Bulbs, Corms, Tubers, and Rhizomes
Making Sense of the Storage Structures of Summer-Flowering Plants

When many people think of bulbs, they think of spring flowering daffodils and tulips planted in the fall. These are hardy bulbs left in the ground over the winter. However, there are also summer flowering plants coming into bloom now and in the coming months that utilize bulb and bulb-like structures.

Bulbs and bulb-like structures can be put into categories including: true bulbs, corms, tubers/tuberous roots, and rhizomes. A plant’s underground storage structure functions to store nutrients for the plant. The plant can then access these nutrients during times when it is not flowering, like during the winter, hot summers, and droughts. Understanding the difference can help you better care for and propagate your favorite plants.

Take note that most summer-flowering bulbs are not hardy, they are planted in the spring after the danger of frost has passed. In the fall when the leaves turn yellow, most may be carefully dug up and stored in a frost-free location, like a garage. Some bulbs can survive in the ground over a mild winter, but use a very heavy layer of mulch for protection. Daylilies and iris are an exception as they are hardy and can handle cold winters in the ground.

Specialized storage organs, often referred to as bulbs.
Illustration and Caption credit: University of Georgia Extension.

True Bulbs:

A true bulb comprises overlapping layers like an onion. It has a growing point at the top and basal plate at the bottom where roots grow out of. Bulbs are planted upright. The outside of a true bulb forms into “scales”. On tunicate bulbs, the scales become dry and papery, serving as a protective layer around the bulb. On non-tunicate bulbs, like a lily, the scales can break off from the basal plate.

Examples:

• Lilly
• Alliums
• Amaryllis
• Grape Hyacinth

Sprouting bulbs.
Photo credit: Cornell Cooperative Extension Rockland County

Corms:

A corm is an underground solid stem enclosed by a dry outer covering. As with true bulbs, this outer covering protects the inner layers. The plant grows from the top of the corm. Corms only grow for one season, with new corms being produced. New corms are called cormels.

Examples:

• Gladiolas
• Ranunculus
• Freesia
• Crocosmia

Gladiola corms.
Photo Credit: Rutgers New Jersey Agricultural Experiment Station

Rhizomes:

A rhizome is a specific kind of stem which grows near the surface of the soil. They can be determinate or indeterminate, depending on whether or not they terminate in a stem. For example, an iris is determinate because the rhizome produces one stem, while Lilly-of-the-Valley is indeterminate because the rhizome produces many shoots. Rhizomes are planted on their sides. You may be familiar with what a ginger root looks like--it’s a rhizome.

 Examples:

• Canna
• Iris
• Daylilies
• Kniphofia
• Agapanthus
• Calla Lilly
• Lilly of the Valley
• Trillium
• Liriope

Canna rhizomes.
Photo credit: UMass Amherst Extension

Iris rhizomes.
Photo Credit: University of Maryland Extension

Tubers/Tuberous Roots:

Tubers are underground, fleshy, modified stem tissue. A potato is a tuber. Tubers have nodes or “eyes” capable of growing into a separate plant.

Tuberous roots form from the swelling of roots near the base of the plant. They do not have eyes and cannot regrow from root pieces. They lack nodes but can produce buds near the stem.

Examples:

• Dahlia
• Begonia
• Caladium
• Elephant Ear
• Peony

Dahlia tuberous roots planted in April by the Rutgers Master Gardeners of Burlington County
at the Burlington County Agricultural Center.

