You grew it from seed or bought it at a plant sale - Now what?
Do not skip this crucial planting step!
Plants that have been grown indoors under grow lights or in a greenhouse require hardening off or acclimatizing prior to being planted outdoors. Hardening off helps desensitize seedlings from the variety of weather conditions they will experience outdoors. If you purchased starts and are unsure whether they have been hardened off, be sure to ask!
The hardening off process can take anywhere between 5 days to several weeks, depending on weather and your degree of caution. Begin hardening plants off as soon as daytime temperatures and weather are agreeable to going outside (temperature tolerance varies by plant, so check your seed packet or Google specific details); ideally 1-2 weeks prior to planting time.
Slow and gradual is the best approach to getting plants ready for outdoor planting. There are many ways gardeners approach hardening off; we are especially cautious due to the temperature and weather extremes in our area. We typically use a doubling approach; we start with plants being outdoors in the shade for 30 minutes at a time, then double that to 60 minutes in dappled sunlight the following day, 12o minutes the next, and so on. We start by putting the plants outdoors in full shade, then split their time in dappled light/shade, then dappled light/full sun. If there are more than three days where plants aren’t able to get outside due to wind or cold weather, we start over at 60 minutes in dappled shade. There is always room for adjustment; if things look happy and healthy, or the weather is sunny in the 60s, we may increase the time spent in full sun more quickly than planned.
Hardening off “don’ts”
Don’t subject seedlings to severe weather. Too much gusty wind, rain, or Colorado’s favorite: hail can damage plants beyond repair.
Don’t subject warm weather plants like zinnias, petunias, tomatoes, peppers, eggplant, okra, squash, cucumbers, pumpkins, beans, corn, to temperatures lower than 50 degrees. Peppers are especially sensitive to cool temperatures; we wait until temps are in the 60s before bringing them outside.
Don’t place seedlings in direct sunlight right away; give them a day or two of dappled sun/full shade before gradually lengthening the amount of time in the full sun.
Don’t forget to check on them frequently - seedlings are particularly sensitive to excessive heat and can dry out much faster once they reach the outdoors. Be sure to have water readily available for dry, wilty plants.
Don’t leave your plants unattended. Have dinner plans? Taking the dog out? Have a day full of back-to-back meetings? Don’t chance it. It’s better to bring things back inside than to be unavailable and lose plants you spent time, energy, and money caring for. There is nothing worse than being across town when a spring storm hits.
Hardening off ‘Do’s’
Keep a close eye on the weather forecast. Both the hourly and extended forecasts are key to ensuring seedlings won’t be subjected to inclement weather or temperatures that are too cold.
Use a thermometer to understand current temperatures in your specific microclimate. Digital thermometers with temperature notifications can be very helpful in preventing exposure to undesired temperatures.
Gradually increase the time spent outdoors and in full sun. Start with shade, move to dappled sunlight, then finally into full sun after the plants have had a few days to adjust to outdoor conditions.
Have a convenient safe space to move things to when weather moves in. Whether it’s a garage, a covered patio, a shed, or a utility shelf, have a nearby space you can quickly move plants to. While there is nothing like running around in a hailstorm as a motivator, having an easy exit can save some heartache.
Have a backup plan. We’re busy people, there is simply no way we can watch our plants 24/7. Having a neighbor on speed dial is helpful if something goes awry.
Happy Planting!
