Growing Sunflowers

Updated: Sep 15

They’re not just beautiful – many sunflowers are also edible. Their seeds, of course, make for a great healthy snack. But some varieties also produce tubers – underground stems – that can be cooked and enjoyed in many different dishes.


To help ensure your Sunflowers thrives, we’ve put together this how-to video and transcript covering topics like:

  • Glossary of Sunflowers terms

  • Varieties of Sunflowers available

  • Starting your Sunflowers seeds

  • Caring for Sunflowers at all stages

  • Fertilizer and/or Mulching

  • Transplanting best practices

  • Companion Plants do’s and don’ts

  • Common challenges and Their Solutions

  • Pests, Diseases and what to do about them

  • Harvesting and storing your Sunflowers



Listen to this Article:



Glossary of sunflower Terms

Before we get started, let’s learn a little bit about sunflowers.


INFLORESCENCE

Each sunflower head is actually made up of two types of flowers: ray and disk.


DISK FLOWERS

The face of the head has hundreds of disk flowers, each of which form into a seed (also known as achene).

DISKING

A soil preparation practice that typically follows plowing, which cuts, granulates, and inverts the soil, creating furrows and ridges. Disking will break up clods and surface crusts, which improves soil granulation and makes for a more uniform surface.


HELIOTROPISM

The directional growth of a plant as it follows the sun. Sunflower heads track the sun early in their development, but later will stay east- facing before facing downwards.


TUBER

An underground stem that is used to store nutrients. Certain sunflowers have edible tubers.


TRUE LEAVES

The first leaves that look like those of a plant’s mature leaves, and are not the first leaves of a seedling. True leaves have

sharper edges and are not as smooth as the seedling leaves.

Sunflowers Growing Outdoors

Varieties of sunflowers

These are the different types you can grow for cooking and eating purposes.


RUSSIAN GIANT & MAMMOTH RUSSIAN


Sunflower: Russian Giant and Mammoth Russian Variety

These plants grow to at least 10 feet tall, sometimes as tall as 15 feet. They usually have one large flower head that’s about a foot across.





KONG

Sunflower Kong Variety

Similar to the Russian Giant, this variety can reach 10 feet tall or higher, with heads that are 1 foot across. This variety has a habit of branching, and will produce multiple flowers per plant.







SUNSPOT

Sunflower Sunspot Variety

A shorter variety, this plant reaches 2 feet tall and has flower heads that are about 10 inches wide.







Starting your sunflower seeds

  • Keep in mind that their optimal soil temperature for germination is between 80 and 90°F (26.6-32.2°C). Your plants won’t germinate in cool soil, which is anything below 60°F (15°C).


DIRECT SOWING

STEP 1

  • Space your seeds about 6 inches apart in a shallow trench about 1-2 inches (2.5-5cm) deep. If you’re planting in sandy soil, then 2 inches deep works best.


STEP 2

  • Cover your seeds, and keep them watered until they sprout – which typically takes 7-10 days.


STEP 3

  • Sow a new row every 2-3 weeks to enjoy continuous blooms until the first frost.


  • NOTE Depending on the variety you grow, sunflowers will mature and develop their seeds in 80-120 days.


TRANSPLANTING

STEP 1

  • If you plan to start your sunflowers indoors, use separate compartments of a seeding tray.


STEP 2

  • Fill the tray with potting mix and plant each seed so that about a half inch of the mix covers the top of the seed.


STEP 3

  • Then, water your soil until it’s moist – and make sure to keep it moist as your seedlings grow.


STEP 4

  • Also, you’ll want to maintain your soil’s temperature around 65-75°F (18-23°C).

A Field of Sunflowers

Caring for sunflower


  • We’ll tell you everything you need to know about thinning, staking, and watering your sunflowers as well as their fertilizer and mulch needs.

  • We’ll also explain how to transplant, which growing structures to use, and the best companion plants to grow with sunflowers.

  • Sunflowers can be grown in USDA zones 1-10, and will thrive in slightly acidic to somewhat alkaline soil, usually with a pH between 6.0 to 7.5.

  • Their ideal soil temperature for germination is between 70-85°F (21-30°C ), and they need sunlight to germinate. In general, seeds should sprout in about 10-14 days.

