Lessons from the Roots

Culture

by Ken Slump

Posted by Sys Admin over 2 years ago.

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Plants Offer Clues to Their Repotting Needs


AT REPOTTING TIME, ORCHID growers can learn much from their plants that can help them evaluate the success or failure of their growing techniques. Careful observation of the plant, particularly its root system, is the key.

In general, the best time to repot an orchid is when its root system is actively growing and producing new roots. Please note that this may also correspond with the orchid’s flowering season, in which case you need to be particularly careful of the developing flower stem, or perhaps even its buds or flowers, as you embark on the repotting process.

Of course, simply growing the plant for a sufficient period of time that repotting becomes necessary is, to a degree, a testament of the grower’s skill. Still, it is not unusual to find some surprises once the plant is removed from its container.

If the timing is right, it is also wise to repot new orchid plants soon after they come into your collection. You will have the advantage of checking the condition of the root system, but will also then have them growing in your own mix and know exactly how long they have been in it. While we are on the subject, to verify the presence of healthy roots it is not a bad idea to either poke gently around the growing medium of prospective orchid pur-chases or give them a gentle tug. More than once I’ve purchased an apparently healthy orchid plant only to discover when I got it home that its root system was trashed.

DECANTING THE PLANT  When the root system is healthy, you may have a difficult time extricating the plant from its pot. In such cases, soaking the pot and growing medium in a container of lukewarm water for a few minutes will sometimes enable removal of the plant with a maximum of the root system intact. Not infrequently, it becomes necessary to destroy the pot to free the plant.

Healthy orchid roots are generally a light tan or whitish color and should be firm to the touch. Hopefully, the plant you have just pulled from the pot has many of these. If you find roots that are brown, soft and mushy, they are no longer viable and should be removed. Certainly, as the plant produces new roots, the oldest ones cease to function and die, so finding some of those is of little concern.

If, however, you discover that most or all of the roots are in a deteriorated condition, it is time to reevaluate your cultural scheme. Even if you should find that all of your orchid’s roots are rotten, as long as new ones are emerging you might still save the plant, but you will have to change some aspect of your growing technique or history will surely repeat itself and the plant is doomed.

The cause of root rot is simply having too much moisture in the root zone for too long a period. Roots of epiphytic orchids are accustomed to rapid drying in open air after they become wet, so air in their root zone is essential. Constant moisture around the roots is a sure recipe for disaster.

For most hobbyists, the goal is to keep the roots sufficiently moist so that daily watering is not required, but to avoid an excess of moisture that can lead to problems. This is a tricky balance to achieve. If you are having root rot problems, your goal is to find a way to dry the root zone faster, and there are several ways you can achieve this.

Perhaps the first consideration is to reevaluate the growing medium. Most of us grow in mixes that contain fir bark or coconut husk chips as the main, if not total, ingredient. It is important to realize that coconut husk chips are much spongier and more water-retentive than chunks of fir bark, but they have the advantage of deteriorating more slowly. If you find that coconut husk chips are too moisture-retentive for you, a change to fir bark chips might solve the problem.

MEDIA  Also, make sure that the size of the bark or coconut husk pieces is appropriate for the orchids you are potting in them. Both are available in fine, medium and coarse pieces. You’ll have plenty of big air spaces if you use the coarse chunks, but they are often too large for orchids with fine roots. When in doubt, try the medium size of either fir bark or coconut husk chips and switch to a finer grade if you later decide you need more moisture around the roots — or try the coarse grade if the reverse is true.

Alternately, you can add in-gredients, or larger percentages of them, to either fir bark chunks or coconut husk chips to help increase the air spaces in the medium and decrease the medium’s water retentiveness too. Coarse perlite and horticultural-grade charcoal are the most common additives. Both need to be rinsed with water before mixing them with bark or coconut chips. For starters, try mixing six parts bark or coconut chips with two parts perlite and one part charcoal. If the mix continues to be too moist, increase the percentages of perlite and charcoal.

Orchid growers who are able to enjoy the luxury of cultivating their plants outdoors for all or part of the year in climates that happen to be rainy or excessively humid sometimes find fir bark or coconut husk chips too moisture retentive, even in mixes. Lava rock and Aliflor are quick draining, but careful attention to adequate nutrition for the plants becomes particularly important with these inorganic alternatives.

CONTAINERS  Another consid-eration is the type of container you choose. Plastic containers are popular, inexpensive and lightweight, but they help retain moisture. I use clay pots for most of my orchids. I like their extra weight for counterbalancing top-heavy orchid plants; clay pots’ ability to “breathe,” thereby drawing excess moisture away from the growing medium, provides an insurance policy against its becoming too soggy. I use regular clay pots when I want longer moisture retention, and orchid pots (those inordinately expensive clay pots that have slits or holes in their sides) when I want the medium to dry more quickly.

In fact, the selection of pot type is one of my favorite techniques for varying the drying rate of the growing medium among the orchids in my collection. I use regular clay pots for many phalaenopsis, as well as juvenile, terrestrial and miniature orchids. I prefer clay orchid pots for many cattleyas and their relatives; and I even employ a few plastic pots for orchids that like to stay wet, such as Phragmipedium species and hybrids. When I find a plant is not growing a healthy root system, I first try a different type of pot in hope of improving the situation.

Of course, it is important to note that watering frequency has a major impact on the opportunity that the growing medium has to dry out. Sometimes decreasing the watering frequency is all that is needed to ensure a healthy environment for the root system. Do not forget that orchids, just like all cultivated plants, more frequently die from overwatering than from any other cause.

Be sure not to overpot orchids. Generally, the pot size should be just large enough to contain the root mass, regardless of the plant size. Environmental adjustments that can help avoid soggy roots include providing additional air movement, slightly higher temperatures and avoiding extremely high humidity levels.

As the roots grow, so grows the plant. Producing a healthy root system should be the first goal of every orchid grower.
 

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