Most difficult perennials to grow

'Some perennials often considered difficult to grow require the right conditions and some patience to fully enjoy their beauty,' 'Some plants I classify as the gold of perennials - they must be successful. Too hot or too cold, too wet or too dry, too much sun or too much shade, and they cannot survive or thrive.

1. Bearded iris

Although bearded iris is one of the oldest and most well-known perennials, there are some common problems that can make it challenging to grow.

"Root rot is a common problem with bearded iris, caused by planting too deep or where the soil doesn't drain well," says horticulturist Katie Sunderlage. ‘To avoid root rot, it is important to plant the rhizome 1-2 inches below the surface of well-drained soil, adding organic matter if needed.

These majestic garden plants are also susceptible to insect and disease problems, particularly leaf spot, iris borer and aphids. Katie continues, 'To prevent fungal leaf spot, allow plenty of space between plants to avoid excess water moisture between stems. Aphids are a common problem if plants are too close together or if there is too much rainfall. Giving plants enough space can help deter aphids, and introducing plants that attract beneficial insects such as ladybugs can help reduce aphid populations.

2. Border phlox

Also known as Phlox paniculata, this tall summer flowering perennial is one of the most popular cottage garden plants. Reaching a height of 6.5 feet in the wild, many short cultivars are now grown to bring color and fragrance to garden borders. With flower shades ranging from red, white, blue, pink and deep magenta, they attract pollinators for months.

Unfortunately border phlox suffer from some common problems, explains Katie Sunderlage. 'One of the most common problems with tall garden phlox is powdery mildew. A destructive fungal disease, powdery spots appear on the leaves and eventually the plant dies back. To prevent powdery mildew, provide good rotation between plants and avoid over-cropping when planting.' Avoid planting in shady areas and choose newer varieties that are more disease resistant.

3. Black-Eyed Susan

Black-eyed Susan, or Rudbeckia goldsturm, is a stunning perennial with its golden luscious petals surrounding a black center, topped with straight, wiry stems. Popular in natural and lawn-style plantings and herbaceous borders, this sun-loving plant attracts numerous pollinators.

"Although this variety is a great addition to a garden, it is very susceptible to a variety of fungal diseases that can shorten the life of the plant," says Katie. 'The most common and devastating fungal disease is leaf spot. They appear as rusty spots on the leaf and quickly spread throughout the plant. The easiest solution is to ensure that the plants are given enough space to spread as water droplets land on the leaves.

4. Dahlia

Grown from tubers, dahlias are spectacularly fragrant and come in an amazing range of colors, flower shapes and sizes. Whether you grow them in pots or borders, these flowers provide a dazzling display from mid-summer until the first frost. Highly addictive and collectible, they are a highly prized plant, but they can be tricky to start and keep year after year.

'Dahlias don't like cold soil and shouldn't be planted outside until the soil warms,' says plant specialist Peggy Anne Montgomery. 'You can start them indoors or in a cool greenhouse, don't make my mistake, and if you overwater, they'll rot. After planting the tubers, water them well and leave them alone until new shoots start to emerge.'

5. Calla lily

With their elegant, swirling inflorescences, these beautiful flowers are very tempting to grow, but they can be problematic for some.

"Some people find calla lilies difficult to grow or establish, but with a few simple guidelines, anyone can succeed," says Peggy Anne Montgomery. At the same time you plant tomatoes outside, don't plant them outside until the soil warms to 50F degrees. They like moist soil and need about an inch of water per week.

When it comes to positioning, partial shade is best and helps keep the soil moist, but Becky Anne advises one key planting tip. 'Don't plant them too deep. It's okay if the 'eyes' are slightly exposed.'

6. Peony

With their showy, rugged blooms, heady fragrance and fleeting beauty, peonies are well-loved in many gardens, but their diva-like behavior can prove a challenge. Is it worth persevering with these cottage garden beauties? Many experts think so.

'Peonies need well-drained soil and consistent moisture, but they don't like waterlogging,' says Tabar Gifford. 'They also need a cool dormant period to flower well, which can be challenging in warmer climates. Additionally, peonies do not like to be moved once established, and will take a few years to settle down and begin to bloom profusely. The saying "sleep, creep, leap" is especially true for peonies, which can take years to bloom when first planted or transplanted. Once happy and established they are long-lived perennials that reliably come back year after year.