plant of the month
Sunflower, Common sunflower, Mirasol, Marigold of Peru
Potted sunflowers are genetically dwarf varieties that have daisylike flower heads, 2 to 4 inches in diameter. The flower heads are made up of “petals” (ray florets) surrounding central disks that comprise hundreds of tiny yellow, brown, green or deep purple flowers (disk florets). Stems are leafy and hairy, with single flowers or branched sprays of blooms.
Natural hues include a range of yellows, bronzes, browns, reddish-browns, cream/tan and bicolors.
Depending on care, environmental conditions, variety and stage of maturity at the time of sale, sunflower plants can last 10 to 14 days indoors. (See “In-store and Consumer Care,”)
Potted sunflowers are grown from seed, in greenhouses, and can be available year-round, depending on grower.
in-store and consumer care
Sunflower plants require bright light indoors: filtered or diffused sunlight is ideal, but they can tolerate some full sun, especially morning sunlight. If placed outdoors, they can have some exposure to full sun.
These plants are easily water stressed, so keep potting medium evenly moist—but not waterlogged. Check the soil daily; the plants’ extensive root systems and large leaves cause it to dry out quickly. (See “Challenges: Leaf Yellowing/Drop,”.)
Standard indoor temperatures, 65 F to 75 F, are acceptable. In your facilities, plants can tolerate one week of cold storage at 36 F to 41 F without any reduction in decorative life or damage to the plants.
HUMIDITY / AIR CIRCULATION
Low to moderate humidity levels are best for potted sunflowers, and good air circulation is a must, particularly in overly humid environments. (See “Challenges: Diseases,”.)
Some cultivars of sunflowers are sensitive to ethylene gas, but many are not affected. To be safe, make sure your purchases are treated with an ethylene inhibitor at the grower or during transportation, and keep them away from sources of ethylene in your facility, especially fresh fruit and other produce.
For their relatively short lifespan, potted sunflowers generally do not require fertilizer. While they do have high nutritional requirements, they typically receive all the nutrients they need at the grower level.
GROOMING / REBLOOMING
Cut off blooms as they fade, and discard plants when they’re finished blooming because they will not rebloom or continue to live.
LEAF YELLOWING / DROP
Aphids, whiteflies, thrips and spider mites can be problems. Treat infestations with insecticidal soap.
Pythium root rot and powdery mildew (a parasitic fungus), which cause leaf yellowing, leaf edge browning and even plant death, are the result of overwatering, poor soil drainage, high humidity and/or poor air circulation.
BROWN OR BLACK EDGES ON LEAVES
In addition to Pythium root rot and powdery mildew, causes can include whiteflies and other insect infestations.
This is most likely a symptom of water stress, the most common cause of which is underwatering; however, indoor environmental conditions as well as too little sunlight, overwatering, poor soil drainage, high humidity and poor air circulation can also result in these problems.
If you have trouble viewing these PDF (portable document format) files, download a copy of the free Adobe Reader.
PRETTY AND PRACTICAL
Sunflowers are commercially grown today primarily for ornamental (cut flowers), oil-seed and food-producing purposes. Confection varieties of sunflowers are grown for their seeds, which are sold for human consumption as well as birdseed. Other varieties are grown for the oil contained in the seeds, most of which is used in food products but also can be found in certain soaps, paints and cosmetics. (See more “Fun Facts” in “Cut Flower of the Month,”.)
• Buy and market potted sunflowers when their ray florets (“petals”) are at least one half expanded (open).
• Cultivar selection is important with potted sunflowers to achieve acceptable height, balance between blooms and foliage, decorative life, and bloom size and form. Among successful varieties in meeting these criteria are ‘Elf’, ‘Pacino’ and ‘Teddy Bear’.
Some information provided by:
A Repetto Nursery Inc., Half Moon Bay, Calif.
Botanica, by R.J. Turner Jr. and Ernie Wasson
Chain of Life Network® , www.chainoflife.org
Greenhouse Product News, Sept. 2001
by Liberty Hyde Bailey and Ethel Zoe Bailey
Silver Terrace Nurseries, Pescadero, Calif.