Hardening off and transplanting
Seedlings raised indoors have never met direct sun, wind or cold nights. Moved outside all at once, they can scorch, wilt or stall. Hardening off is the short period of gradual exposure that bridges the two environments, and it is the step most often skipped by new growers.
Why an indoor seedling is unprepared
Under lights or at a window, a seedling grows soft tissue and thin leaf surfaces suited to gentle, constant conditions. Outdoor sun is far more intense, the air moves, and night temperatures drop. The plant needs a few days to thicken its tissues and adjust before it can cope.
White or bleached patches on leaves after a sudden move outdoors are sunburn. They confirm the plant was exposed too fast.
A gradual week outdoors
Hardening off is usually spread over roughly a week, increasing exposure each day. Timing is flexible; watch the plants and the weather rather than the clock.
- Place seedlings outside in shade and shelter for a short spell, then bring them back in.
- Each day, lengthen the time outdoors and allow a little more direct sun.
- Introduce gentle morning sun before midday sun, which is harshest.
- Toward the end, leave them out longer, including a mild night if no frost is forecast.
- Once they handle a full day and night outside comfortably, they are ready to transplant.
Through this period, keep an eye on watering. Plants outdoors dry faster than they did inside, especially on a breezy balcony.
Transplanting once frost risk passes
Tender crops go into their final container or bed only after the danger of frost has passed for your area, using the same frost-date thinking described in the seed starting note.
- Transplant on an overcast day or in the evening to reduce immediate stress.
- Water the seedling before and after moving it.
- Disturb the roots as little as possible when easing the plant from its cell.
- Settle it at the same depth it grew at, unless the crop is known to root from a buried stem.
A short pause in growth right after transplanting is normal as roots re-establish. Steady watering and shelter from harsh wind help the plant recover faster.
If the destination is a balcony, container choice and ongoing care are covered in the balcony container gardening note.
References
- Agriculture and Agri-Food Canada — growing-season and climate information: agriculture.canada.ca
- Environment and Climate Change Canada — frost and climate normals: climate.weather.gc.ca