  • Sunflowers grow best in spots that get direct sunlight, roughly 6-8 hours a day. They also need long, hot summers in order to flower really well.


STAKING

  • Though there are a few sunflower varieties that don’t need staking, it’s a good idea to support any plants that grow over 3 feet tall or are multi-branched.

  • Plant a stick (or a long metal piece) vertically beside your plant’s stem, attaching one to the other.

  • Tie your plants loosely to these stakes with bits of cloth or other soft material as needed.


WATERING

  • Sunflower roots spread widely and can withstand some drought, but it’s best to still water them regularly during their most important growth period (about 20 days before and after flowering).

  • Deep, regular watering helps to encourage their root growth, which is especially helpful when growing taller sunflower varieties that have top-heavy flowers.


WEED CONTROL

  • Sunflowers are a strong competitor with weeds (especially for light), but they don’t cover the ground early enough to prevent those weeds from starting.

  • That’s why it’s important to control any weeds in the early season in order to get good yields from your sunflowers.


POLLINATORS

  • Bees are super important for a sunflower’s yield.

  • They carry pollen from plant to plant, which results in cross pollination.


PINCHING

  • Taking your thumb and forefinger, pinch out your plant’s tip after 4 leaves have grown.

  • This process will double or triple the number of flowers per plant, although the flowers will be smaller in size.

a Close up of a Sunflower

FERTILIZING AND/OR MULCHING

FERTILIZING

  • Sunflowers are heavy feeders, so their soil needs to be nutrient-rich with organic matter or composted (aged) manure.

  • Since they grow quite vigorously (sunflowers can easily grow 6 feet in just 3 months), it’s a good idea to add some slow-releasing granular fertilizer about 8 inches deep into your soil, especially if it’s poor and thin.

  • The better their diet, the larger the flowers. Just make sure not to add too much nitrogen, because it will delay flowering.

  • When your plants are 30cm (12) tall, dissolve 5ml (1 tsp) of borax (for boron) in 350 ml (12 fl oz) of water and spread this solution over 5m (15 feet) of row.

  • By adding boron, it’ll help your plants produce big seeds and flower heads. Just be careful not to over-apply it, and don’t use it on other garden plants.


MULCHING

  • By spreading a 2-3 inch mulch layer on your soil, it helps to retain moisture while also discouraging weeds from growing.

  • It’s best to use organic material like wood chips, shredded leaves, grass clippings or compost.


TRANSPLANTING BEST PRACTICES

  • When your sunflower seedlings reach 4-5 inches (10-12cm) in height, you should transplant them as long as the weather outside is ideal.

  • You won’t want to transplant your sunflowers until any chance of an overnight frost has passed for the season.

  • NOTE Letting a sunflower grow any taller than a few inches before transplant can weaken their plant structure.

  • Because of this, try not to start your sunflower plantings until late enough in the spring that you can transplant them as soon as they reach the right height.

Growing Fresh Sunflowers in the Sun

GROWING STRUCTURE OPTIONS

RAISED BEDS

  • Sunflowers have long tap roots that need to stretch out - so when you’re preparing a raised bed, make sure to dig down 2 feet in depth and about 3 feet across.


CONTAINERS

  • Big Smile, Elf, Pacino, Sundance Kid, Sunspot and Teddy Bear are some of the varieties that will grow well in containers.

  • Larger sunflowers grow deep, tuberous roots, so it’s best to only plant smaller varieties in smaller containers (under 10-inches wide).

  • As with most container growing, you’ll need to add fertilizer to provide your soil with enough nutrients. Ideally, organic and slow-release fertilizers are what you’ll want to use.


CELL TRAYS

  • Given the large size of sunflower seeds, either 72 or 144-cell trays are best for seedling production.


COMPANION PLANTS DO’S AND DON’TS

DO’S

  • Sunflowers planted near rows of corn can increase yields. Also, cucumbers, peppers, tomatoes, and soybeans are other great companion plants.


DON’TS

  • Sunflower seeds, leaves and stems emit substances that can prevent the growth of certain other plants. They should be separated from potatoes and pole beans for this reason.