Photo credit: Alyson Ricketts, Rutgers Master Gardener of Burlington County

References and Additional Resources:

University of Illinois Extension: “Bulbs”
https://extension.illinois.edu/flowers/bulbs

Rutgers New Jersey Agricultural Experiment Station: “Spring Flowering Bulbs”
https://njaes.rutgers.edu/fs1220/

Rutgers New Jersey Agricultural Experiment Station: “Cannas”, Fact Sheet 1155.
https://njaes.rutgers.edu/pubs/publication.php?pid=FS1155

Rutgers New Jersey Agricultural Experiment Station: “Gladiolis murielae-Without Doubt a Beautiful Flower”
https://njaes.rutgers.edu/plant-of-the-month/gladiolus.php

Penn State Extension Chester County: “Bulbs, Corms, Rhizomes, and Tubers”
https://extension.psu.edu/programs/master-gardener/counties/chester/how-to-gardening-brochures/bulbs-corms-rhizomes-and-tubers

NC State Extension: “Summer and Fall-Flowering Bulbs for the Landscape”
https://content.ces.ncsu.edu/summer-and-fall-flowering-bulbs-for-the-landscape

NC State Extension: “Canna x generalis”
https://plants.ces.ncsu.edu/plants/canna-x-generalis/

University of Georgia Extension: “Flowering Bulbs for Georgia Gardens”
https://extension.uga.edu/publications/detail.html?number=B918&title=flowering-bulbs-for-georgia-gardens

University of Tennessee Agricultural Extension Service: “Flowering Bulbs for Tennessee Gardens”
https://www.shelbycountytn.gov/DocumentCenter/View/1120/Flowering-Bulbs?bidId=

 

 

Squash Vine Borer - Melittia cucurbitae

Introduction

The squash vine borer (Melittia cucurbitae) (SVB)  is an insect pest of plants in the cucurbit family like jack-o'-lanterns pumpkins, summer squash, acorn squash and zucchini. The plants most susceptible to attack by squash vine borers are squash and pumpkins but all cucurbits can be attacked.   Cucumbers and melons are less susceptible.

Natural History

USDA

Life Cycle: The life cycle of the squash vine borer typically begins with adult moths emerging from pupae in the soil or plant debris. These moths are active during the warm months, usually from late spring to early fall, depending on the region.

Adult Moths: The adult moths are approximately 1 inch long with a wingspan of 1 to 1.5 inches. They have clear wings with red-brown markings. After emerging, female moths seek out suitable host plants, particularly plants in the Cucurbitaceae family, such as squash, pumpkins, zucchini, and gourds, to lay their eggs.

Adult squash vine borer, Melittia cucurbitae (Harris). Photographs by Lyle J. Buss, University of Florida.

Egg Laying: Female moths lay eggs near the base of host plant stems or on the undersides of leaves. They typically prefer young, succulent stems for oviposition.

Squash vine borer egg on the left versus squash bug eggs on the right

Larval Stage: Once the eggs hatch, the larvae (caterpillars) bore into the stems of the host plants, where they feed and develop. The larvae have a cream-colored body with a brown head and are legless. As they feed, they create tunnels within the stems, causing wilting, stunting, and eventually plant death.

Squash vine borer and damage to summer squash

Pupal Stage: When larvae are fully grown, they exit the host plant and burrow into the soil or plant debris to pupate. The pupal stage lasts for several weeks, with adult moths emerging from pupae to continue the life cycle.

Overwintering: Squash vine borers overwinter as pupae in the soil or plant debris, emerging as adult moths in the following spring or summer to begin the cycle anew.

Host Plants: While squash vine borer larvae primarily infest plants in the Cucurbitaceae family, they may occasionally feed on other plants, such as sunflowers and some ornamental gourds.

Management Strategies

Managing squash vine borers can be challenging, but there are several strategies that gardeners can employ to minimize damage and protect their squash plants:

1. Cultural Practices:

   • Crop Rotation: Avoid planting squash, pumpkins, and other susceptible plants in the same area year after year.
   • Early Planting: Plant squash crops early in the season to allow them to mature before squash vine borer populations become significant.
   • Cleanliness: Remove and destroy plant debris at the end of the growing season to reduce overwintering sites for squash vine borer pupae.

2. Physical Barriers:

   • Row Covers: Cover young plants with floating row covers to prevent adult squash vine borers from laying eggs on the stems.
   • Collars: Place physical barriers such as aluminum foil, pantyhose, or cardboard collars around the base of stems to prevent larvae from burrowing into the plant.

