Images by Zoe Davis, Ph. D. and Gilroy • Morgan Hill TODAY
Image 1: Do yourself a favor and label your starts! The lettuce seedlings in the front tray were started on the surface with vermiculite( shiny, pebble-shaped stuff on the surface) because they need light to germinate. The back tray of asparagus seedlings were buried under ½” of soil. Image 2: A healthy root system ready for planting or a larger container Image 3: Rootbound root systems robustly retain the shape of their container
Seed packet phrase
“ Requires light for germination”( eg lettuce, many flowers seeds)
“ XX days to germination”
What this really means
Seeds shouldn’ t be covered with soil. Instead, place them on top of the soil, and add a small amount of vermiculite on top to help them stay moist while still getting the light that signals them to germinate.
Some seeds take a few days to germinate while others can take months! Record your start day so you know when to look for seedlings.
“ Cold stratify for XX days / weeks” To the fridge! Some seeds need a cold period( essentially mimicking winter dormancy) to wake up.
“ Cover seeds with XX inches of soil”
“ Start multiple seeds and thin”
“ Space seeds XX inches apart”
Soil depth has the advantage of better moisture retention with the tradeoff of less light. Different seeds have different requirements which are reflected in the planting depth. Don’ t ignore this!!
If you have new seeds( germination efficiency tends to fall off in older seeds) and a good seed starting setup that will give reliable moisture, light and 50-75F temperatures, you can probably skip this. If not, start a few seeds at each spot where you want a seedling and if multiple come up, remove the less robust one by pinching off the stem— pulling it can damage the seedling you want to keep!
This is not straight forward— the same varieties from different seed companies often say totally different things! Typically, more spacing results in bigger plants( up to a limit). If you crowd plants, they will often stay smaller, but they will have less airflow and can be more prone to disease. Generally, stay within the seed packet ranges but know that you can play with it to suit your planting area.
This is hard for a plant to overcome, and can be avoided by planting earlier. While you can try and break up the root system a bit with your hands, be careful to minimize damage to the root system as much as possible. Some plants( including members of cucurbit family like squash, melons and cucumbers) will permanently slow their growth if their roots are overly confined. So don’ t delay: plant today!
Planting depth: Most transplants should be planted so their surface ends up at the level of the soil. Planting them deeper can lead to rotting of the stem and is best to avoid. There is one significant exception to this rule which is tomatoes. The fuzzy hairs on their stems will turn into roots if buried. To encourage a larger and deeper root system, you can plant your tomato starts buried several inches( I usually try to get at least one set of leaves below the soil line).
Remember: The number one reason why germination fails or transplants die is lack of consistent watering. Mature plants need far less water than new starts, which often need hand watering to get established. So set a calendar alert or a daily alarm to water( not drown!) your new plants. When you are enjoying perfect summer tomatoes or a bouquet of home grown flowers, you’ ll be glad you did!
Zoe Davis, Ph. D.
Zoe Davis holds a B. A. in Chemistry, a Ph. D. in Microbiology, and completed a Postdoctoral Fellowship in Biochemistry before trading lab benches for garden beds. After years studying microbes in the lab, she moved to Gilroy to work with them in practice— founding Full Circle Farm, a regenerative farm focused on cultivating soil life to grow nutrient-rich produce. The farm uses minimal tillage, cover crops, and lots of mulch to build fertility the natural way. Full Circle Farm offers a CSA with fruit, veggies, eggs, and flowers from April through November and on-farm produce pickups year-round. Learn more at www. fullcirclefarm. eco or follow along on Instagram @ FullCircleFarm _ CA
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