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New Guinea Impatiens Care: Sun Tolerant, But Never Dry

Unlike bedding impatiens these take real sun and resist downy mildew. What they will not take is drying out — they collapse within hours.

By Salma 3 min read Save to Pinterest — opens Pinterest in a new tab
Impatiens flowers
Photo: ignartonosbg, Pixabay Content License, via Pixabay
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The whole plant is a trade: more sun tolerance and mildew resistance than bedding impatiens, in exchange for an absolute intolerance of drying out.

Why they exist in every garden centre now

Until about 2011, common bedding impatiens (Impatiens walleriana) were among the most widely planted summer annuals anywhere. Then impatiens downy mildew (Plasmopara obducens) spread widely, and plantings collapsed — leaves yellowing and dropping, stems bare within days, whole beds lost.

New Guinea impatiens are a different species (Impatiens hawkeri) and are highly resistant. That resistance, plus genuine sun tolerance, is why they took over the shelf space.

The two impatiens, compared
New GuineaBedding (walleriana)
SunPart to full sunShade to part shade
Downy mildewHighly resistantHighly susceptible
Flower sizeLargerSmaller, more numerous
FoliageLarger, often bronze or variegatedPlain green
Drought toleranceVery lowLow
HabitUpright, bushierMounding

Water is the entire care regime

They wilt harder and faster than almost anything else sold as a bedding plant. A container can go from fully upright to flat on the compost in a couple of hours on a hot afternoon.

The good news: a thorough soak usually brings them back within an hour or two with no lasting damage.

The bad news: repeated severe wilting scorches leaf margins, drops buds and reduces flowering for the rest of the season.

Reducing how often it happens:

  1. Bigger pots. The single largest improvement — small containers cannot hold enough
  2. Moisture-retentive compost, with water-retaining material if you use it
  3. Mulch the surface of containers as well as beds
  4. Afternoon shade in hot regions
  5. Group containers together so they shade each other and raise local humidity
  6. Water in the morning, thoroughly, rather than little and often
  7. Self-watering containers are genuinely worth it for this plant specifically

Judge the pot by weight

Surface compost dries long before the rootball does, and these plants are usually watered too lightly rather than too rarely.

Lift the pot. Light means water it thoroughly, until it runs out of the bottom.

Light, by climate

  • Cool summers — full sun is fine and produces the best flowering
  • Moderate — four to six hours, ideally morning
  • Hot summers — morning sun, afternoon shade, no exceptions
  • Deep shade — they survive and flower sparsely. Bedding impatiens are better there, if mildew allows

Feeding and shaping

  • Balanced liquid feed every two weeks in containers, which exhaust nutrients quickly
  • Slow-release granules at planting as a base
  • Pinch the tips of young plants to encourage branching
  • Cut back by a third if a mid-season plant gets leggy — new growth and flowers follow within a few weeks
  • Deadheading is optional. They drop spent flowers themselves

Keeping them past the first frost

They are tender perennials grown as annuals and frost kills them outright.

Cuttings are the practical answer, and they root very easily:

  1. Take 8–10 cm tip cuttings in late summer, before any cold
  2. Strip the lower leaves
  3. Root in water or damp compost — usually one to two weeks
  4. Pot up and keep on a bright windowsill over winter
  5. Pinch them through winter to keep them bushy
  6. Harden off and plant out after the last frost

A handful of cuttings in August replaces a tray of bought plants the following May, which over a few seasons is the difference between an annual expense and a free one.

Common questions

Do New Guinea impatiens need sun or shade?

They take considerably more sun than common bedding impatiens, and in cooler climates will grow happily in full sun provided they never dry out. In hot regions they do better with morning sun and afternoon shade, because the limiting factor is not light but water loss — a plant in strong afternoon heat transpires faster than its roots can supply and collapses. The usual guidance of four to six hours of sun with shade through the hottest part of the day suits most gardens.

Why do my New Guinea impatiens keep wilting?

They dry out faster than almost any other common bedding plant, and they show it dramatically — a pot can go from upright to completely flat within hours on a hot afternoon. In most cases a thorough watering restores them within an hour or two with no lasting harm. What does cause damage is repeated severe wilting, which scorches leaf margins and reduces flowering. Larger pots, moisture-retentive compost, mulch and afternoon shade all reduce how often it happens.

Are New Guinea impatiens resistant to downy mildew?

Yes, and this is the main reason they are now so widely grown. Impatiens downy mildew, caused by Plasmopara obducens, devastated common bedding impatiens in many regions from around 2011, causing sudden leaf drop and total collapse of plantings. New Guinea impatiens are a different species and are highly resistant, which is why they replaced bedding impatiens in so much commercial planting. The newer interspecific hybrids sold under various trade names share that resistance.

Do New Guinea impatiens come back every year?

Not outdoors in any climate that frosts — they are tender perennials grown as annuals, and they are killed outright by the first frost. In frost-free regions they persist and can be grown as perennials. They can also be overwintered indoors as houseplants in a bright room, or more practically propagated from cuttings taken in late summer, since they root very readily in water or compost and a few cuttings produce next year's plants for nothing.

Should you deadhead New Guinea impatiens?

Not for flowering, since they are largely self-cleaning and drop spent blooms on their own, which is part of their appeal in containers. Removing the occasional tatty flower improves appearance and nothing else. What does help is pinching the growing tips on young plants to encourage branching, and cutting back a leggy mid-season plant by about a third, which produces a flush of new growth and flowers within a few weeks.

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