3. Biological Control:

   • Beneficial Insects: Encourage populations of natural enemies such as parasitic wasps and predatory insects that prey on squash vine borer eggs and larvae.
   • Nematodes: Certain species of beneficial nematodes can help control squash vine borer larvae in the soil.

4. Chemical Control:

   • Insecticides: Apply insecticides containing active ingredients such as carbaryl, permethrin, or spinosad according to label instructions when adult moths are active or when larvae are young and vulnerable. Always read the label, follow safety precautions and consider using organic options if available.
   • Systemic Insecticides: Soil-applied systemic insecticides can provide protection against squash vine borers by being absorbed by the plant and killing larvae as they feed.

5. Monitoring and Early Detection:

   • Regularly inspect plants for signs of squash vine borer activity, including wilting, frass (sawdust-like excrement) at the base of stems, and entry holes.
   • Use yellow sticky traps to monitor adult moth activity and determine when to implement control measures.

6. Hand Removal:

   • If detected early, squash vine borer larvae can be manually removed from infested stems by carefully making a small incision with a knife and extracting the larvae.

Combining multiple management strategies is often the most effective approach to control squash vine borers and protect squash crops from damage. Additionally, maintaining overall plant health through proper watering, fertilization, and disease management can help plants withstand and recover from squash vine borer infestations.

Because of a similarity in names, the squash bug and squash vine borer can easily be confused with one another.  Here are some tips for distinguishing the two insects..

Appearance: 

Squash Bug: These bugs are typically brown or gray in color and are about 1/2 inch long when fully grown. They have a distinctive shield-like shape. 

Squash Vine Borer: The adult squash vine borer belongs to the Sesiidae (clearwing) family and is a moth that resembles a wasp. It has a black body with orange markings and clear wings. The larvae, however, are white with brown heads and can grow up to 1 inch long. 

Adult Squash Vine Borer

Adult Squash Bug

Behavior: 

Squash Bug: Squash bugs primarily feed on the sap of squash plants by piercing the plant with their mouthparts. They can also transmit diseases to the plants. 

Squash Vine Borer: The adult moth lays eggs at the base of squash plants, and the larvae bore into the stems, feeding on the interior tissue. This feeding disrupts the flow of nutrients, causing the plant to wilt and eventually die. 

Damage: 

Squash Bug: Squash bugs cause damage by sucking the sap from leaves, stems, and fruit. This can lead to wilting, yellowing, and stunted growth. They can also transmit bacterial wilt, a disease that can quickly kill plants. 

Squash Vine Borer: The larvae of squash vine borers tunnel into the stems of squash plants, causing wilting, collapse, and death of the affected vines. Infested plants often exhibit sawdust-like frass at the base of the stems, which is a telltale sign of squash vine borer activity.

Additional Information

Squash Vine Borer Fact Sheet 229 - Rutgers University - NJAES

Squash Vine Borer - University of Florida - IFAS

Squash Vine Borer - UMass Extension

Life Cycle Graphic - University of Arkansas Extension

Squash Vine Borer - Biology and Management

Squash Vine Borer versus Squash Bug - University of Kentucky - Department of Entomology

Squash-Vine-Borers Chemical Controls - University of Minnesota Extension

Right Tree for the Right Place!

How to Plant New Trees in the Home Garden

As the weather warms in springtime, many home gardeners consider incorporating new trees into their landscape.  Additionally, April in many communities has been given the moniker of “Earth Month” when environmentalists celebrate by planting trees.  The importance of trees cannot be underestimated as they help improve air quality, provide wildlife habitat, control erosion, offer shade, produce fruit, and are also visually pleasing. Trees are an integral part of our everyday lives.

However, the most important thing to keep in mind is to plant the right tree in the right place. The decisions regarding what kind and where to plant trees should be given careful consideration. Since trees are meant to be long-term fixtures of an environment, taking steps at planting time to ensure healthy growth and longevity is essential for success.

Photo Credit: Oklahoma State University

Tree Selection:

Several factors should be considered while deciding on the type of tree best suited to the landscape. Again, pick the right tree for the right place.

