Wave® is the most popular petunia family, both for nursery plant sales in spring and seed sales from catalogs. Since 1995, I’ve used more than a dozen Wave types and colors successfully in beds, containers, and mixed planters. Five Wave petunia types are currently available in a wide variety of colors and color mixes:
You can buy many of these at local nurseries and big box stores, but since I need more than 60 plants three different colors each year, starting them from seeds saves a lot of money.
Sow thinly in late February on top of a peat based seed starting mix. Petunia seeds are so fine they can be difficult to see, so most suppliers sell “pellets” that have a ball of inert material around each seed making them easier to handle.
Do not cover the seeds: they need light to germinate. Place the seeding flat in a tray with a half inch of water, and cover the tray with clear plastic.
Germination should occur within 5-7 days. Grow on the dry side, but don’t let the plants wilt. When good second leaves appear transplant each seedling to six-packs, handling by the leaves, not the stems.
Grow under fluorescent lights and feed with a half strength liquid fertilizer every week or two. By early May, flower buds should start to form.
Petunias are really half-hardy perennials that we use as annuals, so they can take a late spring chill. But unless you acclimatize them to sun and wind their leaves will burn and fall off when planted outdoors.
So slowly “harden off” the seedlings by giving them increasing amounts of sunshine over a two-week period. Then plant outside after the danger of frost has passed.
Wave varieties in beds should be spaced two feet apart (12-16 inches for Double Waves) and fed monthly with a balanced fertilizer (like 10-10-10.) No deadheading or cutting back is necessary.
One plant is sufficient even for a large container. Feed them monthly with a slow release fertilizer, and deadhead with a fine stream of water (the plants will recover quickly.)
By mid-summer the container may become crowded, resulting in fewer and smaller blooms. If this happens, remove about a quarter of the plant every couple of weeks, cutting back long stems all the way to the base. This forces new growth from the center of the plant and keeps them looking good all summer.
Jim Janke is an Extension Master Gardener Volunteer in Haywood County. For information visit www.haywood.ces.ncsu.edu/, or call the extension Center at 828-456-3575. ©2020 NC State University.