Hardy chrysanthemums are perennial flowers that bloom in the fall, featuring distinctive flowers that resemble daisies. In contrast to florist chrysanthemums, which are cultivated solely for autumn blooms and are typically regarded as annuals, hardy mums are resilient in winter, thriving in USDA Zones 4 to 9, and they offer vibrant colors season after season. These plants flourish in full sunlight, in well-drained, slightly acidic soil, and under average humidity conditions.
Hardy chrysanthemums grow rapidly, achieving their maximum height in their initial year, and continue to expand in fullness in the following years. These resilient plants begin to form buds as the nights grow longer and bloom in the autumn, lasting for as long as eight weeks. It’s important to note that the leaves and flowers of hardy chrysanthemums can be mildly toxic to both humans and pets.
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Light
Hardy chrysanthemums thrive best when exposed to full sunlight, requiring a minimum of six to eight hours of direct sunlight each day. In warmer regions, they can benefit from some shade during the afternoon. These flowers are photoperiodic, which means they respond to the shorter days and longer nights of late summer and autumn in the northern hemisphere by blooming. Consequently, it’s advisable to avoid planting them near streetlights or other artificial lights, as such illumination can disrupt their blooming cycle.
Soil
These plants thrive in soil that is rich in organic matter and has a pH level that is slightly acidic to neutral, ranging from 6.2 to 7.0. It is essential to have excellent drainage, as prolonged moisture in the soil can lead to root rot.
Water
Mums prefer steady moisture levels but cannot handle overly wet soil. Water the plants when the top 1 to 2 inches of soil feels dry. During warmer temperatures and when the plants are larger and flowering, you may need to water them more often. A minimum of 1 inch of water each week is recommended.
Climate and Moisture Levels
Hardy chrysanthemums truly embody their name, as many varieties keep producing flowers even when temperatures fall to 20°F. The roots of most types can endure winter soil temperatures below 0°F. Additionally, they handle heat effectively, thriving in temperatures as high as 100°F, provided they receive sufficient water. Nonetheless, high humidity can lead to fungal issues, including leaf spot.
Fertilizer
Mums require a substantial amount of nutrients. Opt for a fertilizer that has a low nitrogen content and a high potassium level, like a 5-10-5 formulation. You can apply a slow-release fertilizer in the spring or a water-soluble option on a monthly basis, but it’s important to cease fertilization in July. This is to prevent the development of soft new growth that can be vulnerable to cold damage as the fall approaches.
Varieties of Hardy Mums
There is a wide variety of hardy chrysanthemums. These plants are categorized into 13 distinct classes according to the shape of their flowers. Traditionally, garden chrysanthemums were considered to be hardy only in USDA zone 5, but recent cultivars have shown resilience in zone 4, and a few can even thrive in zone 3.
- Anemone is a genus characterized by elongated, flat petals, with flowers that can grow up to approximately 4 inches in diameter. Notable varieties include ‘Dorothy Mechen’, featuring soft purple petals, ‘Samba’, which showcases rose-pink flowers, ‘Rhumba’, known for its coral red blooms, and ‘Harmony’, distinguished by its vibrant yellow flowers.
- Pompon chrysanthemums feature compact, spherical blossoms and are commonly referred to as button mums. Notable cultivars include ‘Patriot,’ which boasts pure white flowers, ‘Garnet,’ characterized by deep red petals that develop bronze highlights as they age, and ‘Barbara,’ which showcases tiny purple flowers.
- The Spoon variety features petals that resemble the shape of a spoon, producing small blooms that can reach a diameter of 4 inches. Notable cultivars include ‘Kimie,’ which showcases yellow-gold petals, ‘Matchsticks,’ characterized by yellow centers that culminate in striking red spoons, and ‘Yellow Quill,’ which has vibrant yellow centers that transition to creamy white edges.
- My Favorite is a relatively recent series known for its remarkable resilience in USDA zone 3b. These plants can reach heights of up to 4 feet and produce flowers in shades of coral, pink, or yellow.
- Morden is a relatively recent series of chrysanthemums. These vibrant, jewel-colored varieties have been developed to withstand conditions in zone 3. Notable cultivars in this series are ‘Morden Canary’, ‘Morden Delight’, ‘Morden Fiesta’, and ‘Morden Garnet’.
Pruning
To promote dense growth and avoid legginess in the plant, it’s advisable to pinch back chrysanthemums when they reach a height of approximately 6 inches. Trim each stem to about 2 to 3 inches above the base, just above a leaf. Every two to three weeks, reduce half of any new growth when it hits 6 inches. Cease pinching around the Fourth of July to allow sufficient time for bud formation, ensuring a blooming display in the fall.
Once the autumn flowering has concluded and the leaves have withered, you have the option to trim the dead stems to just above the soil level. Alternatively, in northern regions, it is advisable to postpone the trimming until spring, as the stems provide insulation for the roots during the colder months.
Cultivating Resilient Chrysanthemums
Hardy chrysanthemums can be multiplied through various methods, with the simplest being the division of root clusters in the early spring season.
Reproducing through Division
- In the spring, when fresh growth begins to emerge, gently excavate the whole plant with a shovel, ensuring to include the crown and the complete root ball.
- Utilize a sharp knife to divide the clump into smaller parts. Ensure that each part contains a robust set of roots connected to a segment of the crown.
- Replant the divisions right away in the chosen spots. When planting in clusters, ensure the pieces are spaced a minimum of 1 foot apart.
Propagation through Stem Cuttings
- During late spring or early summer, when the new growth reaches a height of 6 to 12 inches, utilize sharp pruning shears to trim the stem tips to a length of 3 to 4 inches.
- Remove the lower leaves, then immerse the cut ends of the cuttings in rooting hormone.