Hardiness: Will the tree survive cold and hot temperatures?

Light Requirements: Does the tree require full sun or can it be grown in shade?

Water Requirements: How much water does the tree need to achieve healthy growth?

Size and Shape at Maturity: How tall and wide will the tree grow?

Ornamental Value: Is the tree visually pleasing?

Maintenance: Does the tree drop its leaves or needles in the autumn?

Use: Is the tree being used to provide privacy or block something unsightly? Is the tree being used to produce food? Will it help with erosion control?

Native/Non-Native/Invasive: Will the tree be part of a landscape with other natives? Could the tree be potentially invasive?

·

 Purchasing Trees:

Trees can be purchased in either in a container, balled with burlap and twine, or bare root. Bare root trees do not have any dirt attached to their roots making it easier to buy from mail-order nurseries. Bare root trees must be planted before they break dormancy in the spring or planted in the late fall after leaf drop. Balled and burlapped trees have the soil and roots contained within the burlap. Trees in containers have been dug and then placed in the pot with soil or potting mix.

 Site Selection:

Consider the space you have above the ground. Be mindful of what size the tree will be at maturity. Don’t plant too close to surrounding structures, other trees, or powerlines. Also consider the space you have below ground for the roots to grow out. Be mindful of the depth of your soil as well as proximity to buildings, sidewalks, and roadways. A proper site will give the tree access to adequate water and sunlight. A soil test may be used to assess the soil pH and available nutrients.

 Timing:

The best time to plant trees is in the fall after the tree has gone dormant or spring before the buds begin to open. Do not attempt to plant trees when the ground is frozen solid or during the heat of summer when water loss may become an issue. Planting should be done when temperatures are moderate.

Planting:

Planting depth is very important . A hole should be dug two to three times the diameter of the root ball and only just as deep. The basal flare (where the roots meet the trunk) should not be covered with soil. The flare should sit just above the soil line. Beware of planting trees too deeply. Sometimes the root ball can settle after planting, resulting in the trunk becoming covered with soil. If the roots are balled, remove the twine and burlap before placing the tree in the hole to free up the roots. With potted trees, it may be necessary to gently loosen pot bound roots before planting to avoid girdling.

When placing soil back into the hole, use the original/native soil. It is not recommended to use compost, fertilizer, or potting mix because the added nutrients will eventually constrain root growth. Water thoroughly after planting. Allow to soil to settle in around the roots. Create a basin around the tree by creating a planting berm (a few inches tall) with soil for water retention.

Do not prune trees at planting time as leaves will help the tree develop a better root system. If high winds are an issue at the site, consider staking the tree to prevent the root ball from moving.

 

Figure Credit: University of New Hampshire Extension Fact Sheet,
“Planting and Mulching Trees and Shrubs”, Cathy Neal, Extension Professor/Specialist

Watering:

Regular watering is required, especially during hot and dry months until the tree has time to get established. Keep in mind trees need several years of steady moisture to maintain proper health. The soil around the root ball should be kept moist, but not waterlogged. Monitor the soil moisture to ensure it is not over or underwatered.

Mulching:

Several inches of mulch may be used to suppress weeds and preserve soil moisture. However, keep mulch a few inches away from the trunk to limit bark decay and discourage overwintering rodents.  Do not over-mulch trees or create a “volcano” like mound at the base. This will lead to slow growth and decline by stressing the tree. Mulch can deprive the tree of oxygen and trap excessive moisture against the root flare.

 

Mulch piled against a trunk.
Caption and photo credit: Rutgers University Extension Fact Sheet 099,
“Problems with Over-mulching Trees and Shrubs”

Pruning:

Keep in mind that many trees will need proper pruning at some point in order to remove dead or diseased wood and to maintain the tree’s shape. Depending on the age and size of the tree, different pruning methods and tools may apply. Research the type of tree you have and the proper way to prune it. For example, fruit trees have different pruning needs than other trees. Do not climb into trees, rather leave this type of work for a certified arborist.

