Withstanding the Cold – How Low Temperatures Affect SunPatiens

SunPatiens are a popular hybrid impatiens developed by Sakata that are known for their vigor, floriferous nature, and ability to thrive in full sun where regular impatiens struggle. Their tolerance for heat and sun has made them a garden favorite. However, like all plants, SunPatiens have limits when it comes to cold tolerance. Knowing how chilled temperatures affect SunPatiens can help gardeners provide the best care and overwintering for these beautiful flowers.

Understanding SunPatiens’ Cold Tolerance

SunPatiens are warm weather lovers suited to the same regions where gardeners typically grow traditional impatiens – USDA zones 9-11. They are killed off by freezing temperatures and cannot withstand cold winters outdoors. Like most impatiens, SunPatiens start to suffer damage anytime the mercury dips below 50 degrees Fahrenheit. Prolonged exposure to cold leaves them susceptible to chilling injury, fungal issues, stunted growth, and death.

While not cold hardy, SunPatiens have good tolerance for cool weather in spring and fall. They can handle nighttime temperatures in the 40s and 50s F as long as daytime highs reach up to 65-70F to allow plant processes to operate normally. However, cooler temps slow growth and delay flowering. For best performance, SunPatiens need warm days and nights above 55F.

Protecting SunPatiens from Early and Late Season Chills

Gardeners in zones 9-11 can plant SunPatiens outdoors once spring nights stay above 50F. Earlier in the season cold snaps can damage tender new transplants. Covering plants or moving containers together against a sheltered wall provides some protection. Watering during warm days helps plants withstand chillier evenings.

In fall, SunPatiens should be brought indoors or replaced with cold hardy plants before nighttime lows drop into the 40s. Hard frosts quickly blacken foliage and kill the plants. Row covers, cloches, and cold frames can buy a few extra weeks of flowering into late fall before digging up plants.

Container-grown SunPatiens are easier to shelter and move indoors as needed In-ground plantings are more vulnerable to early and late cold damage. Avoid planting in low-lying or frost-prone areas of the landscape Sites against south-facing walls are warmer. Mulching helps insulate roots from cold soil.

Optimizing the Location for Protection from Chilling Winds

Biting winds intensify the effects of cold temperatures on SunPatiens. A spot out of direct wind and exposed drafts improves resiliency. Areas near the coast or plains are often windier, making inland or sheltered gardens better suited for overwintering tender plants.

Plant on the leeward side of housing, garages, stone walls, solid fencing, or evergreen hedges to block winds. Position smaller plants within the protection of larger specimens. Use cloches, fabric row covers, shade cloth, or plastic sheeting to shield plants during windy cold snaps. Avoid disturbing protected plants until conditions moderate.

Monitoring Temperature Changes and Frost Forecasts

Pay close attention to extended weather forecasts to anticipate upcoming temperature drops. Be prepared to take protective action as cold periods approach. Familiarize yourself with the average first and last frost dates in your area.

Install a minimum-maximum thermometer in the garden to monitor daytime highs and nightly lows. Observe plant health and respond quickly if cold damage appears.

In fall, track frost advisories and freeze warnings issued by the National Weather Service. These indicate when outdoor temperatures are expected to dip below freezing, triggering the need to cover or relocate SunPatiens.

Options for Protecting SunPatiens In Situ During Cold Snaps

When frost or freezing temperatures threaten before SunPatiens can be moved indoors, various methods help protect them in place:

• Row Covers – Drape fabric row cover material over plants and secure the edges with stones, boards, or ground stakes. Use white polypropylene for cold protection rather than floating row covers.

• Cloches – Invert large glass bell jars or cloches over smaller plants to create a greenhouse effect. Anchor securely.

• Cold Frames – Prefabricated cold frames provide a protective enclosure that holds in heat while allowing air flow. Some types use double polycarbonate walls for greater insulation.

• Mulch – Apply a deep 4-6 inch layer of shredded bark, straw, leaves, or pine needles over the soil around plants to insulate roots from sub-freezing ground temperatures.

• Water – Watering plants thoroughly before a freeze allows the water to release latent heat as it converts to ice, preventing soil and foliage from freezing solid. Don’t water if plants are already wilted from cold damage.

Transitioning Container Grown SunPatiens Indoors

Container gardening makes it much easier to shift tender SunPatiens into protected spaces as weather cools. When overnight lows start falling below 50F, it’s time to bring pots inside, or at minimum move them right up against a warm south-facing wall.

Before bringing containers indoors:

• Inspect for insects and diseases. Treat any issues.
• Prune back plants by 1/3 to accommodate indoor conditions.
• Gradually introduce to lower indoor light levels over 7-10 days.
• Maintain moisture but avoid saturating the soil which invites disease.

Indoors, provide as much natural light as possible from a sunny window. Supplement with grow lights to keep plants from stretching toward light sources. Avoid overheating near appliances and fireplaces. Mist leaves periodically in dry indoor air.

Overwintering SunPatiens by Taking Cuttings

As an alternative to transitioning entire plants, gardeners can take cuttings in late summer or early fall to carry stock plants over winter. Cut 4-6 inch tip cuttings from vigorous shoots and remove lower leaves. Place in pots filled with moist potting mix. Enclose in plastic to retain humidity and put in bright light. Keep the soil evenly moist but not soggy until roots form in several weeks. Successfully rooted cuttings will display new top growth by winter. Grow under lights or in a sunny window until spring planting time.

Purchasing New Plants is an Easy Option

Due to their rapid, early spring growth, greenhouse-grown SunPatiens transplants establish quickly when planted after the danger of frost has passed. Well-hardened plants from reputable nurseries and garden centers bolt out of the starting gate come spring planting time. For many gardeners, buying new SunPatiens every season is easier than overwintering tender plants indoors. Just be sure to plant after soil has warmed in spring.

While not cold hardy perennials, SunPatiens bring non-stop color to containers and garden beds through warm seasons. A little extra care protecting them from autumn and springtime cold spells can extend the enjoyment of these heat-loving impatiens hybrids. Follow these tips to safely overwinter SunPatiens or replace with fresh plants each year. With their vigor and flowers even in full sun, it’s easy to see why gardeners everywhere have embraced SunPatiens!