With an educational session on top-rated perennials, another session with a large focus on how to flower perennials when you want and perennials on display in the New Varieties Zone and Ohio State Cultivar Trials, the spotlight didn’t shine away from perennials at Cultivate’19.
The session “Perennial Production: Better Baptisia and Problem-Free Panicum” took place the Sunday of Cultivate, giving growers and other industry stakeholders a feel for these popular perennials and what goes into producing them.
Laura Robles, trials manager at Walters Gardens, presented on Baptisia — a well-liked product that the Zeeland, Michigan, grower and breeder offers.
A member of the Fabaceae family, Baptisia is native to the United States, primarily in the Central and Eastern regions, Robles said. Other organisms evolved along with it, so it serves as a host plant for caterpillars and a nectar source for pollinators.
There are several species of Baptisia, including the popular Baptisia australis, and naturally occurring hybrids.
“A lot of people might be familiar with Purple Smoke, which is actually a naturally occurring hybrid that was found at the North Carolina Botanic Garden between Baptisia australis and alba,” Robles said. “But then there are several other species that have been used in breeding work to develop all the cultivars that we have today.”
Hans Hansen, who became lead breeder at Walters Gardens in 2009, and Tony Avent of Plant Delights Nursery in Raleigh, North Carolina, began breeding Baptisia in the ’90s, Robles said.
“They both went different directions, and Hans' work led to the Decadence series and the Decadence Deluxe series,” she said.
Here are the Baptisia offerings from Walters Gardens:
Decadence series: Blueberry Sundae, Cherries Jubilee, Dark Chocolate, Lemon Meringue, Sparkling Sapphires, Vanilla Cream
Decadence Deluxe series: Pink Lemonade, Pink Truffles
Other Baptisia: American Goldfinch, Baptisia australis, Grape Taffy, Indigo Spires, Violet Dusk
Baptisia plug production
Walters Gardens sells Baptisia plugs from about Week 20 to Week 28, which is the time the operation recommends for planting the plug. When planted at this time, the plug can grow through the summer.
If growers plant Baptisia from a plug, they will need to give it a winter-vernalization treatment and sell it the following year.
“We recommend planting in at least a one- to two-gallon-sized container,” Robles said. “Baptisia is a big plant, even though these genetics have been bred down to be smaller than the original species, it's still a large plant. It develops a very large taproot.”
Robles recommended planting Baptisia plugs below soil level to promote eye and shoot development. Walters Gardens usually pinches the plugs it sells, but if a plug hasn’t been pinched, growers should do so at transplant. After the plant starts to grow, they can give it another pinch.
“You want to bulk it that whole summer, and then in the fall, once temperatures drop, give it at least eight to 10 weeks of vernalization, which is best done between about 35 and 40° F,” she said.
Heading into winter with Baptisia
As winter approaches, growers should check on their roots and avoid any issues, Robles said. Although Baptisia are not notorious for susceptibility to root issues, problems can arise. They can apply a broad-spectrum preventative fungicide drench before cutting foliage back, around a month before overwintering.
“You also want to allow your plants to acclimate,” Robles said. “Don't be going along at nice, warm, ideal conditions and then bam, just drop them into vernalization conditions. You want to let those plants naturally get cooler until you get to that between 35- and 40-degree temperature.”
In preparing the overwintering location, growers should remove any debris from the area and sanitize it.
“You want to trim your foliage back — trim it down to about two inches or so,” Robles said. “If you leave the crown of the plant, or the stems, up too high on a Baptisia, we've found that you'll actually get eyes that try to break up higher on the stem the following spring, and they just don't have the same robust habit.”
In addition, growers should place their plants pot-tight. They should water the soil so it is moist but not water too much, as temperatures will be cold and the plants won’t be transpiring.
“Once you get them into your overwintering house, you want to bait for rodents,” she said. “That's a great place for rodents to find a nice, happy, warm — or relatively warm — place over the winter, so you want to put out some bait to prevent issues from that.”
