Chapter 04 – Herbaceous Ornamental Plants

Learning Objectives

From reading and studying this chapter, you should be able to:

• Understand the categories of herbaceous ornamental landscape plants and their functions in the landscape.
• Recognize the main plants in each category used in Indiana landscapes.
• Use correct terminology to describe the plants and their culture.
• Establish and manage herbaceous ornamentals.
• Select plants for various landscape situations.

Introductory Comments

The best way to learn the large amount of information in this chapter is to break it into smaller groups. First learn the categories of herbaceous ornamentals and how each is used in the landscape. Then, study the images of the ANNUAL plants and learn to associate each picture with the correct plant name. Once you have mastered the names and developed your ability to recognize each plant, then spend some time familiarizing yourself with the characteristics and requirements for each. Repeat the process for the PERENNIALS, the BULBS, then ORNAMENTAL GRASSES. Finally, study the cultural requirements for each group beginning with the annuals. Each subsequent section on cultural requirements will build on the one(s) that preceded it.

Introduction to Herbaceous Ornamentals

This chapter is about those plants that are commonly grown in the landscape or in gardens. Their flower and leaf colors, textures and plant forms add interest to developed sites. The plants can be grouped by life cycle, but also are considered here by growth habit.

Herbaceous refers to plants with stems that do not thicken with age, or become “woody.” Generally, they die to the ground each winter, but may remain alive underground. Their stems are commonly soft and pliable.

An annual (a true botanical annual) is a plant that completes its life cycle in one growing season. It can grow from a seed and produce new seeds in one season, after which time it dies, usually being killed by cold temperature. Many landscape annuals will bloom continuously through most of the growing season. Some plants that we call annuals are really perennials (see below) if grown in a warmer climate, but behave as annuals for us, being “tender” and thus killed each year by cold winter temperatures. A special group of tender perennials that we handle as annuals are the “tropicals.” They die if exposed to temperate zone winter temperatures, but can be carried over winter actively growing in a greenhouse, or as dormant rootstocks, such as tubers or corms. They are “tropical” in appearance, often with large colorful flowers and/or coarse-textured foliage.

A biennial is a plant that requires two growing seasons to complete its life cycle. It grows only stems and leaves the first year, then following winter dormancy, flowers, produces seeds, and dies. Biennial flowering periods are usually short, one to three weeks or so. Biennials are treated like annuals because they require yearly re-planting to assure flowering in the landscape each year. However, they have limited bloom periods like perennials.

A perennial is a plant that lives for more than two growing seasons. A herbaceous perennial usually dies to the ground each winter (a few species are evergreen), but the in-ground part of the plant survives. It may not flower for one or more years following planting, but once it begins flowering, will generally flower every year. The bloom season may only last a few days to a few weeks, but some last longer and some re-bloom late in a season. Life span of perennials varies from “short-lived” types that may survive two or three years to those that last indefinitely.

Hardy bulbs are perennials that form enlarged, distinctive underground structures. The structures may be composed of modified roots, stems, or leaves, and sometimes, flower buds. They vary from above-ground plant parts in that they help store food for the following growing season.

Ornamental grasses are most often perennials, but may be annuals. They are not mown regularly like lawn grasses, but are allowed to grow to their full plant form as other perennials, but with a grass-like habit. Although lacking in bright colorful flowers, ornamental grasses offer unique textures, and may provide tan-colored “dried arrangement-like” winter interest. They are simple to maintain.

Landscape Functions

Annual flowers and foliage plants are grown to make the landscape or garden colorful, often just for their beauty. Functionally, they are used as focal points themselves or to help focus attention on landscape elements such as signs or entranceways. They may also serve as filler plants in new plantings of perennials or shrubs that have large spaces between plants. The continuous color of annuals can be intermingled with perennials so that there is continuous color between bursts of perennial bloom. Annuals, importantly including tropicals, are often used as container plants.

Perennials add variety and interest to the landscape or garden with their colorful flowers, unique plant forms, varied textures and, sometimes, showy fruits. Some are “tidy” in habit and lend themselves to formal planting. Others have a more “loose” growing habit, providing a quality of “naturalness” when planted in informal or ecological compositions. There are perennials that will tolerate most growing conditions so with correct plant selection, they can be used in almost any landscape location. Perennials can provide temporary screening, reduce erosion on slopes, or help emphasize landscape elements. One limitation to perennial usage as ornamentals is their limited bloom period compared to annuals. Also, some perennials die down to the ground at times during the growing season. For this reason, perennials are often planted in diverse groups to provide some interest throughout the growing season.

