Planting
What to Plant in August
The heat says stop; the calendar disagrees. Bearded iris, bare-root peonies, instant fall color, and the bulbs to order before they sell out.
August is the month the garden tells you to stop planting, and the calendar quietly disagrees. The heat is real, and for most perennials and shrubs in the warmest zones the smart money is on waiting a few weeks. But a handful of jobs belong to August and only August: bearded iris wants dividing now, the best bare-root peonies and spring bulbs sell out to the gardeners who order now, and the fall bloomers you plant this month pay you back within weeks.
Timing here follows our planting calendar, which anchors every window to typical zone frost averages. Your own frost dates can differ by weeks from those averages, so treat each month named below as a guide rather than a deadline, and check your zone's page for the detail.
Can I still plant in August?
Yes, with the right list. August is the classic month to plant or divide bearded iris, and in zones 3 to 6 the fall window for hardy perennials is open or opening, roughly six weeks before the first frost. In zones 7 to 9 the soil is still too hot: order and plan now, then plant from September, when the best planting season of the year begins. Frost dates vary by weeks, so check your own.
Bearded iris: the plant whose moment this is
Every plant has a best planting window, and for bearded iris that window is exactly now: July to September, once flowering is long finished and the rhizomes are resting. It is also the season to lift and divide any clump that has gone quiet in the middle, which happens to every clump after a few years. Set each rhizome on the surface of the soil with its top exposed to the sun, never buried deep or mulched over; planted too low, an iris stops blooming and can rot.
Iris germanica
Plant or divide it July to September, a window that holds across its whole zones 3 to 9 range. It flowers May to June; late summer is its rest, which is exactly why it moves so well now.
Bearded iris is not the only plant that prefers to move while it sleeps. Oriental poppies go dormant after their early-summer show, and August or September, while they are down, is the time to plant or move them too. If either is on your wish list, this is the month to act on it.
Order now: bare-root peonies and spring bulbs
Peonies are planted in fall, as bare roots, and the good varieties sell through early, so August is ordering month. The planting itself follows your frost date: the coldest zones plant this month, zones 5 and 6 from now into September, and zones 7 and 8 in September and October, always well before the ground freezes.
The same logic covers the spring bulbs. Daffodils, tulips, crocuses, and hyacinths all go in 6 to 8 weeks before the ground freezes, which means late August or September in the coldest zones and October into November in mild ones. August is for choosing while everything is still in stock: browse the bulbs and the March bloom page to see what each one pays back.
Paeonia
The classic order-now plant: bare roots go into the ground in late summer and fall, from August in cold zones to October in mild ones, and the plant that grows from them can outlive the gardener. It blooms May to June.
Narcissus
The safest bulb order you can make: deer-proof, naturalizing, and planted 6 to 8 weeks before the ground freezes, so the coldest zones start in late August. It pays you back every March and April for decades.
Perennials and shrubs: where August fits in your zone
For everything else that is hardy, perennials, shrubs, roses, and trees, the rule is about roots: plant into cooling soil with about six weeks to establish before real frost, and the fall rains do most of the watering while the top sits quiet. Where August falls in that story depends entirely on your zone.
| Zones | Typical first frost | What August means |
|---|---|---|
| Zones 3 to 4 | Mid to late September | Last call: get hardy perennials in now, roughly six weeks before frost, and start bulbs from late August. |
| Zones 5 to 6 | Early to late October | Prime time: the fall planting window runs from August through September. |
| Zones 7 to 8 | Early to late November | Order and plan: planting waits for September, when the best planting season of the year opens. |
| Zones 9 to 10 | December, or rare to none | Too hot to plant: here the cool season does spring's job, from October onward. |
One August rule holds in every zone: water. Anything set out in late-summer heat needs steady moisture for its first weeks, so water deeply at planting and keep it up until the weather cools and the fall rains take over.
Plant fall bloomers now for instant color
The most satisfying August planting is the kind you enjoy within weeks. Garden centers are full of budded fall bloomers right now, and in zones 3 to 6, where the hardy window is open, an aster or a sedum planted today flowers in its first September. In warmer zones, put these at the top of the September list instead.
Symphyotrichum novae-angliae 'Purple Dome'
Clouds of purple daisies in September and October, and one of the most important late nectar sources there is. Planted now, it flowers in its very first fall.
Hylotelephium 'Autumn Fire'
Already coloring in August: domed heads that open dusty pink, deepen to rust through October, and then stand right through winter.
Anemone hupehensis
Elegant saucers on tall wiry stems from August into October, lighting up part shade just as the rest of the border starts to tire.
Solidago
Sprays of gold from August to October that fuel migrating insects. And no, it does not cause hay fever; that is ragweed, blooming at the same time.
Chrysanthemum
The instant fix: pots of budded mums drop straight into gaps for September and October color. Treat fall-bought mums as seasonal, and plant hardy types in spring if you want them back next year.
Is August too late to plant perennials?
Not in zones 3 to 6. Zones 3 and 4 are on last call, with about six weeks left before typical first frost; zones 5 and 6 have a window that runs from August through September. In zones 7 to 9 it is less too late than too hot: wait a few weeks and plant from September into fall.
When should I divide bearded iris?
July to September, after the flowers are long gone and the rhizomes are resting. Divide a clump every few years, once its center goes quiet, and replant each rhizome on the soil surface with its top exposed, never buried or mulched over.
When do spring bulbs need to be in the ground?
About 6 to 8 weeks before your ground freezes: late August or September in the coldest zones, September and October in most of the middle, and October into November where winters are mild. Order in August, while the varieties you actually want are still in stock.
What can I plant in August for color this year?
Fall bloomers. Asters, sedum, japanese anemones, goldenrod, and potted mums are all budding up in garden centers now, and in the zones where the hardy window is open they flower within weeks of planting.
Design a garden with these plants
Open BloomsEye Studio with this guide's plants ready to drop onto a plan, then watch the whole bed bloom across the year.