How to divide hostas in fall a garden guide

How to divide hostas in fall sets the stage for this enthralling narrative, offering readers a glimpse into a story that is rich in detail and brimming with originality from the outset. It’s like finding a secret passage in your own backyard, where the ordinary transforms into the extraordinary, and the humble hosta reveals its potential for even more garden glory.

Get ready to dig in, because we’re about to unlock the secrets of propagating these leafy beauties when the air gets crisp and the leaves start to turn.

This isn’t just about chopping up plants; it’s about understanding the rhythm of nature and giving your hostas a fresh start. We’ll delve into why fall is actually the prime time for this garden magic, what tools you’ll need to feel like a seasoned pro, and the exact steps to get those divisions thriving. Think of it as a horticultural makeover, where you’re the stylist, and your hostas are the eager clients ready for a fabulous transformation before winter’s slumber.

Understanding the Ideal Timing for Hostas Division

Dividing hostas in the fall offers distinct advantages for both the plants and the gardener. This period allows hostas to establish themselves before winter dormancy and provides a less stressful transition compared to other times of the year. Understanding the optimal conditions and plant signals is key to successful fall division.The autumn season presents a unique set of environmental factors that are highly conducive to successful hosta division.

These conditions minimize stress on the plant and promote robust root development, setting the stage for vigorous growth in the following spring.

Optimal Fall Weather Conditions

The ideal weather for dividing hostas in the fall is characterized by cooler temperatures and increased soil moisture. This environment mimics the conditions that naturally encourage root growth and establishment.

• Cooler Temperatures: Ambient temperatures between 45°F and 65°F (7°C and 18°C) are ideal. This range significantly reduces the risk of heat stress and wilting after division, allowing the plant to focus energy on root development rather than leaf transpiration.
• Adequate Soil Moisture: Moist, but not waterlogged, soil is crucial. The ground should be pliable enough to dig without excessive force, which can damage roots. A light rain a day or two before division is beneficial, or watering the area thoroughly if the soil is dry.
• Reduced Sunlight Intensity: Shorter days and less intense sunlight in fall contribute to a less stressful environment for the divided hostas. This reduces the need for the plant to expend energy on photosynthesis and allows for more resources to be directed towards root establishment.

Hosta Plant Indicators for Fall Division

Observing specific characteristics of the hosta plant itself can signal its readiness for division in the autumn. These signs indicate that the plant has completed its active growing season and is preparing for dormancy, making it receptive to being divided.

• Reduced Growth Rate: As temperatures cool, the visible growth of the hosta will naturally slow down. New leaf production will cease or significantly decrease, and the plant will appear to be entering a resting phase.
• Fading Foliage: While not all hostas display dramatic fall color, the overall vibrancy of the foliage will diminish. Leaves may start to yellow or droop slightly, indicating a natural decline in photosynthetic activity.
• Established Size and Clump Density: Hostas that have been in the ground for at least three to five years and have formed a dense, large clump are typically good candidates for division. Overcrowding within the clump can lead to reduced vigor and flowering.

Benefits of Fall Hosta Division

Dividing hostas in the fall offers several advantages over spring division, primarily related to plant health, establishment, and gardener convenience.

• Enhanced Root Establishment: The cooler soil temperatures in fall promote root growth. Roots are less stressed by heat and can begin to colonize the new soil before the ground freezes, leading to stronger establishment for the following spring.
• Reduced Transplant Shock: With less foliage to support and cooler ambient temperatures, divided hostas experience less wilting and transplant shock. This allows them to recover more quickly and dedicate energy to root development.
• Gardener Convenience: Fall is often a less busy gardening season for many, providing more time to focus on tasks like division. The cooler weather also makes the physical labor of digging and dividing more comfortable.
• Improved Plant Health: Dividing overcrowded clumps in the fall can improve air circulation and reduce competition for nutrients and water among the remaining plants, leading to healthier, more vigorous growth in the future.
• Early Spring Bloom Potential: Hostas divided and replanted in the fall have a greater chance of establishing a strong root system, which can contribute to better flowering in their first spring after division compared to those divided later.

Essential Tools and Preparation for Fall Hosta Division

Successfully dividing hostas in the fall requires careful planning and the right equipment. Proper preparation ensures a smoother process, minimizes stress on the plants, and sets the stage for healthy regrowth in the following spring. This section details the essential tools and preparatory steps necessary for effective fall hosta division.

Dividing hostas in fall, much like planning for a joyous occasion, requires thoughtful preparation. Consider it a prelude to celebrating new beginnings, not unlike how you might learn how to host a housewarming party. Once the guests depart and the festivities wind down, you can return to tending your garden, ensuring your hostas thrive with their timely division.

