Q: I had Mexican petunia in my flower garden for the first time this year. Can I leave it out for the winter or do I have to take it inside? — David Franklin, email
A: Mexican petunia, Ruellia simplex, should grow perfectly well outdoors in the Atlanta area. It might not, however, be winter-hardy in North Georgia. The blue flowers are attractive in late summer through fall. The stems will die back to the ground after the first frost. Rather than leave a bare area for winter, I plant iris, hardy amaryllis and daffodils to give greenery there. Be aware that the common "tall ruellia" can be a bit invasive unless contained. If you plant it at one end of a big flower bed it will spread a couple of feet outward each year. Dig and remove unwanted sprouts every May. There are several improved and shorter ruellia varieties on the market, like 'ChiChi' and 'Purple Showers', that might be less tolerant of cold than tall ruellia.
Q: What is the best way to protect a 3-year-old gardenia plant from the winter elements? If I wrap it in burlap and leave that around it until spring, would it help? — Rick Mente, Roswell
A: Generally speaking, gardenias don't need to be protected unless temperatures are going into the teens overnight. On the other hand, some varieties are definitely hardier than others. 'Kleim's Hardy' and 'Daisy' are reputed to be more cold-hardy than most. 'August Beauty' is a bit less cold-tolerant, but it has more attractive flowers. If you decide to protect your shrub, buy some floating row cover, which is also known as frost cloth. When temperatures are forecast to be low overnight, cover the plant to the ground on all sides, anchoring the edges with stones or firewood. Leave the material in place until the weather moderates. Do not keep the cover on your shrub all winter.
Q: While on vacation in Maine, we loved seeing beach roses. They smelled beautifully. Would these roses grow here? — Joni S., Marietta
A: I'll bet you were seeing rugosa roses. The leaves have a characteristic corrugated surface. They would be very happy growing anywhere in the northern half of our state. They are rarely affected by disease and sport colorful seed pods in winter. I think we don't see them commonly in local gardens because they only bloom once a year and they tend to be large and gangly. If you have space for them, rugosa roses are well worth planting.
Q: I have two young rosemary bushes outdoors. Should I put them in pots and bring them in the house during the winter? — Rossee McLellan, email
A: There's no need to bring rosemary indoors. It's one of the hardiest herbs you can grow. I've also had outdoor success with oregano and thyme. They came through the past two winters unscathed. Both of them are near a wall that provided a bit of shelter. The University of Georgia has an excellent online herb growing guide at bit.ly/UGAherb.
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