of the Society of Environmental Journalists and the Garden Writers Association. Contact her at InTheGardenWithCharlotte@gmail.com.

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Seed Starting 101
by Charlotte Kidd       #Advice

Take a tip from the experts. Each professionally grown 'Twinkle' eggplant seedling has its own pot and label.1

A friend was helping me tidy my apartment. She noticed oat grass and penstemon seedheads in vases in the living room. "No dead things allowed," she said, shaking her head. "That's bad feng shui."

"Those aren't dead. Seeds are living things," I pointed out. "They are dormant embryos."

The germinating green pea has its first white root. The two beige cotelydons (half pieces of the pea) hold the endosperm with nutrients.2

Seeds are actually quite miraculous. Think of each seed as a kind of botanical equivalent of an egg. Both have a protective, hard coating. Each seed has a seedcoat, each egg has its shell. Inside is an embryo surrounded by just enough food to get the chick or plant started. The liquid yolk is food for the forming chick. Seeds have endosperm, a plant's first food. Take apart a plump, sprouting pea seed. Inside are two small, hard, half-round cotyledons with endosperm. There's also a tiny root tip.

Each cotyledon holds endosperm — a nutritious combination of starches, fats, oils, proteins and sucrose — which feeds the seed's first root and shoot. The cotyledon shrivels as nutrients leave it to fuel the emerging root and the green shoot.

As gardeners, our part is to provide conditions for the seed to break dormancy, germinate and grow. Germination involves moisture and oxygen, soil temperature, darkness or light.

First step. The seed needs water and oxygen to activate the embryo. Most vegetable and flower seedcoats are water permeable. Moisten them and water and air make their way through the seedcoat to the embryo. Voilà! The seed germinates.

Often seeds with a hard or thick seedcoat require special conditions such as scarification or stratification to break dormancy. Scarification is scratching, notching or gently abrading the seed coat so moisture and air can enter. Stratification involves moist-chilling the seed.Many seeds from trees and shrubs need to be stratified.

For some seeds, hot water scarification is helpful but not necessary. Take New Zealand spinach, the Brassica family, celery, coriander and parsley, for example. Dropping their seeds in hot water, letting the water cool, and leaving seeds to swell for a few hours or overnight hastens germination. Plant them immediately, though.

Water absorption activates germination. The seeds swells. The seed coat splits. Oxygen joins water in a chemical reaction (respiration) to start using the endosperm nutrients.

The embryo root grows down for more water and nutrients. The green shoot pushes upward to the light for photosynthesis.

Water and oxygen are universal for all seed germination. Darkness or light and soil temperature vary according to plant species. Many seeds, such as beans, squash, tomato, eggplant, cabbage, broccoli and basil germinate in the dark. Plant them at the depth indicated on the seed packet.

Other seeds need light to germinate. Lettuces, petunias, daisies, foxgloves and impatiens, for example. Look to the seed packet for plant-specific instructions. Press light-preferring seeds into the seed-starting mix or lightly sprinkle them with mix.

Why should you start seeds indoors? To get a headstart on our favorite summer vegetables. Maybe we want unusual varieties not likely to be sold at garden centers. I grow impossible-to-find, Mexican sunflower (Tithonia spp.) seedlings for my clients' gardens. Maybe we want large quantities. I can never get enough basil so I start lots of seeds.

Tips from Renee

Renee Shepherd of Renee's Garden (reneesgarden.com), which sells heirloom vegetable, herb and flower seeds, notes it is important to read the seed packet . Learn when to plant the transplants. Does the plant need sun or shade? What is the plant’s size at maturity? How deep should you sow the seeds? How many days will it take to germinate? How many days until first vegetable, fruit and flower? What type of soil?

Be selective about which seeds to start indoors for summer transplant. For example, Renee advises, don't start annual flowers indoors. Sow annual flower seeds directly in the garden according to the package directions when the weather is warm. They're best sown directly in the garden at the right time.

Definitely start tomato, pepper, eggplant and melon seeds indoors in early spring. Transplant seedlings into the garden in early summer when night temperatures routinely warm to the 50s F. In addition, it's fine to start seeds from the Brassica family (cabbage, broccoli and cauliflower) indoors for early spring planting in the garden.

Be aware of timing; don't be in a hurry. "People tend to start things too early," observes Renee. "Sometimes a month before they should."

A healthy seedling has a thick and strong stem, lots of roots and lush green leaves.1

What's wrong with planting too early? The seedlings get leggy — they have spindly, weak stems. Then people are eager to transplant seedlings before the soil and the air are warm enough for them to thrive.

March is soon enough to start most seedlings indoors to be garden-planted in early May or later. That gives seedlings six to seven weeks to grow indoors under grow lights before going into warming garden soil.

Renee calculates garden planting by the nighttime temperature. When do the nighttime temperatures hold steady in the 50 F range? That's garden planting time for many vegetable seedlings.

So for indoor seed-sowing, we gardeners should calculate six to seven weeks before our area's night temperatures regularly hover in the 50s F.

Renee also suggests having a fluorescent shop light or other grow light ready. “The seeds need light immediately as soon as they germinate," she says.

After seeds germinate and you see the first set of leaves, water with liquid, diluted organic fertilizer at half the recommended strength. One tablespoon of liquid kelp and 1 tablespoon fish emulsion per gallon of water is good too.

As seedlings grow, keep the soil lightly moist. “Most people keep the soil too wet,” notes Renee. Wet soil encourages damping off fungus, fungus gnats and root rot.

Once seedlings begin to become large enough to handle, thin them out. Thin seedlings to leave only one healthy plant per pot. “It very, very important to thin out the seedlings early and according to the package directions," Renee urges. "This gives the remaining seedlings space to grow, access to food, and reduces possibility of damping off (the fungus that kills seedlings)."

Seed-Starting Supplies

Large cell packs sit in a plastic tray on an electric heating mat. The tray holds water for bottom watering.1
Sterile, soilless, seed-starting mix. Always use sterile, soilless, seed starting mix. Plant seeds according to package directions. Keep mix evenly moist, not wet.

Sterile cell-packs and trays. The larger the plastic cell packs and planting pots, the more room for roots. And the mix stays moist longer. Place cell packs in trays. Fill cell packs with soilless mix. Plant seeds according to package directions. Water from below by pouring water into the trays. The soilless mix will absorb the water for seedling roots.

Milled sphagnum moss. Sprinkle milled sphagnum moss on top of the mix after seed planting. This sterile, fine moss help prevent the damping off fungus that kills seedlings.

Half-strength liquid organic fertilizer or 1 tablespoon liquid kelp and 1 tablespoon fish emulsion per gallon of water. Watering with a diluted solution of organic fertilizer feeds the growing seedlings. Sterile, soilless mix usually has no nutrients.

Heating mat. A heating mat designed especially for starting seeds provides just enough bottom heat to warm the soilless mix and support germination.

Grow light.
A good grow light system provides light for seedlings to photosynthesize and grow healthy enough to transplant after six weeks or more.

Sturdy plastic or wood labels. Seedlings can look so much alike. Make at least one durable label with plant name and seed planting date for each cell pack. 

Indelible marker.
Use a permanent marker so you can transfer labels to the garden when transplanting.


1. Photo Courtesy of Territorial Seed Company
2. Photo by Charlotte Kidd


Posted: 02/24/14   RSS | Print


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