The Art of Grafting Chrysanthemums

Tri-colored dome chrysanthemum on display at Longwood Gardens, 2009 (photo: L. Albee)

Ever wonder what is going on in the greenhouses at this time of the year? While you are enjoying the beautiful summer display, Longwood’s growers are already getting ready for fall! One of our biggest projects at this time of year is to complete the grafting process that allows us to grow the large specialty chrysanthemums that will be on display during our Chrysanthemum Festival.

Grafting chrysanthemums is not a common subject you learn in school. We were taught this special technique from Chinese and Japanese specialty chrysanthemum growers, and use it to make eye-catching specialty mum forms for our display. Grafting mums is very common in China and has a long history, but there are no written records of when it started. In Japan, the first record is found on an 18th century Ukiyoe, a wooden block printing. We began practicing this new technique a couple of years ago and are continually learning and experimenting to create new forms.

During last year’s display, we had many different forms, including the tri-colored dome, 100-cultivar, pagoda, tri-colored shield, and pom-pom. We first trialed the tri-colored dome in 2008. You might remember the first one was not perfect, but with practice we are getting better. We saw our first pagoda shape in 1995 when somebody brought us a picture. We had no idea how to make it until we saw a Chinese display in 2010. We had tried various, small experiments but were unable to finish until we learned hands-on, and last year’s pagoda was our first on display.

100-cultivar chrysanthemum, 2011 (photo: L. Albee)

Pagoda chrysanthemum, 2011

Tri-colored shield chrysanthemum, 2011

Pom-pom chrysanthemum, 2011

We graft our chrysanthemums on two different stocks—either on chrysanthemum stock or Artemisia (Artemisia annua) stock. You may be familiar with Artemisia annua, commonly known as sweet Annie or annual wormwood. We use the Artemisia to get the benefit of its strong root system for summer heat, disease and insect resistance. It also has many side shoots that grow close together on the stem and a tall growth habit.

Artemesia with grafted mum tips

The grafting style we use is called “cleft style.” As you see in this video, we slice the stock stem down the center and insert the tapered grafting tip into the slit. Then we carefully wrap it with Parafilm, which is commonly used in laboratories. It holds the grafted tip tightly in place, seals the cutting area and helps the cut surfaces not to dry out. In two weeks, the tip tissue connects to the stock and it starts growing. The key to successful grafting is for the stock stem to be young and fresh (the inside green with no pith). Sometimes the Artemisia stem accepts the graft with some pith inside, but it’s difficult to get good results. Matching the stem thickness between stock stem and grafting tip is also important to connect the vascular systems together.

In hot and dry conditions, the grafted plants are kept under shade cloth and misted as needed. Sometimes, we use small plastic bags to keep the grafts moist. In this year’s wet and cloudy conditions, grafting is going well without misting or using the plastic bags, but it depends on the day.

A pagoda form with the grafts protected by plastic bags

Creating our specialty mum forms is a year-long process. For example, to make the pagoda form, we start Artemisia seeds in fall and grow in cool conditions. Then we graft the chrysanthemum tips in May and June, once the Artemisia stems get thick enough to match to the chrysanthemum shoot. As the Artemisia stems grow thicker, we will graft several chrysanthemum stems, according to thickness, at a time. We pinch the tips to promote more stems until the middle of July, and disbud to one flower in September. Just before flowering, we arrange the flowers to make the roof shape, using twist ties and bamboo.

Soon we will begin grafting the 100-cultivar chrysanthemum for this year’s display. Stay tuned to our blog for more on that later this summer!

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The Art of Cascade Chrysanthemums at Longwood Gardens

Some of the forms currently being grown for Longwood's 2010 Chrysanthemum Festival

Cascade chrysanthemums have long been at the heart of Longwood Gardens’ annual Chrysanthemum Festival.  Longwood grows specialty mums (Chrysanthemum x moriflorum) that originated in China and Japan and are selected for their ability to create beautiful and lasting forms.  Over the years, Longwood’s amazing show of form and color has been continually modified and refined.  Guests marvel at the captivating shapes and often ask us how we create these wonderful pieces of horticulture.  The following is meant to highlight a little behind-the-scenes action and hint at some of the spectacular forms you will see this November in our Conservatory.