Hardy bulbs are primarily providers of spring flower color. Some of the best bulb species bloom in the early spring before most perennials get going and before it is warm enough to plant annuals. Other hardy bulbs, notably true lilies, bloom in summer and are used like other perennials.

Ornamental grasses bring distinctive form and textural interest to the landscape. The flowers of grasses, while part of the texture and form of the plant, are not brightly colored. Some grass plants get very large and are useful as focal elements, for temporary screening or filling up vacant space. Smaller grasses may work like groundcovers, while intermediate size plants can function much like small shrubs. A few grasses change from green in summer to a tan color in winter, but maintain their form. This allows them to provide a landscape function in the dormant season much as they do during the growing season.

Annuals

Site Selection

Most annuals grow best in the full sun and in well-drained soil. Those that are shade tolerant such as impatiens (Impatiens) and wax begonias (Begonia) grow well in the shade, but the majority that require full sun grow weakly and produce fewer flowers in shade. A slow draining soil will result in weak roots and poor performance by most annuals.

Soil Preparation

Soil for growing annuals should be well drained, and when it is handled, it should be loose, crumbly, and should not clump together. Heavy soils usually benefit from the addition, and thorough mixing, of 3” +/- of organic amendments such as leaf mold or compost. Spade or rototill to a depth of 8-10 inches. Soil amending is best done in the fall or early in the spring, but while early soil preparation is best, amending a heavy soil even just at the time of planting is still better than no improvement.

Soil pH should be in the range of 6 to 7. A soil test will show if it is out of this range. Use lime or sulfur to raise or lower the pH as directed by the soil test results.

Fertilizer should be worked into the planting soil prior to setting plants. Use a complete, quick-release fertilizer such as 5-10-5 (or equivalent) at a rate of 2 to 4 pounds of fertilizer per 100 sq. ft. of bed area. Slow release fertilizer may be used at a slightly higher rate, and higher cost, but should eliminate the need for midseason fertilization (see below).

The container growing of annuals is done primarily in commercially prepared, soilless growing medium. A fresh mix usually has fertilizer incorporated. Soilless mixes can be re-used many years in a container and only require annual recharge with fertilizer. Use a slow-release fertilizer at label recommended rate. A simple recipe if you construct your own container mix is 1/3rd loam soil, 1/3rd organic matter, and 1/3rd vermiculite or perlite. Containers must have drainage holes in the bottom to allow excess water to drain away. Otherwise, root rot and poor plant performance is likely.

Planting

Annuals are mainly planted after most danger of spring frost is past. In Indiana, that is generally early May in the south to late May in the north. A notable exception is the pansy which is quite tolerant of cold weather. Pansies are often planted in the very early spring as soon as the ground is workable. Sometimes, landscape managers even like to take risks by planting pansies in the fall in hopes that a mild winter will allow a flower display all winter, or at least allow them to get a very early start in the spring.

Plant spacing depends on several factors including a client’s need for “instant effect,” transplant size and budget. Be sure to allow enough room between plants for future growth and to avoid excessive competition. The goal is to keep every plant healthy for the entire growing season.

Annual transplants produced in cell packs or pots must be removed from their containers at planting. Root systems found to be tightly bound should be gently loosened before planting. In extreme cases, cutting of some roots may be desirable to encourage root growth into the surrounding soil. Plants grown in peat pots, or other bio-degradable systems can be planted still in the pot, but be sure to completely cover the pot with soil or remove any excess pot material that is above ground. Newly planted annuals should be thoroughly “watered-in” immediately. A dilute liquid fertilizer may be applied.

Some annuals, primarily small seedlings, may benefit from a “pinch” at planting. Pinching is the removal of the primary growing point resulting in more branching and flowering. However, it will usually delay the development of the first flowers. CAUTION: don’t expect to pinch all annuals. Some grow tall and erect naturally and do very little branching, even if pinched. Often, newer cultivars of annuals branch more naturally than the older types. Larger plants that are fully in flower at the time of installation typically should not be pinched.

Mulch such as compost, shredded bark, pine needles, etc. may be applied for weed control, moisture retention and soil cooling. Avoid mulch deeper than 2 inches and keep the mulch away from plant stems. One useful approach is to mulch a bed before planting, then plant through the mulch. Be sure, though, that plant roots get placed into the soil, not just in the mulch.

