Growing petunias can offer long term color in the summer landscape and brighten dreary borders with lovely pastel colors. Proper petunia care is simple and easy. After learning how to plant petunias you can include them in your flower bed and container garden.
Four species of petunias include hundreds of cultivars and offer a perfect addition to the home landscape:
- Grandiflora petunias are the most common type of growing petunias. This species features 3 to 4 inch (7.5 to 10 cm.) blooms which often grow upright, but may spill over the side of your container or window box.
- Multiflora petunias have smaller flowers and a more abundant bloom.
- Milliflora petunias are miniature versions of growing petunias; they are compact and reblooming.
- Spreading petunias are only 6 inches (15 cm.) tall and can rapidly cover a selected area to function as a blooming ground cover.
How to Plant Petunia Seeds
Petunias are slow to emerge in the beginning, but once established, are low-maintenance, consistent growers.
Start indoors.
To get a head start on planting petunias, start seeds indoors about two months before the last frost date. Fill peat pots with a seed-starting mix (a finer blend of nutrient-dense potting soil available at any garden center or nursery), and place in a tray. Sprinkle petunia seeds over the top of each pot. To sow, gently press petunia seeds into the soil, but do not cover: These sun-loving blooms need light to germinate, too. Mist with a spray bottle, and cover with plastic wrap before setting in a warm, well-lit place like a sunny windowsill (or on a heat mat with a grow light, if full sun is unavailable). Keep the soil moist by pouring water directly into the tray to avoid disturbing the tiny seeds. After 15 days, seedlings should fully sprout. To supercharge their growth before transplanting, stick them under fluorescent lights during the day.
Pick the site.
Petunias thrive in direct sunlight, unlike their lookalikes, impatiens flowers. While partial shade can work, aim for a planting site that gets at least six hours of sun per day. Like most plants, petunias need fertile, well-draining soil with a slightly acidic pH—6.0 to 7.0, which is achieved by incorporating organic materials or fertilizer as needed.
Prepare the site.
To ensure that the soil has proper ventilation, till organic matter like compost into the first eight inches or so with your hands. Dig holes about the same size of the starter pots before planting.
Plant.
Carefully remove the petunia seedlings from their containers, or, as is the norm with many biodegradable seed starter pots, simply place the pot directly into the hole. Fill in with soil, tamping down gently around the delicate stems. Space petunias according to their type: compact Millifloras can be closer together, around six inches, while other petunia types may need around 10 inches, depending on their size. Water well to establish the root systems.
How to Care for Petunias
Petunias are relatively simple to grow. The colorful flowers require routine watering, pest control, and mulching to thrive.
Water regularly.
Petunias have relatively shallow roots, and depending on the container they’re planted in and their sun exposure, some plants may need daily watering. Check the soil and keep an eye on the health of the leaves to determine the right watering schedule for your petunia plants.
Control pests.
Aphids are a common petunia pest, especially for young plants; if you notice curling, sickly leaves or spot the clusters of pale green insects, remove the infected leaves, or treat with insecticidal soap. Companion planting offers a chemical-free way to curb the problem.
Mulch.
A light layer of soft organic material like straw or grass clippings will regulate the temperature and moisture of the soil and keep weeds from taking hold.
Deadhead.
Deadheading is a form of pruning that simply refers to the removal, either by pinching or clipping, of dead flowers to encourage new growth. Some varieties will not require deadheading, but Grandiflora and Multiflora petunias should be regularly deadheaded to maintain appearance and productivity.
Fertilize.
Prolific petunia plants benefit from the occasional application of liquid fertilizer, either applied directly to the soil, or sprayed in diluted form over their foliage. Pelleted slow-release fertilizer is another option for plants planted in a soilless growing medium.
