Set up a perennial maintenance schedule for longer-lasting plantings

By Jon Cooner

One of the biggest benefits of Imperial perennial blends is they’re designed to last up to five years without replanting. Helping them last as long as possible isn’t hard. It just requires a little maintenance. In this article, we’ll look at how to set up an effective maintenance schedule. You can read a much more detailed version of this article, including an example of what a perennial maintenance plan looks like, in the Web version of this article, available on-line at

Step-By-Step Planning

First, let’s look at the order in which you should set the dates at which you’ll perform each maintenance step. Then, we’ll look at why we use that order. 

Perennial Maintenance Steps

Now, let’s look at why the dates for each maintenance step should be set in the order shown. Grass control is the most important maintenance step to time properly.

“When it comes to maintaining perennial food plots, grass control is your number-one priority. The best time to spray Arrest to control grass depends on the age of the grass. For best results with Arrest, spray after grasses have started to actively grow and, for best results, before it matures to more than about 6 to 12 inches tall.” 

  Dr. C. Wiley Johnson

Arrest for Grass Control in Imperial Perennials Your No. 1 Maintenance Priority

The foregoing quotation is one of the many things the Institute’s former director of plant breeding, Dr. Wiley Johnson, hammered into our heads. The best way to control grass is with selective grass herbicides such as the Institute’s Arrest™ herbicide product. Like other small-weed herbicides, Arrest offers the best control of “seedling” grasses (grass that is actively growing but has not yet matured to more than 6 to 12 inches). For additional details on this subject, visit  

Mowing Imperial Perennials

Our maintenance instructions for all Imperial perennials include mowing them a few times in spring and summer, and maybe again in early fall. Mowing helps keep energy and nutrients in the forage plants and can also help with weed control.  Generally, you should mow whenever you see one of two things: (1) the forage plants or upright weeds look like they’re getting ready to put on seed heads, or (2) the plot reaches a height of about 10 to 12 inches. If you can’t mow until after they flower, though, still do so as soon as possible, because mowing will yield other benefits, such as thickening the forage plants at their lower levels.  Mow the forage plants to about 4 to 6 inches tall in spring and summer, and try not to wait until the forage gets more than about 12 to 14 inches tall before you mow. If you wait too long and your forage is taller than about 12 inches when you’re ready to mow, reduce the height a couple of inches the first time you mow, wait a few weeks for the plants to recover, and then mow a little bit lower. Try to mow the plot a few times in spring and summer. Finally, do not mow when conditions are excessively hot or there is a drought, or within a couple of weeks before or after you spray herbicides.  For additional details on this subject, visit  

Slay for Broadleaf-Weed Control in Imperial Whitetail Clover

As mentioned, many upright annual weeds can be controlled well by mowing. If you waited too long to mow and let your weeds flower, or if you have other broadleaf weeds that mowing didn’t tackle, you might have another option if you’re maintaining Imperial Whitetail Clover or any other clover or alfalfa. That option is the Institute’s Slay herbicide. Slay is designed to control most broadleaf weeds, and it can be sprayed on Imperial Whitetail Clover and any other clover or alfalfa. However, it should not be used on any other Imperial forage because it will damage one or more of their components.  For optimum results, spray Slay just before spring green-up or a few weeks after. Like Arrest, Slay offers optimum control of young weeds. However, it also contains something Arrest doesn’t: a “pre-emergent.” That means it’s designed to provide optimum results not only if sprayed when weeds are actively growing but also if it’s sprayed just before spring green-up, before broadleaf weeds reappear. The pre-emergent in Slay also helps Slay continue to control many weeds well after spraying.  Remember, our perennial-maintenance schedule is based on the date we plan to spray Arrest to control grass. Slay applications should be timed so they are done at least three days before or after any Arrest application. Also, don’t spray Slay (or any other herbicide) within two weeks before or after mowing, or when conditions are excessively hot or when there is a drought. 

For additional critical information on Slay, the full article, the Slay label and a FAQ visit

Soil Testing

Performing a proper soil test through a professional soil-testing laboratory is the only way to determine exactly what your soil pH and nutrient levels are and how much lime and fertilizer you must buy. Most folks already do a good job of testing their soil before they plant. But when you consider how much the costs of lime and fertilizer have increased the past year, you see how important it is to test your soil any time you are considering buying lime or fertilizer. 

Use a soil-test kit that sends the soil to a lab for testing. The cheap do-it-yourself slurry or probe testers might not give you the detailed or consistently accurate readings you will get with a lab test. Also they don’t tell you exactly how much lime or fertilizer you need.  Be sure to identify the forage you’ll be maintaining on the soil-test submission form so the lab can precisely tailor its recommendations. Try to perform your soil test far enough in advance so you won’t be rushed when your schedule says it’s time to lime and fertilize. Usually, a month before is sufficient. 

Liming and Fertilizing

These maintenance steps are very important. Like our other maintenance recommendations, they should not be skipped. Soil pH is perhaps the most critical factor when it comes to the overall health of any plant. In simple terms, soil pH is a direct measurement of how well your forage plants will be able to uptake nutrients from the soil. Likewise, plants need food just like any other living thing, and you feed them by adding fertilizer to the plot every year.     

Timing lime and fertilizer applications is not as critical as timing grass control. Accordingly, the dates you set in your maintenance schedule to lime and fertilize should depend on when you plan to do the other maintenance steps. Apply any additional needed lime at almost any time. Apply fertilizer when plants are actively growing, but when the foliage is dry. Generally, most folks lime and fertilize in spring or fall. The only requirements for timing fertilizer applications are: (1) the plants should be actively growing, (2) the plants should not be in stress, such as just after mowing, and the foliage should not be damp, which might make the fertilizer stick to the leaves, and (3) if possible, leave a few weeks between lime and fertilizer applications. For additional details on this subject, visit  

As you can see, maintaining an Imperial perennial isn’t hard. But you must follow the steps. Once you  understand how to set up a perennial-forage maintenance schedule you can cover all the bases efficiently and economically. 

And remember, order your soil test kits early so that you’ll have them on hand as you start maintaining your plots. 

Again, if you would like to read more, a much more detailed version of this article is available at  
 Also, our in-house consultants are available (800) 688-3030 to answer any questions you might have.