Perennials continue to be in high demand by consumers that want horticultural plants that last for more than one year. However, perennials are susceptible to insect and mite pests, and because there is a wide diversity of perennials, there is a complex of insect and mite pests that will feed on perennials.

Insect and mite pests that feed on perennials can be grouped based on their feeding behavior, which is associated with the damage that insect and mite pests cause to the leaves, stems, or flowers of perennials. The major feeding behaviors of insect and mite pests that feed on perennials are chewers, suckers, miners, and borers.

The primary insect and mite pests of perennials, based on their feeding behaviors, are listed in Table 1 (page 76).

Management of perennial pests

The management of insect and mite pests of perennials involves implementing cultural control, pesticide (insecticides and miticides), and biological control strategies in a holistic plant protection program.

Cultural control

Remove or prevent the growth of weeds inside and outside greenhouses because weeds may serve as reservoirs or alternate hosts for insect pests including aphids, caterpillars, leafhoppers, mealybugs, thrips, and whiteflies. The presence of weeds in or around the greenhouse may lead to increases in insect pest populations. Furthermore, weeds may harbor diseases such as viruses, which may be transmitted by insects that initially feed on weeds and then feed on perennials. Insects that may transmit viruses from weeds to perennials include aphids, leafhoppers, thrips, and whiteflies.

Practices that may minimize problems with weeds in and around greenhouses include the installation of geotextile fabric barriers, physical removal, mowing, and using herbicides. Regarding the use of herbicides, few pre-emergent herbicides are registered for use inside greenhouses and those that are labeled should only be applied when greenhouses are empty because of the potential for plant damage. In addition, post-emergent herbicides should never be applied inside greenhouses when perennials are present.

All plant and growing medium debris needs to be removed from inside and outside greenhouses because plant and growing medium debris may harbor insect pests, and immediate removal should decrease insect populations; thus preventing insect pests from infesting any perennials.

Maintain plant health as perennials that are properly watered and fertilized may be able to tolerate some insect or mite pest feeding without showing noticeable symptoms. Use well-drained growing media and avoid over-watering perennials to prevent problems with fungus gnats and/or foliar nematodes.

In addition, do not over-fertilize perennials, especially with water-soluble, nitrogen-based fertilizers, which may increase susceptibility to insect and mite pests, such as aphids and the twospotted spider mite (Tetranychus urticae). Moreover, over-fertilizing perennials may stimulate insect and mite pest development and reproduction.

Always use new containers and growing medium and dispose of old stock plants because these may serve as a source of insect and/or mite pests. If need be, remove and dispose of any perennials that are heavily infested with insect or mite pests.

Scout/monitor perennial crops at least once per week visually and/or use yellow sticky cards to detect the presence of insect and mite pest populations. Record when insect and mite pests are present on specific perennials during the growing season.

Pesticides (insecticides and miticides)

There are many pesticides (insecticides and miticides) registered for use against insect and mite pests of perennials. These pesticides may have contact, stomach poison (ingestion), translaminar, or systemic activity.

Microbial insecticides are derived from fungi and/or bacteria and are selective in the types of insects they kill. For example, the bacterium, Bacillus thuringiensis subsp. kurstaki, which is a stomach poison, only has activity on caterpillars. However, the insecticide is not harmful to humans, pollinators, or beneficial insects.

Timing: apply pesticides when the most susceptible life stages (larva, nymph, or adult) of insect or mite pests are present.

Coverage: when applying a pesticide, it is important to obtain thorough coverage of all plant parts including leaves, stems, and flowers. Spray applications must reach leaf undersides because most insect and mite pests feed on the underside of leaves.

Frequency: apply pesticides within timely intervals, which is dependent on the residual activity of a given pesticide. Read the pesticide label carefully for information associated with frequency of application.

Contact your local extension service or university-based entomologist for recommendations on those pesticides that can be used for specific insect and mite pests.

Biological Control

Biological control is a plant protection strategy which entails releasing biological control agents such as parasitoids or predators that will regulate insect or mite pest populations below plant damaging levels. Certain parasitoids will attack aphids, whiteflies, or caterpillars. Predators, in general, will feed on a wide-range of insect and mite pests that feed on perennials.

In addition to parasitoids and predators, entomopathogenic nematodes (Steinernema spp., or Heterorhabditis spp.) can be applied to the growing medium to suppress fungus gnat or black vine weevil (Otiorhynchus sulcatus) larval populations.

