Question

leaf  

stem under top leaves   Dear Will,

I would really appreciate it if you help me to save these two plants. I bought them approximately in the same time but in different stores last spring. Here are the dimensions:
1) Plant's height (the highest of three stems) - 54 inches, pot's height - 16 inches, diameter - 17 inches.
2) Plant's height - 27 inches, pot's height - 13 inches, diameter - 14 inches.
Pots are furnished with a drainage (stones are on the bottoms of the pots, layers are around 2 inches) and a soil that prevents over-watering. We pour them once in two-three weeks. Before pouring I always test the soil with a long thing wood stick to be sure that it is fully dry. We never allowed to stay in water. In spring and summer we sprayed them with water once or twice a day, in fall and winter - twice a week. Both are located near east-sided windows in corners. Spots are light but filtered. Indoor climate is 68-70 F year round. Air-conditioner holes are everywhere, but we closed these that near the plants.
This December I noticed that top new leaves of lower stem of the bigger plant is faded and light. Then the top leaves were getting dry and wither. In a month the same appeared on the higher stem and on the second plant. Today I realized that it begins on the highest stem too. Stems are not soft. Other leaves are hard and dark green. Also I noticed a rust-colored/brown film on stems on tops under leaves.
Please help me to safe them if there is any chance to do it.
I am attaching the pictures for your convenience. Thank you in advance.

Answer
Hi Nataliia,

When new growth is distorted or discolored, that is almost always a sign of a root rot problem.

Despite your best efforts, your Yucca is staying too moist for too long and it is not getting enough light. An east window will provide barely enough light for a Yucca, but only if the window is completely uncovered and the plant is directly in front and center of that window, not off to the side.

Apparently your Yuccas were repotted out of their nursery pots (probably 10-inch diameter) into the larger pots they are now in. Putting stones in the bottom of pots is a discredited practice because it actually prevents proper drainage.

Here is what happens when a plant is moved to a pot that is too big. All the excess soil that  you add acts like a giant sponge, absorbing water and holding onto it for a long time. The roots are then surrounded by the wet/damp soil and slowly begin to rot. Roots need oxygen as well as water and when wet soil deprives them of oxygen for an extended period of time, the roots will rot.

I am sure your plant did not need a larger pot, but even if they had, repotting has to be done properly. They should not have been moved into pots more than one size larger. You need to use a good quality, peat-based, soilless potting mix. Miracle-Gro potting mix contains material that retains moisture for a long time ("moisture control") and lacks porosity throughout which is what creates good drainage. Pro-Mix is a good potting mix if you can find it. Otherwise, mix up 4 parts of peat moss with 1 part of perlite. Perlite mixed into a potting mix is the best way to increase drainage.

When yours were repotted, they probably made the common mistake of adding soil to the top surface. That added soil prevents evaporation and it also prevents you from accurately assessing how dry the soil is in the root zone where it matters.

The root rot has already started, but let's hope it has not damaged too many of the roots. To remedy the situation, carefully un-pot your plant, removing all of the soil that was added around the original rootball. Try to keep the original root bound rootball intact. Then, put that rootball back into its original or similarly sized pot with drainage holes, but without drainage stones. It should fit snugly and you may need to add just a small amount of a porous potting mix to fill in any spaces left from portions of the original rootball falling off.

The goal here is to get things back to where they were prior to repotting. That way the soil surrounding the roots will dry out regularly and allow oxygen back into the root zone. Recovery will take time, so expect continued leaf loss for a while. Look for healthy new growth as a sign of recovery.

I have written articles on repotting and on Yucca care that I will email for free to you (or anyone else) who emails a request to me at [email protected].

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to HorticulturalHelp.com

Regards,
Will Creed
Horticultural Help, NYC
Cell: 917-887-8601

Visit my website at www.HorticulturalHelp.com