Walters Gardens uses a minimally heated greenhouse for overwintering, running its vernalization greenhouses around 36° F. When its growers need to force their plants, they move them into warmer ranges.
Other options for overwintering are growing under a protective thermal blanket in an unheated white-poly house; or, outdoors, under a white-poly plastic sheet and a thermal blanket under that.
There’s another approach that Robles calls the “sandwich method,” which works best in regions where winter temperatures are consistently cold.
“[The] sandwich method is where you put down a layer of plastic, and then you put about 12 inches of straw and then you put another layer of plastic,” Robles said. “It really gives good insulation, but it's going to be hard to remove that material if it warms up.”
Baptisia production from bare root
Walters Gardens sells bare root product from Week 2 to Week 23. The operation suggests growers plant bare-root Baptisia in a two- or three-gallon pot with the eyes slightly below the soil surface. The eyes will rise out of the soil.
“Sometimes you're going to get these plants in, and you're going to be like, 'This isn't even going to fit in a three-gallon pot. These are huge,’” Robles said. “What you can do is trim those root systems down so that they fit. It's more important that you get the eyes planted below the soil surface than it is to worry about trimming roots. So, if your roots aren't going to allow those eyes to fit down under the soil surface, go ahead and trim off whatever level you need so that they will fit within that pot.”
Robles warned growers not to pinch bare-root Baptisia. Because the plants already vernalized, a pinch would prevent flowering for the year.
“Baptisia really like to be grown rather cool,” she said. “About 55 to 60° F is typically the best for the quality growth of the plants.”
They can be grown at up to 70 to 72° F, but they will require more growth regulators.
The ideal pH range for Baptisia is moderate — 5.8 to 6.5. EC should be between 2.0 and 3.0 using the pour-through method.
In containers, growers should apply a moderate nitrogen liquid feed of 75 to 100 parts per million.
“You can also use controlled-release fertilizer, which would be applied at about one and a quarter pounds per cubic yard of media,” Robles said.
Baptisia are day-neutral, so they will bloom naturally regardless of day length after they have experienced vernalization. However, they do like high light, so growers can use supplemental lighting.
“Something else that we do when we're forcing very early plants for trade shows — especially where we live in West Michigan, we're under poly, we usually have snow on the roof, it’s really, really dark and cloudy,” Robles said. “So we usually run supplemental lighting just to help out with that light accumulation.”
Pests and diseases are not a major issue on Baptisia, but growers should still scout for issues such as spider mites, powdery mildew, rust and leaf spots.
If growers are forcing Baptisia at 68 to 70 degrees, they can flower in six to eight weeks. In cooler temperature ranges, they will flower later — in about nine to 10 weeks.
“Then you can actually quite easily delay flowering if you need to,” Robles said. “If you're growing them early on and you have a colder greenhouse, we've found that putting them back in a 35- or 40-degree greenhouse can really delay them by two to three weeks if you need to hold those flowers for any reason.”
Growers of bare-root Baptisia can also stagger their crop by planting material at different times and sell the plant for longer.
Robles described Baptisia as a low-maintenance crop, a shrub substitute and a good alternative to Lupine. In the landscape, the plants grow large, so growers’ customers should not plant many of them. They also don’t typically respond well to transplanting, and that process is difficult once their root system has been developed.
Baptisia australis is hardy to Zones 3 to 9, and most of the hybrids are hardy to Zones 4 to 9. They grow best with at least six hours of sunlight each day.
“Help your customers to remember that it is going to sleep, creep and leap,” Robles said. “That first year when you plant it, it doesn't really do a whole lot. Don't let that discourage your customers. It’s basically working on root development. The next year it’ll come up and you’ll start to see a little bit faster growth and development. But then really after the third year is when you see the most noticeable bigger plants, more flowers by that time period.”
Hoffman Nursery, in Rougemont, North Carolina, produces ornamental grass liners, Hall said in his presentation on Panicum.
“It's got a wide native range from Nova Scotia to Mexico, west of the Rockies,” he said.