Management

Irrigation is essential most years in Indiana to assure top-quality annuals. About 1 inch of water is needed by most annuals per week. New transplants should be watered frequently the first week, but once plants become established, irrigation is best limited to a single deep watering once per week. However, in extreme heat conditions, more frequent irrigation may be required.

Less watering may be possible if water-holding polymers are used. If added to the soil when beds are prepared, polymers may retain enough water near plant roots to extend the time between waterings to several more days than usual.

Fertilizer, like that used in bed preparation (i.e. 5-10-5), should be applied about six weeks after transplanting at a rate of 1-2 pounds per 100 sq. ft. It should be repeated six weeks later. If a slow-release product was used in bed preparation, midseason fertilizing may be omitted.

Deadheading is the removal of spent flowers. It is useful to improve appearance in some plants, notably geraniums. It may promote stronger continued flowering by eliminating seed production. Many annuals, like petunias and impatiens “hide” their spent flowers with new growth and are not deadheaded.

Some annuals, especially petunias, benefit from cutting back in the later part of the summer to promote late season branching, much as pinching does in the early season. This should be accompanied by fertilization.

Weed control is best practiced in annuals with a combination of hand weeding, mulching and growth of the annuals themselves to compete successfully with weeds. Herbicides, especially those applied after the flowers are planted, but before any weeds appear (pre-emergence herbicides) may be useful, but must be used with knowledge and caution. Read the label!

Insect pests and diseases are rare in annual plantings, but can occur. Regular monitoring of plant health and quick attention to problems is part of successful management.

Perennials

Plant and Site Considerations

Success with perennials requires a compatible union between the characteristics of the site and the requirements of the perennial plant. Also, design functionality of the plant in the site must be correct. Perennials offer so much diversity that plants are available for just about any site. Remember that only perennials with similar site requirements should be planted together.

Light level, the degree of shadiness and the duration of that shade, is fundamental. Shade may be from a natural source such as trees or from architectural elements. It may only be for part of the growing season or may be year round. Commonly used categories for light level are:

• Sun (S) – Six or more hours of direct sun per day
• Partial Shade (PS)- part day (less than 6 hours) direct sun, or all day filtered shade through a loose, open tree canopy
• Full Shade (FS)- only a few minutes of direct sun in a day, little filtered light
• Deep Shade (DS)- no direct sunlight, dense, continuous overhead canopy – this degree of shade is unsuitable for all but the most shade-tolerant perennials

Soil condition (drainage, root aeration, moisture retention) is the other basic consideration. Certain perennial flowers will grow in standing water, others in dry gravelly soils, many in between. The match is the key. Check the soil drainage characteristics before making plant choices.

Winter hardiness is important given perennials must survive from year to year. Indiana is in USDA hardiness zones 5 and 6 with average annual winter low temperatures ranging from the extremes of about -20 degrees F in the north to -10 degrees F in the south (see: https://planthardiness.ars.usda.gov/). Perennials tolerant to colder temperatures than these will usually survive here, but those adapted to warmer zones may be killed over winter. Microclimates near buildings and special winter protection from mulching may allow less-hardy species to survive.

Summer heat tolerance can also limit a perennial’s adaptability to a location. For example, lupines and delphiniums take the cold of Indiana all right, but are better suited to cooler summer conditions than are typically found here. The American Horticultural Society began to map this effect in the late 1990’s. The AHS “Plant Heat-Zone Map” may be useful in helping determine southern limits to adaptability. It can be found here: https://ucanr.edu/blogs/dirt//blogfiles/37486_original.jpg, but it is no longer an official publication of the AHS.

Climate change is making cold hardiness zone and heat zone mapping difficult. At present, the global climate is very dynamic and past history may not be an accurate indicator of current reality. The available maps are still useful as guides, but one must be mindful of changing conditions.

Disease and insect pest tolerance is an important aspect of perennial selection. While most problems can be controlled with enough management input, the choice of less problem-prone plants is generally preferred. Planting a diversity of species tends to reduce such problems.

The mature size of a perennial is important to consider. Crowding of a large plant into a small space can mean the plant is weakened from lack of resources to grow. It probably also means the plant is a nuisance functionally, requiring constant attention to size control. Be aware of a plant’s mature size before planting.