Step-by-Step Guide to Dividing Hostas in Fall

Dividing hostas in the fall is a rewarding process that rejuvenates mature plants and expands your collection. This guide Artikels the essential steps, from excavation to replanting, ensuring a successful division for healthy, thriving hostas. Careful execution at each stage is crucial for minimizing stress on the plants and promoting robust new growth in the spring.

Excavating the Hosta Clump

The initial step in dividing hostas involves carefully unearthing the entire clump. This requires patience and the right tools to avoid damaging the root system. The goal is to lift the entire plant with as much of its root ball intact as possible.

To excavate the hosta clump:

• Begin by loosening the soil around the perimeter of the hosta using a garden fork or spade. Insert the tool about 6-8 inches away from the center of the plant to avoid cutting through major roots.
• Gently work the fork or spade deeper into the soil, gradually undercutting the root ball.
• Once the soil is sufficiently loosened, carefully lift the entire clump from its original location. If the clump is very large or heavy, you may need assistance.
• Place the excavated clump on a tarp or a designated work area to prevent soil loss and make cleanup easier.

Physically Separating the Hosta Root Ball

After excavating the hosta, the next critical phase is dividing the clump into smaller, manageable sections. This can be achieved through several methods, depending on the size and density of the root ball. Each section should ideally contain both roots and at least one healthy “eye” or growing point.

Methods for separating the root ball include:

• Using Hands: For smaller, less dense clumps, you can often pull the sections apart by hand. Gently tease the roots apart, working from the outer edges inward.
• Using Two Garden Forks: This is a common and effective method. Insert the tines of two garden forks back-to-back into the center of the clump. Then, twist the handles in opposite directions to split the root ball. Repeat this process as needed to achieve the desired section size.
• Using a Sharp Spade or Knife: For very dense or woody root balls, a sharp, clean spade or a sturdy knife may be necessary. Carefully cut through the root ball, ensuring each division has a portion of the crown and roots. Clean the cutting tool between each cut to prevent disease transmission.

Trimming Damaged or Excessively Long Roots

Once the hosta clump has been divided into smaller sections, it is important to prepare the roots for replanting. This involves removing any damaged or overly long roots, which can improve the plant’s ability to establish in its new location and reduce the risk of rot.

To trim the roots:

• Inspect the roots of each divided section. Look for any broken, mushy, or discolored roots, which indicate damage or disease.
• Using clean, sharp pruning shears or a knife, trim away all damaged roots. Make clean cuts to promote healthy healing.
• If any roots are excessively long and appear to be tangled or would be difficult to accommodate in the new planting hole, trim them back. Aim to maintain a balanced root system, generally no longer than 4-6 inches for most divisions.
• It is also beneficial to remove any soil that is tightly bound to the roots, as this can sometimes harbor pests or diseases. A gentle rinse under water can be helpful for this.

Replanting Divided Hostas

The final stage of the division process is to replant the divided hosta sections into their new homes. Proper planting techniques will ensure that the hostas establish quickly and thrive. This involves selecting an appropriate location, preparing the soil, and planting at the correct depth.

Steps for replanting divided hostas:

1. Select New Locations: Choose planting sites that offer the appropriate amount of shade and moisture for the specific hosta variety. Ensure the soil is well-draining.
2. Prepare Planting Holes: Dig a hole that is at least twice as wide as the root ball of the division and deep enough to accommodate the roots without bending them.
3. Amend the Soil: Mix compost or other organic matter into the soil removed from the planting hole. This will improve soil structure and fertility.
4. Position the Division: Place the hosta division in the center of the hole. The top of the root ball and the crown (where the leaves emerge from the roots) should be level with or slightly above the surrounding soil surface. Avoid planting too deep, as this can lead to crown rot.
5. Backfill the Hole: Fill the hole with the amended soil, gently firming it around the roots to eliminate air pockets.
6. Water Thoroughly: Water the newly planted hosta divisions deeply to settle the soil and provide essential moisture for root establishment.
7. Mulch: Apply a layer of mulch around the base of the plant, keeping it a few inches away from the crown. Mulch helps retain moisture, suppress weeds, and regulate soil temperature.

Post-Division Care for Hostas in Fall: How To Divide Hostas In Fall

Proper aftercare is crucial for the successful establishment and overwintering of newly divided hostas. The fall season presents unique challenges and opportunities for ensuring these plants thrive through their first winter in their new locations. Attention to watering, mulching, and protection will significantly impact their future growth and vigor.The transition to a new planting site can stress any plant, and hostas are no exception.

Providing the right environment and support in the fall months helps them recover from the division process and prepare for dormancy. This period is not about encouraging new growth, but rather about facilitating root development and preventing desiccation and frost damage.

Watering Requirements for Newly Divided Hostas in Autumn

Newly divided hostas require consistent moisture to help them establish new roots and recover from the transplant shock. While the cooler temperatures and increased natural precipitation of fall generally reduce watering needs compared to summer, it is essential to monitor soil moisture levels diligently. Overwatering can lead to root rot, especially as temperatures drop and microbial activity slows, while under-watering can cause the delicate new roots to dry out and die.The goal is to maintain a consistently moist, but not waterlogged, soil environment.

