How to Grow Sunflowers
The sunflower, Helianthus annuus, is a flower native to the Americas. Sunflowers have bright yellow blooms that mature into a dense seed heads. The stem and leaves of sunflowers are rough and hairy. Sunflowers possess a unique ability called heliotropism, which allows the flower head to turn and always face the sun.
Growing sunflowers is relatively easy. Most varieties are drought and heat resistant making them ideal for hot summers. The only difficulties that surround growing sunflowers is the demand of direct sunlight and depletion of soil nutrients. Sunflowers deplete nutrients much more rapidly compared to other plants, which may cause some problems if planted in a garden or flower bed. Keeping the soil nutrient-rich is simple to do with common flowering fertilizer.
There are plenty of seeds for snacking once the sunflower life cycle ends. Many people eat the seeds directly from the seed head, while others salt or roast them. If consuming the seeds isn't desired, then leave the seeds for birds and other animals to enjoy.
Sunflower seeds can be sown directly into the ground, or seedlings can be grown first and planted later. Sowing the seeds directly into the soil is preferred, because the flowers will experience no transplant shock and the root system will develop quicker and stonger compared to transplanted seedlings. Establishing the roots early on is vital for the growth and health of the plant.
Plant the sunflower seeds no more than 1 inch deep and about 5 inches apart in tilled, loose soil after the ground has warmed up around mid-April to late May. Rows should be around 30 inches apart to allow for future growth and avoid overcrowding. Pluck out seedlings that have grown too close to each other as well.
Sunlight Requirements for Sunflowers
Sunflowers grow best in full sun throughout most of the day. 8 hours of direct sunlight is ideal, and more than 8 hours is even better. Long, warm summers produce great flowers and seed heads.
Sunflowers have a unique ability that is shared with several other plants around the world. Heliotropism is a trait that allows the flower head to turn and face the sun, despite the location of the sun in the sky. Sunlight usually isn't a problem as long as sunflowers are grown in open, unshaded areas.
Soil for Sunflowers
Sunflowers need soil that drains well and does not become waterlogged. Performing a percolation test will determine how well soil can drain. Soil nutrient testing is beneficial to determine how fertile the soil is before planting and applying fertilizer. Sunflowers also prefer soil that falls between 6 and 7.5 pH. Sandy soils that drain too quickly need organic matter such as mulch or compost thoroughly worked into the soil. Clayey soils retain a lot of water and need amendments such as mulch, sand, compost, and/or perlite to facilitate drainage.
Prepare the soil by digging an area about 2-3 feet in circumference to a depth of about 2 feet. Thoroughly work amendments into the soil to facilitate drainage if necessary. Rows of sunflowers should be at least 30 inches apart to prevent overcrowding.
Sunflowers are tolerant of short droughts and wet spells. Watering sunflowers involves a few factors that are simple to understand.
When to Water
Watering comes down to the weather. Very hot, dry summer days may require sunflowers to be watered every few days or even daily during a severe drought. Sunflowers will require little or no watering during rainy periods. Overwatering promotes unhealthy roots, diseases like root rot, and causes instability to the tall stalk of the flower. Soggy soil does not provide a firm medium for the roots to keep the stalk upright. When in doubt, always keep sunflowers on the slightly dry side.
A soil probe is a very handy tool to have around and can be used to see how moist the soil is a foot or more below the surface.
How to Water
Sunflowers have an extensive root system that requires thorough watering. Watering needs to soak most, if not all, the root zone. Drench the soil and do not water again until the soil starts to become dry. This method will help build a strong and resilient root system. Water a few feet away from the stalk as well. Sunflower roots are spread out and some watering needs to occur away from the stalk to give the outstretched roots a drink.
Sunflowers are very taxing on the nutrient content of soil. Fertilizer should be worked into the soil prior to sowing due to the high demand for nutrients in the spring.
Common fertilizer with nitrogen, phosphorus, and potassium will work fine for fertilizing sunflowers. The combination of the nutrients should be a 10-15-10 fertilizer. Granular fertilizer is ideal in the spring due to a slow release of nutrients over time. Work in a little granular fertilizer into the soil prior to planting, if the soil is not rich in nutrients. A water soluble fertilizer can be used once the sunflower has become more mature. An organic route can be pursued and compost can worked into the soil, along with manure and other chemical alternatives.
Beware of Over-Fertilizing
Be careful when fertilizing. Preventing over-fertilization is a must. Leaves will burn and the plant may actually die when subjected to high amounts of fertilizer. A soil test is very useful to determine how rich the soil is before fertilizers are added. Always use half of the recommended amount listed on the fertilizer package if in doubt of how much fertilizer should be applied.
Sunflowers grow tall and may require support to keep the stalk upright. Bending and drooping stalks can be stressed to a point where the stalk buckles or snaps. Driving stakes or posts into the ground and tying straps or thick string/rope to the sunflower stalk will help keep it vertical. Do not use thin string or cables, because these can cut into stalk and cause damage. Overall, straps are the best choice. Sliding a small section of tubing onto string or rope will help prevent abrasion against the sunflower stalk. Old, unused garden hoses work great and can be cut up to make several segments to place over support ropes for sunflowers, young trees, and many other upright plants.