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Monday, December 29, 2014

What Causes Brown Leaves on Yucca?

Q. Why are the tips of my yucca leaves turning brown? 
Brown leaf tips on yucca. Can be from soil or irrigation problems.
A. This is pretty common on yucca in our climate and soils unless they are grown in filtered sunlight and the soil has been prepared well before planting. They always tend to have brown tips. In the case of your plant, judging from your picture, it does seem excessive.
When we see brown tips on the foliage of desert plants it usually means a watering problem, a soil salt problem or lack of drainage.
This particular yucca is native to the Chihuahuan desert so infrequent irrigation is critical to its health. Most of the soils in the Chihuahuan desert are better than our landscape soils created by the builders of our homes.
Regarding your irrigations, compare your watering with how these plants might be watered in their natural habitat. This is a guideline for how you should water. They won’t need watering that often so if you are watering more frequently than every two or three weeks in midsummer, I would suggest this is too often.
If this plant is on the same irrigation circuit as other landscape plants, and these other plants are not a desert plants, then I would suggest the plant is being watered too often.
The volume of water you give the plant is not as critical as the frequency it receives water. In other words, you can give it a large volume of water and not hurt the plant as long as you wait long enough before the next irrigation. Giving large volumes of water may waste water but it seldom keeps the soil too moist for the plant between irrigations.
If this plant is watered too often, remove it from that irrigation circuit and water it by hand every few weeks. It will like a couple of deep winter irrigations, a spring irrigation, a couple of midsummer irrigations and a fall irrigation and that's about it.
If the applied water is close to the trunk, then the trunk could be rotting. Keep frequent irrigations away from the trunk. However, it is okay to water in a large basin beneath the plant if it is done infrequently.

If there are other plants around it, it is probably getting enough water from its neighbors. But I would still give it an occasional drink to be on the safe side.

1 comment:

  1. Living in the Chihuahuan Desert, our soils aren't better, until up in the juniper-oak-pinon belt. Having designed many gardens with Yucca rostrata over 12+ years, *every* one looks like this in every garden in Albuquerque, Las Cruces and El Paso. No matter the irrigation amount. Unless the Y. rostrata came from others, and there are many, many large Y. rostrata in those 3 towns to demonstrate this; those consistently do not look like this.

    Until there is actual research on this (not led by marketing people, either), my guess is part-water, but a larger part is via skinning off all the insulation on the trunk...i.e. skirt of dead leaves. It's insulation against heat and cold. As an LA, it's apparent some of my colleagues need to appreciate why plants do what they do, and appreciate that aesthetic...just like many should do with palms. And some growers insist on this practice, though they should lead the way in healthy plants; some cannot seem to.

    An exception might be where those skirts on mature plants harbor wasp nests, like in palms in some areas. But even then, skinning might just move such a problem into the live foliage or nearby plants. There are pruning standards for palms, so maybe that needs to be done for desert monocots / accents, too.

    Then there are the property owners, developers to homeowners - they now think skinning off insulation / skirts is normal on Yucca, Dasylirion, etc, but they then take it further and make the problem worse. They or their maintenance people skin upward into the crown and remove live leaves, as well - bad idea.

    Solution for existing yuccas with brown leaf ends - stop pruning all skirts off; at most clip frayed ends. In 3-4 years, they will start to recover and new foliage will begin to stay blue/green like it's supposed to. And never return to pruning off the skirts, as it will take even more years to mostly heal the wounds started by the grower. And always give yuccas good, but infrequent irrigation soakings in dry / hot periods.

    Solution for new yuccas - install only among plants of similar water needs, as found in nature, such as Bouteloua spp., Salvia spp., etc., not the driest-loving plants. But not the higher water-need plants either, like lawn or most exotic subtropicals.
    - - -
    I used to specify seed-grown yuccas when available, but I am unlikely to continue that, until nurseries doing such counterproductive practices admit their folly and leave the leaves alone. I like greener (bluer) leaves, not brown ones, especially since we have to pay a premium.