 

 Additional Information:

Rutgers University Agricultural Extension: “Transplanting Trees and Shrubs”
https://njaes.rutgers.edu/pubs/publication.php?pid=fs376

Rutgers University Agricultural Extension: “Problems with Over-Mulching Trees and Shrubs”
https://njaes.rutgers.edu/fs099/

Penn State Extension: “Pruning Landscape Trees”
https://extension.psu.edu/pruning-landscape-trees

University of New Hampshire Extension: “Planting and Mulching Trees and Shrubs Fact Sheet”
https://extension.unh.edu/resource/planting-and-mulching-trees-and-shrubs-fact-sheet

The Arbor Day Foundation: “Planting the Right Tree in the Right Place”
https://arbordayblog.org/treeplanting/need-know-planting-right-tree-right-place/

Trees Are Good: “Tree Owner Information”
https://www.treesaregood.org/treeowner

 

Spring Invasive - Lesser Celandine - A Springtime Menace

As the winter chill begins to thaw and the first signs of spring emerge, one of spring's ephemeral flowers makes its debut: the lesser celandine (Ficaria verna previously Ranunculus ficaria L.). Often heralded as a harbinger of spring, this petite yet vibrant plant holds a unfavorable place in the hearts of nature enthusiasts and gardeners alike. 

Botanical Characteristics: 

Belonging to the buttercup family (Ranunculaceae), lesser celandine is a low-growing perennial herb native to Europe, western Asia, and northern Africa. It typically blooms from March to May, carpeting woodland floors, meadows, and riverbanks with a burst of golden-yellow blossoms. Each flower consists of eight to twelve glossy petals surrounding a bright yellow center, creating a striking contrast against the lush green foliage. 

Lesser Celandine, a.k.a. Fig buttercup (Photo: David Nicholls, NatureSpot.org National Biodiversity Network Trust [NBN Trust], UK)

Map of Lesser Celandine’s invasive range in the United States and Canada

Source: https://plants.usda.gov/core/profile?symbol=RAFI

Ecological Impacts: 

Despite its delicate appearance, lesser celandine plays a crucial role in undermining biodiversity. In its introduced range, it arrives very early in the spring, this gives the invasive plant an advantage over native ephemerals such as mayapple or Dutchman’s breeches that are still mostly dormant in those temperatures.  It spreads out over the ground, creating a thick carpet, making it virtually impossible for native understory plants to grow and survive.  Native wildflowers and pollinators are particularly negatively impacted by this invasive specieshroughout history, lesser celandine has been intertwined with various cultural beliefs and folklore. 

Cultural and Folklore Significance

In ancient Greece, it was associated with the god of love, Eros, and was believed to have the power to attract affection. In Celtic mythology, it was considered a symbol of regeneration and renewal, often appearing in springtime celebrations. In Christian tradition, the lesser celandine is sometimes known as “pilewort” due to its traditional use in treating piles or hemorrhoids. Legend has it that the plant’s knobby tubers, resembling piles, were thought to possess healing properties. 

Garden Cultivation and Management: 

Gardeners should avoid incorporating lesser celandine into their landscapes, because of its vigorous growth habit.  Controlling lesser celandine can be challenging due to its ability to spread rapidly. Here are some methods to control it:

• Hand-pulling: Remove lesser celandine by hand, making sure to remove the entire plant including the tubers. This is most effective when the soil is moist, making it easier to pull out the roots.
• Mulching: Apply a thick layer of mulch, such as wood chips or straw, to smother lesser celandine and prevent it from receiving sunlight.
• Herbicides: Selective herbicides containing glyphosate or triclopyr can be effective in controlling lesser celandine. Always follow the manufacturer's instructions carefully when using herbicides.
• Repeat treatments: Since lesser celandine can regrow from small root fragments, it may be necessary to repeat treatments multiple times to completely eradicate it.
• Plant competition: Planting competitive native species in the area can help suppress the growth of lesser Celandine.