Biological control agents can be purchased from biological control suppliers or distributors. It is important to release biological control agents when insect or mite pest populations are low. Furthermore, be sure to assess the quality of the biological control agents to ensure that they are alive before releasing into greenhouses.

In conclusion, it is important to correctly identify insect or mite pests that are feeding on perennials, which will help determine those cultural control, pesticide, and biological control strategies that should be implemented to prevent damage to perennial crops.

© JohanSwanepoel | Adobestock

Landscape Prescriptions by MD Ornamental hot peppers (Capsicum sp.) and their exciting use throughout the landscape are finally entering the lexicon of most gardeners. The contributions of colorful fruits in white, cream, yellow, orange, red, purple and black are significant, particularly later in the season as the fruits ripen up over the hot summer months. Many varieties will go through a colorful transition with multiple colors of fruiting on the same plant.

The ornamental impact of these increasingly vivid fruits can rival any bedding plant late in summer. Most ornamental hot peppers have some common traits which include shorter stature, the fruits are frequently staged and held above the foliage and, of course, the colorful fruiting show that is exceptional until the hardest of frost.

Why ornamental peppers?

It is important to note that while “ornamental hot peppers” are edible, they are not bred for culinary value and frequently lack the depth of taste that many traditional hot pepper varieties provide in terms of a flavor profile. Most ornamental hot peppers have muted taste, but a whole lot of heat.

With limited to no culinary history, most of the ornamental hot peppers haven’t been researched for Scoville heat units (SHU) that reflect the heat of these fruits. Be wary of the unknown. Keep in mind that some people have severe allergic reactions in relation to eating, handling or even being near hot peppers in the garden.

It is important to also note that some of our most common hot peppers (i.e. ‘Jalapeno’, ‘Tabasco’, ‘Scotch Bonnet’, etc.) are also beautiful when the fruits transition to more intense color as they ripen.

A feature of merit that is often overlooked in the category of ornamental hot peppers is the contribution of ornamental foliage. As with any type of plant, having multiple features of interest diversifies the ornamental contributions of the plant, adds additional or lengthier interest and in the case of ornamental foliage, may become the primary feature of interest.

With ornamental hot peppers becoming so popular in bedding schemes, container arrangements, later season displays and simply for general use, the contribution of ornamental foliage broadens the opportunity for using these plants in showy and imaginative combinations.

Classification and deployment

Ornamental foliage for these hot peppers falls into some basic categories based on my observations. There are those that have a white to cream variegation on the leaves. Some varieties will have a variegation that includes hints of violet and purple. Some of my personal favorite selections have near black foliage throughout the growing season. The last category are those selections that have foliage that deepens to a black coloration in late summer at the time when the fruiting show is at peak.

We’ll examine some selections in each of those categories further in the article.

In terms of using these plants in the landscape, certainly evaluating the merit of the colorful fruits in the landscape is a primary consideration. While most traditional ornamental hot peppers aren’t offering much interest in terms of fruit coloration until later in the summer, those with colorful foliage are immediate contributors to the composition.

For example, those selections with near black foliage offer a depth of richness even prior to the fruiting which then offers interest while using that same foliage as a backdrop or foil for the ripening fruits. Selections with variegated foliage will attract the eye over the entire growing season and become a nice backdrop for colorful, ripening fruits. Ornamental hot peppers at peak fruit coloration are becoming hot sellers in late summer as they not only provide instant, vivid color but limitless potential as late season “filler” in garden beds and later season container arrangements.

Ornamental hot peppers in general really need full sun locations and will thrive in the bed, border or container. Drainage is vital and they don’t mind rich or amended soils. Some fertilization may be in order, particularly for container specimens and while these peppers all have some degree of drought tolerance and like it hot, don’t let them dry out. Keep up with a watering regime that accommodates a moist and well-drained situation.

Planting any sort of pepper out in the garden shouldn’t occur until the soil temperatures are minimally 70°F and the evening temperatures are nearing 60°F on average. There is danger in planting peppers too early with damp and cool soils offering little incentive for the peppers to actively establish or grow. If sowing seeds of select varieties, target your sowing 10-12 weeks in advance of the last frost date in your area and keep seedlings happy and safe until planting in a warming soil in their final destination.

And keep in mind that peppers of all kinds have a wide range of potential insect and disease issues that can be addressed as needed, although healthy specimens will be the least likely to show evidence of being compromised and needing that additional TLC.

