Like a tall, gangly supermodel, sunflowers (Helianthus annuus) need thoughtful care to look their best and not overshadow other residents of the garden. One sunflower per square foot is the recommended spacing in a square-foot garden plan, where plants are plotted out on an optimally spaced grid. Smaller varieties can be planted more closely together and still give a good flower display, as can taller varieties when the size of the flower head is of no particular concern.
Square Foot Gardening
This style of gardening turns the traditional row-planting system on its head by dividing the garden into a grid made up of 1-square-foot blocks and spacing seeds within each block at an ideal interval for that particular crop. This allows gardeners with limited space to use more of the available planting area and achieve higher yields. Small-statured vegetable crops like carrots and onions can be planted more thickly within a block, at a rate of 16 plants per square foot, while large, resource-hungry crops like sunflowers should only be seeded at a rate of one plant per square foot block.
Spacing for Sunflowers
In a traditional garden with rows, experts usually recommend spacing sunflowers 4 inches apart in rows 1 foot apart. This allows sunflowers the room they need not only to grow tall enough, but also to branch outward with their broad leaves. Frequently, depending on the type of sunflower grown, side shoots also produce smaller flower heads in addition to the main central bloom.
Effects of Overcrowding
Some gardeners may intentionally overplant a row of sunflowers to create a hedge-like effect. However, sunflowers that are planted too near to their neighbors usually end up displaying their suffering by growing thin, spindly stems that are prone to falling over and produce underwhelming small flowers. In addition to potentially shading out other nearby plants, crowded sunflowers are also more susceptible to disease because of reduced airflow.
Appropriately Spaced Plants
Sunflowers grown at a proper distance from one another in a square foot gardening system will have a thick, strong central stem, broad leaves and many side branches off the main stem. Mammoth varieties that grow to 8 feet or more should always be given appropriate space to allow the seed head to develop to its full potential. Smaller varieties grown for their flowers are usually much shorter, to 6 feet or less, and can still produce plenty of attractive, bouquet-worthy flowers when seeded at two plants per square foot. One planting technique for assuring one strong plant per square foot is to plant two or three seeds, allow them all to sprout, and then snip off the two weakest plants at the ground once they have reached 6 inches in height. This method of thinning is also recommended for traditional row-based gardens.
- Arcadia Farms: Square Foot Gardening Plant Spacing
- University of Minnesota Extension: Sunflowers
- Burpee Seeds: Sunflowers
- Missouri Botanical Garden: Helianthus Annuus
- University of Wisconsin Extension: Specialized Gardening Techniques
- University of Florida IFAS Extension: Square-Foot Gardens
- University of Minnesota Extension: Sunflower Plant Population and Its Arrangement
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