Sunflower: June 2019 Houseplant of the Month

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The Story of the Sunflower

The potted sunflower is a not a permanent houseplant, but rather a temporary one, designed to beautify your home for a month or so. Usually available only during the summer months, it can make a wonderful and sunny gift plant.

Potted sunflowers (Helianthus annuus) are dwarf varieties and don’t grow as tall as the garden variety. They do, however, offer the same unique and cheerful bright yellow flowers with a dark heart and attractive dark green leaves. A perfect companion for the kitchen worktop, the (garden) table, an office, or any room that could do with a touch of summer. Place a couple together in a container or in a group to make it feel like a flowering field. You can add a touch of lilac or purple to visually offset all that yellow.

Origin 

The sunflower originates from North America, but is now grown all over the world. It grows quickly from seed and turns into a fabulous yellow sunflower in just a few months. Potted sunflowers are widely grown in greenhouses specially for indoor use. 

Sunflower Range

Indoor sunflowers are dwarf plants, well-adapted to home décors.

The sunflower is best known as a garden plant: one tall stem bearing one enormous flower. The potted range is more compact, better suited to pot culture. Also, it is pollenless, without the yellow pollen that can fall on clothes and furniture. This also keeps the heart nice and dark, giving an attractive contrast with the yellow ray flowers (petals).

The sunflowers that Vincent Van Gogh painted—flowers with yellow ray flowers and a dark heart—are the most common form offered as cut flowers and container plants. But there are also potted sunflowers with a yellow or brown heart and with lemon, orange or brick red petals. Cultivars such as ‘Sunsation’ or ‘Funshine’ are among the most popular.

What to Look for When Buying Potted Sunflowers  

  • Look at the proportions between the pot size, the number of plants per pot, the number of buds per stem, the height and maturity of the plant.
  • The main flower should be half to fully open at the time of purchase. 
  • Also check that the stems are healthy and sturdy, and the soil is sufficiently moist: wilting leaves are an ominous sign.
  • Give the plants a thorough inspection. Sunflowers are vulnerable to aphids, leaf-miner flies and slugs. Botrytis mold on leaves, stem or flower does nothing for their decorative value either. 

Care Tips  

Give sunflowers a lot of sun.
  • As their name suggests, sunflowers love sunshine and can tolerate a lot of light.
  • The plant needs a lot of water. The soil should always be a bit damp.
  • Wilted flowers can be removed to give the new buds more space.
  • A bit of fertilizer once a week keeps the flowering going.
  • Once the last flower has faded, the plant’s useful life is over and you can put it into the compost bin without feeling any guilt. 

Can You Grow Your Own?

It’s easiest to buy potted sunflowers in bloom rather than grow your own.

Seed for dwarf pollenless sunflowers suitable for container culture is widely available, but growing sturdy, attractive dwarf sunflowers indoors is a huge challenge, as it’s hard to find an indoor spot with enough sun to bring it off. Instead, start yours in pots outdoors in late spring or early summer in full sun, then bring them indoors as they come into bloom.


Potted sunflowers: they bring a touch to summer to any décor! 

Text and photos adapted from a press release by Thejoyofplants.co.uk
Styling by Elize Eveleens, Klimprodukties

The Giant Sunflower That Came Out of Nowhere!

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The giant sunflower found in Louise Labrecque’s vegetable garden. Source: Louise Labrecque

Question: A giant sunflower grew in my vegetable garden without my having planted it. It’s gorgeous and looks like a big bouquet of flowers. Is it common to see such a tall sunflower?

Louise Labrecque

Answer: Sunflowers (Helianthus annuus) come in a wide range of sizes, from dwarf (less than 1 foot/30 cm) to giant, normally between 9 and 13 feet (2.7 m and 3.5 m) tall. Your plant is therefore a bit taller than normal and certainly very impressive, but far from the tallest sunflower ever grown (the world record height for a sunflower is 30 feet 1 inch [9.17 m]), or almost 3 stories high!

Also, it’s very common for sunflowers to show up all on their own in gardens or fields. Often birds or squirrels carry sunflower seeds a good distance from their source, usually a sunflower field or a bird feeder. For example, I find sunflowers in my container gardens every summer, plus peanut plants, all planted by a busy family of chipmunks.

That said, a self-sown sunflower of this size, with this many flowers, remains extremely very rare. You certainly won the luck of the draw with this one!

