Cold hardiness & minimum temperature

Is Phlox of Sheep Annual Phlox (Phlox drummondii)cold hardy? Hardiness zone & min temp

Also called Annual Phlox, Drummond's Phlox, Texas Pride.

More about phlox of sheep annual phlox

About Phlox of Sheep Annual Phlox

Phlox drummondii · also called Annual Phlox, Drummond's Phlox · flowering

Phlox of Sheep Annual Phlox is a compact, free-flowering annual with tight clusters of vivid blooms in red, pink, purple, and white atop sturdy stems. Native to Texas, it thrives in warm, sunny borders with good drainage. Classified as mildly toxic; Phlox sap can cause skin irritation and mild GI upset if ingested.

Cold limit: USDA Annual in zones 2-11; self-sows in zones 8-11 · RHS H3 (10-28°C)

Watch for — Premature flowering finish: Plants stop blooming in very high heat. Shear back by one-third, water well, and apply a liquid feed; repeat flowering occurs when temperatures ease.

What phlox of sheep annual phlox's hardiness rating actually means

Hardiness works differently for phlox of sheep annual phlox: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". Its RHS rating of H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA Annual in zones 2-11; self-sows in zones 8-11 — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for phlox of sheep annual phlox as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can phlox of sheep annual phlox go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when phlox of sheep annual phlox can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline phlox of sheep annual phlox

Phlox of Sheep Annual Phlox is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Phlox of Sheep Annual Phlox hardiness — frequently asked questions

Is phlox of sheep annual phlox cold hardy?

Hardiness works differently for phlox of sheep annual phlox: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Phlox of Sheep Annual Phlox is grown as an annual in USDA Annual in zones 2-11; self-sows in zones 8-11; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature phlox of sheep annual phlox can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is phlox of sheep annual phlox?

Phlox of Sheep Annual Phlox is rated USDA Annual in zones 2-11; self-sows in zones 8-11 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can phlox of sheep annual phlox survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect phlox of sheep annual phlox from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.