When should I order dahlia tubers?

In winter, and earlier than feels necessary. Popular varieties sell out within minutes of a farm opening its sale, so make your list in the cold months and order as soon as sales open. Waiting until spring usually means choosing from leftovers.

When do I plant dahlias outside?

After the danger of frost has passed and the soil has warmed to around 60 degrees Fahrenheit a few inches down, often about when you would plant tomatoes. Frost kills the tops and cold, wet soil rots the tuber, so this timing matters more than any fixed date. In frost-free zones it shifts earlier.

When should I dig up dahlia tubers in fall?

After the first hard frost blackens the tops, in climates where the ground freezes. You can wait a week or two for the tubers to firm up, then lift before the ground itself freezes. In frost-free zones you can leave them in the ground under mulch.

Does this dahlia calendar work for my climate zone?

Treat the months as a guide tied to frost and soil temperature, not fixed dates. Dahlias plant out after the last frost and come up before the first frost, and those arrive on very different calendars by zone. In frost-free regions the cycle slides earlier and tubers can stay in the ground.

The Dahlia Care Calendar: A Month-by-Month Guide

Updated 2026-06-13

Growing dahlias is a year-round rhythm, even though the flowers come in a rush from midsummer to frost. Order in winter, start in spring, support and harvest through summer, then lift and store in fall. Each step has its season.

This calendar walks the whole cycle. Treat the months as a guide, not a law, because dahlias take their cues from frost and soil temperature, and those arrive on very different calendars in different zones. Where we say a month, read it as the point in your own season when frost has passed or returned.

This page also works as the season overview. The detail for each job lives in its own guide; here is how the year fits together.

Winter: plan and order

Winter is buying season, and it is busier than it sounds. The best tuber varieties sell out fast, often within minutes of a farm opening its sale, so the gardener who waits until spring is left with leftovers. Make your list in the cold months and order early.

This is also when stored tubers need checking. If you lifted your own last fall, look in on them every few weeks. Pull any that have gone soft or moldy, and lightly dampen the medium around any that are shriveling. A tuber checked through winter stores far better than one packed away and forgotten until April.

Use the quiet weeks to plan the bed too. Decide where the sun is best, where drainage is good, and how you will support the plants once they are tall. The work you do on paper in January saves scrambling in June.

Early spring: start indoors

A few weeks before your last expected frost, you can give tubers a head start indoors. Pot them up in one-gallon containers of barely moist potting mix and keep them warm and bright, a sunny window, a greenhouse, or under grow lights. They wake up in the warmth and are ready to plant out as growing plants once frost has passed.

Starting indoors earns the most in short-season and cool climates, where every early week of growth counts toward an earlier bloom. It also lets you spot a dead tuber before it wastes a spot in the garden. In warm regions with long seasons, you can skip this and plant directly.

Keep the indoor soil only just moist. Tubers sitting in wet pots in cool rooms rot as readily as they do in cold garden mud.

Late spring: plant out

Plant after the danger of frost has passed and the soil has warmed, around 60 degrees Fahrenheit a few inches down. Frost kills the top growth, and cold, wet soil rots the tuber, so this timing is the hinge of the whole season. A useful rule of thumb: plant dahlias about when you would set out tomatoes.

Set tubers four to six inches deep, eye up, in full sun and well-drained soil, spaced roughly twelve to twenty-four inches apart. Drive stakes or set your support in now, while you can still get to the root zone without spearing it. Supporting later, after a plant flops, usually means broken stems.

Then resist the hose. Do not water at planting, since a rootless tuber cannot drink and just sits wet. Wait for green growth to show, then begin watering in earnest. In zones with no real frost, all of this slides earlier in the year.

Early summer: pinch and support

When the plant is about a foot tall and has three to four sets of true leaves, pinch out the central growing tip. Penn State Extension gives this height and leaf count. Pinching makes the plant branch low and bushy, trading roughly two weeks of delay for many more flowers over the season.

Keep up with the supports as the plants climb. Tie main stems loosely to stakes with soft twine, or, in rows, raise the next layer of netting or corral string as the plants grow into it. Dahlia stems are brittle and top-heavy, and a single storm can snap an unsupported plant loaded with buds.

Now growth is fast and the plants are thirsty. Water deeply and regularly. This is the stretch where the plant builds the frame that will carry the whole season of bloom.

Mid to late summer: harvest and deadhead

From midsummer the flowers arrive, and they keep coming as long as you keep cutting. Dahlias bloom from roughly midsummer until the first hard frost, with the heaviest flush often in late summer and early fall. The more you cut and deadhead, the more the plant makes.

Cut for the vase in the cool of the morning or evening, choosing blooms about three-quarters to fully open, since a dahlia does not open further once cut. Deadhead spent flowers every few days so the plant pours energy into new buds instead of seed. Learning to tell a spent bloom from an unopened bud is a small skill worth practicing: opening buds are round and firm, spent ones are pointed and soft.

Keep watering through any late-summer heat and dryness. A plant that dries out in August stops setting buds, and the fall display suffers for it.

Fall: lift, divide, and store

The first hard frost ends the show and blackens the tops. In cold climates where the ground freezes, that is your signal to lift. You can leave the tubers a week or two after the tops die back to firm up, then dig before the ground itself freezes. Penn State suggests cutting stems back and waiting several days before digging.

Lift each clump carefully with a fork, rinse off the soil, and let the tubers cure for a day or a few in a cool, airy spot out of direct sun. You can divide now, while the clump is fresh and easy to cut, or wait until spring when the eyes are easier to see. Either way, label as you go.

Then store cool and barely moist. Penn State points to storage temperatures between 32 and 50 degrees Fahrenheit, above freezing but no warmer than the low 50s, which keeps tubers dormant without letting them dry out or rot. In frost-free zones you can leave tubers in the ground under mulch and skip lifting entirely. Then the calendar comes full circle to winter, and the next year's ordering begins.

Common questions

When should I order dahlia tubers?: In winter, and earlier than feels necessary. Popular varieties sell out within minutes of a farm opening its sale, so make your list in the cold months and order as soon as sales open. Waiting until spring usually means choosing from leftovers.
When do I plant dahlias outside?: After the danger of frost has passed and the soil has warmed to around 60 degrees Fahrenheit a few inches down, often about when you would plant tomatoes. Frost kills the tops and cold, wet soil rots the tuber, so this timing matters more than any fixed date. In frost-free zones it shifts earlier.
When should I dig up dahlia tubers in fall?: After the first hard frost blackens the tops, in climates where the ground freezes. You can wait a week or two for the tubers to firm up, then lift before the ground itself freezes. In frost-free zones you can leave them in the ground under mulch.
Does this dahlia calendar work for my climate zone?: Treat the months as a guide tied to frost and soil temperature, not fixed dates. Dahlias plant out after the last frost and come up before the first frost, and those arrive on very different calendars by zone. In frost-free regions the cycle slides earlier and tubers can stay in the ground.