- Place the cuttings in a rooting substrate, like coarse sand or perlite.
- Maintain moisture in the cutting until the roots start to form, which typically takes about four to five weeks.
- Once a strong network of roots has formed and the cutting begins to produce new leaves, gently transfer the cuttings into the garden or into pots containing a regular potting mix.
Transplanting and Replanting
Choose a container that has ample drainage holes and utilize a peat-based potting mix. Remember that potted plants require more regular watering compared to those planted directly in garden soil.
Transfer the plant to a bigger pot every two to three years when it starts to become root-bound.
Overwintering
In the garden, chrysanthemums do not require winter safeguarding. Nevertheless, if you prune the stems during the autumn, it’s advisable to cover the base with a generous layer of dry mulch, such as straw or evergreen branches, to shield the roots from freezing temperatures.
Container plants need to be prepared for winter or relocated to a cold frame or a protected area.
Frequent Insects and Plant Illnesses
Chrysanthemums possess an inherent ability to fend off various insects. A whole category of natural insecticides includes pyrethrin, extracted from chrysanthemum blooms. However, garden mums can still fall prey to minor pests like aphids, thrips, spider mites, and leaf miners. If you observe any leaf distortion or detect fine webs or trails on the foliage, applying an organic pesticide like neem oil can be an effective solution.
Garden chrysanthemums are vulnerable to numerous ailments, including botrytis, which leads to a gray mold that causes flowers to wither, and aster yellows, a viral infection that results in yellowing leaves. Additionally, they are prone to various fungal issues, such as powdery mildew, verticillium wilt, and leaf spots. Applying a fungicidal spray can be beneficial for treating fungal infections, but often, the most effective strategy is to remove the affected parts of the plant, or even the entire plant if the infection is extensive. To minimize the risk of soil-borne diseases, it is advisable to avoid watering from above, as fungal infections thrive on wet leaves but not on dry ones.
Tips for Encouraging Hardy Mums to Flower
Flowering Periods
Hardy chrysanthemums typically flower during the autumn season, although they may begin to blossom as early as late summer.
How do Hardy Mum Flowers appear and what is their fragrance like?
Resilient chrysanthemums are available in a variety of fall colors, featuring either multi-layered, daisy-shaped petals or tightly clustered, button-like flowers, all characterized by a dense, bushy growth habit. These hardy flowers emit a slightly spicy aroma, complemented by a touch of sweetness.
Ways to Promote Increased Flowering
Resilient chrysanthemums typically produce vibrant flowers when their essential care requirements are fulfilled, which include ample sunlight, sufficient watering, and timely pruning of the stem ends.
If you purchased potted hardy chrysanthemums, you should transplant them into the soil once the flowers have wilted, typically by late October. Ensure they receive adequate watering, apply mulch, and trim them back to about 3 inches above the soil for the winter months. This same care should be given to any established mums in your garden after they have finished blooming. Additionally, safeguard the newly planted mums from frost to help them establish their root systems.
Removing Spent Blooms from Hardy Mums
To encourage a denser and more compact growth with abundant flowering, it’s important to pinch back the plants. Additionally, removing faded flowers, or deadheading, is essential to maintain a tidy appearance and to promote further blooming.
Frequent Issues Encountered with Hardy Mums
Garden mums are generally simple to cultivate as long as they are provided with suitable conditionshowever, they require a fair amount of care, so it’s not uncommon to encounter some issues. These are not the type of plants that can be simply planted and forgotten.
Golden Foliage
Discoloration of leaves on garden chrysanthemums frequently indicates a viral infection or a severe fungal issue. The most effective approach is to prune all impacted sections of the plant or, in severe cases, to completely eliminate and dispose of the plant to prevent further spread of the disease.
Tall, Slouching Foliage
If chrysanthemums are not significantly trimmed back when they start to grow in the spring, they tend to produce long, weak stems that can fall over due to their own weight. To achieve optimal growth, it’s advisable to prune or pinch back hardy mums at least twice during the spring and early summer, prior to the blooming period in late summer and fall. This practice helps to prevent the plants from becoming excessively tall and leggy.
Keep in mind that garden chrysanthemums require plenty of sunlight. If they are situated in shaded areas, they will likely grow elongated stems in an effort to seek out additional light.
Plants Snap Off at the Soil Level
Establishing the correct watering schedule for these plants can be challenging. They require consistent and dependable watering, but excessive moisture, particularly in heavy or clay-rich soil, can lead to root rot, weakening the stems and resulting in breakage. It’s important to modify your watering habits in response to the amount of natural rainfall. If your plants receive over an inch of rain each week, they may be susceptible to root rot.
Is it possible to plant a flowering mum plant that I’ve received as a gift in my garden?
Typically, potted chrysanthemums given as gifts are of the florist or exhibition variety, which are not well-suited for transplantation. These flowers are encouraged to bloom prematurely and lack the robust root system needed to survive the winter. Appreciate the beauty of the gifted mum while it flowers, and then dispose of it afterward.
What is the lifespan of a garden mum plant?
Garden mums are perennials with a relatively short lifespan, typically lasting no more than four to five years. After this period, the root clusters tend to become dense and woody, leading to the plant’s decline. Nevertheless, by dividing the roots every two to three years, you can successfully maintain the plant or produce identical replicas, ensuring its continued growth.
What are the best ways to incorporate hardy mums into a landscape design?
Consider planting these autumn-flowering varieties as annuals during late summer and autumn to take the place of summer-blooming annuals that are losing their vibrancy. Chrysanthemums are also great as potted plants for outdoor spaces like decks and patios. When treated as perennials, they serve as enduring bedding plants, ensuring that the colorful display continues well into the late fall.
