Q: I have been growing seedlings indoors. What do I need to do to plant them in the garden?
A: Plants over-wintered indoors, seedlings started indoors, and seedlings from nurseries must be acclimated, or “hardened off,” to reduce transplant shock. May 8 is our average last day of frost in Colorado Springs, so they might freeze if you put them outside before then.
Your plants have been growing in a controlled and cozy environment while inside. Our strong, drying wind and sun will damage tender plants, if they are not properly hardened off.
Daily care needed
Hardening off is a simple, but important process, where you help your seedlings or over-wintered plants get used to being outdoors. A week to 10 days prior to date you want to plant them in your garden, move your plants to a sheltered area of your garden, where they are protected from wind, but still get some sunlight.
The first few days, leave your plants out for only 1-2 hours. Each day, slowly increase the time your plants are exposed to sun and wind, bringing them in each night.
Spring weather here in Colorado can be harsh and unpredictable, so be prepared to bring your plants indoors if the weather suddenly turns bad. A strong wind could destroy your fragile plants in a brief moment.
It is important that seedlings remain moist at all times. Outdoors, you may have to water them a couple times a day, in warm, sunny conditions.
Give them a good start
Once your plants have been successfully hardened off, they are ready to be transplanted to your garden or container with a minimum of shock.
We have poor quality soil in this region, so any effort you make to improve the soil will make a big difference to your new plants. Use a shovel to loosen soil and mix in compost and organic material, like dried leaves or grass clippings. For more information about soil amendments, visit Colorado State University’s site at www.ext.colostate.edu/Pubs/Garden/07235.html.
On cold or windy days give your newly transplanted plants some added protection. The added protection can be as simple as placing a plastic milk container, with the bottom cut off, over the plant. This will protect them from the wind and cold. Keep the milk container lid and put it on a night to create a mini greenhouse. Be sure to take it off during the day so the plant doesn’t get over-heated.
To ensure your plants get off to a good start, give them a little fertilizer and water them consistently, so the roots do not dry out.
Contributed by Rich Young, Colorado Master Gardener. For answers to your horticultural questions, contact the Master Gardener Help Desk at 636.8921 or CSUmg2@elpasoco.com. Access fact sheets and seasonal information on the El Paso County Horticulture website http://elpasoco.colostate.edu/horticulture/. (A version of this article appeared in The Gazette on 5/2/09.)