Almost any rose survives a Los Angeles winter, because the reference station there records no freeze in an average year. The rest of California is harder on roses. The Sierra, the Central Valley and Northern California do freeze, and summers are long, dry and hot. Rugosas, Explorer roses, Knock Out, Therese Bugnet, Hansa and New Dawn handle that range best. Many grafted hybrid teas on the shelf need extra work.
Which roses survive a California winter
California runs from USDA hardiness zone 5a through 11a. That is the USDA Plant Hardiness Zone Map system, which rests on one number: the average annual extreme minimum temperature. A range that wide means one state-wide answer does not exist. The coast and the Southern California lowlands sit at the warm end, and the high Sierra sits at the cold end.
The Los Angeles reference station shows how mild the warm end is. It has about 365 frost-free days, and no freeze occurs there in an average year. Frost never decides which rose lives in Los Angeles. Heat, drought and water restrictions decide it. Northern California, the Central Valley and the Sierra are different. They freeze, and the colder the site, the more the choice of rose matters.
Which types handle the coldest California sites?
Rugosas and the Explorer series are the toughest group. Rugosas are the wild-type shrub roses with crinkled leaves, and they take hard cold without protection. The Explorer roses were bred in Canada for prairie winters, so a Sierra foothill or high-elevation garden is easy for them. Shrub roses bred for toughness, such as Knock Out, come next. Old garden roses on their own roots, including many climbers, also do well.
Where do hybrid teas run into trouble?
Hybrid teas are the long-stemmed florist-type roses, and they are the weak point. Most are grafted, and their canes are the least cold-tolerant of any group. Near the 5a end of the range, and at the colder high-elevation sites, they need help to come through winter. In the coastal and Southern California lowlands they need none, and they make up for it by demanding more water in summer. Their winter care, where it applies, is covered in Protecting Roses Through a California Winter.
The overview of growing roses in California covers planting and general care. The sections below stick to which roses hold up and which ones do not.
Named roses that hold up here
Each rose below earns its place for a specific reason. Some take cold, some take heat, and some take neglect. All of them are sold widely, either at garden centers or through mail-order nurseries.
| Rose | Type | What it survives |
|---|---|---|
| Knock Out | Shrub rose | Heat, drought once established, black spot, cold winters |
| Therese Bugnet | Hybrid rugosa | Severe cold, poor soil, wind |
| Hansa | Rugosa | Severe cold, poor soil, drought, salt spray |
| New Dawn | Climber | Cold winters, partial shade, neglect |
| William Baffin, John Cabot | Explorer climbers | Severe cold, shorter growing seasons |
Why is Knock Out so widely planted?
Knock Out blooms in repeated flushes from spring until frost, or all year where frost never comes. It resists black spot and powdery mildew better than most roses. It also copes with the dry summers of the Central Valley and inland Southern California. The disease side of that is worth reading about in Rose Diseases in California: What the Climate Here Actually Brings. Its one demand is water in the first dry season, so water deeply through the first summer and it will need much less afterward.
What do the rugosas and Explorer roses bring?
Therese Bugnet and Hansa both belong to the rugosa family. Therese Bugnet is a tall, upright hybrid with fragrant pale pink flowers and canes that tolerate very hard cold. Hansa has deep magenta, strongly scented double flowers, followed by large orange-red hips in fall. It also spreads by suckers, so give it room or plant it where spreading is welcome, such as a hedge or a slope. Both do best where winters actually bite: the Sierra foothills, the mountain valleys and the colder parts of Northern California. They are less at home in the warmest coastal gardens, where they never get a proper rest.
William Baffin and John Cabot are climbing Explorer roses. They are bred for brutal winters, so a Sierra garden is no test for them. Give them a fence, an arbor or a trellis, and expect them to bloom heavily in early summer.
And New Dawn?
