Two weeks ago I purchased a Dracaena Warneckii from a local gardening store. Over the last week it has been developing brown spots on its leaves with yellow margins and long thin holes or cuts in its leaves. These have mostly affected the longer older leaves.
The plant is sitting in an internal office, but gets bright artificial light for 8-10 hours M-F. I have watered it with purified water, but it is tough to tell what it was watered with at the store. I have done some reading on the issue and it sounds similar to Phyllosticta maculicola, however, the spots are mostly occuring on the older leaves. I have also heard that improper watering might cause a similar problem. Is there a way that I would be able to determine the definate cause?
Plants often shed leaves in response to decreasing photo-exposure and/or photo-period. Older leaves are usually the first affected. It's hard to tell from here what it might be, but favored by the odds are over-watering and the reduction in light. You aren't misting, are you? Have you fertilized since you acquired the plant?
I have not fertilized since I bought the plant and I think I have misted once. I have read some sites that recommend that I should be misted as much as once a day to compensate for dry conditions in the winter. It sounds like maybe you are suggesting that I should not? I hope you are right and that it is simply a period of adjustment for the plant with new lighting conditions, however, being new at this, I just worry that it might be something more like a fungal infection or pests. Thanks for your response.
A picture would be helpful, but dry air/low humidity is generally only a contributing factor to spoiled foliage. The underlying cause is usually compromised root function due to over-watering or a high level of accumulating salts (from tap water &/or fertilizer solutions) in the soil. Misting only raises humidity surrounding the plants for a matter of a few minutes until the mist has dried. Humidity levels almost immediately return to what they were, making misting very ineffective. Humidity trays can me marginally effective. (You can make very good humidity trays from large cake covers you can buy at bulk food stores - the kind where you buy supplies for large parties, large families, restaurants ... They can be filled with stones, then water. The stones increase the surface area from which water can evaporate. A humidifier is the best way to raise humidity so the roots can keep up with transpiration rates.
One of the most important influences on whether or not your soil will remain unspolied is your choice of soil. Choosing a soil that remains well-aerated, even after you saturate it, allows you to flush out accumulating salts every time you water. Heavy soils demand that you water in sips to reduce the chance of root rot, and the practice of watering in sips ensures the build-up of the solubles that make it difficult for plants to take up water.
Here is what I grow all my houseplants in. It is very fast draining and remains well-aerated ALWAYS. It allows me to water as often as I want or need without risking root rot, and it makes fertilizing simple. Lots of people are using it with wonderful success.