Q. I have several heavenly bamboo that are well established in my yard. I recently noticed a lack of robust growth and signs of disease or pests or maybe both. I sent you some pictures. What do you think?
|Leaf discoloration, marginal burning of heavenly bamboo aka Nandina, not a true bamboo.|
|This damage looks more like nutrient related but it could also be from water, too much or too little, or possibly salts. But this plan likes richer soils so I would dump some compost around the base of it and work it in.|
|This is different from the other pictures. It is probably not related to plant nutrients but it looks more like damage from thrips.|
A. Heavenly bamboo, aka Nandina, is not a bamboo and not even closely related to it. It sort-of looks like a bamboo, hence its name. It comes from places where the soils have organics in them naturally. Not from deserts and it does not grow well in desert soils.
In warmer climates it may keep its leaves during the winter. Usually not in Las Vegas. It drops its leaves due to leaf damage from winter cold.
|When heavenly bamboo is surrounded by rock it usually turns yellow due to iron chlorosis. Heavenly bamboo does not come from soils like this so the problem is the rock mulch around them.|
Heavenly bamboo DOES NOT like desert soils unless organics like compost is added to it and the soil kept moist. So rock mulch and planting in a desert landscape with cacti is a no-no. Might work for the first couple of years and then they slowly turn yellow, scorch, decline in health, drop their leaves and look bad.
The discoloration of the leaves, brown edges and yellowing, is probably related to the soil degrading and losing its organics over time. My guess, it has gotten progressively worse over the years.
|The primary problem with this Nandina is a lack of soil improvement and in proper pruning. If this plant were pruned correctly and organics were added to the soil such as compost it would not be in its current condition|
Heavenly bamboo comes from Eastern Asia where soils are rich and not “deserty”. When surrounded by rock, Nandina declines in appearance and its health takes a dive over time. Nandina looks good after planting because of stored food supplies inside the plant and amendments added to the soil. But these both disappear in a few years.
There does seem to be insect damage to the leaves, possibly by thrips. Thrips are very tiny insects that can fly only well enough to travel a few inches. Flower thrips like to feed on soft flower petals and other thrips on new, emerging leaves.
Leaf damage to Nandina by thrips is a first for me in the desert so I had to do some digging in references. Fresh damage appears as “water soaked” areas. Later on these areas dry out and scarring or obvious surface damage appears as tiny brown or white spots on leaves.
|Western flower thrips, even though they are very tiny, cause problems like this scarring from their feeding on young nectarine fruit.|
If there is rock surrounding them, rake it back and work some compost into the soil surface as deep as you can and water it in. Replace the rock on the soil surface with woodchips. Water enough in one day so you can skip at least s day in the summer and more when its cooler.Organic sprays such as Spinosad do a good job controlling thrips. Read the label.