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All About Petunias

CAN I GROW PETUNIAS?

A definite Yes! Petunias are moderately easy to grow from seed, and extremely easy to grow from commercially grown seedlings.

Use petunias everywhere there is sun. The low growing types are ideal for the front of a flower border, in planters near doorways and pools, or on patios. Tuck petunias in between evergreen shrubs to brighten the area. Use the 'Wave' petunias as groundcovers. Because they tend to attract lovely moths after dark, many homeowners plant petunias near landscape lighting located near a window or patio where they can enjoy the flowers and their visitors at night.

While all types of petunias are great for window boxes and planters, the double flowered ones are best used in containers rather than in beds. Cascading petunias are ideal for hanging baskets. Whatever the type of petunia chosen, plant 3 seedlings per 10-inch basket. Space seedlings about 10 inches apart in a window box or planter.
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PETUNIA SEEDS OR PLANTS?

There are many, many kinds of petunias available as transplants in the spring either mail order or at local garden centers. You can also start petunias yourself if a certain type or color is not available as a transplant.

Be advised that growing seedlings of any plant is something of an art and it takes some extra knowledge and equipment to produce sturdy, healthy plants. Petunia seeds are notoriously slow to germinate, so start them ahead indoors in order to have seedlings ready when warm planting weather arrives. Petunias are also very tiny, so mix the seed with some dry sand so they sprinkle evenly on the growing medium.

Six to ten weeks before the date of the last expected frost in your area fill 2-inch deep flat boxes or peat pots with moist seed starter mix or soilless potting mix. Then sow the petunia seeds, pressing down lightly on them to be sure they are in contact with the growing medium.

Do not cover petunia seeds with soil, because they need light to germinate. Water from below so the seeds are not disturbed. Petunias will germinate in 5 to 15 days at normal indoor house temperatures, sooner if set on a heat mat. For optimum growth, place new sprouts under fluorescent lights for 12 hours daily to simulate late spring light conditions.
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CULTIVATION

While petunias will bloom in bright, indirect light, they do their best in full sun. Petunias like fertile soil which drains well and is neutral to slightly acid (pH 6.0 to 7.0). Light, sandy soil is ideal.

Break up the soil by digging down 6 or 8 inches, mix in some organic matter, and then smooth and level it. Dig a hole for each petunia seedling about the size of its container. Carefully pop each one from its container, set it in its hole, and then fill in the dirt around the roots, pressing gently. Do not set the seedling any deeper into the soil than it was in its container. Water generously.

Group seedlings in threes or more or, where space is narrow, side by side from 8 to 12 inches apart in rows. After transplants grow to 6 inches tall, pinch back their central stems to force them to develop side stems and become bushy. The new, tiny milifloras can be planted as close as 6 inches apart as they are slow growers and finer textured plants. Sprinkle a teaspoon of all-purpose, slow-acting granular fertilizer on the soil around each newly planted seedling for the rain to soak in. This will provide consistent, basic nutrition for the petunias over the season.

Because they are such profuse bloomers from late spring to mid-fall, petunias appreciate an energy boost from diluted liquid fertilizer either poured onto the soil or sprayed on their foliage every so often. Feed petunias in containers by adding the granular, slow-acting fertilizer to their soilless growing medium. Otherwise, water with diluted liquid fertilizer periodically. Petunias need regular moisture because their shallow roots dry out quickly. If they are in soil rich in organic matter they will not need to be watered as often. Petunias in containers in the sun need watering every day--especially those in clay pots.
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PETUNIA GROWING TIPS

Spread a 2- or 3-inch layer of some organic material to mulch the soil around petunia plants. Use chopped leaves, dried grass clippings, wood chips or shredded bark products. Organic mulch suppresses weeds, keeps the soil cool and moist by blocking evaporation from its surface and improves its texture as it gradually decomposes.

Remove the spent flowers from petunias in containers as they fade. By midsummer when the plants begin to get leggy and the spindly, stems produce fewer and smaller flowers. Cut each stem back by half to revitalize the petunia plant. After a pause, they will resume flowering with gusto.
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INSECTS & DISEASES
If petunia foliage puckers and turns yellowish, check for aphids. About the size of a pinhead, these insects have soft, pear-shaped bodies. They cluster and suck juices from tender new petunia stems and leaf undersides. Pinch off infested plant tips. Spray major infestations with commercial insecticidal soap according to label instructions.

Tomato hornworms, yellow woolybear and other caterpillars sometimes feed on petunia foliage, skeletonizing it. Simply pick off these very visible pests and drop them into a plastic bag for the trash. [Be aware that some caterpillars, tend to be solitary rather than clustering in large hoards. These may be the larvae of desirable butterflies, so you may prefer to tolerate the damage for a few weeks until they pupate]. Then pinch off the damaged plant parts, feed and water, and the petunias will rebound. Spray or dust infested large bedded areas with a product containing Bacillus thuringiensis (Bt) while the caterpillars are feeding. Follow label directions.

Petunias are susceptible to several viruses such as curly top, mosaic, ringspot, and spotted wilt which are not curable. Controlling pest insects such as aphids that may transmit disease in and around the yard is the best defense. Dig up sickly, wilted petunia plants and discard them in the trash so that they do not infect other plants. Do not use tobacco products around petunias. Disinfect any tools that come in contact with infected plants.

Hungry deer will eat petunias. Protect plants in a large garden with electric fencing around its perimeter or plant petunias in hanging baskets out of their reach. Try spraying plants with repellents that work either by taste or odor. Follow label instructions and renew the spray after it rains. Install unobtrusive black polynetting around the entire property if you have intractable deer problems.

Rabbits generally prefer vegetable plants to flowers, but if new petunia seedlings disappear totally overnight, then it is likely rabbits are the culprits. The best defense is to enlist the help of a pet dog or cat. Clear all piles of brush off the property to deny them a home. Plant petunias out of the reach of rabbits in hanging baskets, window boxes and tall planters.
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Gardening Tip of the Day

  • Several options are available to overwinter a favorite geranium. The first is to cut it back and pot it up as a houseplant for the winter to replant outside in the spring. The second is to pull it up, brush off any clinging soil, and hang it upside down in a cool, humid basement until replanting in spring. Or, you can cut 4-inch lengths of new stem and put them in water or damp vermiculite to root. Once rooted, transfer to individual pots and treat as houseplants.