Why All the Buzz About Pollenless Sunflowers?

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20180226A Zohar www.johnnyseeds.com.jpg

Pollenless sunflowers, like ‘Zohar’ above, look much like any other sunflower, but don’t produce pollen. On a normal sunflower, there would be a ring of yellow pollen-tipped anthers around the disk, absent here. Source: http://www.lowes.com

If you’ve checked the sunflower (Helianthus annuus) page of any seed catalog lately, you’ll see that pollenless sunflowers are all the rage. They’re very popular with florists, for example, as they don’t produce annoying yellow pollen that falls unto furniture and clothes. But what the catalogs fail to mention is that they aren’t very bird and pollinator friendly either and if you’re trying to attract wildlife to your garden, they’re exactly what you don’t want!

History of the Pollenless Sunflower

Pollenless sunflowers originated as a mutation, a genetic error. They are male-sterile: the hundreds of individual florets that compose the composed inflorescence of pollenless sunflowers (Helianthus annuus) produce no pollen. This would be a disaster in the wild, but for hybridizers, it’s a boon.

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Creating sunflower hybrids used to require a lot of time-consuming manipulation. Source: lambley.com.au

Previously, hybridizers had to cut off all the tiny pollen-bearing anthers from the flower they wanted to use to create a new variety so as to avoid accidental self-pollination, then carefully carry pollen from the male parent flower to the emasculated female parent flower by hand, a long and tedious process. With pollenless sunflowers, they can just release a few bumblebees into a greenhouse containing a normal bisexual (hermaphroditic) sunflower and a pollenless one. The bees will then carry fertile pollen from the bisexual flower to the male-sterile one and any seeds formed on the pollenless flowers are therefore hybrids. Bingo!

At first, pollenless sunflowers were strictly used for hybridization purposes and never made it to people’s gardens, then someone realized that there would be a market for pollenless sunflowers in the florist industry. Indeed, flower arrangers love them: no extraneous pollen to brush away and also pollenless sunflowers have a longer vase life. What more could a florist ask?

Ideal for Allergy Sufferers?

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People rarely develop allergies to sunflowers as their pollen is not wind-borne. Source: www.theodysseyonline.com

An odd thing that is brought up by promoters of pollenless sunflowers is that they are nonallergenic and therefore ideal for hay fever sufferers. But then, regular sunflowers rarely cause problems for hayfever sufferers either. So why the fuss?

You see, sunflower pollen is not wind-borne and will not be carried in the air like tree, grass and ragweed pollen is. You’d practically have to stand under a blooming, pollen-rich sunflower and shake it while breathing heavily to absorb any pollen into your nostrils. This occurs so rarely that few hayfever suffers have ever come into contact with sunflower pollen … and you need a previous exposure to any new type of flower pollen before you’ll react to it.

So, unless you’re a commercial sunflower grower given to working in fields of sunflowers or a florist who manipulates many sunflowers, the pollen allergy conundrum is of little importance. Certainly, the casual sunflower grower has nothing to fear from sunflower pollen.

The Birds and the Bees

Today, pollenless sunflowers are widely available to home gardeners who, I suspect, grow them without realizing their full effects on wildlife.

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Bees need both pollen and nectar and will therefore prefer bisexual sunflowers. Source: www.kidsdiscover.com

Bees of all sorts visit sunflowers seeking nectar and pollen: they need both to feed their young. Pollen, for example, is their principal source of protein: they can’t survive without it. They will visit pollenless sunflowers, as they still produce nectar, but will then have to put in extra hours collecting pollen somewhere else. In these times when bees are struggling to survive, does it really make sense planting flowers that will make their life even more stressful? Bees eventually learn to avoid pollenless sunflowers, preferring pollen-rich flowers.

Other pollinating insects may or may not frequent pollenless sunflowers. Most pollinating beetles, for example, will avoid pollenless sunflowers: they’re pollen eaters. Butterflies and hoverflies, however, feed mostly on nectar and are unfazed by pollenless sunflowers.

If you’re like me, the main reason you grow sunflowers is to feed the birds. I leave mine standing all winter and get to enjoy visits by birds of all sorts. And if you sow pollenless sunflowers near bisexual sunflowers, they probably will be pollinated to some degree and will therefore produce seed. Great! But if you planted only pollenless sunflowers in your garden and none of your neighbors grow bisexual sunflowers, you can forget about feeding birds: no seed will mature. Bummer!

