Our goal is to keep you informed of lawn and landscape issues we are experiencing each week as we visit sites in the Oklahoma City area. I’m sure it is no surprise to you that we are starting to see plant problems related to the excessive amount of rainfall we are receiving.
Normal annual rainfall for the Oklahoma City area is 36.5”. In the past 365 days, the metro area has received nearly 54”. In the last 30 days, 12.5” has fallen with 6” in the last week.
It is common for us to be discussing watering tips as we head into the summer. I have only one watering tip today – turn your irrigation system off! Early this morning I witnessed 3 irrigation systems running in my neighborhood alone. Established plant materials – lawns, shrubs, trees, flowers – are showing signs of over watering stress.
Roots are the foundation to a healthy plant. They are the primary source of water, nutrients, and oxygen. Yes, oxygen. Plants breath through their root system. Plants, just like humans, can drown when water replaces air.
So, why is it common for so many to water more when a plant is struggling because of too much water? Plants respond in very similar ways to draught and too much water. The first symptom of too much water is yellowing leaves followed by wilting. The wilting leaves, whether it is too much or too little water, look nearly the same. When you see wilting leaves, you must stop and think about the conditions and check the soil.
For example: A couple of weeks ago I planted a tropical hibiscus in a patio pot. This week I noticed it was wilting, grabbed a pitcher full of water and headed out the door to water it, all the while wondering why it would be dry. What I discovered was a plant sitting in water because of clogged drain holes. Either way, the hibiscus was wilting. The same is true about your lawn, your flowers, your shrubs and your trees. It is just a lot easier to diagnose when it’s in a container.
Here are a few problems we noticed this week:
Photinia Leaf Spot – A fungal disease that is common on photinia even in dryer periods but is rampant in cool periods with a lot of rainfall. It is hard to control and requires repeated applications of a fungicide in the spring and the fall. Once a plant develops the disease, it typically returns each season. Photinia are best planted in full sun areas with good air circulation. Many seasons in Oklahoma we can get away with planting them in partial shade and tight areas, but then you have a May like this year, and you remember why the experts said not to plant it where you did. Or, it could just be that your landscape has matured and now it finds itself in a less than ideal spot.
Yew – A plant that is notorious for quickly yellowing and dying in wet or waterlogged soil. They can be temperamental, but given the right conditions with moist, but well drained soil, they do well. They won’t tolerate waterlogged soils and this spring many are finding they are in just too wet of soil. As with many shrubs, the first signs of yellowing suggest too much water.
Annual Color – It is always best to wait until May to plant seasonal color varieties that thrive in the summer heat. May is the month when soil temperatures are warm enough for them to establish roots for the summer. But, the best annuals for surviving the summer heat don’t like saturated soils. We are seeing periwinkle (annual vinca) with yellowing leaves. Penta, known for its tough nature in a draught, struggling to get established because of root rot. Lantana, maybe the best in hot, sunny, draught prone locations, struggling in wet soils.
Xeriscape – Selecting more draught tolerant plants has become more and more popular. Overall, I think it is a good idea - in the right location. But, yucca and many other xeriscape favorites, are having a rough start to the year. These plant selections don’t need particularly great soil, but they do need to have good drainage and be soil that stays on the dryer side.
Bermuda Lawns – Large patch is a fungal disease that is a problem in cool, wet spring weather. This has been a perfect season for it to develop with the excess rainfall and temps that have lagged. It starts as a small area with leaf blades that appear light in color with some orange-bronze spots, and it gradually spreads to larger patches. We have noticed it more in poor drainage areas and in tight soil conditions. The best solution is for temperatures to consistently stay in the 70’s at night. After the lawn has improved in June, aerating would help with soil structure and drainage.
Fescue Brown Patch – This is fescue’s biggest problem. It is closely related to large patch, but only it causes problems on cool season turf instead of warm season. Also, the disease starts when it is hot and wet, instead of cool and wet. When nighttime temperatures are consistently in the 70’s and the fescue leaves stay wet more than 8 hours per day, brown patch grows. It is almost a given that your fescue will struggle if you have poor soil drainage, low air movement because of structures or landscape plantings, dense shade, heavy morning dew several days in a row, over watering or too much rain, or if you water in the evening. If you have a fescue lawn, the best thing that could happen until we dry out is for temps to remain mild – the exact opposite of what we need for bermuda. Don’t help the disease out by watering – leave the irrigation off. Mow your lawn around 3-3.5”. Too short and too tall will promote the problem. When it is time to start watering again, water in the early morning only, and not every day. Leaf blades must have time to dry completely. Aeration every fall on fescue lawns will improve soil drainage.
Much of what we discussed today are climate issues we can’t control. But, the excessive rainfall has reminded me why a few things are very important:
1. Water based only on need. Too much water damages plant roots.
2. Always plant a little above grade so that excess water will move away from the plant.
3. Select the right plants for the right location. This is more than just sun or shade. It includes soil type and water requirements.
Remember – the most common problem of plant stress is unhealthy roots. This applies to lawns, flowers, trees and shrubs.
Lorne Hall
Hall | Stewart Lawn + Landscape
(405)367-3873