Honey Bee on a Sunflower

Common challenges and their solutions

  • Sunflowers are a tricky crop to grow – and there are a few different types of issues, pests, and diseases that can potentially harm them.

  • Not to worry, we’ve listed them below, as well as how to either avoid or fix the problem.


SEEDLING ROOT FEEDERS

WIREWORMS

The larvae of this pest feed on germinating seeds or young seedlings, and infestations are more likely to happen where grasses (especially perennials) have been growing. The stems of young seedlings may emerge shredded, while damaged plants are likely to wilt and die soon after becoming infected.

  • Solution: If the risk of wireworm damage is high, seeds can be treated with an approved insecticide to protect them while germinating, and to further protect them as seedlings.


SUNFLOWER BEETLE

Adult beetles and larvae feed on your sunflowers, which can cause poor seed set and seed filling, reduced yields, and delayed maturity.

  • Solution: Natural predators usually keep sunflower beetle populations below damaging levels.

  • Sunflower beetle eggs are eaten by lady beetles, while the larvae of the common green lacewing will eat both the eggs and larvae. Damsel bugs and the two- spotted stink are also known to eat these pests.


CUTWORMS

These can be a serious problem in many field crops, as they cut your plants at the soil level. There are a number of different species, but the most common are redbacked, darksided and dingy cutworms.

  • Solution: Young cutworm larvae can be starved before spring seeding by allowing volunteer growth (like weeds) to reach 3-5 cm (1.2 to 2 inches) in height, before cultivating these weeds and then seeding your sunflowers 10-14 days later.

  • Many insects, parasites, and birds will also prey upon cutworms, and can help lower their numbers.


INSECTS IN THE STEM

SUNFLOWER BUD MOTH

Most of their damage will be found in the stems of your sunflowers. Occasionally, they can cause damage to the developing heads.

  • Solution: Unfortunately, there’s not much you can do to control these pests since insecticide is not a recommended fix.

  • The good thing is that these pests have not been known to cause any substantial economic problems.


SUNFLOWER STEM WEEVIL

There are two main stem weevil species: the Spotted Sunflower Stem Weevil and the black sunflower stem weevil. They typically weaken stems, and occasionally can cause substantial yield loss.

  • Solution: By delaying your planting until late May or early June, it can help to reduce the amount of larvae in the stem.

  • Fall tillage practices (which either bury or break up sunflower stalks) will also help to kill off the stem weevil larvae over the winter.

  • Natural enemies of the stem weevil, like certain wasps, also help to keep them in check.


SUNFLOWER MAGGOTS

There are three main species that, while in their larval stage, will feed on your sunflowers and cause seed sterility or stalk breakage. Typically, this damage happens when there are high numbers of this pest - otherwise, the damage is usually not that serious.


INSECTS ON THE HEADS

SUNFLOWER MIDGE

The larvae of this pest can affect the growth of your sunflower heads. Heavily-damaged heads become gnarled and cupped inwardly, and won’t produce as many seeds.

  • Solution: Delayed planting (until late May) can help you avoid the first major appearance of overwintering midges (i.e. ones that have survived the winter), but later infestations can still be severe.

  • Some commercial hybrids are tolerant or resistant to the sunflower midge, so it’s best to consult your state/provincial agricultural representative for more localized information on the most resistant varieties.


BANDED SUNFLOWER MOTH

The larvae feed on kernels, causing seeds to not fully develop while also lowering their oil content. Oftentimes the kernels are only partially fed upon, making it quite tricky to separate healthy seeds from those that are weevil-damaged.

  • Solution: Cultural control methods, like tillage and planting early, have both been effective ways to reduce damage from these pests.


SUNFLOWER SEED WEEVILS

The larvae feed on kernels, causing seeds to not fully develop while also lowering their oil content. Oftentimes the kernels are only partially fed upon, making it quite tricky to separate healthy seeds from those that are weevil-damaged.

  • Solution: Early planting helps to reduce seed damage because your sunflowers will have completed their flowering.

  • That means they’ll no longer be susceptible to egg laying during peak weevil populations.

  • Fall or spring disking can also help fight off these pests.

