Not all seeds have the same light requirements. Most seeds germinate best under dark conditions and might even be inhibited by light (e.g., Phacelia and Allium spp.). However, some species (e.g., Begonia, Primula, Coleus) need light to germinate (Miles and Brown 2007).
Some seeds such as beans need darkness in order to germinate; other seeds such as lettuce need light. Seeds that require darkness should be covered with fine soil or vermiculite to a depth equal to twice the seed's diameter.
Seeds that require light for germination are usually small. Milberg et al. (2000) suggested that a light response and seed mass coevolved as an adaptation to ensure germination of small-seeded species only when close to the soil surface.
Most seeds can germinate in darkness or light (one exception is lettuce, which needs light) but once the seeds have sprouted, keep the lights on about 12-16 hours per day.
They perform important respiratory functions at night. Seedlings should have at least 6 hours of darkness per day, and more mature plants at least 8-10 hours a day.
The light slows stem elongation through hormones that are sent down the stem from the tip of the stem. In the darkness, the hormones do not slow stem elongation. The seeds in the dark-grown condition rely upon the stored chemical energy within their cells (lipids, proteins, carbohydrates) to power their growth.
Some seeds like Allium 'Purple Sensation' and Eryngium giganteum need a long period of cold-moist stratification with alternating temperatures. These are the most difficult seeds to germinate.
All seeds need water, oxygen, and proper temperature in order to germinate. Some seeds require proper light also.
You'll be on the safe side and the warmer soil and air temperatures will get your plants off to a robust start. Tomato seeds need darkness to germinate, which means they should be planted about 1/4 inch deep in a light-weight, sterile potting mix.
Some of the slowest to germinate are peppers, parsley, and eggplant, so be patient! Watering your seeds every day to keep the surrounding soil moist is vital to the germination process. The moisture acts as an alarm bell for your seeds to “wake up” and sprout.
Yes, cucumber seeds need light to germinate. Make sure that the soil is exposed to at least 8 hours of sunlight each day for the best results. If you are planting indoors, it's important to provide a strong source of artificial light as well.
Your seeds will require dark to germinate, so they must be planted at the appropriate depth. For most sunflower varieties, that's somewhere between a half and three-quarters of an inch deep, but you should look up the depth specific to your variety just to be sure.
Many variables can affect the germination rate of seeds. How the seeds were stored, their age, the depth at which they were planted, the weather, the soil they were planted in, moisture, and temperature can all play a role in the success or failure of germination.
Speed sprouting by presoaking seeds
I pour hot tap water into a shallow container, empty a packet of seeds into the water, spread them out, and let them stand for up to 24 hours. Soak the seeds for any longer and they might rot. The seeds swell as water penetrates the seed coat and the embryo inside begins to plump up.
By soaking the seed, it enables the new growth from the inside to push through the hard shell and grow. The seeds that could benefit from a good soaking include: corn, pumpkin, beans, chard, beets, and peas. The seeds you shouldn't soak include: carrots, lettuce, radish, celery, turnips, and spinach.
Some are quick to germinate, taking 1-2 weeks at most, such as chillies, beans, sunflowers and pumpkins. Some seeds take more like 2-4 weeks, such as mango and parsley. Others, depending on how warm/cold it is, take closer to 2 months, for example avocado.
The fastest germinating seeds include everything in the cabbage family – bok choi, broccoli, kale, cauliflower etc, and lettuce. The slowest seeds to germinate are pepper, eggplant, fennel, celery, which may take 5+ days.
It's official: beans, peas, and pumpkins are among the top ten easiest plants to grow from seed, according to a list created by the Home Garden Seed Association.
The oldest seed germinated is a 2,000-year-old date seed originally discovered at Masada in the 1960s and planted by Dr Sarah Sallon (Israel) of The Louis Borick Natural Medicine Research Centre in the Hagasa Medical Organization, Jerusalem, and Dr Elaine Soloway of Kibbutz Ketura, Israel, in 2005.
Plants, shrubs and trees use sunlight for photosynthesis during the daytime, but at night they need darkness to regenerate a key compound - phytochrome. Nighttime lighting can reduce vegetation's ability to properly create this compound.
The process of keeping a plant in the dark for a day or two is known as destarching. The plant is kept in the dark for 24-48 hrs. During this time, photosynthesis is halted due to an absence of light. Therefore production of new starch is also stopped.