Remember to combine methods for the most effective control of lesser celandine, and be persistent in your efforts to prevent its spread.

Despite its allure, it’s important to exercise caution and not introduce lesser celandine to a garden setting. In New Jersey, where it is not native, the plant can become invasive, outcompeting native species and disrupting delicate ecosystems. Therefore, it’s crucial to consider alternative native plants that offer similar benefits without posing a threat to the environment. 

Additional Information

Native Plants of New Jersey - New Jersey Native Plant Society

Lesser Celandine - University of Maryland Extension

Lesser Celandine - USDA Plant Database

 

Spring Weeds: Deadnettle and Henbit. What's the difference?

Its spring and spring plants are beginning to flower.  Have you ever notice the little purple/pink flowering plants that appear in your gardener on your walks? They are probably two of the most common spring weeds found in gardens: deadnettle or henbit.  How can you tell them apart?

Deadnettle or purple deadnettle and henbit are often mistaken for each other.  Once you know what to look for they are easy to differentiate.  First some background.  In some of the literature you will see these plants referred to as purple deadnettle(Lamium purpureum) and henbit deadnettle (Lamium amplexicaule).  Unlike some other nettles, these deadnettles do not sting.  In other words it is a "dead" nettle.  The common name henbit comes from observations that chickens like to eat it.

Deadnettle and henbit are winter annuals.  Both plants germinate in the fall and resume growth in the spring as the temperature rises, they set seed and then die in the late spring or early summer.

Square (quadrangular) stems

Purple deadnettle and henbit are members of the Laminaceae (also Labiatae) mint family.  There are over 250 genera of mints and approximately 7000 species.  Mints range in size from small herbaceous plants like henbit and purple deadnettle to trees.  There are certain characteristics that are common to all mints:

• Square stems
• Opposite, fragrant leaves
• Bilabiate flowers 
• Flowers ovary is segmented in four lobes

Purple deadnettle (on the left) and henbit (on the right) have square stems which are a common identification characteristic of members of the mint family.

Henbit - Photo by Dr. John Meade, weed scientist emeritus

Rutgers NJAES Cooperative Extension

Henbit (Lamium amplexicaule)

Lamium amplexicaule L. - henbit deadnettle - Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 3: 121. Provided by Kentucky Native Plant Society. Scanned By Omnitek Inc.- USDA Image Library

Henbit has petioles on the lower leaves but not the upper leaves.  The upper leaves are clasping, hence 

the species name amplexicaule which means clasping.

Deadnettle - Photo by Dr. John Meade, weed scientist emeritus
Rutgers NJAES Cooperative Extension

Deadnettle (Lamium purpureum)

Lamium purpurem L. - purple deadnettle - Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 3: 121. Provided by Kentucky Native Plant Society. Scanned By Omnitek Inc. - USDA Imahe Library

The leaves on deadnettle all have petioles.  The length of the petioles tend to get smaller as you move upward on the plant.  The upper leaves on henbit do have petioles and leaves on the lower portion of the plant have long petioles.

Deadnettle (on the right)  and Henbit (on the left) Leaves

Notice that the leaves on the deadnettle are more triangular in shape and not as deeply lobed as the leaves on the henbit.  The leaves of henbit have a more rounded shape, are deeply veined and have hairs on the upper and lower surfaces.

Visit the weed control links listed below for information on controlling these weeds around the home or in the lawn.

NOTE: Always read and follow herbicide directions carefully. Do not use herbicides for controlling broadleaf weeds in turf such as dandelion in or near ornamental planting beds. If weeds are a persistent problem in landscape planting beds homeowners may wish to consult with a professional landscape contractor. 

Additional Information

New Jersey Weed Gallery - Rutgers NJAES Cooperative Extension

Weed Control in Home Lawns - Rutgers NJAES Cooperative Extension

Weed Control around the Home Grounds - Rutgers Cooperative Extension

Meet the Mints - University of Georgia

Illustrated Glossary - Flora of the Chicago Region -Conservation Research Institute

Henbit - Purdue University