White/cream variegated ornamental hot peppers

I’m personally a big fan of variegation in any type of plant. While we might be selecting certain plants for interesting form, flowers, fall color, etc., having the additional contribution of variegation just adds to the extended show. That’s certainly the case with variegated ornamental hot peppers as well.

Some great selections with the white/cream contribution include Uchu (9 inches), ‘Sparkler’ (18 inches) and the classic selection ‘Fish’ (24 inches). It’s interesting to note that in some instances, the variegation extends to the fruits as well. This is the case with both ‘Sparkler’ and ‘Fish’. This variegation, while varying in prominence, is still visible throughout the color transition of the fruits. All of these selections have a fruiting transition from cream to yellow, orange and finally red with multiple colors on display depending on the maturity of separate fruits.

If you are interested in variegated sweet pepper selections, look for ‘Confetti’ or ‘Candy Cane Red’ which are both mini-bell selections with impressive variegation of foliage and fruits.

Violet/purple variegated ornamental hot peppers

For simply the sheer value of foliage contribution, these selections are excellent. I’ve grown ‘Purple Flash’ ornamental hot pepper for over 20 years and never tire of the reliable, variable, purple variegation seen throughout the foliage with no two leaves being identical.

Reaching 15 inches in height, this is truly a bedding plant known for prominent foliage as the fruits are jet-black, quite small and truly a secondary asset to the foliage.

The variety ‘Tricolor Variegata’ (18 inches) is another classic selection with similar splashes of purple and cream over the foliage. However, the thin, long fruits of this selection become more prominent as they transition from deep purple to bright red.

Dark foliage ornamental hot peppers

My personal favorite ornamental hot pepper is the variety ‘Black Pearl’ which displays near-black foliage in full sun. The fruits emerge a glossy black and age to a bright red late in the season. This 2006 All-America Selections (AAS) winner reaches 24 inches in height and offers a rich, bold color with and without the fruiting contribution.

Additional AAS winners with black foliage and similar impact include ‘Black Olive’ (18 inches), ‘Black Hawk’ (12 inches) and Onyx Red (9 inches). All of these selections have the same colorful fruit transition from glossy black to bright red.

The variety ‘Count Dracula’ (16 inches) was another favorite with a black, matte-finish foliage contribution with short, elongated fruiting that also goes from black to red. Full sun is absolutely necessary to get the deepest black foliage coloration on all of these selections. Emerging foliage, while having hints of green, will all deepen and darken in full sun during the hot summer months.

Ornamental hot peppers with darkening foliage

This might seem like an odd category when considering the topic of ornamental foliage on these hot pepper selections. However, these two varieties in particular have an interesting foliage transformation from dark green with maroon overtones in the summer to a very deep black when the fruits are aging to their best coloration. Seek out both ‘Explosive Ember’ (12 inches) and ‘Midnight Fire’ (14 inches) for this feature along with fruits aging from glossy purple to a deep red with many colors in between that transitioning gradation of coloration. ‘Explosive Ember’ actually has a “cross-over” audience for culinary use with the peppers having decent flavor and heat of a cayenne pepper.

As the lead grower at Hoffman Nursery (Rougemont, North Carolina) – an industry leader and 30-plus year grower of greenhouse ornamental and native grasses (slogan: We Grow Great Grasses!) – Bill Hall knows all-too-well the difficulties that can arise in getting some of the varieties to root prior to shipment.

Hall and his production team typically receive grass varieties in large clumps, which they then break down into smaller plots that they call divisions.

“We’ll pot those divisions into liner pots, and then we’ll typically put them in our houses under our misting systems for about 14 days,” Hall says.

Misting involves lightly applying recycled irrigation water atop of the divisions multiple times throughout the day. The grasses should respond accordingly with vegetative growth increases within about two weeks, according to Hall.

“We should see them start to root in about 10 to 14 days, and typically by day 14 they're off of the mist and they are ready to go,” he adds.

The specific timing around your preferred rooting is another important aspect to consider. If you are hoping to start the production cycle early and overwinter them in cold frames until shipping season hits – which is what Hoffman does – you’ll want to get the cycle going in the late fall or early winter. In that case, you will want these activities to occur inside a heated structure and keep your ambient temperatures above 60° F to encourage root development.

“This time of year, it’s warm enough here in North Carolina that we can do it outside and still have success,” he adds.

Trending varieties, grasses for backup?

Hall confirmed that the rumors this spring are indeed true: greenhouse and nursery operations of all sizes are seeing constrained young plant supplies as we turned the page from early to late-spring.

