Courting Cordyline

Ransom Nichols

Over the last few years, the ornamental industry has seen more than a few new cordyline varieties introduced. To me, the plant still has not come full circle. Everywhere I travel—from the northern states to Hawaii—I see more applications of this plant in the garden and yardscapes. The newest varieties coming out have various shades of color and are truly unique. When visitors walk through our greenhouses I make it a point to go through our cordyline range. Physically seeing the multi-colored blocks of these plants is a great conversation piece.

For 2010, Smith Gardens Bellingham will be growing Red Star, Purple Sensation and about eight others, as well as trialing two or three other varieties. Each one brings its own selling points to the customer. Color, habit and hardiness are the most important factors for growing operations and their sales team. Consumers care about those points, too, in fact.

We’ve grown cordyline for a few years now, and there are a few helpful hints I have to offer. First, not all cordyline are created equal. A vast of majority of cordyline is created in tissue culture labs across the world, and the differences between them can make or break you. Some labs may have a 10-degree difference in cold hardiness from the next tissue culture lab. This is an important point for a growing operation that may be trying to overwinter a large cordyline crop. For greenhouse operations trying to run heat as low as possible for cost-saving reasons, the hardiness issue becomes a big factor.

How cold is cold for cordyline? The only way to know is to trial and find out. We’ve had success even with below-freezing temperatures on crops that were mature. Until you trial and find out what temperatures you can run without damaging your crops, a few degrees above 32F (0C) is always a safe bet. Along with differences between labs, it’s important to know some varieties also don’t fare as well as others in the cold. What might appear to be signs of rust could be mottling—the plant’s response to colder temperatures. These spots are mostly permanent, and your crop likely won’t rebound from the scarring. Breeders are weeding out less hardy offerings, and it’s up to us to let them know when a variety has an unsatisfactory characteristic so it can be remedied.
 
The most common disease that I run into is fusarium. I have lost more cordyline to fusarium wilt than pest or cold combined. Use caution when applying pesticides to the crop. Spikes are all foliage, and the last thing you want from a foliage crop is any amount of residue before selection. There are a few pesticides that are phytotoxic to cordyline, and I can think of a few fungicides that have a growth regulation effect when applied to the crop. There are also some insecticides/miticides that may bleach off cordyline’s color, so beware.

When it comes to planting, depth is so important with cordyline. This is especially true with small transplants. Larger plugs may be spendy, but well worth it. The smaller plugs are more top-heavy and thus more likely to settle or shift after laydown and overhead irrigation.

Cordyline aren’t heavy feeders, so it’s important that salts do not build up in the root system. If they do, the foliage will likely show signs of it. Cordyline exudes unused salts from their spike tips. If you see tip burn on your crop, you’re likely overfeeding. Tip burn may also be a sign that you have high levels of fluoride in your water. Here in Bellingham, we’re one of the last holdouts for fluoridated water. That’s great for my crop, but not so great for my son’s teeth. My wife the dental assistant could care less about my cordyline. GT

Ransom Nichols is head grower and in technical services for Smith Gardens in Bellingham, Washington.