Some seeds can be direct-sown while others do better when started in a nursery environment prior to the start of the growing season.
Sowing Directly
This method works well when you have a long growing season and plenty of time for the plants to mature and produce a full harvest. Large seeds, such as beans, corn, peas, cucumber and gourds all do well sown directly in the soil in which they will mature. Likewise, root vegetables and deeply rooted vegetables do better when they can grow freely, unencumbered by shallow seed pallets. These include carrots, potatoes, and even tomatoes for their deep root system.
As a general rule, seeds are planted at a depth of about 1 x the width of the seed. There are exceptions, including coconut and avocado, but for most vegetable varieties this allows enough soil, moisture, and warmth for seed germination. For more precise planting depths refer to the links at the bottom of this page.
There are also those like potatoes, yams, and bananas that do not grow from seed at all. For potatoes, simply cut a 1 inch chunk containing at least one “eye” and plant it at a depth of about 2 inches or 5 centimeters. As the vine matures, continue to add more soil burying the vine and encouraging the development of more potatoes. Leeks and celery can also be started simply from a bundle purchased at the market. Just eat the tops and plant the rooted ends, adding soil around the base of the plant as it develops.
The tiniest of seeds may simply be broadcast, or scattered, over the growing bed, dusted with a fine layer of sand or soil, and thinned as they mature. These would include salad greens, the young greens eaten as they are thinned to allow space to develop mature heads.
Starting Indoors
Starting seeds indoors is primarily used to take better advantage of short growing seasons. With late and early frost dates in certain regions, it makes more sense to start seeds indoors or in greenhouses one to several months prior to the last frost date before planting. Most seeds purchased in cooler climates will come with specific instructions for starting each variety indoors, but in general they all need the same things: a growing medium, warmth, and moisture.
Seed pallets or other small containers should be prepared with fine, rich soil containing organic matter but no stones or large pieces of wood that might obstruct growth. Most seeds require a soil temperature of at least 70 degrees to germinate, so it is important to start your seeds in a protected location free from drafts. It is also important to keep the seeds and seedlings evenly moist while they develop.
Once the first true leaves (not the first leaves after sprouting) appear, they will need light to continue to grow. A draft-less window sill or a simple lamp will do, making sure to provide them with at least six hours of light per day. Then, after the last frost and before planting, seedlings should be hardened off prior to transplanting. This simply requires placing seed pallets outdoors during the day and bringing them in at night for about 1 week to allow them to acclimate to the cooler temperatures.
See the planting dates and seed depths for the Northern and Southern hemispheres for more details.
Still have questions? Feel free to ask us or share your experiences in the comments!