Harvesting Seed?

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If you intend to harvest seeds, you’ll want to grow “ordinary” (bisexual) sunflowers. Source: myculturedpalate.com

If you like to harvest seed of favorite sunflowers for next year’s garden, you won’t appreciate pollenless sunflowers. They are never true to type whereas non-hybrid sunflowers will be. There is therefore no use harvesting the seed of pollenless sunflowers.

As for harvesting seed for eating, that’s easy. The large-seeded types grown for that purpose are always bisexual. It would make no sense to develop pollenless large-seeded sunflowers: they would likely never produce a normal crop!

You Choose

So, here’s the situation in a nutshell. For most gardeners in most situations, pollenless sunflowers are not pollinator- and bird-friendly, nor are they good for harvesting. So, when you see the mention “pollenless” in a seed catalog, take that to mean a variety that’s best avoided. However, if you’re specifically growing sunflowers for use as cut flowers, you’ll probably be thrilled with pollenless sunflowers.

Clear enough?

Why Do Sunflowers Follow the Sun?

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Why do sunflowers follow the sun? Photo: Pixabay

It’s well-known that the sunflower (Helianthus annuus) follows the sun: its flower buds face east in the morning, south at noon and west in the afternoon, then return to their original position overnight. When the inflorescence finally opens, however, all movement ceases and the flower remains in an eastward orientation. But why?

Circadian Rhythm

Almost all living things, from germs to plants to mammals, follow a timetable of about 24 hours. This is called circadian rhythm and is a sort of biological clock. In its simplest expression, the clock tells the cells when to wake up and when to sleep, but its effect is much more extensive than that. In the case of the sunflower, in particular, it tells the stem how to grow.

A Stem That Grows at Different Speeds

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The stem elongates more quickly on the shady side, causing it to bend towards the sun. Illus.: ScienceMag

During the day, beginning in the morning, the sunflower stem elongate more rapidly on the shady side than on the sunny side, which makes the stem tilt in the opposite orientation. As the day progresses, shade moves eastward and so does the part of the stem that elongates fastest, pushing the bud westward. As a result, the flower bud follows the sun.

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At night, the stem elongates fastest on the west side, bringing the flower back to its eastern position. Illus.: ScienceMag

When the sun sets, the stem changes tactics and elongates mostly on the west side and this continues all night, thus pushing the flower bud back to its original position facing east.

So that’s how it’s done… but what advantage does the plant find in this movement?

More Sun, More Energy

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The flower bud is covered in green sepals and carries out photosynthesis. Photo: Tobyotter, Flickr

Before it opens, the inflorescence is covered with green leaf-like sepals that, like all the green parts of the plant, carry out photosynthesis. By always facing the sun, they help the plant gain more energy. When a sunflower stem is attached to a stake to prevent it from moving, this reduces the plant’s biomass, a proof that photosynthesis was not as effective in providing storable energy as in a free-moving sunflower.

When sunflowers are subjected to 30-hour days under laboratory conditions, this totally upsets their circadian rhythm: they lose the ability to redirect their flower buds eastward overnight.

Flowers are For Bees

But why then does the stem stop moving and remain facing east once the flower opens?

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When the flower opens, the sepals are now at its back and less efficient at photosynthesis. Photo: Pixabay

As the inflorescence expands and yellow ray flowers open, the green sepals, once out front, are pushed back behind the flower so they are largely hidden from the sun and therefore become less useful as a source of energy.

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Bees prefer eastern-facing flowers in the morning. Photo: Pixabay

However, a flower that faces the morning sun warms up faster than a flower facing any other direction. And bees and other pollinating insects, being cold-blooded, need extra warmth in the morning to overcome the chilliness still in the air. That’s why, in the morning, when the air is still cool, they tend to pollinate flowers oriented to the east over those facing any other orientation and to stay on them for a longer time.

One study showed that, in total, about five times more pollinators visited east-facing sunflowers than sunflowers that were staked to face other directions.

Later in the day, when the air is warmer, insects become indifferent to the position of flowers, but its eastward-facing habit has already given the the sunflower a clear advantage over the other flowers in its surroundings in the battle to attract pollinators.

And that is why sunflowers follow the sun!20170707A Pixabay

Source: ScienceMag20170707A Pixabay