Perennial flowers require management. To be at their best, some take very little, while some a lot. For example, some perennials must have structural supports to keep them from flopping over, especially when in bloom. Plant selection should be limited by a realistic awareness of the likely future intensity of landscape management.

Site Preparation

Perennials are available to match most soil conditions. However, it may be desirable to alter the existing soil conditions to allow the growing of plants that require a different set of conditions. And often, plants that will tolerate poorly drained, tight soils will grow better if provided with improved soil conditions.

Site preparation for perennials is best done well ahead of plant establishment. A growing season ahead of planting is ideal. However, practically, such advance work is often not possible. Soil preparation is often done immediately prior to planting. Be sure to follow up installation with monitoring to respond to any issues that may arise such as weediness, or uneven settlement, drainage or nutrient availability. The key is to do preparation thoroughly, remembering it is intended that perennials should grow for a long time without replanting.

If a site has an established perennial grass or other weedy plant cover growing on it, the weedy plants should be eliminated before perennial planting. If time permits, repeated tillage or smothering with organic or plastic mulch is effective. If time is short, a non-selective systemic herbicide (for example Round-Up^® or Finale^®) can be used.

Soil should be worked more deeply for perennials than annuals, because perennial root systems may grow deep into the soil over many years. Prepared soil depth should be as deep as practical. It is usually limited to 12” – 18”, but even deeper preparation, particularly on sites with significant soil compaction will pay long-term benefits.

Slow draining soils usually can be improved by the addition of liberal amounts of organic material. Add organic matter amendments up to one-third by volume. In extreme cases of poor drainage when plants requiring good drainage are to be grown, consider total soil replacement or creating a raised bed.

Optimum soil pH for perennials can range from below 6 to above 7. Be sure there is a good match between the requirements of the selected plant species and the soil at the site. Use lime or sulfur to raise or lower the pH, if needed, as directed by soil test results.

Fertilizer should be added to the planting soil as it is worked. A soil test will point out significant deficiencies. Phosphorus is especially difficult to add once plants are in place. In the absence of a soil test report, use a complete fertilizer such as 10-10-10 (or equivalent) at a rate of 2 to 6 pounds of fertilizer per 100 sq. ft. of bed area.

Planting

Planting of perennials is best done in spring or in late summer to early fall. In Indiana, that means April to early June and late August through early October. Planting of perennials is most often done with container grown plants. In some cases, especially large commercial plantings done in early spring, bare-root plants may be planted.

When perennials grown in plastic pots are planted, remove the container completely. Loosen any tightly bound roots and plant them into the soil of the new location. If the container is a bio-degradable fiber pot, cut gashes in the sides of the pot in 5 or 6 places vertically, tear off the pot rim that extends above the soil in the pot, and then plant, pot and all. The finished planting depth for both pot types should be the same as in the container.

Bare root plants, because they are dormant, must be kept cool and moist, not wet, until planted. Spread the root system fully when planting and gently place soil completely around the roots. Firm the soil by hand. Correct planting depth is very important and varies with species. For example, the buds on the crown of a peony should be planted at 2” below soil level (not deeper). Iris rhizomes, however, should be planted right at the soil surface (not fully covered with soil) with the roots extending into the soil below. Always check for proper planting techniques for the species you’re handling.

Mulch such as compost, shredded bark, pine needles, etc. may be applied for weed control, moisture retention and soil cooling. Avoid mulch deeper than 2 inches and keep the mulch away from plant stems.

Planting should be followed promptly by thorough watering. A dilute liquid starter fertilizer may be included in this irrigation.

Management

Water (from irrigation or rainfall) is essential for newly planted perennials, especially during the early part of the establishment period. In most years in Indiana, it is desirable to be able to irrigate perennial plantings during the hottest, driest parts of summer. In some years with an extended period of heat and dryness, supplemental irrigation may be essential for plant survival. However, perennials in unique sites, such as wet bog gardens or dry rock gardens may require special aspects of water management.

One or two fertilizations, in spring as growth commences , meet the needs of most perennials. The nutrient needs of perennials vary widely though, so you’ll need to check into specific plants. On average, one pound of 5-10-5 per 100 sq. ft. used in early spring and again 6-8 weeks later is adequate. Be sure dry granular fertilizer doesn’t rest on leaves or foliar burn may result. Wash it off with a light irrigation.

Continued soil building by adding organic matter should be done in the spring, too. Annually, add an inch or two of compost or other organic material along with the fertilizer described above. Work it in with the top few inches of soil around each perennial taking care to disrupt existing roots as little as possible.