This encourages the plant to invest energy in root growth rather than foliage. As winter approaches and the plant begins to enter dormancy, watering frequency can be reduced, but the soil should not be allowed to become completely dry.

• Check the soil moisture by inserting a finger about two inches deep. If it feels dry, watering is necessary.
• Water deeply to encourage root penetration into the surrounding soil.
• Water in the morning to allow foliage to dry before nightfall, reducing the risk of fungal diseases.
• Reduce watering frequency as the weather consistently cools and the hostas show signs of natural senescence (leaf yellowing and dying back).
• Ensure good drainage to prevent water from pooling around the crowns of the divided plants.

Importance of Mulching Around Divided Hostas After Replanting

Applying a layer of organic mulch around newly divided and replanted hostas in the fall offers several significant benefits. Mulch acts as a protective blanket, moderating soil temperatures, conserving moisture, and suppressing weeds that would compete for resources. This protection is particularly vital for divisions that may not have developed an extensive root system before winter.Mulching helps to insulate the soil, preventing extreme temperature fluctuations.

This is beneficial in early fall when daytime temperatures can still be warm, and in late fall and winter, when freezing and thawing cycles can heave plants out of the ground, damaging roots. A consistent soil temperature also supports ongoing, albeit slow, root development.

• Apply a 2-3 inch layer of organic mulch, such as shredded bark, compost, or straw.
• Keep the mulch a few inches away from the crown of the hosta to prevent moisture buildup and potential rot.
• Mulch helps retain soil moisture, reducing the need for frequent watering.
• It insulates the soil, protecting roots from extreme temperature fluctuations and frost heave.
• Mulch also suppresses weed growth, which can compete with the young hostas for water and nutrients.

Protecting Divided Hostas from Early Frost or Winter Conditions

While hostas are hardy perennials, newly divided plants are more vulnerable to the stresses of early frost and harsh winter conditions. Their reduced root mass means they have less stored energy and a diminished capacity to withstand extreme cold or desiccation. Proactive protection measures can significantly improve their survival rate and ensure a strong start in the spring.The primary concerns are frost damage to any remaining foliage, which can weaken the plant, and the risk of the crown freezing and thawing repeatedly, leading to heaving and root damage.

Protecting the plant’s crown and any tender new growth is paramount.

• For divisions planted in late fall, consider covering them with a layer of evergreen boughs or straw once the ground begins to freeze. This provides insulation and prevents rapid temperature changes.
• If an early frost is predicted and the hostas still have significant green foliage, a light covering of horticultural fleece or burlap can offer temporary protection. Remove the covering once the frost danger has passed to allow for air circulation.
• Ensure the planting site has excellent drainage. Waterlogged soil is more prone to freezing and thawing cycles, which can damage roots.
• Avoid fertilizing in late fall, as this can stimulate new, tender growth that is susceptible to frost damage.

Approaches to Fertilizing Divided Hostas in the Fall

Fertilizing newly divided hostas in the fall is generally not recommended, as the primary goal during this period is root establishment and preparation for dormancy, not active growth. Introducing fertilizers can stimulate new foliar growth, which is tender and vulnerable to frost damage. Furthermore, it can encourage root growth at a time when the plant should be slowing down its metabolic processes in preparation for winter.Instead of fertilization, focus on providing the necessary conditions for the plant to recover and overwinter successfully.

The nutrients from the soil and any organic matter in the mulch will typically suffice for the plant’s needs during this transitional phase.

• Avoid using synthetic fertilizers on newly divided hostas in the fall. These can promote growth that is not hardened off before winter.
• If a soil amendment was incorporated during the division and replanting process (e.g., compost), this often provides sufficient nutrients for the fall and winter.
• The focus should be on encouraging root development through adequate watering and soil moisture, not on stimulating above-ground growth.
• Any necessary fertilization should be deferred until early spring, when the hostas begin to actively grow and can utilize the nutrients effectively.
• The organic matter from mulch will break down slowly over winter and early spring, providing a gentle release of nutrients that supports healthy spring growth without the risk of overstimulation.

Common Challenges and Solutions in Fall Hosta Division

Dividing hostas in the fall, while generally advantageous, can present a few challenges that, if anticipated and addressed, can ensure the success of the operation. Understanding these potential issues and their practical solutions is crucial for a smooth division process and healthy, thriving hostas in the subsequent growing season.This section will detail common problems encountered during fall hosta division and provide actionable strategies to overcome them, ensuring the well-being of both the parent plant and its divided sections.

Root Rot Prevention and Management

Root rot is a significant concern, especially when dividing plants in cooler, moister fall conditions. Excessive moisture retained in the soil can lead to fungal diseases that attack weakened root systems.

