The time to dig up dahlias in Nevada is one to two weeks after the first frost blackens their leaves. That frost reaches northern Nevada and higher ground months before it reaches Las Vegas, where many gardeners can skip lifting entirely. Cannas and gladiolus follow the same signal, with small differences in handling and storage. Your location decides whether you lift at all, and your first hard frost decides the date.
Do you have to dig them up in Nevada?
Dahlia tubers, canna rhizomes and gladiolus corms can stay in the ground under mulch only where the soil does not freeze deeply. In Nevada, that means the warm southern valleys. Everywhere else they come up. The USDA Plant Hardiness Zone Map 2023, built on 1991-2020 normals, rates the state at 4a-10a. The system rests on one variable, the average annual extreme minimum temperature, so a single zone number says little until you know which part of the state your garden sits in. Lift every tender bulb wherever winter ground freezes hard, which includes Reno, Carson City and any garden at elevation.
These three are summer bloomers. They belong to a different group from the Spring Bulbs you plant in fall and leave in place for years.
Can they stay in the ground around Las Vegas?
Usually, yes. NOAA’s 1991-2020 Climate Normals for Las Vegas put the mean daily minimum of the coldest month at 39.6°F. Overnight lows can dip near freezing in the coldest month, and a brief surface freeze on a clear night is a different thing from frozen ground. A thick layer of shredded bark or straw over the planting spot is enough insurance for most winters.
In the low desert, wet soil is often a bigger risk than winter cold. Caliche, the cement-like layer under many valley yards, and heavy clay hold water around tubers and rot them from the outside in. If water stands in your bed after a winter storm, lift the tubers or move them to a raised bed with a gravelly mix. Neighborhoods on higher ground around the valley run colder than the airport readings, so treat 39.6°F as a reference point rather than a promise for your own yard.
Where does the line fall between staying and lifting?
There is no tidy county border. The line runs between the southern low desert and everywhere colder, and elevation moves it more than latitude does. Reno, Carson City and the high valleys in between all sit on the lifting side. A practical test works anywhere: if your soil gets hard enough in January that a spade will not go in, the tubers would freeze solid, and they need to come out.
Towns in the middle ground, where winters are mild some years and sharp others, deserve a call to the county office of University of Nevada, Reno Extension. Staff there know the local soil temperatures and which gardeners in your area have gotten away with leaving dahlias in. For other planting questions across the state, the Nevada guides cover the regional differences.
When to lift them
The cue is a frost that turns dahlia and canna foliage black and limp. Once that happens, lift the plants one to two weeks after the first frost that blackens the foliage. The delay is deliberate. Those days give the tubers time to firm up and set their skin.
How do you know it is time to lift?
Dahlias and cannas make it obvious. A killing frost leaves the leaves dark, wilted and mushy. Gladiolus is slightly different. Its leaves yellow and brown on their own as the season ends, and frost speeds that up. When the foliage has mostly died back, the corms are ready.
The calendar depends on where you garden. At Las Vegas airport, NOAA’s 1991-2020 normals put the median date of the first 32°F freeze at about December 8. In that valley, lifting would follow that date by a week or two, if you lift at all. Those readings come from a desert urban heat island, though, and they do not describe Nevada as a whole. Reno, Carson City and anywhere at elevation get frost months earlier in fall. The colder your garden, the earlier the lifting window opens, so in northern Nevada it falls in autumn, well ahead of the Las Vegas dates. Look up your own town in First and Last Frost Dates in Nevada, then add the week or two.
When you lift, the steps run in a simple order:
- Cut dahlia and canna stalks down to a few inches, leaving a short handle.
- Loosen the soil with a garden fork well out from the stem, so the tines do not spear the clump.
- Lever the clump up gently and shake off loose soil.
- Pull gladiolus whole, then cut the dead leaves off just above the corm.
Why does lifting early cause rot in storage?
Green leaves keep making sugars and sending them down to the tubers. Lift too soon and the tubers are still watery, with thin skins that never toughen. Wounds from the fork stay open, and storage rot gets in through them. A tuber that has been through a frost and then sat a week or two in cool soil has a firmer skin and a healed surface, which is what lets it last until spring.
Waiting too long has its own cost. In cold parts of the state, a deep freeze that reaches the tubers kills them, and cold, wet soil in late fall invites rot. The one to two week window sits between those two problems. When a hard freeze is forecast before the foliage has blackened, cut the tops back and lift within days instead of waiting on the plant.