Newly potted chrysanthemum cuttings in January, 2010

At two months old the mums are ready to begin training.

Beginning 15 months before the display date, the design team, in conjunction with the grower, makes final chrysanthemum cultivar choices for the following year.  Stock plants—from which we take all of our final plants—are created in order to bulk up on material.  In mid-December the final plants are started as small cuttings.  We begin heavy

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Mum’s the Word: Longwood Grows Mammoth Mum

Longwood’s Largest Thousand Bloom Chrysanthemum Ever on Display in the East Conservatory

What is it?

The Thousand Bloom Chrysanthemum (known in Japan as Ozukuri) refers to a technique, originating in China and expanding to Japan several hundred years ago, for growing an extremely large Chrysanthemum, with a goal of producing the maximum number of flowers possible on a single plant.

If that doesn’t sound difficult enough, the technique also requires that there is only a single bloom on the end of each individual branch; none of the flowers on the sides of the branch is used.  And to further complicate matters, each flower must be perfectly placed in concentric horizontal rows on a dome-shaped frame!

The largest specimen recorded in Japan had over 2,200 flowers—only a few growers in the entire world have been able to produce a plant that large.

How do we do it?
First, we choose a suitable cultivar—one that has large flowers, the ability to produce long stems, can grow well under a wide range of temperature and light conditions, and the ability to produce 3-4 branches each time the stem tip is pinched. The mum variety used this year is ‘Kenbu’, a Japanese variety that produces large, white, fully double flowers on long stems.
Our grower, Yoko, started the plant from a cutting taken in July 2008, and grew the plant in a greenhouse for about 15 months, enabling it to grow large enough and produce enough stems to be shaped into a Thousand Bloom.

During winter months, when days were short, supplemental lighting was provided to prevent the plant from flowering, and to insure the stems grew long enough.  The plant was watered very carefully, fertilized frequently, and the container size was increased multiple times to provide enough space for good root growth.  Temperatures were kept as close to 65-70 degrees Fahrenheit as possible to encourage continual growth.

Thousand Bloom Chrysanthemum just prior to its move to the East Conservatory

Yoko and her team pinched it (removing the shoot tip) periodically to cause the side branches to grow out. Every time a stem is pinched, 3-5 new branches will form below the pinch. The number of flowers on the finished specimen is dependent on the number of branches, since ultimately only one flower will bloom at the end of each branch.
In late September, the shortening day lengths caused the plant to produce flower buds.  When the flower buds are still very small, Yoko and her helpers removed the ones that formed on the sides of each branch, leaving only the bud at the end of each branch.

In mid-October, the metal frame was installed by a Dave B., a metal worker from our Maintenance Department.  The ribs and horizontal wires that create the dome shape used to hold the flowers in their proper positions was prefabricated by Dave B and his colleague Dave T.  Special wire circles are attached to each wire post to provide additional support for the flowers.  The overall frame size is determined by how long the branches are (the tips of each branch must be long enough to reach the frame) and how many branches there are.  It takes several days to install the frame.  The frame on this year’s Thousand Bloom is about 9 feet in diameter at the base.

Yoko and a member of her team at work, placing each flower into the dome-shaped frame.

Once the frame is in place, Yoko stopped watering the plant, allowing it to wilt slightly. This makes the stems more flexible so they can be moved easily without breaking.  She then brought together a team of four gardeners to place the flowers in their proper positions on the frame.  First, each flower is placed in a soft fabric sleeve to protect it during handling. Then, starting at the top of the frame, the flower buds are attached to the wire supports—resulting in perfectly spaced concentric rings of flowers. Once the flower buds are in place, the sleeves are removed so the flowers can fully open.
When the flower arranging was done, the Thousand Bloom was placed in its final location in the East Conservatory to be enjoyed by Longwood’s guests.

This year, Longwood has grown its largest Thousand Bloom ever—and one of the largest ever grown in the United States—featuring 718 perfect blooms and measuring more than 8 ft in diameter! This magnificent chrysanthemum is on display now through November 22.

Longwood would like to thank Japanese Master Growers Mr. Katsuo Ito, Mr. Minori Yusa & Mr. Tadashi Imafuku for sharing their knowledge and skills with us and helping us to produce our classic mum forms.

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