Onion seeds do not need light to germinate, but they prefer a thin layer of soil covering them. According to the University of California Extension, the ideal soil temperature for onion seed germination is 65 to 85 degrees Fahrenheit (18 to 29 degrees Celsius).
Will onion seeds germinate in the dark?
Onion seeds don’t need light to germinate, but the seedlings will require 12 hours a day as soon as they begin to emerge.
Can you grow onions in the dark?
Onion plants need between 12 to 16 hours of light, varying by whether they are long-day or short-day onions. Supplement sunlight with artificial light if needed. While you can start with onion seeds or sets, you can easily turn leftover onion bulbs or sprouted onions from your kitchen into an indoor garden.
Can germination occur in the dark?
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).
How do you germinate onion seeds fast?
Provide bottom heat. The tops of my florescent plant lights are flat, and they give off just the right amount of bottom heat needed to help onion seeds germinate quickly. Onion germination is fastest as 68-77°F (20-25°C), with slight temperature drops at night.
What seeds germinate in the dark?
Some other popular types which prefer darkness for germination are:
- Calendula.
- Centaurea.
- Delphinium.
- Gazania.
- Nemesia.
- Primula sinensis.
- Schizanthus.
How much light do onion seeds need?
Start onion seeds indoors about 8 to 10 weeks before the last spring frost date in your area. Follow the common best practices for indoor seed-starting: use a sterile seedling potting medium, keep the soil damp but not soggy, and provide at least 12 hours of bright light per day after germination.
Can onions grow without direct sunlight?
Can Onions Be Grown in Shade? Except for green onions, all other onions need plentiful sunshine to grow. Onion bulbs grown in shade likely won’t produce edible onions. They’ll also be more susceptible to onion maggots and bulb rot.
Why do onions sprout in the dark?
In complete darkness, a struggling plant will respond to gravity by growing upwards in a process called gravitropism. This gives it the best chance of reaching light and surviving.
How many hours of light do onion seedlings need?
Sowing Seed Indoors
Keep moist and maintain a temperature of about 60-65 degrees F. Seedlings emerge in 7-14 days. As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night.
Does darkness help germination?
1073. Seeds will not germinate so well in light as in darkness ; because light decomposes the carbonic acid gas, expels the oxygen, and fixes the carbon; thus hardening all the parts of the seed, and preventing vegetation.
Why it is better to germinate in the dark?
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. In dark environments, the gases remain undisturbed and germination is favoured.
How does darkness affect germination?
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.
Why won’t my onion seeds germinate?
Onion seeds germinate at temperatures above 40°F; the optimum soil temperature is 75°F. If seeds are planted too early, cooler air and soil temperatures will delay germination and emergence (15- to 25-day requirement), and cause seedling growth to slow.
Does it take 2 years to grow onions from seed?
Answer: All onions and leeks are biennial, meaning that they normally take two years to grow from seed, flower and set seed again. First, they grow “vegetatively,” forming roots, leaves and other plant growth.
How long do onions take to germinate from seed?
6-12 days
Optimal soil temperature for germination: 21-25°C (70-75°F). Seeds will emerge in 6-12 days, depending on conditions.
How many hours of light do seeds need to germinate?
16-18 hours
A sprouted seed is no longer a seed but a seedling, a miniature plant. The most important thing to consider and deliver is adequate plant light. Seedlings need more light than full grown plants, ideally as much as 16-18 hours a day.
How long should seedlings be in the dark?
Yes, it is true that your seedlings need lots of bright light to grow healthy and strong—but they also need a period of darkness in order to thrive. In general, seedlings should receive roughly 14 to 16 hours of light a day when situated in a south-facing window.
Do seedlings grow better in the dark?
Growth of Seedlings
If there is not enough light, the seedlings will grow taller but will be thin and leggy. They will be less likely to survive transplanting. If there is too much light for plants that naturally grow in low light, they will be weak and begin to burn and turn brown around the edge of the leaves.
When should I start onions indoors?
When and How to Start Indoors. Plant onion seeds indoors 8–10 weeks before transplanting them outside just before the average last frost date in your area. Seeds should be sown ¼ inch deep. Onions require an open and sunny site, fertile soil, and good drainage.
What is the best way to start onion seeds indoors?
To start onion seedlings indoors in February or March, fill a container nearly to the top with a seed starting mix and then make two furrows, about 1/2-inch deep, for the onion seeds. Sprinkle seeds in the furrows and cover them lightly with more soil mix. Label the container with the name of the onion variety.