Storing them over winter
How do you cure and clean the tubers?
Curing means letting the surface dry in a shaded, airy spot that stays out of rain and above freezing, such as a garage bench or a covered porch. Spread the clumps in a single layer. Dahlia tubers and canna rhizomes are ready when the skin feels dry and no longer clammy. Gladiolus corms take longer, until the husk rustles and the old shriveled corm at the base snaps off easily.
Clean lightly. Brush off dry soil with your hands or a soft brush. Scrubbing and soaking wash away the protective skin and leave moisture trapped in crevices. If a clump is caked with heavy clay and you rinse it, dry it completely before packing. Cut away any soft or damaged pieces and toss them. Dahlias are easier to divide in spring, when the growing eyes show, so store the clump whole and label it with the color.
How do dahlias, cannas and gladiolus differ in storage?
All three want a cool, dark place that stays above freezing and slightly moist, so they neither rot nor shrivel. They do not want the same packing.
| Bulb type | Packing | Moisture level | Watch for |
|---|---|---|---|
| Dahlia tubers | Ventilated box or crate with barely damp peat moss, vermiculite or wood shavings | Slightly moist, never wet | Wrinkled skin, soft or mushy spots |
| Canna rhizomes | Loose packing in a box, similar medium, a little more moisture tolerated | Slightly moist so the rhizome stays plump | Mold, shrinking, soft ends |
| Gladiolus corms | Paper or mesh bags, single layer, no packing medium | Dry, with good airflow | Mold, soft corms, insects |
Skip sealed plastic bags, which hold condensation against the tubers and cause rot. Nevada’s dry air also works against you, especially in the south, where a heated home or garage pulls moisture out of exposed tubers fast. In northern Nevada, an unheated detached shed can drop below freezing in a cold snap, so an insulated garage, basement or crawl space is a safer bet.
How often should you check stored bulbs?
Check them regularly, from the day you pack them until planting time. Open each box or bag monthly through winter and look for soft spots, mold and shriveling. Remove any tuber that has gone soft before it spreads rot to its neighbors. If tubers are wrinkling, mist the packing lightly. If you see condensation or mold, open the container and let it air for a day. This quick routine catches problems before they spread.
What goes wrong
How do you spot rot and shriveling?
Rot shows up as soft, dark, often smelly patches, sometimes with gray or white fuzz. It starts where the tuber was cut or bruised, or where moisture sat against the skin. Cut out small spots with a clean knife and let the cut surface dry. A tuber that is mushy all the way through goes in the trash. Prevention comes down to full curing, light cleaning, airflow and packing that is damp, never wet.
Shriveling is the opposite problem. The skin wrinkles and the tuber turns light and leathery. It happens when storage air is too dry, which is common in desert homes and in garages with a furnace running nearby. Slightly dampen the packing and the tubers often plump back up. A shriveled tuber that still has a firm center and a visible growing eye will usually sprout.
What if you lifted too early or left them in too long?
Tubers lifted before frost has blackened the foliage are prone to rot in storage, with soft, watery skin and wounds that never seal. The fix is to wait for the frost and then give them the extra week or two. The reverse mistake is leaving tubers in the ground where winters are cold. If your soil freezes hard, lift them every fall, because mulch slows the cold but does not stop it from reaching tubers in northern Nevada or at elevation. Frozen tubers turn black and mushy by spring.
Common questions
Can I leave dahlias in the ground in Las Vegas?
Generally yes. With the coldest month’s average overnight low at 39.6°F, according to NOAA’s 1991-2020 Climate Normals, the ground does not freeze deeply there. Mulch the planting spot and make sure the bed drains. Standing water in winter can be a bigger threat than cold.
Do I need to dig up cannas in Reno or Carson City?
Yes, in most winters. Both cities get hard enough soil freezes that rhizomes left in the open are at serious risk. Lift cannas one to two weeks after the first frost blackens their leaves, then store the rhizomes in slightly damp packing in a cool, dark, frost-free spot.
Should I wash tubers before storing them?
Brush off dry soil and leave the rest. If you must rinse off sticky clay, dry the tubers completely before you pack them. Moisture left in crevices is how storage rot gets started.
When do the stored bulbs go back outside?
After the last spring frost has passed and the soil has warmed. That happens later in the cold parts of the state than around Las Vegas. Hardy fall-planted bulbs follow a different schedule, covered in Planting Spring Bulbs in Nevada.
Sources: ncei.noaa.gov