Anna Sara Hill, Extension Horticulture Agent
Have you ever planted seeds in your garden and had them germinate slowly, unevenly, or not at all? What about when a heavy rain comes a few days after direct seeding and the seeds float? These incidents can be frustrating after all that time and effort you put into planting the perfect garden. Many factors can affect seed germination, and sometimes it is difficult to pinpoint the exact reason. A good alternative method to direct seeding is transplanting, but it is not foolproof. Is it worthwhile to go the extra mile to germinate seeds in containers and transplant healthy seedlings into the garden? This article will explore the pros and cons of both methods and offer tips to improve the probability of success.
Factors that affect seed germination include genetic, morphological, physiological, chemical, biological, and environmental factors. Not all seeds are created equal, and some plant species require special treatment. Seeds with hard seed coats require scarification for good germination. Most vegetables do not require scarification, but many flowers do. Pre-soaking can soften the seedcoat and enhance absorption, thereby improving germination and breaking dormancy. An example of a seed that needs to be pre-soaked is corn. Some seeds, such as leafy greens, require cold stratification to break dormancy. Other seeds will readily germinate without any special treatment. It is important to know the specific seed requirements of each plant. This information can be found on the seed packet or on educational and government-affiliated websites (enter site.edu or site.gov after the search criteria to obtain reliable research-based information).
All seeds have an optimal planting depth. A good rule of thumb for vegetable seeds is to plant them at a depth of ¼ to ½ inch. Seeds planted too deeply can take a long time to germinate, will not be uniform, are generally weak and can result in a poor stand. Shallow seeds germinate quickly but are more susceptible to poor root systems and to drying and withering. Sowing seeds at an incorrect depth increases their susceptibility to frost burn, temperature fluctuations, and pests. After planting, seeds need to be watered well, but if a heavy or extended rainfall event occurs within several days of planting, the seeds may float.
Transplants may seem like a lot of effort to plant and maintain, but they are generally more robust and often yield better than plants started from direct seed. Spring transplants grown in a greenhouse or indoors can be planted in the garden after the last frost date and will grow and mature before the summer heat affects them. Healthy seedlings exhibit greater pest tolerance than seeds and can outcompete weeds.
Adequate moisture is key to uniform germination and growth. Seedling trays can get wet and dry very quickly. Water well after planting. After the seeds have germinated, water the plants when the leaves start to droop (also known as flagging). Stop watering as soon as water starts running out of the bottom of the tray. The goal is for the soil to stay moist, but not saturated.
Zack Snipes, ©2020, Clemson Extension
Some drawbacks of transplants are that they require temperate conditions with plenty of light. Grow lights and heaters can be used to create optimally controlled environments for plant growth. Light placement is very important. Light within 2-4 inches of the plant will produce sturdy, uniform plants, as the light is close and evenly distributed. Poor lighting or lights farther away will cause the plants to reach, making them lanky, leggy, and weak. The same effect is seen when growing in a sunny window. If trying to germinate and grow plants in a sunny windowsill, rotate them daily, so that each side gets the same amount of light. Another problem with indoor plants is hardening off. This can be corrected by using a fan at the 2 true leaf stage. When plants are around three inches tall, they are ready to transfer. Gradually move them outdoors to acclimate them. Start by moving them to a porch or protected area during the day and bringing them in at night. Progressively move them to direct sun and leave them out for longer periods over a few weeks. It is best to transplant when cloudy.
Most vegetables are easy to transplant and do well once transplanted, but there are a few exceptions. Cucurbits and celery can be successfully transplanted with extra TLC. Other plants, such as carrots, corn, beans, and peas, are unsuitable for transplanting due to their growth habits.
When deciding whether to direct seed or transplant, consider factors such as the size of the garden you want to plant and how many plants you will need. Also consider how much time and effort you want to put into gardening. When planting a small garden, it may be easier and more economical to purchase transplants. When purchasing seeds or transplants, always look for the healthiest plants and for resistant varieties.
For additional information on transplanting, please see the following HGIC fact sheets:
