by the sunflower moth (Homeosoma electellum), the banded sunflower moth (Cochylishospes), and the sunflower budworm (Sulemia helianthana). These pests killed more than two percent of the seeds and damaged a quarter of the heads. Many of the diseases and insects of domestic sunflower probably also attack common sunflower.

Palatability: Seeds are edible for humans and livestock. Common sunflower can be used as forage at any stage of growth, but because it has a high Ca/P ratio, it shouldn’t be the only food source.

How to Grow Sunflowers Successfully At Home

How many seeds are in a sunflower?

The seeds are harvested from the plant’s large flower heads, which can measure more than 12 inches (30.5 cm) in diameter. A single sunflower head may contain up to 2,000 seeds. There are two main types of sunflower crops. One type is grown for the seeds you eat, while the other — which is the majority farmed — is grown for the oil.

How far apart should sunflower seeds be planted?

Plant seeds 1-2 inches deep, spaced 12-18 inches apart in rows at least 24 inches apart. This allows room for plants to grow to their mature size without crowding. Water gently after planting and keep soil consistently moist until seeds germinate. What ongoing care do sunflowers need? Once established, sunflowers are quite low maintenance.

What are sunflower seeds?

Sunflower seeds are technically the fruits of the sunflower plant ( Helianthus annuus ). The seeds are harvested from the plant’s large flower heads, which can measure more than 12 inches (30.5 cm) in diameter. A single sunflower head may contain up to 2,000 seeds. There are two main types of sunflower crops.

How do you plant sunflower seeds?

The soil for sunflowers should be loose, fertile, and well-draining. You can mix in compost or other organic matter to enrich the soil. Remove any weeds before planting. When is the best time to plant sunflower seeds? Most gardeners plant sunflower seeds directly in the ground after the last spring frost.