Starting plants from seed is an integral part of gardening. Here at Gardening Know How we get lots of questions about starting seeds, and our goal is to provide answers to those inquiries to the best of our knowledge. The following information includes the 10 most commonly asked questions about germinating seeds and caring for seedlings.
Seeds retain their viability when stored at cool temperatures, lower humidity and reduced light exposure. Begin by harvesting high-quality seeds from healthy produce. Next, be sure to thoroughly dry the seeds, then seal them in an airtight container. A jar or zippered plastic bag works well. Next, place the sealed container in the refrigerator or freeze them for storage. Be sure to label the seeds to avoid mix-ups in the spring. It’s advisable to use seeds as soon as possible for the quickest germination rate.
How long seeds stay fresh depends upon the type of seed and how the seeds were stored. Seeds stored in a cool, dry, dark location will remain fresher for a longer period of time. On average, most types of vegetable seeds will be viable for 2 to 3 years. Lettuce seed is particularly long-lived and can last for up to 5 years. On the other hand, parsnips rarely germinate after 1 year. To determine freshness, conduct a germination test on the seeds by placing 10 seeds on a moist paper towel. Seal the paper towel in a plastic bag or container. Wait ten days and count the number of seeds which sprouted.
Legginess in seedlings is a symptom of inadequate exposure to light. This condition causes seedlings to grow tall and narrow stems which can’t support the weight of the leaves. Most vegetable plants require 6 to 8 hours of direct sunlight per day. When sowing outdoors, plant vegetable seeds in a sunny location. Artificial lighting is often necessary when starting seedlings indoors. Florescent tubes were a popular choice in the past, but have since been phased out. These are being replaced with LED bulbs. Most indoor seedlings require 16 hours of artificial light per day to prevent legginess.
Yes! In northern climates, seeds from native plants frequently lay in frozen ground before germinating as soil temperatures rise in the spring. In fact, seeds of some species require a cold period, or stratification, before germination can proceed. Additionally, seed banks freeze their seeds in order to preserve and extend their freshness. To freeze seeds, be sure they are thoroughly dry as moisture can cause the seed to crack as it freezes. Place the seeds in an airtight container and avoid exposing frozen seeds to bursts of warm, humid air. Keep the frozen seeds at a constant temperature until they are thawed for planting.
Soaking seeds is a gardening trick to speed up germination rates. Larger seeds, those with a tough seed coat or ones which are traditionally slow to germinate, will benefit the most from soaking. Soaking seed is also useful whenever faster germination is desirable. To soak seeds, place them in a bowl of warm water. Large seeds, such as peas and beans, require an overnight soak of 8 to 10 hours. Smaller or thin-walled seeds can benefit from soaking for as little as 1 to 2 hours.
Covering seedlings is not necessary but it helps retain moisture levels which is essential for completion of the germination process. If seeds dry out at critical times, they may fail to sprout. If a cover is not used, it’s advisable to regularly check the seeds and mist with water to maintain a moist medium. Some seeds also require light to germinate, so any cover should be 100% transparent. Many seed starting trays come with clear covers, but these often get lost or damaged over the years. Plastic wrap can be used a substitute to cover seed cells. To prevent fungal disease and rotting, be sure to remove any covering once the seeds have sprouted.
Instructions to “sow thinly” often accompanies packets containing very small seeds. The challenge with sowing small seeds is getting them spaced far enough apart to prevent overcrowding once the seeds germinate. Trying to thin overcrowded seedlings can result in root damage and lost plants. To thinly sow seeds, space small seeds 3/16 to ½ inch (5 to 10 mm.) apart. Using a seed syringe or mixing the seeds with fine sand can make this task easier.
Seed-starting discs are used for germinating seeds, growing seedlings and in hydroponic gardening. Coir discs are manufactured using the husk or shell of coconuts and are considered eco-friendlier than those made with peat. To use seed-starting discs, soak them in warm water until they are fully expanded. The top of the disc contains an indent or small hole in the material covering the discs. Use this hole to insert the seeds. Keep the discs moist and warm while the seeds germinate. Once seedlings have 2 to 3 sets of true leaves, the disc and seedling can be planted into a pot, transplanted directly into the garden or placed into the growing chamber of a hydroponic system.
Credited as being a “whole habitat in a tiny clay ball,” seed balls are an easy way to distribute seeds in hard-to-sow areas. They contain seeds, humus and clay. Making seed balls is fairly easy (and a fun project with kids): Mix the clay and humus with enough water to give the consistency of modeling clay. Knead in the seeds and roll the mixture into 1-inch (2.5 cm.) balls. For the best results, use pottery clay. Look for it at your local craft or art supply store.
The generic answer is 2 to 3 seeds per hole. This ensures each pot will sprout a seedling. Once the seedlings have developed true leaves, choose the strongest plant in each pot and cull any “extra” seedlings by cutting them off at ground level. This eliminates competition and gives the stronger plants room to grow. However, different species have different seed germination rates. When planting large numbers of the same seed, conduct a germination test and adjust the number of seeds per hole to better reflect the germination rate.
We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.