Persistence is key

Growers from all over the country often face different challenges, but there is one challenge that all growers have in common — weeds. These pesky plants come back to haunt growers year after year. After talking with three growers across the United States, it is clear that it takes multiple methods to keep weeds under control.

Because of the hot and humid weather in Florida, the battle against weeds never seems to slow down or end at May Nursery. Richard May, president and general manager of May Nursery, believes all southeastern nurseries have this in common — weed control is expensive and never ends. But he believes it’s always easier to stay ahead than to get behind, even though staying ahead is more expensive.

“There’s been times when you’re just praying for winter to get here and kill the weeds so you can try to get things back under control,” Richard says. “You can get into a situation where you’ve got half or all of your employees in the field pulling weeds trying to get caught up, and that’s more expensive than staying ahead. It’s much easier to stay ahead than it is to catch up when you’ve gotten out of control.”

May Nursery’s most problematic weeds are spurge during the summer, bittercress during the winter, dog fennel and crabgrass.

“The spurge and bittercress luckily have light roots, so they’re easy to pull out,” says JB May, vice president and sales manager of May Nursery.

Richard explains that dog fennel, marestail and crabgrass can be problematic because their roots tend to take over the container.

“If you miss pulling any of those particular weeds, within a couple of months you’re going to have to throw that plant away,” Richard says. “The weeds will literally take over the root ball, and you can’t get it out without killing the plant.”

The team at May Nursery handles weed control by using pre- and post-emergent herbicide, rotating chemicals and staying on top of pulling weeds before they set seed. The nursery uses post-emergent herbicide only on roads to keep non-crop areas clean.

One manager scouts for weeds when the team isn’t putting out pre-emergent herbicide according to the schedule. He also hand weeds the plants that don’t get an herbicide treatment like grasses and perennials.

“Over the last two years, we started putting out rice hulls as a mulch barrier to help keep weeds under control,” Richard says. “I think that’s been fairly effective. It’s not perfect, but it’s another tool in the toolbox. … The jury is still out on whether or not they’re truly cost effective — are we getting enough weed control out of the rice hulls to make it worth it.”

Stick to a strict schedule

The team at May Nursery follows a chemical rotation schedule. In the summer, pre-emergent herbicide goes out every eight weeks, and in the winter, pre-emergent herbicide goes out every 10 to 12 weeks. It takes the team two to three days to put out pre-emergent herbicide on one field. Once they’ve weeded the field that was scheduled for herbicide, the team works on weeding other locations the rest of the week.

The pre-emergent herbicides that May Nursery currently have in rotation are:

1. Tower/Pendulum or FreeHand G/Corral G
2. Marengo G
3. Tower/Pendulum or FreeHand G
4. Double O SPC Granular or BroadStar G
5. Gemini
6. Regal OO and FreeHand

JB notes that it is very important to go back over with pre-emergent herbicide within a week of a plant being potted.

Marestail has become more and more problematic at May Nursery. The weed doesn’t grow around the plants, it’s mostly found in the roads and ditches, and it’s resistant to Roundup. The team must go back with an alternative herbicide to keep it under control.

Around 15 to 20 years ago, May Nursery didn’t have as extensive of a rotation of herbicides, and at that point in time, they were having resistance problems.

“We were using a lot of Rout at that time, and it just was not working,” Richard says. “We’re in better shape now with resistance because we are rotating so many different chemicals.”

Timing is the biggest weed management challenge facing May Nursery. It is important to stick to a strict schedule when applying herbicides.

Richard believes that a successful weed control program starts with a clean liner. Pre-emergent herbicide needs to be applied to a plant within a few days of potting.

“From there, it’s about constantly monitoring all plants and constantly rotating different pre-emergent herbicides through your nursery on a regular rotating basis,” Richard says.

It is also important to ensure the plants are clean and free of weeds before putting out pre-emergent herbicide. Richard further explains that applying pre-emergent herbicide on top of weeds is a waste of herbicide, and that keeping roads and ditches free is a key part of any good weed control program.

“If you allow crabgrass to grow up in all your roads, you’re going to get crab grass in all your plants,” Richard says.

Richard and JB give th late Charles Gilliam the credit for May Nursery’s successful weed management program. Gilliam was Richard’s professor while he was a horticulture student at Auburn University, and starting in 2011, Gilliam worked with JB on the nursery’s weed control processes.

“He worked with us extensively for several years to help us get to where we are,” Richard says. “I would say that in general, we are probably one of the cleanest nurseries in the Southeast, and we owe a lot of that to Charles Gilliam. He was a good friend, a good mentor and had a lot of patience.”

“Without him, we would not be clean,” JB says.

Switch up your mixtures

The most problematic weeds for Bailey Nursery’s Minnesota location are marestail, lambsquarters, velvetleaf, various grass weeds and most recently Poa annua. Some of the greenhouse crops have problems with purslane, bittercress, oxalis and liverwort.

“We get quite a range [of weeds] in our pots and in the gravel,” says Zach Brown, head of the plant health department at the Bailey Nursery Minnesota location.

Before plants are put in the beds and on the gravel, Brown’s production staff sprays a mixture of pre- and post-emergent herbicides with adjuvants mixed in. Most of the gravel will get two applications per year, and the coverage can range between eight and ten weeks.

