Initially place seedlings outdoors in a sheltered spot – protected from wind and direct sun. Each day following, expose plants to another 30-60 minutes of filtered sunlight. Work your way up to giving plants direct morning sun, followed last by noon-day sun.
Most seeds will not germinate without sunlight and will perform best with 12 to 16 hours each day. Indoors, place seed containers in a sunny, south-facing window and give the container a quarter turn each day to prevent the seedlings from overreaching toward the light and developing weak, elongated stems.
Check seed packets for information on when to start seeds indoors in relation to your region's last frost date. Many plants don't need light until they've sprouted, so you'll start using grow lights once your seeds begin to germinate and the first leaves poke through the soil.
High insolation results in heat and moisture stress to the seedling and can cause mortality. Insolation is most likely to damage seedlings on drier habitat types and on south- and west-facing slopes.
A south-facing window is your ideal. To be honest, anything else is going to get gnarly. I've had some success on less-than-ideal windowsills, but only with older seedlings that got a good start elsewhere. Plants grown underneath grow lights receive bright light from above as they would outdoors.
Most of the seeds germinate best in dark environments. The presence of light tends to inhibit their growth. The light decomposes carbonic acid gas and expels oxygen which leads the seed to harden. These gases are key factors that promote germination.
If you have larger windows, you can place plants farther away and they will still receive plenty of light, while the smaller windows will only provide a limited range of sunlight. If you can, it's best to place plants directly in the window, especially if there are obstructions or no more than 2-3 feet away.
Sunscald injury of plants is easy to prevent, though there is no cure. Once leaves are damaged, all you can do is support the plant until it manages to grow new, stronger leaves.
Seedlings need to be watered at least once a day to keep the soil evenly moist, but not soggy.
Just as plants can suffer from too little light, they can also suffer from too much light. Overexposure to grow lights can cause light stress or photoinhibition, where the plant's ability to photosynthesize is inhibited due to excessive light. This can lead to stunted growth, bleaching of leaves, and leaf burn.
Typically, your seeds will stay in their seed tray for 4-6 weeks. After this period, you will either need to transplant the new seedlings into larger pots or transplant them outside. Check your seed instructions and pay attention to your frost dates before transplanting young plants outside.
Once leaves have sprouted, sunlight is the primary energy source for plant growth through the process of photosynthesis. A seed has everything it needs to begin a new life. Inside the seed coat, is an embryonic (baby) plant composed of an embryonic root, stem and leaves.
Is There A Limit To How Long You Can Leave Lights On? Short answer: yes. Even long-day plants need a daily respiration period of at least 6 hours (for seedlings) and ideally 8-10 hours for mature plants. We do not recommend providing more than 14-16 hours of light per day, even for long-day varieties.
Slowly Acclimate Seedlings to Outdoor Space
Continue this same pattern, increasing outdoor daylight hours by small increments each time. This process may seem tedious a few days in, but it is essential from strong, healthy starts. Avoid putting seedlings out on days that are particularly windy, chilly, or rainy.
Good air circulation is essential for preventing fungal diseases and promoting sturdy seedling growth. Avoid overcrowding seedlings by giving them enough space to breathe and grow. Use a small fan or gently move the air around the seedlings to improve airflow and strengthen their stems when growing indoors.
When should I remove the lid (dome) on my seed starting kit? As soon as half of the seedlings have sprouted.
WATERING SEEDLINGS FROM BELOW. Our preferred method of watering is from below. In our experience, it offers the most effective and reliable of the two options. Watering from below relies on capillary action, wicking of the water through the soil from the bottom working its way up to the top.
A gloomy, cloudy day is the best time to plant seedlings in the garden. If it's lightly drizzling, all the better. But if the forecast is for fair weather, avoid planting seedlings in the hot, mid-day sun. Get an early start in the morning, or wait and set a few plants in the ground at the end of the day.
All plants require light for photosynthesis, the process by which a plant uses light to convert carbon dioxide and water into carbohydrates (energy). Oxygen is released as a byproduct of photosynthesis. Plants require this energy to grow, bloom and produce seed.
Initially place seedlings outdoors in a sheltered spot – protected from wind and direct sun. Each day following, expose plants to another 30-60 minutes of filtered sunlight. Work your way up to giving plants direct morning sun, followed last by noon-day sun.
Direct sunlight and high temperatures should be avoided as much as possible. This may sound contradictory, because light and heat are essential for the growth of plants, so-called photosynthesis. For an optimal growth there should be a good balance in climate between temperature, light and humidity.
Recovering from Chemical Damage: Leach the Soil: If you suspect over-fertilization, flush the soil with water to remove excess salts. Remove Damaged Leaves: Prune away any severely damaged leaves. Replant in Fresh Soil: If the damage is extensive, consider transplanting the seedlings into fresh, uncontaminated soil.
Direct sunlight reaches the Earth's surface when there is no cloud cover between the sun and the Earth, while cloud cover causes indirect sunlight to reach the surface. In gardening, sunlight falling directly on the plant is direct sunlight, while indirect sunlight refers to shaded areas.
The natural light from a window is seldom enough for good, strong seedling growth.
Indirect sunlight occurs when something in the path of light from the sun diffuses or filters the sunlight before it hits your plants. Examples include sheer curtains, a piece of furniture, a tree outside your window, or even another indoor plant placed in front to protect the lower-light plant.