When it comes to sowing seeds, the general rule of thumb is to sow seeds twice their diameter.
And while that applies to most vegetable seeds, it does not apply to all vegetable seeds. It’s not so sure about herbs and flower seeds.
As you know, some seeds actually need light to germinate. If they are buried on the ground, they will not break dormant.
This may sound counterintuitive, simply by plunging holes into the soil and dropping seeds, or covering the seeds with a layer of soil after sowing. However, many common plants need light to germinate, or at least they may surprise that when the seeds are exposed to light, they germinate more successfully.
When seeds are light dependent, they are known as photoblast species. These seeds are sensitive to the presence or absence of light and come in two main types.
Positive photoblast seeds require light to begin germination. Negative photoblast species germinate best in the darkness and can even be blocked by light.
So, what kind of light will it have?
If you are starting seeds indoors, light quality is important. The light source can affect germination too weak (or too little). This means that in some homes it may not be enough to simply set the tray in front of the window (unless you can clearly see the sky).
I use an inexpensive LED Grow light with a seed starting setup, the same full spectrum light used for seeds, and hang it near a seed tray about 3-4 inches. Next, set the light on the timer and turn it on from 4am to 8pm every day. This is 16 hours.
The minimum light required is 10 hours a day, but seeds germinate faster and provide 14-16 hours of light daily to make the seedling stronger. (However, do not leave lights 24/7. All plants need a period of rest in the dark.)
Seeds that need light to germinate
About a third of the species we generally start out do not germinate without being exposed to light. These plants are:
Ageratum Amaranth Ammobium anemone Angelica Anise Hyssop Arugula’s Breath Bee Balm Begonia Bellower Billyflower Billy Buttor Bill Vervain Bonet Browallia Butterfly Bush Calceolaria Catnip Celry CemoGerbera Gloves Amaranth Gloves Thistle Gloxinia Heather Holly Hock Impatience Joe Pie Weed
Lavender lettuce lisianthus lobelia love-in-a-mist marjoram meadowweet mint mint mint mugwort nepeta nettles nicotiana nigella oregano osteospermum pampas pelargonium petunia poppy primrose (most species) rosemary savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savoia savo
Many of these species will notice that they are smaller or very thin seed coats that are not larger than pinheads.
Reading the back of the seed packet is often instructed to push the seeds firmly into the soil. And you can see why! Covering these seed spots puts them in the dark even in the thinnest layers of soil.
A species that requires darkness to germinate
On the other hand, some strange seeds will not germinate unless they are in the dark. You may have noticed this because our tendency tends to cover the seeds with soil after sowing them.
But if you’ve ever wondered why your seeds are germinated badly, the lack of darkness can be the reason!
Calendar of the Bachelor’s Degree Button* cilantro* delphinium* forgate-me-not* gazania madagscar periwinkle or vinca*
Nasturtium nemesia* Pansy* Phacelia* Phlox* Schizanthus or Butterfly Flower* Sweet Pea Verbena, Hybrid*
Plants with an asterisk show seeds that either sink to the surface or are barely covered in the soil. Of course, this presents a dilemma. How do you provide darkness if the seeds are sitting on top?
There are several options:
Cover with an upside-down seed tray with a seed tray placed on top to prevent any light that does not reach the seeds. Use a simple thin board on a blackout humidity dome (such as) or seed tray. Place the seed tray in a dark closet or cupboard (it rarely opens). Place the seed tray in a black garbage bag to seal all the light.
Whichever method you use, it is important to provide light as soon as most of the tray sprouts. Plants that require darkness to germinate also need light for healthy growth. The lack of bright light at this stage is the main cause of etiolation (Legy seedlings).
Seeds indifferent to light
The majority of seeds in home gardens germinate either exposed to light or unexposed. All vegetables (except lettuce, arugula and celery) fall into this category, making it easier when growing edible gardens. If you’re adding herbs or annuals to your mix, be sure to check the list above.
With light indifferent seeds, I usually sow them indoors, but do not turn on the cultivation light until the first few buds appear.
I’m lazy too. That is, sprinkle most of the darkness on the soil (except for those that require darkness to germinate), and place a clear humidity dome (I like this short model) on the tray until the seeds germinate.
Doing this means that hundreds of seeds can be seeded more quickly each day and kept them moister. As soon as half of the tray sprouts, the humidity dome will come off and the growth light will turn on for 16 hours a day.
