Caplan’s July Newsletter

Hot and Dry Weather Hurting All Landscape and Garden Plants

Although southern Indiana is not officially under a drought yet, it is extremely dry in the landscape. Temperatures have been in the 90s for several weeks, and most of us have not received any appreciable rain since May.

At greatest risk are herbaceous plants, especially annuals. This includes annual flowers and vegetables. Perennial plants that are well established seem to be surviving, but they are definitely struggling. Trees and shrubs that were planted within the past 12 months are also extremely vulnerable, since they have not been able to produce a widespread root system yet. Many lawns, especially Kentucky bluegrass lawns, are going dormant, even if they are being irrigated.

The best advice I can give is to irrigate what you can. Those of you reading this who pay for sewer when they irrigate may need to make decisions on which plants are most important to water. This also goes for those using well water, or who may eventually face watering restrictions if we enter full drought conditions. I would prioritize newly planted trees because of their value and the time needed for them to mature, followed by edible vegetables.

If you are going to irrigate, it is better to water heavily and infrequently. This means apply the equivalent of 1 inch of water all at once, once per week. A heavy soaking allows the water to infiltrate down deeply into the soil, where the roots are. Watering lightly every day merely moistens the surface dust, and promotes shallow rooting.

With newly planted trees, apply 1/2 gallon of water per square foot of planting hole. If you dug a 2 foot wide hole, that’s about 4 square feet, so you’d need about 2 gallons of water. Do this once a week under normal conditions. Since we are under abnormally high temperatures, I would do this twice per week.

For lawn areas: I generally would not spend the money irrigating the lawn, but you do you. Tall fescue lawns are fairly drought tolerant, and can go many weeks without rain and still survive. Zoysiagrass should be thriving in this weather. However, Kentucky bluegrass is a cool-season grass, and goes dormant in hot weather, even if there is plenty of rain. Although your bluegrass may look dead, right now it is merely dormant. However, if the lawn goes without any moisture for more than 6 or 8 weeks, it will actually begin to die. To keep these lawns alive, I recommend applying 1/2 to 1 inch of water over the lawn once every 3 weeks. This is not enough to cause the bluegrass to green back up again, but it’s enough to keep the roots and crowns hydrated and alive. Hopefully, this will keep the bluegrass alive until temperatures cool off again in the fall.

The last bit of advice: if you are using any type of overhead sprinkling system, do your watering early in the morning. This allows the leaves to dry off quickly as the sun rises. If you water in the evening, the leaves will stay wet all night, and this increases the chances of various fungal diseases.

Leaf Spot Disease

I’m fielding lots of questions about various leaf spot diseases on trees, shrubs, and other ornamentals. The vast majority of these diseases began their infections earlier this spring, when the weather was cool and wet. Right now, the fungal diseases are already inside the foliage and ravaging the infected leaves, but are not doing much in the way of spreading.

If you are noticing various spots and blotches on your plants, you can send me some photos of the symptoms, along with the name of the plant. I can help you identify the disease, and tell you if there is anything we can do now. If necessary, we can schedule me to come out for a site consultation.

What Are Your Weeds Telling You About Your Lawn?

Many people strive to have a beautiful, uniform, weed-free lawn. I personally don’t bother in my yard…I simply call the clover, violets, and other assorted non-grasses “wildflowers” and leave it go at that!

For many folks, any weed found is a call for nuking it with various herbicides. And while herbicides often have a role to play in overall weed control, they are a short-term fix. Unless you correct site factors that inhibit lawn growth and allow for the weeds to thrive, they will simply come back again and again. Truly, the best weed control is a healthy and thick lawn.

Often, by looking at the major weeds in the lawn, we can get a pretty good idea as to what the major management problems are, and how to correct them. For example, if your lawn has a lot of knotweed and spurge growing in it, this indicates that you have compacted soil. This is because these weeds grow very well in compacted soil, but turfgrass doesn’t. Although herbicides will kill these weeds, if we don’t alleviate the soil compaction with core aeration, the grass will never fill in and the knotweed will eventually come back.

If you click on this link, you can see a list of common indicator weeds for lawns: https://imgur.com/gallery/KRP7HNZ . By identifying the weed, you can have a good idea as to what the site problems are in your lawn, and then take steps to mitigate them. As always, you can have me come out to consult with you to be sure we are headed in the right direction with your lawn management problems.