Plant Diagnosis Needed

Question: Our once beautiful blooming grass plants have turned spotted and brown. The purple flowers that usually occur in the spring did not this year. I do not know what the plans are, We moved here when they were mature. I don’t see any type of insect or mold on the leaves, they are just spotted and dry.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 02, 2024, 11:58 AM EDT
response: These plants are Liriope, and despite their appearance and common name of lilyturf, they aren't a grass, but rather a member of the Asparagus family. There are two species of Liriope commonly grown, a clumper and a spreader, and despite the density of this planting, this variegated (striped-leaf) form is probably that of the clumping species, Liriope muscari. The purple blooms of Liriope do not emerge in spring; they appear around late summer, so it's normal that they did not bloom yet this year.  The spots and dry leaf sections are a classic symptom of anthracnose fungal infection, which can be quite commonplace on Liriope, especially in wet years or after frequent irrigation that gets the leaves wet. Fungicide use might suppress future infections, but it cannot cure existing infection and also comes at a risk of harming other organisms (even though the pesticide targets fungi). In our opinion, trying to suppress a recurring anthracnose infection with fungicide is not worth attempting in most situations. (Fungicides also don't always work completely, so some re-infection is still possible. Treatments would require repeat applications, likely well into summer, and rain can interrupt a re-treatment pattern and allow some infection to take place.)  Instead, cut back all the old foliage and let the new growth emerge and cover-up the stubble. Although Liriope is evergreen, it's typical for even healthy leaves to look tired and worn by the end of winter, so they are cut off to refresh the plant's appearance. While there is no guarantee a plant will remain leaf spot-free after that grooming, if we have drier weather or if the plants are not watered with sprinkler too often, the level of reinfection should be minimal. Usually, Liriope foliage from the prior year is cut back around March (leaving a couple inches of stubble off the ground), in order for this to be done before there is a risk of accidentally cutting into emerging new growth, as might happen this far into spring. Even so, if a few new leaves are cut, it's not serious damage, and the plant should eventually produce replacement foliage that will emerge later. Throw out the removed debris since a home compost pile likely won't get hot enough to kill infectious spores.  Occasionally Liriope in damp areas or poor drainage succumb to root or crown rot, and it is possible for plants to contract both this and anthracnose. If any don't recover well after being drastically trimmed, that might be a factor. Aside from that issue, you do not have to dig up and remove any entire plants unless you prefer to replace them. (Root/crown rot would result in leaves pulling up fairly easily, since they detach from the dying roots, and in that case, the entire plant would best be removed. From what we can see, we don't think that is the case here, though.)  It might be worth looking into alternatives as a replacement, though to be fair, no plant is without a risk of some pest or disease issue, especially if stressed. As a potential replacement, for example, there are some species of sedge (botanical name Carex) that look almost identical to Liriope foliage, though they won't have the purple flowers that Liriope does. Some sedge species are native, but those that are variegated (striped in yellow or cream) are non-native species. Depending on the site conditions (how much summer sun, soil drainage, deer browsing risk, etc.), there are plenty of other alternatives to plant of similar stature, though few other plants will provide a grassy look, especially with leaf stripes, if that is the preferred aesthetic.  Miri

responder: The Question Asker Replied May 02, 2024, 1:01 PM EDT
response: Thank you for your prompt and detailed response!Beverly

responder: The Question Asker Replied May 02, 2024, 1:35 PM EDT
response: I have one other question. If I replace these plants with what you suggested, does anything need to be done to the soil Before planting?  Thank you. Beverly

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 02, 2024, 1:59 PM EDT
response: No, the soil is not a infectious threat and doesn't need to be treated or replaced. While spores for this or other plant diseases can lie on the soil surface in some cases, they can also be carried on the wind or splashed about in heavy rain. Plus, sterilizing (or replacing) soil so it's pathogen-free is not possible or practical to attempt, since spores in the environment can recolonize it at any time.  Fortunately, individual plant species are only vulnerable to a subset of such pathogens, and even then, generally when they are first stressed by something like drought, over-watering, or injury. Weather also plays a large role in plant disease spread and severity, so some years the risk is lower than in others.  Miri

responder: The Question Asker Replied May 02, 2024, 2:06 PM EDT
response: Thank you! I am at Home Depot now, looking for a replacement, and they only have the lariatope , Forgive my spelling, , Would that be a bad idea to replace what I have in kind?Beverly

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 02, 2024, 2:17 PM EDT
response: Hardware store nursery departments will not have the depth of selection as garden centers (full-fledged nurseries) will have, which are almost sure to have the sedges, especially among the larger stores. If you wish to replace the plants with new Liriope, you can, but it would be easier to just keep the existing plants and trim off the eyesore foliage, since they are already well-established (and there is no guarantee that the new plants have no asymptomatic fungal infection themselves). The existing plants will fill back in faster than new installations would fill-out since the new ones still need to settle in and grow more roots. We are not aware of a Liriope cultivar that has a high resistance to this particular disease.  Miri