“We’re using flumioxazin mixed with glyphosate and prodiamine, and then in the spring we switch to [a mixture of] indaziflam, glufosinate and prodiamine,” Brown says. “We’re switching up what we use, so we don’t have as much resistance, as well as trying to keep levels in any of our reclaimed water lower on specific actives.”

At Bailey Nursery, they use “potting dump wagons,” to keep the pots close together for a few weeks. This method allows the production staff time to first leach the plants and get them watered in. Then they put the granular herbicide on top of the pots. After this they space the plants to prevent putting more actives on the gravel.

For the containers, the production staff primarily uses two granular herbicide options. For the more sensitive varieties like hydrangeas and smaller pot sizes such as the one gallons and perennials, they apply FreeHand right after planting. For the varieties that are more tolerant, they use BroadStar (flumioxazin).

“We tend to get really good control with [BroadStar] on some of our larger woody shrubs,” Brown says. … “For FreeHand (pendimethalin + dimethenamid-P), we’re fairly limited by the label because a lot of what we’re putting that on is going to be hydrangeas, and you can’t do subsequent apps without something else in the middle. So, for hydrangeas, we do one application per season. Whereas with some of our other varieties, if the label allows, we will do two applications. — For us that would be spring and then fall as stuff is put back together for winter covering. We try to do that several weeks in advance, so we’re not creating herbicide injury under the cover.”

Reclaiming water has become more common in nursery operations across the country, and growers must know what’s in their reservoir.

“It’s important to be aware of what you’re putting down and where it ultimately goes,” Brown says. “[Reclaiming water] is a very useful tool, and it can help you with resistance and other things by rotating and making sure that you’re aware of what’s on the ground and in your water.”

Because Brown and his team switch up their mixtures, they haven’t seen much herbicide resistance.

Efficient communication

Brown and his team also have a decent list of plants that don’t receive any herbicide because of undesired stunting or delayed effects. His team communicates this using flags. As the potting line places the plants out in the field, they use red and green flags to mark the plants. The green flag tells his group to put herbicide on it, while a red flag tells them not to put any herbicide on it.

“It’s a really effective way to communicate without actually communicating verbally,” Brown says. “The red flag stays with the plant its entire life cycle, so that we can have a good signal in the field that we need to weed these more often. Then as my group puts the granular herbicide down on the green flagged items, they pull those flags and give them back to the planting line. Then that tells their production counterparts that they can go ahead and space the plants in the field. It’s a multiple use system for us, and it really is helpful.”

Weather

Weather is one of the biggest weed management challenges growers face. Brown explains that his team tries not to spray the gravel right before or right after a rainstorm to avoid puddling. Even with granular herbicide, his team makes sure it’s not too windy and that they’re hitting the target.

“There’s all sorts of things involved, whether it be drift or just the efficacy of things — making sure that our spray is not diluted on contact,” Brown says. “I’d say weather and the timing of those applications is probably the hardest thing to manage.”

This year has been really wet for Minnesota. There’s been over 30 inches of rain already, and that is typically the yearly average if not less. Because of the rain, some weeds are exploding, and Brown emphasizes the importance of hand weeding at a nursery.

“There’s still no replacement for hand weeding, and I think most people in the industry agree that regular hand weeding is definitely part of a good herbicide program — keeping things tended to so that they don’t become such a big problem to where your chemistry won’t work,” Brown says.

Approach weeds with multiple methods

Co-founders of Columbia Nursery Wayne and Amanda Staehely try to attack weed control in a variety of ways. They have a pre- and post-emergent spray program, hand weed and use cultivation techniques such as disking and tilling.

The most problematic weeds for Columbia Nursery, located in Oregon, are horsetail, blackberries, liverwort in the liners and Queen Anne’s lace in the field.

At Columbia Nursery, the go-to pre-emergent herbicides are SureGuard and Marengo. For field production, they typically apply these twice a year. For container production, they apply granular herbicide whenever the plant is potted and repotted.

“We can do a really good job maintaining Queen Anne’s lace with the spray practice we have on it,” says Amanda. “But if the weather does not cooperate, it becomes ridiculous here.”

As a small nursery with 10 full-time employees, all employees are trained to scout and look out for problematic weeds. An employee once found Japanese knotweed in one corner of the nursery, so they dug it out and flagged it as a weed to lookout for.

“We’re just trying to be really mindful,” Amanda says. “You want a clean nursery, but you also want to be careful that you’re not over spraying. You still need good stuff in that soil as well. … So, if it’s possible, we won’t spray for blackberries. We dig them out and take them out of the field.”

Wayne and Amanda also shared that the timing of weather and having enough labor are some of their biggest weed management challenges.

“Because of the weather and how small we are, labor is always an issue,” Amanda says. “I don’t have a huge amount of people to pick from and weather here in Oregon is always dicey. There’s usually a lot of rain, so you have to be mindful of that as well.”

Utilize the knowledge of your local supplier

Wayne explains that their local supplier representatives are a huge asset to the nursery, especially when a grower is first starting out in the industry. Labels and costs can change over time, so it’s beneficial to talk with your supplier to figure out what works best for your nursery with your budget.

“Always work with the people who do it every day for a living,” Wayne says. “You can’t just bury your head in the sand because it’s a constantly changing environment.”

Amanda says that people shouldn’t be afraid to talk with other growers in the area to get advice and find out what method works for them.