Pinching of some perennials in spring through the end of June can promote branching, reduce overall plant size (to reduce flopping when in bloom) and prevent flowering until fall. Chrysanthemums and asters may be handled in this manner. Deadheading, or spent flower removal, may be practiced for aesthetic reasons, to reduce self-sowing, maintain compactness, and to promote stronger plant growth for future years. However, many perennials produce interesting fruits and dried flower structures. In addition, birds feed on the seeds of some perennials. They may be left on the plants to be enjoyed long after flowering is past.

An often overlooked aspect of growing perennials is plant support. Vining plants, obviously, require support such as a trellis or fence to grow on. Many other species do not perform well without supplemental staking to support weak stems bearing the weight of large flowers. Staking takes many different forms. Rough twiggy shoots (from the pruning of woody plants) can be placed in the ground extending above some perennial plants in the early spring. The perennial then grows up through the twigs hiding them, and the twigs lend support to the perennial. Wire or twine frames between stakes can function in a similar manner. Single stakes and plant ties can be effective for perennials that have a strong single stem growth habit. For perennials that tend to splay open from the center, such as peonies or false indigo (Baptisia), wire rings and stakes, a wire grid or linking stake frames are effective.

Weed control is not usually a major problem in established perennial plantings. Thin mulching may be used effectively in the first years to reduce weed presence. Later, hand pulling or shallow cultivation is usually sufficient. Occasionally persistent weeds may become a problem. Perennial grassy weeds such as quackgrass, for example, may be controlled using certain grass-selective herbicides. If a weed problem becomes bad enough, complete renovation involving lifting the perennials, attacking the weeds by hand removal, with non-selective herbicides or by soil fumigation, and replanting may be necessary.

Insect pests and diseases can be a problem in perennials. Regular monitoring of plant health and quick attention to problems is part of successful management.

All perennial plants expand over time, some slowly and some more rapidly. Most will grow undisturbed for many years. Examples of slow expanders are false indigo (Baptisia), poppies (Papaver), peony (Paeonia) and Lenten rose (Helleborus). Others, like iris (Iris) may benefit from division more often. If plants become crowded, they should be divided. Division can rejuvenate a planting, reduce the size of a planting, or restart a plant in its proper location after the center has died out. Division is done in spring for many species, and may generally be done in any non-bloom season. Bearded iris, for example, grow less actively in mid-summer so that is optimum timing for their division. Showy stonecrop (Hylotelephium) blooms in fall, so spring division is best.

Division consists of lifting the crown and roots of the plant from the soil and separating it into pieces. Each piece must have functional crown tissue (usually with buds) attached to functional roots. The division may be done with just hands, with one or two digging forks, or may require a knife or other cutting tool. Each perennial species divides in its own unique way so check the proper method for the species you handle. Re-set the plants at about the same depth as they were growing prior to lifting. A few may be set just slightly lower, some a bit higher to allow for settling of the soil.

Transplanting of perennials is sometimes required as design changes are made or landscape conditions evolve and change. Transplanting consists of lifting whole plants, intact, with a large clump of soil adhering to the roots and replanting immediately. It should be done in spring or early fall, and should be followed with thorough watering. If transplanting must be done in summer, plant tops should be cut back somewhat to reduce water loss.

After a few hard freezes, the perennial planting may be cleaned up and dead plant tops moved off-site or to the compost pile. A short piece of stem may be left in some cases to mark plant locations. In this way, late emerging perennials such as butterfly milkweed (Asclepias) may be saved from inadvertent damage. Alternatively, plant debris may be left in place over winter to offer habitat and promote bio-diversity.

Once the ground is frozen, but before severe cold weather occurs, a winter mulch of several inches of organic material may be useful to protect from frost heaving any perennials that were planted or transplanted late. Winter mulching can also help protect marginally hardy species from the coldest temperatures of winter. Winter mulches should be pulled away from plants in early spring before or just as new growth emerges.

Hardy Bulbs

General

Most hardy bulbs are spring blooming. These include the larger plants such as tulips (Tulipa) and daffodils (Narcissus), and minor bulbs such as crocus (Crocus) and snowdrops (Galanthus). The spring blooming bulbs go dormant during the summer and are not seen above ground at that time. They require the low temperature exposure of winter before they will bloom again. Some hardy bulb species are summer blooming, such as true lilies (Lilium). Lilies are often used with other perennials and their cultural requirements are similar to many perennials.

