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Chrysanthemum Flowers: What Are "Hardy Mums"?

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No other flower says

No other plant says "fall" like hardy mums.

David Beaulieu

Taxonomy of Hardy Mums:

Although formerly referred to as Dendranthema, plant taxonomy now classifies chrysanthemums under the genus, Chrysanthemum. This is a case where the scientific plant name has become a commonly used name (in such instances I do not capitalize). Other common names for these colorful fall characters are based on the shortened version ("mums") of the genus name. Thus one will hear "hardy mums," the focus of this article, versus the less hardy "florist mums."

Plant Type:

These plants are usually considered herbaceous perennials. However, if you wish to grow chrysanthemum plants in your area as perennials, select an appropriate cultivar (which, in cold climates, will mean one of the hardy mums). Your local county extension can offer advice in this matter. A spring planting is best, giving them time to become established before winter.

Characteristics of Chrysanthemums:

Chrysanthemum is from the Greek, chrysos (gold) and anthos (flower). These plants come in a wide variety of floral colors, including not only gold but also white, off-white, yellow, bronze, red, burgundy, pink, lavender and purple. Mum plants can grow to be 2-3 feet high, depending on the cultivar and growing conditions. Chrysanthemums also come in many flower forms; that is, they are often grouped by the shape and arrangement of their petals. The most popular flower form is the "decorative," which is so packed with long, broad petals that you can hardly see the center.

Planting Zones:

Chrysanthemums are grown in planting zones 3-9. Their hardiness, however, varies greatly, depending on the cultivar.

Sun and Soil Requirements:

Plant in full sun and well-drained soil, enriched by compost. Chrysanthemums are "photoperiodic"; i.e., they bloom in response to the shorter days and longer nights experienced (in the Northern Hemisphere) in fall. Therefore, do not plant chrysanthemum flowers near street lights or night lights: the artificial lighting may wreak havoc with their cycle. Also, don't overcrowd chrysanthemums: good air circulation reduces the chance of disease.

Types of Chrysanthemum Flowers: Hardy Mums Versus Florist Mums:

As mentioned earlier, there are "hardy mums" and "florist mums." Hardy mums put out stolons. Florist mums put out few or no stolons and are less likely to over-winter in cold regions. I also mentioned above the classification of chrysanthemums by flower form. But adding to the diversity are differences in growth habit between cultivars. For instance, the "cushion" type is a popular group; they exhibit a compact growth habit.

Care:

By every third spring, divide chrysanthemums to rejuvenate them. Fertilize chrysanthemums once per month through July (any growth after that is too late to harden off for winter). Hardy mums will be even hardier with winter protection. Mulch them and create a microclimate to shelter them from winter winds. If you can't plant them on the south side of your house, build a modified version of the shrub shelters used for winter protection. Don't prune in fall: existing branches offer the roots protection.

Pinching Chrysanthemum Flowers:

Pinching chrysanthemums yields compact, bushy plants with more blooms. "Pinching" simply means removing the tips of new growth, thereby stimulating the plants to send out side-shoots. It's called that because, on non-woody plants, one can generally accomplish the task simply by grasping the stem (at the targeted spot) between thumb and forefinger and severing it with a pinching action.

Start in the spring when the new growth has reached 4-6" in length. Thereafter, every 2-3 weeks, pinch the center out of any more growth when it reaches 6". But stop pinching chrysanthemums around the beginning of summer, or else bud formation won't occur soon enough to ensure flowering.

Uses in Landscaping:

Chrysanthemum flowers have traditionally been boiled in China (their place of origin) to make a tea, used in folk medicine for influenza patients. In landscaping, chrysanthemums are valued for the fact that they bloom in fall, helping you to achieve four-season interest in your yard. They look best planted in a mass (but for health, don't overcrowd). Chrysanthemum flowers are also a favorite of florists for arrangements, due to the longevity of their blooms.

Growing Chrysanthemum Flowers -- Selecting Hardy Mums:

Growing these plants requires getting a few things right; they're fussier to grow than many other plants.

In the North, it all begins with buying cultivars that are hardy mums in your area. I.e., for you, "hardy mums" is more than a nickname: it's what you truly need. Potted chrysanthemum flowers are sold by the millions at nurseries in fall, because they've become a staple for outdoor fall decorating. But first of all, what you're buying in this case are not necessarily cultivars meant to grow locally as hardy mums. Secondly, because these chrysanthemum flowers are bought specifically for fall displays, folks often fail to plant them early enough to allow them to become established: they should be planted at least 6 weeks before a killing frost, and even that may not be soon enough.

Fortunately, there are hardy mums available in most flower forms. But once you've selected chrysanthemum flowers suitable for your area, you have to care for them properly. Pinching will improve the plant's looks, but pinching is only part of the formula. You also have to be ever-mindful that, while chrysanthemum flowers hold up against light frosts, hard frosts will damage the blooms you've worked so hard to produce. Your pinching activities, then, must be balanced with the fact that you're in a race against time to get blooms before a hard frost: that's why it's so important to stop pinching at the right time, based on the cultivar you have. Stop pinching:

  • Early-blooming cultivars by mid-June
  • Cultivars that bloom in September by late June
  • Cultivars that bloom in October by July 4

Since it's so important to know what cultivar you'll be working with, it's wiser to buy mail-order hardy mums (single-stemmed rooted cuttings) from a catalog and plant them in spring, rather than planting potted mums you've purchased in fall. In a good catalog, you have all the relevant information in front of you. Also, spring planting gives the plants longer to become established.

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