Many brave prognosticators have forecast that operations will likely be forced to grow something, anything, beyond their usual crop mixes to keep plants available for their customers into mid-to-late-summer. Many thought perhaps ornamental and native grasses would fill the hole left by the expected flower, tree, and shrub shortages.

Not so fast, according to Hall.

“We’re basically sold out across the board right now on everything in our houses,” Hall explains. “That’s across the board for both warm and cold season grasses. We’re just completely sold out.”

The specific ornamental grasses that Hall is seeing increased consumer and landscaper demand on are Carex varieties, which are sedge grasses, and include such notables as Carex Bunny Blue (bit.ly/CarexHobb), Carex Everest (bit.ly/CarexEverest), and Carex ‘Everillo’ (bit.ly/CarexEverillo).

“Unfortunately, the biggest issue right now is the shortage of supply that everyone is encountering on plant material, and that will exist for the grasses as well. Believe me, we know this because we’ve been looking for ourselves, too.”

Photos courtesy of Leider Greenhouses

Supplemental lighting can be as unique as the crops a greenhouse owner grows. Greenhouse Management magazine spoke with Elizabeth Leider, assistant production manager of Leider Greenhouses in Buffalo Grove, Illinois, to get a glimpse into how one greenhouse operation tailors its lighting to achieve better production results.

Greenhouse Management: What crops do you grow and in what type of greenhouses?

Elizabeth Leider (EL): We are a wholesale flower grower. We grow spring and summer annuals, and we also grow a few perennials. Most of the annuals we grow are used for container gardening or as bedding plants. In the summer, we grow hardy mums and we grow poinsettias for the Christmas season. We also grow Easter lilies, hydrangeas, and a few indoor-blooming plants. Our facility was built in 1963 and we’ve expanded onto it multiple times, so we have glass greenhouses, double polycarbonate greenhouses and polyethylene greenhouses.

GM: What types of supplemental lighting do you use and on which crops?

EL: Originally, we only used HPS. I would say in the last eight years we’ve started investing in LED. The HPS lights are primarily still used for our indoor bloomers and for propagation. We use them to either extend the day length or just increase the amount of light in the greenhouses.

The LEDs we primarily use for propagation. We also use them to further speed up some of our crops. For instance, we noticed just this year that the zinnias we put under LED lights were about a week ahead of those that weren’t.

The LED lights are newer toplighting. I believe the color spectrum is a red spectrum, but they’ve really improved it recently, so it’s not as harsh on your eyes. It’s got a white quality to it. So, we have some older lights and we have some newer ones as well. Our older lights are definitely pinker, harsher, and the newer ones are a lot easier to work under.

GM: Do you have different lighting setups based on the type of greenhouse?

EL: In general, glass lets in more UV light, whereas the polycarbonate filters it out a little bit more. We don’t have any LEDs in our glass houses. Those are very traditional-style houses, and we just use them for specific crops. Easter lilies, for example, really like the glass houses and won’t get enough light if you put them in a polycarbonate house.

Our propagation houses are, I believe, double polycarbonate. All of our greenhouses were built to grow indoor-blooming plants. They weren’t built to grow annuals, so we really need the supplemental light to help the annuals beef up.

GM: Can you talk more about why you use supplemental lighting and how important it is to the success of your crops?

EL: In regard to propagation, it definitely increases the rooting speed for a lot of the unrooted cuttings that we propagate for most crops. And supplemental lighting in general, it’s a more uniform distribution of light because some of our houses are kind of old and they’re not very tall. There are certain places that get shadows. In the past, that shadow would really impact the uniformity of the crop. Especially when we’re just beginning to propagate. Being able to have a toplighting makes the lighting way more uniform.

We also need supplemental lights for certain crops because of short days. We’re in Chicago, so there can be periods of time when we have very low light that goes on for a week on end.

GM: Are you planning to expand your supplemental lighting?

EL: We’re probably going to put more lights in some of our outside poly houses that we tend to grow cold crops in. We grow some early spring crops that are grown cold, but they like high light. This last year we did an anemone trial and anemones really like a lot of high light, so they did really well grown cold in these poly houses with the supplemental light. We did full LED and HPS light for those.

We’re also trying to transform some existing space that we used to cool bulbs. We don’t grow nearly as many bulbs as we once did, so we have a lot of cooler spaces essentially sitting empty. I’m working on a project to convert that vertical space into an LED-lit vertical operative type system.

Answers were edited for length and clarity.