Site Selection

Most hardy bulb species require full sun. However, many spring bloomers complete their growth period prior to the leaf-out of deciduous trees in the spring. Thus, a site that is shady in mid-summer may be suitable for bulbs due to the high light level in the spring. Lilies need full sun and, for those that grow very tall, should be located out of strong winds. Cool soil temperatures are best for lilies, so mulch or shade from surrounding plants is desirable.

Soil Preparation

Soil for growing hardy bulbs should be like that for annuals (see above), except bulbs, on average, require even better drainage. Attempting to grow bulbs in soil that retains too much water, especially in winter, will result in bulb rot and death. A sandy loam is ideal. Consider soil replacement to improve very poorly drained sites, or make raised beds.

Depth of soil preparation should be deeper than for annuals, to 12” or more. Large bulbs are often planted 6” below the soil surface and then need another 6” or more for the roots to penetrate into the soil below the bulb. Fertilizer should be worked into the planting soil prior to planting bulbs. Use a complete fertilizer such as 5-10-10 (or equivalent) at a rate of 2 to 4 pounds of fertilizer per 100 sq. ft. of bed area.

Planting

Plant only good quality, large bulbs for the best landscape performance. Bulbs should be firm and heavy with the tip and basal plate intact. The surface should be free of substantial injuries and of even color.

The planting period for hardy bulbs is from late August until November (or until the ground freezes). The later the planting, the less time the plant will have to develop strong roots to support spring flowering.

Spacing of bulbs depends on desired effect and budget. High impact is gained with tulips spaced just 4” apart, but wider spacing can expand the size of a planting with the same quantity of bulbs. Daffodils may be spaced more widely as they will expand over time and need room to grow before becoming overcrowded. If bulbs are used with other plants such as among shrubs or perennials, groups of bulbs are generally more effective than widely spaced individual plants.

Bulbs can be planted using a trowel, bulb planter, or power auger. Pre-determine each bulb location, excavate, and then place each bulb in its hole at correct depth. A handy rule-of-thumb is to plant bulbs at a depth 2.5-3 times the bulb’s height. Be sure the top of the bulb (usually some-what pointed) is facing upward. For mass plantings, an entire bed may be excavated to proper depth, bulbs placed, and then covering soil carefully added over the top.

Certain newly planted bulbs in loose recently-worked soil, and even long established bulbs can be targets for rodents. Tulips, crocus and some minor bulbs may be destroyed by the feeding of chipmunks, squirrels or mice. To help prevent damage from these pests, lay fine mesh hardware cloth over bulb beds. This remedy will not prevent animals from burrowing to deeper bulbs. Hardware cloth placed in the ground surrounding such bulbs is effective, but is not practical on a large scale.

Irrigate following planting to settle the soil around the bulbs. Mulch may be useful following planting. It should typically be applied after the ground is frozen to minimize freeze-thaw cycles that can disrupt newly planted bulbs. In cases where bulb planting was done very late (i.e. December), mulch may be useful immediately following planting to help keep the ground warm to extend the season for root growth.

Management

The Indiana climate generally provides adequate moisture for hardy bulbs. If natural rainfall is below normal amounts during the spring period of active growth, apply supplemental water. Flooding or soaker hoses are better than overhead sprinklers.

A complete fertilizer such as 5-10-10 (or equivalent) should be applied annually to bulb plantings as the plants emerge. Application rate should be 1-2 pounds per 100 sq. ft. with larger bulbs at the high end, minor bulbs lower.

Deadheading spent flowers before seeds enlarge is beneficial with the larger bulbs. It is generally impractical for minor bulbs.

The leaves of hardy bulbs should be allowed to grow for six weeks or so following the bloom period. This time is generally adequate to insure flowering the next year. During this time, do not bind the leaves together. To maximize bulb growth, allow leaves to stay on the plants until they begin to yellow and die back naturally.

An abundance of foliage with few or no flowers is an indication that bulbs have become crowded. Once the foliage dies, the bulbs can be lifted, divided, and replanted immediately or stored (70oF, dark and dry) and replanted in fall. Large bulbs may flower the following year; small bulbs will reach flowering size in future years.

Weeds are best controlled in bulb plantings by starting with a weed-free planting bed, applying a thin layer of organic mulch in early winter and hand weeding during the bulb flowering season. Cultivation and other measures including herbicides may be useful on the soil surface above bulbs during the bulb dormant season.

