Lee Valley & Veritas

Gardening Newsletter
  Volume 9, Issue 2 - February 2014  
Forcing Woody Plants
Forcing woody plants such as redbuds is easy if you follow a few simple techniques.
Visitors to winter-season garden shows are often amazed to see masses of blooming forsythia, magnolia, flowering dogwood (Cornus florida), redbud (Cercis canadensis), Chinese witch hazel (Hamamelis mollis) and cornelian cherry (Cornus mas). These flowering woody plants are a real feast for the eyes. It’s easy to force them by following a few simple steps.

Trees and shrubs that flower on old wood (meaning their flower buds develop the previous summer and fall rather than on new spring wood), are just waiting to break bloom with the onset of spring. To enjoy their blooms before the winter thaw occurs, select branch tips with a circumference of approximately 2cm to 2.5cm and a length of 0.6m to 1m from plants that have plenty of other strong branches, ample buds and good form. Flower buds are typically wrinkly, plump and scaly and may show a tinge of bloom color, while leaf buds tend to be narrow, smooth and pointed. If you don’t have access to suitable species, ask your neighbors for permission to cut a few of their branches or visit your local florist or garden center.

Most forced branches require six to seven weeks of outdoor dormancy at temperatures below 3°C prior to cutting. The later you take the cutting, the quicker it will bloom indoors as it approaches its natural bloom period. Some early bloomers, such as forsythia, cornelian cherry, and Chinese witch hazel, that are cut in February can produce indoor blooms in a couple of weeks. Others that normally flower later in the spring, including magnolias, serviceberries (Amelanchier spp.), apple, cherry, redbuds, and quince (Chaenomeles spp.), can be cut in early to mid-March to bloom in three to four weeks. Don’t forget to include some branches from shrubs with sweet-smelling blooms, such as the fragrant viburnums (Viburnum carlesii and farreri), mock orange (Philadelphus spp.) and February daphne (Daphne mezereum).
Later-flowering apple tree branch
Cut later-flowering apple tree branches in March to bloom in three to four weeks. (Photo by EK Bowell)
Branches are easier to cut on warmer days when the temperature is above freezing since they are more flexible and less subject to breakage and cracks. Bring the cut branches to a cool room, such as a basement, and submerge them in lukewarm water for two to four hours to ensure the branches and bud scales are supple. After the branches soak, cut them to fit the size of the container in which you plan to display them. The branch ends should be cut at an angle to maximize water uptake. Shallow slits (approximately 2.5cm to 4.5cm) made upwards from the ends will also help maximize water uptake. Some gardeners strip the outer bark a length of 2.5cm from the cut end, and some hammer the cut ends. I prefer not to crush the tissue. Remove any buds at the bottom of the branch that would be submerged in the vase water.

Keep the branches in the water-filled container for two to three days in a cool, low-light environment. (Again, I keep mine in my basement.) Some gardeners prefer to hold the branches over in a wrap of moist newspaper for a couple of days before moving them to their vase.

When the buds swell and start to show color, move them to a warmer and brighter area that’s not in direct sunlight. Avoid placing the branches in south-facing windows and near heating vents, stoves, or fireplaces, as this will significantly shorten bloom duration. An east-facing window usually works nicely. Ideal daytime temperatures are around 15°C to 19°C and slightly cooler at night. If flower-bud development takes longer than expected, mist the branches daily. After each misting, immediately place a clear plastic bag over them. Bloom time can be extended by changing the water every three to four days and by using a florist’s preservative to keep the water clean. Each time you change the water, re-cut the branch ends to expose new cambium tissue.
  Pussy willows
  Pussy willows add texture to your display.
To add interest to your display, include some branches with distinctive forms and colorful bark and berries. Try corkscrew willow (Salix matsudana ‘Tortuosa’) and corkscrew hazel (Corylus avellana ‘Contorta’) for form, and red and yellow twig dogwood along with paper birch (Betula papyrifera) for bark color. Pussy willow (Salix discolor), with its furry flower catkins, adds texture and is a real harbinger of spring. For background filler, boughs of cedar work nicely.  

Forcing woody plants is a rewarding experience that will boost your spirits long before the snow melts. Try it this winter and remember to keep track of your successes.

Text by Frank Kershaw

Photos by Marnie Wright
Frank Kershaw is an award-winning horticulturist with more than 35 years of experience. He teaches garden design and horticultural courses at George Brown College in Toronto, Ontario, and at the Toronto Botanical Garden. Frank is also a presenter at the Lee Valley seminars at the Toronto stores.

Marnie Wright (gardenwright@muskoka.com) is a lifelong gardener, writer and passionate garden photographer. Her Rocksborough Garden, developed over 30 years, is located in Bracebridge, Ontario.
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