  • For the most part, insecticides (sometimes in combination with trap-cropping) are typically the best way to manage these pests and to reduce their damage.



LYGUS BUG

They’ll feed on developing seeds, which can cause kernel brown spot. This appears as small brown to black spots on the blunt end of sunflower seeds.

  • Solution: Certain insecticide treatments can help reduce feeding damage when you apply them at the beginning of the flowering process.


BENEFICIAL INSECTS


DAMSEL BUGS

  • These prey on sunflower beetle larvae as well as banded sunflower moth eggs and larvae.


TWOSPOTTED STINK BU

  • It preys on sunflower beetle larvae.


PARASITIC WASP

  • Attacks both the eggs and young larvae of banded sunflower moths, sunflower seed weevils, and sunflower stem weevils.


GROUND BEETLES (CARABID BEETLES)

  • They can destroy 40% of the overwintering larvae (ones that survive the winter) and pupae of sunflower beetles.


HOVER FLY

  • Increases crop yields by enhancing pollination, while also feeding on aphids.

HONEY BEE

  • Increases sunflower yields by enhancing pollination.


LADY BEETLES

  • They consume sunflower beetle eggs, aphids, and banded sunflower moth eggs and larvae.


GREEN LACEWING

  • They’re predators of a variety of sunflower pests including aphids, sunflower beetle eggs and larvae, and banded sunflower moth eggs and larvae.


MINUTE PIRATE BUG

  • Both immature stages (nymphs) and adults feed on a variety of sunflower pests like aphids and the eggs and larvae of banded sunflower moths.


HOMEMADE INSECTICIDES

Soap Spray


  • STEP 1 Fill a jug or pitcher with one gallon of water. Then, measure out 2 tbsp. of dishwashing liquid (preferably organic) and 2 tbsp. of baking soda. Mix these well with a wooden spoon.

  • STEP 2 Grab an industrial-type plastic spray bottle, and label it with your mixture. Using a funnel, fill the spray bottle with your soap spray.

  • STEP 3 Spray the soapy mixture directly on pests that are hiding within your sunflower’s branches. Check the undersides of leaves, spraying them completely. You’ll want to apply this to your sunflower plants daily until the pests disappear.


Oil Spray

  • STEP 1 Fill a liquid measuring cup with 1 cup of vegetable oil, then gradually add 1 cup of dishwashing soap. Mix well with a spoon and then set it aside.

  • STEP 2 Fill a spray bottle with 1 tbsp. of your oil/soap mixture. Using a funnel, fill the spray bottle with water. Save the remaining vegetable oil and soap mixture in a jar or plastic container to make more oil spray as needed.

  • STEP 3 Apply directly on pests and sunflower leaves, shaking the bottle to mix it as you go. You’ll want to apply this to your sunflowers on a weekly basis.


Garlic Spray

  • STEP 1 Fill a pitcher with 1 quart of water, measure in 1 cup of vegetable oil, then mix well using a spoon.

  • STEP 2 Add 3 tbsp. of dishwashing liquid to your garlic mixture. Cover the container, and refrigerate overnight.

  • STEP 3 Add 3 tbsp. of dishwashing liquid to your garlic mixture. Cover the container, and then refrigerate it overnight.

  • STEP 4 The next morning, strain out the garlic pieces. Using a funnel, fill a labeled plastic spray bottle with your liquid mixture. Apply directly to pests and to your sunflower’s leaves, using it weekly to keep pests away.

Sunflowers Growing Outside

POTENTIAL DISEASES

ALTERNARIA LEAF BLIGHT

Small, yellow-brown spots with a yellow or green halo will first appear on the oldest leaves. As the disease progresses, leaves will begin to curl and eventually will die. This disease is common in growing areas with high temperatures and frequent rainfall.

  • Solution: Water your plants from below to avoid having soil splash up onto the lower leaves.

  • If you can water from below using a soaker hose or drip irrigation AND provide a well-ventilated cover for your plants to protect them from the rain, you’ll be all set.

  • Be sure to clean any equipment between uses to prevent the spread of bacteria, and do not prune or handle your plants when they’re wet.

  • Also, establish a crop rotation and stick to it. If you do spot some blighty leaves (usually on the bottom of the plant closest to the soil), remove and destroy them.