Insect pests and diseases are seldom a major problem in hardy bulbs in the landscape. Regular monitoring of plant health and quick attention to problems is part of successful management.

Ornamental Grass

General

The best ornamental grasses for use in conventional designed, developed and controlled Indiana landscapes are perennial, clump-forming, or “bunch” grasses that spread only very slowly by tillering. They may be native or introduced. They tend to stay as individual plants compared to the rhizomatous, or sod-forming turf grasses that are commonly used for lawns. Ornamental grasses range from a few inches to many feet tall and tolerate a variety of growing conditions.

Native ornamental grass species may be used in a more informal manner in which a clump forming growth habit is not as important. Interplanting grasses with other native perennials can create a meadow or prairie-like effect.

Some introduced species of ornamental grasses are INVASIVE. Chinese silver grass (Miscanthus) has spread into natural areas in Indiana. Cultivar selection and planting context are important for this species. A few new, sterile cultivars have begun to appear in the market. These should be given serious consideration. Fountain grass (Pennisetum) may be invasive into lawns via self-sowing. It should only be located where it is not adjacent to turfgrass.

Site selection

Almost all grasses require full sun to be at their best. A few tolerate various degrees of shade. Protection from the strongest winds is desirable, but some wind exposure usually results in a stronger, more “stocky” plant. Ornamental grass species can be found that will tolerate soil moisture conditions from continuously wet to consistently dry. It is critical to match the plant species choice to its site.

Soil preparation

Grasses are remarkably able to tolerate most “unimproved” soil conditions. However, like other perennials, they usually grow more vigorously and reach larger size if the soil conditions are favorable. Soil improvement for ornamental grasses is the same as described for perennials (see above).

Planting

The spacing of ornamental grasses is dependent on the desired landscape design effect and on the need for adequate room to grow to insure a healthy plant. Grass clumps expand in size over time so original plant spacing should allow room for this expansion. Tight spacing may be desirable in certain cases and inter-plant competition may slow the rate at which the clumps expand.

Container plants of varying sizes are the typical planting-out material for ornamental grasses. They may be nursery size containers (one gallon and up) or smaller units such as quarts or narrow, deep-root tubes. Plants of named cultivars are commonly produced by division from parent stock plants. When species plants are produced, especially natives that are intended for naturalizing, they are commonly grown from seed to maintain some degree of genetic diversity.

Planting is best done in spring or in late summer to early fall. In Indiana, that means April to early June and late August through early October. Remove the container completely. Loosen any tightly bound roots and plant them into the soil of the new location. If the container is a bio-degradable fiber pot, cut gashes in the sides of the pot in 5 or 6 places vertically, tear off the pot rim that extends above the soil in the pot, and then plant, pot and all. The finished planting depth should be the same as in the container.

Planting should be followed promptly by thorough watering. A dilute liquid starter fertilizer may be included in this irrigation.

Management

Irrigation is generally not needed in Indiana for most ornamental grasses, once they are established, except in the most severe conditions of drought. Wet site adapted plants are an exception. Grasses may grow somewhat smaller in a dry year compared to wetter conditions.

Annual fertilization with a complete fertilizer such as 10-10-10 (or equivalent) at one or two pounds per 100 sq. ft. is usually adequate. Don’t over fertilize. Grasses can become weak and flop over (lodge) if growth is too fast and soft.

Once each year, the dead vegetation should be removed from a grass plant. This is best done in very early spring, before new growth commences. Cut just above the crown. The shoots of some larger grass species can be quite woody and tenacious. A power hedger, weed whip, pruning loppers or a chain saw may be needed. Grasses may be cut back in late fall. However, any winter effects will be lost this way and some people suggest this may increase winter injury.

Periodic division of ornamental grasses nay be needed, but the frequency varies greatly among species. Some, such as feather reed grass (Calamagrostis) may go many years with little need for division. Others, like many Chinese silver grass (Miscanthus) cultivars tend to open up in the center of the clump after several years. When dividing, the entire grass clump should be lifted, then a part of the clump should be reset in the original planting location. Grass clumps of some larger species can be quite woody. Division may require use of an ax or saw in addition to a shovel. Do this work in late winter or early spring.

Ornamental grasses are generally free from pest problems. Regular monitoring of plant health and quick attention to problems is part of successful management.