Houston's subtropical climate is a gift for outdoor gardening — until it isn't. While true hard freezes are relatively rare compared to northern climates, they do occur, and when they do, they can cause catastrophic damage to tropical and subtropical plants that haven't been properly protected. The winter of 2021 — Winter Storm Uri — reminded Houston homeowners that even our climate can deliver deep, sustained cold that kills plants and damages landscapes on a massive scale.
At Heaven on Earth Landscaping, we help clients both select cold-hardy plants appropriate for our climate and protect more tender specimens when cold weather threatens. Here's what you need to know.
Understanding Houston's Freeze Risk
Houston sits in USDA Hardiness Zone 9a/9b, with average annual minimum temperatures between 20°F and 30°F. But averages don't tell the full story. Houston experiences freeze events — temperatures at or below 32°F — on average 20–30 nights per year, mostly between December and February. Hard freezes (below 28°F for multiple hours) occur several times per decade. And rare severe events like Uri can push temperatures into the single digits for extended periods.
Understanding which plants can survive which temperatures — and for how long — is the foundation of good cold-weather plant protection.
Plants Most Vulnerable in Houston
- Tropicals — Bird of paradise, heliconias, gingers, elephant ears. Damaged below 32°F, killed below 28°F.
- Palms — Queen palms are very cold-sensitive. Windmill palms are much more cold-hardy (to 5°F).
- Citrus trees — Meyer lemons, satsumas, and other citrus need protection below 28°F.
- Bougainvillea — Top-kills in a hard freeze; may resprout from roots.
- Plumeria — Very cold sensitive. Must be brought inside or have roots protected.
- Succulents and cacti — Many are surprisingly cold-hardy, but extended wet freezes can be fatal.
Protection Methods That Work
Frost Cloth and Row Covers
Lightweight frost cloth draped over plants traps ground heat and can raise the temperature under the cover by 4–8°F — enough to protect plants through a typical Houston freeze. The cloth must be secured to the ground to trap heat effectively. Remove during the day when temperatures rise above freezing to prevent overheating.
Mulching
A 4–6 inch layer of mulch over the root zone of tender plants protects roots even when above-ground foliage is damaged. Many plants that appear killed by a freeze will resprout from protected roots in spring. This is the most important protection measure for established plants.
Moving Container Plants Indoors
Container-grown tropicals should be moved inside a garage or covered porch when hard freezes are forecast. Even an unheated garage provides substantial protection against short-duration cold events.
Watering Before a Freeze
Moist soil holds and releases heat more effectively than dry soil. Watering thoroughly before a hard freeze — if the soil isn't already saturated — can help moderate root zone temperatures overnight.
"After a freeze, resist the urge to prune damaged foliage immediately. The dead material actually provides some insulation for the plant tissue underneath, and additional cold may follow. Wait until consistent warm weather returns before assessing the true damage."
Best Cold-Hardy Plants for Houston
The most reliable long-term strategy is to select plants that are genuinely cold-hardy for our zone, so that most winter events require no intervention:
- Live oak — Evergreen, cold-hardy to well below 0°F. The backbone of any Houston landscape.
- Windmill palm — Surprisingly cold-hardy (Zone 8) and adds immediate tropical character.
- Salvia greggii — Native Texas sage. Reliably perennial in Houston.
- Cast iron plant — Virtually indestructible. Handles both freeze and deep shade.
- Sago palm — Cold-hardy to 15°F. Classic Houston landscape plant.
- Confederate jasmine — Evergreen vine/ground cover, cold-hardy to 10°F.
After a Hard Freeze — Assessing the Damage
Once consistently warm weather returns (typically by March), carefully scratch the bark of damaged stems. Green tissue underneath means the plant is alive and will recover. Brown, dry, or black tissue means that section has been killed. Prune back to healthy tissue and be patient — many plants that look completely dead will push new growth from the base or roots weeks after the freeze event.
Have questions about protecting your landscape this winter? Contact us or call (281) 286-7335 — we're happy to walk your property and assess the cold-hardiness of your specific plants.