Ornamental grasses, like fountain grass, stand out in landscaping, making great accents to trees, shrubs, and flowers.
However, when they aren’t healthy and start turning yellow, it’s time to take action or risk your fountain grass dying.
Why is my fountain grass turning yellow? Fountain grass turns yellow for several reasons, some worse than others. The most common reasons include watering issues, problems with pH, lack of sufficient sunlight, temperature fluctuation, excessive fertilization, bacteria, disease, and natural pests.
Read on below to explore 11 common issues that cause fountain grass to turn yellow (and what you should do)!
Why Your Fountain Grass Is Turning Yellow – 11 Possible Causes & Solutions
Fountain grass, or Pennisetum as it is known botanically, is a mound-forming plant species that belongs to the grass family.
These species of grass are native to warmer regions of the world but do well enough in climates further away from the equator as well (so long as they receive plenty of sunlight and only have to endure mild winters).
In the following sections, we discuss each of the 11 most common problems and solutions for why your fountain grass is turning yellow:
Overwatering your fountain grass is an easy mistake to make. It’s also one of the easiest ways to help turn your plant’s leaves yellow.
When you overwater your plants, you are essentially suffocating them. In turn, they start shutting down and turning yellow.
Keep track of how often you water your fountain grass, and avoid watering it more than once in any 10- to 15-day period.
If the plant has received rain, extend your next watering session out for another 10 to 15 days.
Before watering, take the time to use a moisture meter (find it here), or stick your hands in the soil to see if there is any moisture present within the top few inches.
When you underwater your fountain grass, there is a great possibility it’ll being to turn yellow due to a lack of nutrients.
Without adequate moisture, the plant struggles to uptake practically any nutrients or oxygen through its roots.
The best way to keep from underwatering your fountain grass is simple: set yourself a reminder to do so every 10 to 15 days.
Double-check before watering with either a meter or your fingers to see if it actually needs water.
3. Natural Die-Back
Plants often turn yellow when they are dying back naturally.
Whether it is simply the time of the year for them to shed plant matter and start storing energy for its dormant growth stages during the winter or it’s gotten too big and needs to let some of itself die off in order to survive, yellowing leaves is a typical sign of natural die-back in fountain grass.
Natural die-back isn’t necessarily a bad thing, but it isn’t always good either.
If you let your grass get so big that it can’t support itself, even if you otherwise take good care of it, you’re putting the entire plant at risk of dying.
Pruning your grass each year is the best solution.
4. Not Enough Sunlight
When your fountain grass isn’t receiving enough sunlight, the rate of photosynthesis that occurs is too low.
Yellow leaves may be a direct result as time goes on and your grass continues to lack enough sunlight.
Consider transplanting your fountain grass to another location on your property (one that gets more sunlight).
Furthermore, simply taking the time to pick the right place to plant in the first place solves this problem before it even happens.
5. Too Much Fertilizer
Fountain grass doesn’t require much fertilizer. In fact, if your fountain grass is well cared for and located in a good spot, it may not need any fertilizer at all.
Too much fertilizer can burn the grass, quickly turning it yellow.
Fertilize your fountain grass sparingly, doing so very lightly whenever you apply fertilizer. Avoid fertilization more than once or twice (very lightly) annually.
6. Root Rot
Excessive overwatering commonly leads to a development called root rot. If left untreated, root rot quickly kills entire plants by causing the root system to rot and die.
Once the roots are shot, the entire plant turns yellow, brown, and eventually black as it dies.
Plant your grass in soil that drains quickly, and avoid overwatering.
Keep a record of how often you water, use a moisture meter before you water, and/or set reminders on your phone so you don’t accidentally overdo it.
7. Soil pH Is Not Ideal
A pH of 5.5 to 7.0 is ideal for most types of fountain grass. When the pH level drops below or shoots over the preferred range, yellowing is one of the first signs of a problem.
Sulfuric acid or limestone can be used to lower the pH of your soil. Alkaline materials may be added to raise pH when it’s low.
8. Soil Does Not Drain Well
When your soil does not drain well, it often causes plant roots to suffocate.
Roots that lack proper amounts of oxygen aren’t able to uptake essential nutrients. That means they quickly begin turning yellow.
Aerate the soil around your fountain grass to ensure it has proper oxygen levels, and avoid overwatering your grass to begin with.
Pests are a natural problem for just about every plant out there, and fountain grass is no exception.
Slugs, rust fungus, and snails are among the most common pests that are naturally drawn to fountain grass.
Keep your fountain grass in the best health possible, and avoid overwatering. Also, be sure to plant your fountain grass at least 3 to 5 feet away from other plants.
Fungal rust, leaf spots, and anthracnose disease are among the most common disease-based issues for fountain grass.
Furthermore, your fountain grass may be susceptible to additional soil-borne and pest-borne diseases.
Keep an eye on your plants, maintaining them properly and noting any changes that occur with them.
When a disease is identified, deal with it quickly before it spreads or kills the rest of the grass.
11. Cold Temperatures
Fountain grass originates from tropical regions of the world, where temperatures range from 70°F to 85°F regularly.
If you live in a cooler area, especially one that has cold winters, your fountain grass may turn yellow every time the temperature bottoms out.
During the wintertime, cover your fountain grass with plastic sheets or barrels.
You may also consider pruning it extra short (it is easier for the root system to withstand the cold because it is underground).
How To Rejuvenate Ornamental Grass
Rejuvenating ornamental grass is generally a straightforward process. Just follow these steps:
- Prune the grass back during the spring and again in the early winter.
- Fertilize your ornamental grass one time in the spring.
- Water newly planted/pruned ornamental grass every other day or so for 3 to 4 weeks in the spring.
- Reduce watering to once every 10 to 15 days by mid-spring.
- Dig up, divide, and replant plants that are 3 to 5 years old.
Will Purple Fountain Grass Survive Winter?
Purple fountain grass isn’t known for surviving winter outdoors without a bit of help.
Either bring it inside for the winter and give it minimal light and a stable temperature or cover it up well with breathable barrels or plastic.
Is My Ornamental Grass Dead or Dormant?
If your ornamental grass is dormant, it will typically be a solid color (all brown or all yellow).
Dead patches/sections of your ornamental grass, however, have brown or black spots that stand out from the rest of the plant.
Most of the common issues that cause fountain grass to turn yellow are easily avoidable for you now that you know what they are!
In the case that your fountain grass turns yellow on you anyhow, you also know the solution to each of the common problems. If you need a reminder, just return back to this guide!