By Yvonne Rasmussen, UC Master Gardener of Napa County
Growing plants from seeds rather than from nursery starts has many advantages and can be an awe-inspiring experience. By using seeds, you have more options than nurseries offer. You can focus on heirloom varieties, if you like, and you can start the seeds on your own schedule.
Starting plants from seed is more economical as seed packets typically contain many more than six seeds and cost less than a six-pack of seedlings. In Napa County and other communities, free seed libraries and seed exchanges allow you to trade with fellow gardeners.
Many commercial seed packets provide information on planting and growing, so keep the packets for reference after you plant. The packets may advise you on when and where to plant, as well as the ideal seed spacing and planting depth, the preferred light exposure and the plant's watering needs. They often also provide the days to germination and to maturity or the mature height of the plants and sometimes offer other suggestions about care.
Some seeds are best planted directly into the soil. Others can be started inside or in a greenhouse. Starting seedlings indoors is one way to get a head start on your garden or to minimize the lag time between crops.
If starting seeds indoors, use sterile pots or trays and a sterile seedling mix or potting medium. Be sure the pots or trays have good drainage and keep the potting mix moist but not wet. This will help prevent fungal diseases like damping off, where seedlings die or fail to emerge. Once planted outdoors, young seedlings need continually moist soil and protection from snails, slugs, insects and birds.
Seeds are stimulated to germinate when conditions give seedlings the best chances for survival. Planting depth, light exposure and soil temperature can trigger the seeds to stay dormant or germinate.
A seed has to protect the embryo until conditions are right for germination and for the seedling to survive. It also has to provide the food to get the new plant started. The new seedling cannot create its own energy until it has roots, stems and leaves for photosynthesis.
By definition, all seeds contain an embryo and a protective seed coat, but many are more complex. Flowering plants (angiosperms) are seed-producing plants characterized by their seed structure. The embryo in these seeds is surrounded by food reserves to help get it started, like a backpack full of food. In angiosperms, this packet is called the cotyledon. As the name suggests, dicotyledons such as beans have two cotyledons, or food packs. Monocotyledons, like corn, have only one.
If you have ever split a bean or a peanut in half, you may have noticed the tiny embryo between the two halves. In a peanut, if you look closely, you can see the embryo's parts: a leaf-like structure, the epicotyl; a stem, the hypocotyl; and what will become the root tip, the radical.
By comparison, you can't easily break a corn kernel in half. The tiny white part at the bottom of the kernel, where it attaches to the cob, is the embryo. It is surrounded by one cotyledon or food packet. These sweet or starchy cotyledons are the part we usually eat.
Each seed times its germination to maximize the chances for seedling survival. To get this timing right, seeds have built in triggers or stimuli. Soil and air temperature, soil moisture and light are common triggers for germination, but some seeds need scarification or stratification as well.
Scarification is another word for abrasion. Seeds can be scarified from movement in soil or by passing through the acid environment of an animal's gut. Scarification can help soften the seed coat, allowing moisture to get in and the embryo to emerge.
Other seeds require stratification, a process of subjecting them to cold or warm temperatures to mimic the changing seasons and trigger germination. In places where fire is a common part of the ecology, fire can stimulate dormant seeds to germinate and replace parent plants that may have perished.
If your seeds are not germinating well, you may need to try some of these techniques for breaking dormancy. Also consider your seed source, how old your seeds are (viability often declines with age) and if they have been stored properly. Check online for seed-storage guides and longevity charts. I hope you will enjoy some of the wonder of growing plants from seed in the coming year.
Rose Pruning Workshop: Join UC Master Gardeners of Napa County for a workshop on “Winter Rose Care” on Saturday, January 11, from 10 a.m. to noon, via Zoom. Learn pruning techniques for all types of roses along with everything you need to know to make your roses a success in 2025. Attendees will be invited to a hands-on pruning workshop at Fuller Park Rose Garden on January 18 to practice what they learned. Register here.
Home Orchard Workshop: Join UC Master Gardeners of Napa County for a workshop on “Winter in the Home Orchard” on Saturday, January 11, from 1 p.m. to 3 p.m. Learn about winter fruit tree pruning and how to plant a bare-root tree. The workshop will be held outdoors at a private residence.You will receive the location after registering. Be prepared for muddy soil and hands-on practice. Register here.
QWEL Training: Napa County landscape and irrigation pros are encouraged to become Qualified Water Efficient Landscapers (QWEL). Earn this EPA WaterSense award-winning professional certification and save water and money for clients. The City of Napa is sponsoring free in-person QWEL training in English on four Wednesdays starting January 15. Space is limited. Register at qwel.net/pub/class/491.
Help Desk: The Master Gardener Help Desk is available to answer your garden questions on Mondays and Fridays from 10 am until 1 pm at the University of California Cooperative Extension Office, 1710 Soscol Avenue, Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number and a brief description of the problem.
2009 UC MG Napa County additional article on seed starting: https://napamg.ucanr.edu/Seed_Starting/