DOWNY MILDEW

Small yellow areas and irregular brown lesions will appear on the upper leaf surface, while gray mold grows on the lower leaf surface.

  • Solution: Plant resistant varieties when possible, prune or stake your plants, and remove any weeds to improve air circulation.

  • Water your plants early in the morning or use a soaker hose, which gives your plants time to dry out during the day. Also, keep the ground under

  • any infected plants clean during the fall and winter to prevent the disease from spreading.

  • Be sure to remove and destroy any plants with a serious infection. Keep in mind that downy mildew is much easier to control when your plants are kept protected by a copper spray.

  • You can begin treatments two weeks before the disease normally appears, or when you’re in for a long period of wet weather.

  • You can also begin treatments when the disease first appears, then repeat at 7-10 day intervals for as long as you need to.


SEPTORIA LEAF SPOT

Water-soaked circular or angular spots will appear on the leaves with a greasy, greenish appearance on the lower ones. Lesions are usually gray with a darker edge, though some may have a narrow yellow border. Tiny black fungal fruiting growths can also sometimes appear in the lesions.

  • Solution: Plant high quality seeds that are free of diseases. Also, rotate your crops away from sunflowers for a period of 3 years, especially if you’re using overhead watering.


POWDERY MILDEW

Powdery white patches initially appear on the lower leaves, but they can eventually spread to the rest of your plant. White patches will then turn gray in color, and black fungal growths will appear. Also, severely infected leaves may turn yellow and dry up.

  • Solution: Avoid this disease by spacing and pruning your plants to provide good air circulation.

  • Use a thick layer of mulch or organic compost to cover the soil after it’s been raked and cleaned, which will help prevent the disease spores from splashing back up onto the leaves.

  • Milk sprays, made with 40% milk and 60% water, are an effective home remedy you can try. For best results, spray your plant leaves as a preventative measure every 10-14 days.

  • Also, you can occasionally wash the leaves of your plant to disrupt the daily spore- releasing cycle. Neem oil and PM Wash, used on a 7-day schedule, will also help prevent fungal attacks on plants grown indoors.

  • Finally, water in the morning so that your plants have a chance to dry out during the day. Drip irrigation and soaker hoses are both options that will help keep your plant leaves dry.


VERTICILLIUM WILT

When affected by this disease, lower leaves will look spotted and discolored – that’s because the leaf tissue between the veins will turn yellow and then brown, and infected leaves wilt, dry out and eventually die. The stems of your plants might also turn black near the soil line.

  • Solution: Plant high quality, disease-free seeds, and avoid planting sunflowers in fields that were previously infected with Verticillium wilt.

  • Also, plant resistant sunflower hybrids in spots where the disease is known to be problematic.

Rows of Sunflowers Outside

Harvesting and Storing

HARVESTING


  • FOR SEEDS

  • Let the flower dry (either on or off the stem) until the back of the head turns brown, the leaves turn yellow, the petals die down, and the seeds look plump and fairly loose.

  • To harvest seeds ahead of birds and squirrels, cut off the seed heads with a foot or so of the stem still attached. Then, hang the heads in a warm, dry place that is well-ventilated and protected from rodents and bugs.

  • Keep your harvested seed heads away from humidity to prevent mold from spoiling them, and then you’ll want to let them cure like this for several weeks.

  • Once the seeds are totally dry, dislodge them by rubbing two heads together. You can also try brushing them off with your fingers or a stiff brush.


FOR TUBERS

  • In cooler climates, you can start harvesting tubers after the first frost, once your plants have begun to die back.

  • If you live in a warmer climate, you can actually leave your harvest until mid-winter. Simply dig them up out of the ground, taking care to be gentle.


STORAGE FOR SEEDS

  • Allow them to dry for a few more days, then store in airtight glass jars in the refrigerator to keep their flavor.


FOR TUBERS

  • They’re not the easiest to store, but one cool benefit about tubers is that they’re quite happy to be left in the ground until you need them.

  • If you would like to keep some stored, make sure to put them somewhere very cool and with high humidity.

  • The perfect spot (with these conditions) will help prevent them from shriveling.



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