Panicum, also known as switch grass, has many functional uses. It’s heat- and drought-tolerant. It’s also used as nesting cover for wildlife and increasingly, in stormwater projects and for biofuel.
“It's adaptable to some conditions that are less than ideal, and it'll thrive,” Hall said.
Panicum can be used as a focal point, planted with herbaceous perennials or planted with asters in the fall.
“It's a major component of the tall-grass prairie, just like our Baptisia is, and it grows in dry sloped sand, woodlands, marshes,” he said.
Here are some of the best-selling Panicum offerings from Hoffman Nursery:
Panicum virgatum, P. virgatum ‘Cloud Nine’, P. virgatum ‘Dallas Blues’, P. virgatum ‘Heavy Metal’, P. virgatum ‘Northwind’ and P. virgatum ‘Summer Sunrise’.
Ecotypes of Panicum
There are different ecotypes of Panicum with different attributes and appearances, Hall said.
“You have an upland variety that tends to be more northern, drier soil conditions, more drought-tolerant, [with] higher nitrogen demand — tends to be a little smaller and shorter and, of course, [has] greater cold-tolerance,” Hall said. “The lowland cultivars tend to be in more southern latitudes. They're found in more moist soil conditions. They tend to grow larger, oftentimes have blue-green leaves, have a later flowering time and appear to be more resistant to rust.”
If growers produce Panicum in the north, they will have approximately 3- to 4-feet plants, while growers producing it in the south will have roughly 5- to 6-feet plants.
“That begs the question: these cultivars that are available today — are they lowland types or are they northern types? What are they?” Hall asks. “The truth of the matter is we don't quite know — we're still trying to sort that out. In some cases, I think they're probably intercrossed.”
Generally, Panicum is a warm-season grass compared to other grasses, such as Carex, Hall said.
“Warm-season grasses, like Panicum, use water and nutrients more efficiently,” he said. “They utilize 80 percent of the sunlight. The initial energy is in producing root growth rather than top growth, so it takes a little while to establish those.”
Panicum are drought-tolerant because at night they can open pores to reduce moisture loss. They thrive in soil temperatures of 70 to 90° F and air temperatures of 80 to 95° F.
In container production, Panicum begins growth in late spring and grows through the summer, flowering in July and August. It is dormant in the winter and a late-bloomer in the spring compared to other grasses. At Hoffman Nursery in mid- to late March, many switch grass crops appeared dormant, but upon closer inspection, they showed signs of emergence.
When transplanting a liner, Hall says, plant right at the soil line. Water an average amount. Use a porous soil mix. Hoffman Nursery’s mix is 60 percent pine bark, 30 percent peat and 10 percent perlite; the operation also applies dolomitic lime and slow-release fertilizer.
Hall said one of the common questions he gets asked about Panicum involves yellowing. He is able to resolve the issue with a 20-10-20 fertilizer with iron.
Insect pests are usually not a major issue for Panicum production at Hoffman Nursery.
“Probably our biggest issue is spider mites in the heat of the summer,” Hall said. “We'll occasionally get spittlebug, Japanese beetles, thrips, but for the most part, spider mites in the summer is what we battle.”
From a disease standpoint, rust can cause problems on Panicum. Hoffman Nursery rotates fungicides to prevent autumn rust from wreaking havoc.
“We notice that ourselves. For us, in our region, our biggest intensive rust is [in the] fall — September through November,” he says. “We get proactive, and we start doing a spray every 10 to 14 days in August.”
Because Panicum is a warm-season grass, Hoffman Nursery assumes growers will grow in warm temperatures. Assuming 65 to 70° F conditions, taking a 32-cell tray to a one-gallon pot would take roughly seven to nine weeks. Taking a 72-cell tray to a one-gallon pot would take about 10 to 12 weeks.
“For a two-gallon or larger, we recommend you put it in, in the growing season, overwinter it, let it go dormant — just like we were suggested for growing Baptisia — and let it re-emerge in the spring,” he says. “You're going to have a beautiful plant.”