How to Sow and Plant

Impatiens may be grown from seed sown early indoors and transplanted outside after frost, or from potted plants.

Sowing Seed Indoors:

• Sow indoors 8-10 weeks before last frost using a seed starting kit. Sow seeds shallowly lightly covered with fine seed starting soil.
• Keep the soil moist at 70-75 degrees. Impatiens can benefit with bottom heat.
• Seedlings emerge in 18-28 days.
• As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
• Thin to one seedling per cell when they have two sets of leaves.
• Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
• Transplant hardened-off seedlings to the garden after the frost.
• Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.

Planting in the Garden:

• Select a location in full to part shade with good rich moist organic soil. New Guinea Impatiens may be planted in full sun.
• Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
• Most plants respond well to soils amended with organic matter. Compost is a wonderful form of organic matter with a good balance of nutrients and an ideal pH level, it can be added to your planting area at any time. If compost is not available, top dress the soil after planting with 1-2 inches of organic mulch, which will begin to breakdown into compost. After the growing season, a soil test will indicate what soil amendments are needed for the following season.
• Plants should stand 12 inches apart in the garden.
• Dig a hole for each plant large enough to amply accommodate the root ball.
• Set level with the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand leaving a slight depression around the plant to hold water.
• Water thoroughly, so that a puddle forms in the saucer you have created. This settles the plants in, drives out air pockets and results in good root-to-soil contact.
• Use the plant tag as a location marker.
• Water thoroughly, so that a puddle forms in the saucer you have created. This settles the plants in, drives out air pockets and results in good root-to-soil contact.

How to Grow

• Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. 
• Mulches also help retain soil moisture and maintain even soil temperatures. For annuals an organic mulch of shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
• Keep plants well-watered during the growing season, especially during dry spells. Plants need about 2" of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It's best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
• Until plants become established, some protection from extreme winds and direct, hot sunlight may be necessary. Good air movement is also important.
• After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
• Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
• Remove plants after they are killed by frost in fall to avoid disease issues the following year.

Growing Tips

• Impatiens make beautiful temporary groundcovers in shade gardens. They also can be planted among shade-loving perennials, such as hostas, to bring summer-long color to shady flower beds. Plant them in large drifts and let them fill in, or use them as edging plants along walkways, terraces, or at the front of a bed or border.
• Impatiens make fine additions to container plantings. In fact if you have experienced downy mildew in the past, container growing in fresh commercial potting soil is the only way you can grow impatiens (other than New Guinea impatiens).
• Hummingbirds, butterflies, and other beneficial insects love to visit impatiens.
• New Guinea impatiens can take the sun, but be careful to not allow plants to dry out.

Common Disease Problems

Alternaria Leaf Spot: Small, round reddish brown spots with white to gray centers form on the upper surface of the leaves. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.

Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.

Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves.  The whole plant may defoliate and die. Burpee Recommends: Remove plants as soon as symptoms occur and destroy them. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet. Once regular impatiens (not New Guinea) have had downy mildew they cannot be grown in the same area again. Plant in containers.

Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.

Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Practice crop rotation and do not plant related crops in the same area for several years. Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.

Common Pest and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects that can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Cyclamen Mite: These mites damage plants by sucking juice from stems and leaves. They multiply rapidity in hot, dry weather. They can only be seen using a magnifying glass. Plants will look distorted and stunted, and may not bloom. Flowers will be distorted, streaked and blotched. Leaves can become cupped, curled, dwarfed and thickened. Burpee Recommends: Discard plants that are severely infested. Avoid working with infested plants. Keep plants watered in dry weather. For heavy infestations consult your Cooperative Extension Service for insecticide recommendations.

Mealybugs: Mealybugs are 1/8 to ¼ inch long flat wingless insects that secrete a white powder that forms a waxy shell that protects them. They form cottony looking masses on stems, branches and leaves. They suck the juices from leaves and stems and cause weak growth. They also attract ants with the honeydew they excrete, and the honeydew can grow a black sooty mold on it as well. Burpee Recommends: Wash affected plant parts and try to rub the bugs off. They may also be controlled by predator insects such as lacewings, ladybugs and parasitic wasps. Check with your Cooperative Extension Service for pesticide recommendations.

Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.

Sunscald: Leaves are bleached and faded, often turn white with brown crispy edges. There are no signs of pests and diseases. Plants were usually recently moved. The bright light and heat from the sun break down the chlorophyll which leads to death of the leaf. Burpee Recommends: Transplant impatiens to a spot that has more shade in the afternoon. Do not place impatiens in a south or south-west exposure. Choose a sun loving plant or a New Guinea Impatiens for sunnier locations.

FAQ

Do you have any impatiens varieties resistant to downy mildew? Yes, all New Guinea Impatiens are resistant to downy mildew.

Should I deadhead my impatiens? Impatiens are self-cleaning so you do not need to remove the spent flowers.

Can I prune leggy impatiens? Yes, you can pinch it back. Pinch it back to right above the leave node on a stem. Only pinch back 1/3 of the plant at a time.

My impatiens are not blooming the leaves look great? Avoid over fertilizing the plants with a high nitrogen fertilizer.

Can I overwinter impatiens in the house? Yes, you can! They need morning sun, be sure to keep the soil evenly moist. Impatiens need high humidity so place the pot on a tray of damp pebble to raise the humidity around the plant. Over time impatiens will grow woody and you will want to start with fresh plants.