Two weeks ago, we introduced our readers to the joy of seed starting. After seed starting comes the process of seedling hardening. If you have started you seeds as per our instructions, you probably have a healthy-looking tray of sprouts popping up in your peat pots,
You have done it! The long and lonely weeks of coddling and coaxing your little baby seedlings have paid off! The owner of the first greenhouse I ever worked at in Upstate New York, Mary Leonard, always said to me: “Having a greenhouse full of seedlings is like having a greenhouse full of baby chicks. You leave them alone for one day, and they will die!”
Now that you have a collection of healthy sprouts, with at least two cotyledons, you can begin the process of hardening off. The two cotyledons that appear first on the stem are not true leaves, but appear before leaf growth.
Set your tray of seedlings in a cool indoor area for at least one week, until true leaves have formed, and the stem appears strong and upright. The cooler indoor temperature will prepare them for the great outdoors. I sometimes set my seedlings next to the patio screen door for about a week, which is cool enough to get their green growth strengthening.
THE GREAT OUTDOORS
When your seedlings have been toughened by enduring a cool week indoors, and have perked up enough to produce two true leaves, they are ready to be moved outdoors. Remember, those precious seedlings that look healthy and hardy can be at risk of “sudden death” when subjected immediately to a full day of direct sun or a gentle breeze.
OUTDOOR RULES
The key to this phase, and always the most difficult, is the window between too little and too much sun, and exposure to the elements.
Little steps – I usually start my outdoor transfer process early in the morning when the sun is slightly filtered in the clouds, and the wind has not picked up. There is an unusual phenomenon that occurs in much of North County, in which the early afternoon produces light wind off the coast.
The strength of the sun’s heat is between noon and 2 p.m. If you will be leaving the plants outdoors all day, it is best to provide a protective cover such as a window frame, balanced on the side of a patio or a wall in the yard. You could also use a large piece of clear Plexiglas to balance against the wall at an angle, placing the seedlings underneath.
Sunlight – Start your outdoor sessions with just a few hours of exposure to filtered sun. Gradually increase the amount of direct sun the plant receives. At the end of the week, the seedling is able to take full sun.
Wind – Within a few hours, a perfectly upright seedling can be knocked over, or worse, suffer a bent stem, which will stunt its growth or cause it to die prematurely. Once again, providing a sheltered area for your young plants will prove beneficial.
Fertilizer – A light watering with fish emulsion can strengthen the green growth and produce healthy stems.
Cold – Cold outdoor temperatures pose a less serious threat to your cold-hardy seedlings such as those in the Brassica family such as broccoli, cabbage and cauliflower. But warm weather crops such as peppers and melons need to be certain to be protected from dropping temperatures. It is always best to keep an eye on the temperature in your yard, and bring the seedlings in at nighttime for the first few weeks.
THE TRANSPLANT
When your tiny seedlings have become stable, with strong stems and at least two sets of true leaves, it will be time to transplant into 3-inch pots. Use a light weight potting soil, mixed with compost for each pot. Fill pot half full with soil and water thoroughly. If you have used peat pots or peat pods, you can simply transfer to the small 3-inch pot. Add a little more soil to cover, press down and finish watering.
Allow your 3-inch pots to acclimate to the weather, being outdoors throughout the day, until time to plant them all in your garden. This second set of seedling care will strengthen their growth until you are ready to plant in the garden. The plants can be left in the pots for weeks until ready to be placed in the garden.
HAPPY GARDENERS
One of my students, Atsumi Flores of Carlsbad, has been tending, coaxing and rotating her seedlings to find the perfect conditions in her tiny apartment to start growing her vegetables.
“It hasn’t been easy, with a small space, but I started the germination process indoors, and then as soon as I saw a few leaves, alternated indoors and then outdoors on my patio,” she says. “Now, I have four tiny zucchinis growing in my peat pots, and they are on their way to a full day on the patio this week! It has been a long process, but I will do it again!”
Our future articles will dig into what to do with all those lovely vegetable and flowering transplants in your raised bed or containers. Until then, happy gardening. Please send questions to [email protected].
Jano Nightingale is a Master Gardener and horticulturist who teaches vegetable gardening at the Carlsbad Senior Center Community Garden. Call 442-339-2650 to find out about her classes.
