Plan your garden around the sun
Understanding daylight hours is essential for successful gardening. Plants use day length to regulate growth, flowering, and dormancy. Use our calculator to optimize your planting schedule based on your location's photoperiod.
Light is the primary energy source for plants and a critical environmental signal. Understanding these factors helps you optimize your garden for maximum productivity.
Plants produce energy through photosynthesis during daylight hours. More sunlight means more sugar production for growth, flowering, and fruit development.
Most vegetables need 6-8 hours of direct sunlight. Leafy greens can tolerate partial shade (4-6 hours), while fruiting plants like tomatoes require full sun (8+ hours).
Plants measure day length to determine when to flower, fruit, or go dormant. This biological clock evolved to optimize reproduction for specific seasons.
Onions form bulbs based on day length. Long-day varieties need 14-16 hours; short-day varieties bulb with 10-12 hours. Choosing the wrong type for your latitude results in poor harvests.
Plants have internal clocks that regulate growth hormone production, stomata opening, and nutrient uptake based on light and dark cycles.
Consistent light cycles improve plant health. Interrupting dark periods with artificial light can stress plants and disrupt flowering in photoperiod-sensitive species.
Dawn and dusk provide different light spectrums than midday sun. Blue morning light promotes vegetative growth; red evening light encourages flowering.
Position gardens to capture morning sun for heat-sensitive crops. Afternoon sun is more intense and can stress plants in hot climates.
Average Day Length: 10-14 hours increasing
As daylight hours increase, plants emerge from dormancy. This is prime time for starting seeds and transplanting.
Start indoors 6-8 weeks before last frost when days reach 12+ hours
Direct sow when soil warms; bolt-resistant in longer days
Need 14-16 hours of light for optimal seedling growth
Plant early when days are still short (10-12 hours)
Thrives in cool temperatures with 10-14 hour days
Photoperiodism is a plant's response to the relative lengths of light and dark periods. Understanding your plants' photoperiod requirements helps you predict flowering and optimize harvests.
Flower when days exceed 12-14 hours
Best planted: Early spring or late summer
Flower when days are less than 12 hours
Best planted: Late summer for fall bloom
Flower regardless of day length
Flexible: Temperature matters more
Morning sun (eastern exposure) is gentler and preferred for heat-sensitive crops like lettuce and peas. Afternoon sun (western exposure) is more intense and suits heat-loving plants like tomatoes and peppers. Track sunrise and sunset times to understand your garden's light exposure throughout the day.
Use the day length calculator to identify your garden's peak sun hours. Paint fences white to reflect light onto plants. Position tall crops on the north side (in the Northern Hemisphere) to prevent shading. Consider vertical gardening to capture light at multiple levels.
When starting seeds indoors in late winter, natural daylight is insufficient. Seedlings need 14-16 hours of light daily. Use grow lights to supplement the short winter days. Calculate the difference between natural day length and required light hours to set your timer correctly.
The summer solstice (around June 21 in the Northern Hemisphere) marks the longest day. Days shorten afterward, triggering fall crop development. The winter solstice (around December 21) is the shortest day, after which daylight increases. Plan succession plantings around these pivotal dates.
Use our comprehensive sunrise and sunset calculator to track daylight hours throughout the year. Bookmark this page and check back seasonally to optimize your planting schedule.
Full Sun Calculator