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Garden Guide » Sunflowers


A gardening guide on how to plant, grow and care for sunflowers.

Sunflower seeds and growing

Sunflowers and Germination

Helianthus annuus, also known as sunflowers,  brighten any size garden with their large daisy-like flowers in  shades of yellow, orange, red and bronze. Tall varieties of this easy-care annual are usually used for back-of-the-border plants, cutting gardens and food for wildlife. Shorter varieties make colorful additions to traditional cottage gardens and any container. Sunflowers are an easy plant to start from seed, germinating quickly under the right conditions and growing rapidly.

Choosing the Right Soil for Sunflowers

Sunflower seeds should be  sown directly into the soil outdoors or started indoors in peat pots several weeks before transplanting time. For outdoor planting, a location in full sun with well-drained soil is required. If drainage is an issue, 2 to 4 inches of compost can be spread over the soil. Adding 2 cups of complete organic fertilizer, such as a 4-5-4 formulation, per 10-foot row and tilling the amendments into the soil to a depth of 6 inches will provide nutrients during the growing season. Indoors, sunflower seeds are started in 3- to 4-inch pots filled with a well-draining soiless planting media.

Sunflowers and Moisture

Sunflower seeds are planted one to one-half inch deep. Because sunflowers are an oil-rich seed, they require a bit more water for germination. This requires watering the ground thoroughly outdoors after planting and not allowing the soil to dry out completely until germination occurs, and the baby sunflower plant has arrived. Indoors, the soilless media is completely saturated and allowed to drain before 2 or 3 seeds are planted in each pot. Covering the pots with clear plastic wrap slows evaporation, and maintains the proper moisture levels.

The Right Temperature for Sunflowers

Sunflowers germinate best at a soil temperature of 70 to 85 degrees Fahrenheit, but can be planted once the temperature is over 60 degrees. Outdoor planting time is typically several weeks after the last spring frost when the soil has warmed thoroughly. Indoors, a heating mat under the pots can raise the soil temperature to at least 70 F. The seeds will sprout in 7 to 14 days outdoors. Indoors, where the growing environment can be more closely controlled, germination often takes place in six to 10 days.

Sunflowers and Light Requirements

Sunflower seeds do not require light for germination. However, when grown indoors in pots, the plastic wrap is removed at the first sign of germination and the uncovered pots are placed in bright, indirect light. When the plants have their first set of true leaves, the seedlings are thinned to 1 per pot and an all-purpose water-soluble fertilizer is applied at half strength weekly. Outdoors, thinning small varieties to 6 inches apart and large varieties to 3 feet apart allows ample light and airflow around sunflower seedlings.
Sunflower gardening

How To Plant Sunflowers

Planting and Growing Sunflowers

So, if you found us, you have one big thought on your mind…how do I grow the sunflower plant?  This garden guide page will give you all the information you need for planting and growing sunflowers.   Below is an overview of all the steps you need to get growing.  If you like pretty pictures and visuals, see our All About Sunflowers page.

How and where do I get sunflower seeds?

So, you can just plant those sunflower seeds you have been eating from the bag in the cupboard, right?  Well, cant do that…those are roasted and dead to growth.  You have a number of options for getting seeds.  If you already have a sunflower plant, you can read this article on harvesting and collecting sunflower seeds.  If you have a neighbor that is giving, you can do the same with one of their sunflower blooms.  You can also purchase a number of different varieties of sunflowers at just about any home store, like Lowes or Home Depot, or you can get some from any of the internet seed providers (We use Johnny’s Seeds here at Celtic Farm).

Where do I plant sunflowers?

Sunflowers absolutely love the sun (imagine that), and they will grow best in a planting location that receives full sun.  In fact, they love the sun so much, their heads actually move for maximum sun exposure (no kidding).  As for soil, they are extremely durable, and will do well in just about any soil type, as long as it is not waterlogged.  Because of their size and head weight, soft soil can allow them to uproot during windy days. Sunflowers do quite well in a broad range of soil acidity, usually 6.5-7.0 if you like to measure that stuff.  I also like to note that the sunflower plant does emit substances that will inhibit the growth of neighboring plants, and they should be separated from beans and potatoes.

Can I start sunflower plants indoors?

Sunflowers are not keen on root disturbance, and direct seeding is the best way to plant.  But if you are hard over on getting them started as early as possible, they can be placed in peat pots indoors to get a jump on the growing season.

When do I plant sunflower seeds?

Like most plants, you want to plant your sunflower seeds after the last frost, and once the soil temperature has reached 55-60 degrees.    They can take minimal chill, so if you are in a short growing period area, they can be placed two or so weeks before the last chill.

How do I plant sunflower seeds?

Plant the seeds about 1 inch deep,  and about 6″ apart.  If you want rows, common wisdom says to place them 24-30″ apart.  If you want to have flowers all summer, do succession planting and do the same every 2-3 weeks.

How much do I water my sunflower plants?

Sunflowers are fairly drought tolerant, but need sufficient water until established.  Water your sunflower babies daily, and then once flowers appear you can water more infrequently, even to once a week with a single heavy water.

Do I fertilize sunflowers?

If you plant your sunflowers in soil rich in organic matter, they will do just fine, but to get amazing blooms you should fertilize .  You can add light fertilizer or granules, but feed sparingly as over-fertilizing can create brittle stalks.   See the side column for a suggested fertilizer.

How do I harvest and collect sunflower seeds?

You can harvest and collect sunflower seeds from your spent flower heads to plant next season, or to eat.   Some of the larger species have 1500-2000 seeds per head!!  It is a fairly easy drying procedure that will allow you to gather seeds.   See the link above for more info on step by step procedures for collecting.

What are pests common to sunflowers?

Sunflowers are not a favorite of the insect population, and can remain insect free as long as they are kept healthy.  Mildew can be a problem, but can be controlled on sunflower leaves with neem oil or other fungicide.  If you do want to collect your seeds, you will need to keep birds and squirrels away.