I've been growing seedlings indoors in anticipation of planting them in a friend's garden. I, on the other hand, live in a 2nd-floor condo with a sunny window (where the seedlings have been growing with supplemental lighting) and a small shaded balcony that is overhung by the roof above. In other words, the balcony doesn't jut out into the sun and wind; it's sheltered on three sides by walls, and only the front wall is open.

Would it be possible for me to harden off my seedlings on the floor of the balcony for a week or so without moving them back inside every night? I had to repot most of them as they've grown quite large, and it's cumbersome to lug them in and out (which I've been doing for a few days). What if I covered them with plastic bags at night to help keep them warmer?

Second question that just occurs to me: If they're not getting a great deal of sun and wind on the balcony, will they need to be further hardened off elsewhere, say at my friend's place?

Thanks for your responses! I'm very much in the experimental stages of gardening.

Never cover plants with plastic unless it is not touching the plants. If you cover with plastic to protect from frost and it is touching the plant it will freeze harder. If it touches the plant in the sun it will burn faster. I don't suppose you have to worry about frost though in your zone.

Hardening off is preparing your plants to be set out. The plants don't have to be kept warm at night when there is no frost. When they are planted out they won't be always the same temperature. They will be cooler at night and maybe hot, but at least warm in the daytime