Plant Guide: Peonies

Plant Guide: Peonies

Peony Plant Guide

1. Peony Types

There are three main types of peonies:

  • Herbaceous Peonies: These are the most common type, dying back to the ground each winter and emerging anew in spring. They are known for their large, often fragrant flowers.

  • Popular Varieties: 'Sarah Bernhardt' (soft pink), 'Karl Rosenfield' (vibrant red), 'Festiva Maxima' (white with crimson flecks), 'Coral Charm' (deep persimmon to coral).

  • Tree Peonies: Unlike herbaceous peonies, tree peonies have woody stems that remain above ground all year. They tend to have larger, more exotic blooms and often flower earlier than herbaceous types.

  • Itoh Peonies (Intersectional Peonies): A hybrid between herbaceous and tree peonies, Itohs offer the best of both worlds. They have the sturdy stems and large, often unique-colored flowers of tree peonies but die back to the ground like herbaceous varieties, making them easier to manage.

  • Popular Variety: 'Bartzella' (bright yellow with red centers).

2. Planting

  • When to Plant: The best time to plant peonies is in the fall, typically October or November, before the first hard frost. This allows the roots to establish well before spring growth.

  • Location:

  • Sunlight: Peonies are sun-lovers and require at least 6-8 hours of direct sunlight daily for optimal growth and abundant blooms. In warmer climates (Zone 8+), some afternoon shade can be beneficial to protect them from intense heat.

  • Soil: Peonies thrive in fertile, well-drained soil with a mildly acidic to neutral pH (6.5-7.0). They do not tolerate soggy or waterlogged conditions, which can lead to root rot.

  • Improving Soil: If you have heavy clay or depleted soil, amend it with plenty of organic matter like compost or aged manure to improve drainage and fertility. Raised beds can be a good option for areas with poor drainage.

  • Air Circulation: Choose a spot with good air circulation to help prevent fungal diseases.

  • Spacing: Allow adequate space for mature plants, as they can become quite large.

  • How to Plant:

  • Bare Roots: When planting bare roots, ensure the "eyes" (small reddish buds on the root) are facing upward and are planted shallowly, about 1.5 to 2 inches below the soil surface in most regions. Planting too deep is a common reason for peonies failing to bloom.

  • Potted Plants: Plant at the same depth they were in their nursery pot.

3. Watering

  • Newly Planted: Keep the soil consistently moist (but not soggy) for newly planted peonies to help them establish a deep root system.

  • Established Plants: Once established (after a few years), peonies are relatively drought-tolerant. They typically need about 1 inch of water per week, either from rain or supplemental watering, especially during dry spells. Water deeply, allowing the water to reach the roots, and try to avoid getting water on the foliage, which can encourage disease.

4. Fertilizing

  • Peonies are not heavy feeders. If your soil is well-amended at planting, they may not need much additional fertilizer.

  • When to Fertilize: If your soil is poor or you want to give them a boost, fertilize in early spring as new growth emerges and again after the blooms are gone for the season.

  • Type of Fertilizer: Use a balanced fertilizer (e.g., 10-10-10) or one that is lower in nitrogen (which promotes leafy growth over flowers), such as a bulb fertilizer or bone meal. Mushroom compost is also a good option for providing micronutrients.

  • Application: Apply fertilizer around the drip line of the plant, keeping it a hand's length away from the peony crown to prevent "fertilizer burn."

  • Frequency: Established peonies generally only need to be fertilized every few years, if at all. Over-fertilizing, especially with high nitrogen, can lead to fewer blooms.

5. Pruning

  • Herbaceous Peonies:

  • Deadheading: Remove spent flowers to encourage the plant to put energy into root development rather than seed production.

  • Fall Cutback: In the fall, after the foliage turns yellow (typically after the first hard frost), cut herbaceous peony stems back to the ground. This helps prevent diseases and pests from overwintering. Dispose of the cut foliage, don't compost it.

  • Tree Peonies:

  • Tree peonies require very little pruning. Remove dead or damaged wood in spring before new growth starts.

  • Deadhead spent flowers if you don't want to collect seeds.

  • If you need to reduce the size or rejuvenate an old plant, you can carefully prune back a few old stems to new buds at soil level or within 15 cm of the ground in spring. Be aware that this may sacrifice some blooms for that year.

  • Itoh Peonies: Similar to herbaceous peonies, their stems die back to the ground in winter and should be cut back in the fall.

6. Pests and Diseases

Peonies are generally robust, but they can occasionally face issues:

  • Pests:

  • Ants: Ants are commonly seen on peony buds, attracted to the sugary nectar they produce. They do not harm the plant or aid in opening the buds. Once the flowers open, the ants will disappear.

  • Thrips, Mealybugs, Scale Insects: These sap-sucking insects can cause stunted growth or distorted foliage and flowers. Address with appropriate organic or chemical controls if infestations are severe.

  • Diseases:

  • Botrytis Blight (Gray Mold): This is a common fungal disease, especially in cool, moist conditions. It causes buds to rot, stems to wilt, and gray mold to appear on leaves. Good air circulation, proper spacing, and promptly removing infected plant parts are key.

  • Powdery Mildew: A white, powdery coating on leaves, usually in late summer. It's largely cosmetic and rarely harmful to the plant's health.

  • Root Rot/Crown Rot: Caused by overly wet soil. Ensure good drainage to prevent this serious issue.

  • Peony Blotch (Measles): Irregular reddish-purple spots on leaves.

  • Prevention: The best defense against diseases is proper cultural care: good air circulation, well-drained soil, and removing diseased plant material.

7. Support

Some peony varieties, especially herbaceous ones with very large, heavy blooms, may benefit from support to prevent their stems from flopping. Peony rings or wire tomato cages can be placed early in the season as the plants emerge.

8. Long-Term Care

  • Peonies are known for their longevity and can thrive in the same spot for decades, even generations.

  • They dislike being moved, so choose your planting spot wisely. If you must transplant, do so in the fall.

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