New Dawn is the old reliable among climbers. Its pale pink flowers repeat through the season, it climbs vigorously, and it tolerates part shade and ordinary soil. It copes with cold winters and with mild coastal ones alike, which makes it one of the few roses that does well from the foggy coast to the interior.
Sold here, but not for this zone
Garden centers in California stock roses nationally. A rose that does well in the Midwest or the Northeast can sit next to a better local choice on the same shelf, with no warning on the tag. A few categories on those shelves will not make it through a hard winter in the colder parts of the state without work.
Which shelf roses are the risky ones?
Grafted hybrid teas, grandifloras and floribundas are the main group. Their canes are only moderately hardy, and a hard freeze can kill them back to the ground. They are fine on the coast and in the Southern California lowlands. In the Sierra foothills, the mountain valleys and the colder parts of Northern California, they need mounding. Mound soil or mulch over the bud union before the first hard freeze, as the winter protection guide explains.
Tree roses, also called standards, are the most exposed. The graft sits at the top of a bare trunk, high above any soil you could pile around it. In a freeze, the whole variety is at risk, not just the canes. Tree roses are a coastal and mild-valley plant. Treat them as a container plant where freezes are common, and bring them under cover on freezing nights.
What about the heat?
Heat is the other problem on the shelf. Many hybrid teas bred for cooler climates drop their blooms and stall in triple-digit Central Valley and inland Southern California afternoons. They survive, but they ask for more water and afternoon shade than Knock Out or the old garden roses do. Water restrictions in many cities make that a real cost.
What to check on the label before buying
Three things on the tag or the bag decide how a rose will do in the colder parts of the state. They are the grade, whether the plant is own-root or grafted, and the variety name itself.
What does the grade mean?
Bare-root roses are sold in grades, and No. 1 is the best. A No. 1 rose has more and thicker canes than a No. 2, so it starts with more stored energy to push through a hard winter or a hot first summer. A lower grade usually costs less, but it is the weaker plant. Look for the grade printed on the bag, and take the better one if the price is close.
Why does own-root matter more in the cold?
A grafted rose is a variety joined to a different rootstock. You can see the join as a swollen knob near the base of the canes, called the bud union. An own-root rose grows on its own roots, with no graft at all. In a frost-free garden that difference hardly matters. In a freeze, the canes can die, and what grows back from an own-root plant is still the variety you paid for. What grows back from a grafted plant, if the union freezes, is the rootstock.
The colder the winter, the more often the canes die back, and the more the graft is a liability. Ask whether the rose is own-root before you buy for a cold site. Many tags say so in small print. Rugosas, most Explorer roses and many climbers are sold on their own roots, which is part of why they handle cold so well. Hybrid teas are mostly grafted, so check each tag, and ask the staff if it is not stated.
Checking this against your own county
The zone range of 5a through 11a is a state-wide span. Your garden sits at one point inside it, and a valley floor can differ sharply from a ridge a few miles away. The local office for University of California Agriculture and Natural Resources runs the county Cooperative Extension offices and the Master Gardener programs, and they know which roses do well in your county. Contact your county Cooperative Extension office for local recommendations before you buy in volume.
Common questions
Do roses in Southern California need winter protection?
No. Coastal and Southern California lowlands are frost-free in an average year, so roses there never need winter protection. Their challenges are heat, drought and water limits.
Which rose is the toughest for cold California winters?
Rugosas like Hansa and Therese Bugnet, and Explorer roses like William Baffin and John Cabot, are the toughest. They suit the Sierra, the mountain valleys and the colder parts of Northern California.
Is Knock Out a good choice for California?
Yes, in most of the state. It handles heat, repeats its bloom and resists black spot. Water it deeply for the first dry season, and it will need less after that.
Should I buy own-root or grafted roses?
Where winters freeze, own-root is the safer buy, because the plant regrows true to its variety after a hard freeze. In frost-free gardens, grafted roses are fine, and you will find many more hybrid teas that way.