To mitigate the risk of root rot:

• Ensure excellent drainage in the planting location. Amending the soil with organic matter like compost or well-rotted manure can improve aeration and water percolation.
• When dividing, carefully inspect the roots for any signs of decay, such as mushy, dark, or foul-smelling sections. Remove any affected parts with a clean, sharp knife or trowel.
• Allow the cut surfaces of the divided root balls to air dry for a few hours before replanting. This helps to callus over any wounds, reducing susceptibility to infection.
• Avoid overwatering newly divided hostas. Water them thoroughly only when the top inch of soil feels dry to the touch.
• Mulch lightly around the base of the divided plants, keeping the mulch a few inches away from the crown to prevent moisture buildup.

Handling Dense Root Systems

Some hosta varieties develop exceptionally dense and intertwined root systems, making separation a physically demanding task. Forcing the separation can damage delicate roots, hindering establishment.

Strategies for tackling dense root balls include:

• Soaking: Submerging the entire root ball in a tub of water for an hour or two can help to loosen soil and make it easier to identify individual crowns and root sections.
• Gentle Teasing: After soaking, use your fingers or a blunt tool, like a wooden dowel or the handle of a trowel, to gently tease the roots apart. Work from the outside in, following the natural growth lines of the plant.
• Strategic Cutting: If teasing is not effective, a sharp, clean spade or a stout knife can be used to cut through the root ball. Aim for clean cuts between crowns, minimizing damage to the main root mass. For very tough root balls, a reciprocating saw with a clean blade can be employed as a last resort, though extreme care is necessary.

• Divide Larger Sections: If a large clump is proving exceptionally difficult, consider dividing it into larger sections rather than trying to achieve very small divisions. These larger divisions will have more stored energy and a greater chance of survival.

Pest Infestation Prevention

Autumn can bring its own set of pest challenges, and newly divided hostas, with their exposed roots and disturbed soil, can be particularly vulnerable. Slugs and snails are common culprits, attracted to the tender new growth that might emerge even in fall or the residual moisture around the plant.

To safeguard divided hostas from pests:

• Cleanliness is Key: Remove any debris, fallen leaves, or decaying plant matter from around the division site. This eliminates hiding places for slugs and snails.
• Physical Barriers: Consider placing barriers around the base of newly planted divisions. Copper tape, diatomaceous earth, or crushed eggshells can deter slugs and snails.
• Manual Removal: Regularly inspect the divided plants for signs of slug or snail activity (slime trails, chewed leaves) and remove them manually, especially during early morning or late evening when they are most active.
• Encourage Natural Predators: Create a garden environment that supports natural predators of slugs and snails, such as birds, toads, and ground beetles.
• Monitor for Other Pests: While less common in fall, keep an eye out for other potential pests like grubs or root aphids. If detected, appropriate organic pest control methods can be applied, ensuring they are safe for the cooler temperatures.

Visualizing the Division Process

Understanding the visual cues and stages of hosta division in the fall significantly enhances the success rate of the process. This section provides a descriptive walkthrough, from identifying a suitable hosta clump to observing the newly replanted divisions. By visualizing each step, gardeners can better anticipate the outcomes and ensure the health of their plants.

Describing a Healthy Hosta Clump for Division

A hosta clump ready for division in the fall exhibits robust growth and a well-established root system. The foliage, though beginning to senescence, still retains its characteristic form and coloration, indicating good vigor. The overall size of the clump is substantial, often exceeding 18-24 inches in diameter, and displays multiple distinct shoots or eyes emerging from the crown. This dense growth signifies that the plant has accumulated sufficient energy reserves to withstand the stress of division and successfully establish itself in its new location.

The soil around the base of the clump will appear well-integrated with the root mass, suggesting a mature and healthy plant.

Appearance of Hosta Roots in Fall

During the fall, hosta roots are typically firm, fleshy, and a pale creamy white to light tan color. They are generally thick and substantial, reflecting the plant’s stored energy from the growing season. While some finer feeder roots will be present, the prominent feature is the network of thicker, storage roots that anchor the plant and provide nourishment. The roots should be free from rot or damage, appearing healthy and resilient.

In fall, the root system is actively preparing for dormancy, so while growth may have slowed, the integrity of the root structure is paramount for successful division and overwintering.

Appearance of a Divided Hosta Section Immediately After Replanting

Immediately after replanting, a divided hosta section will appear somewhat diminished in its foliage compared to its pre-division state, as some leaves may have been trimmed or are naturally senescing. The crown, where the shoots emerge, will be clearly defined and situated at or slightly below the soil surface. The root system, now exposed and replanted, will be visible around the base, ideally spread out and in good contact with the surrounding soil.

The division itself might show a clean cut or a natural separation point, with no significant damage to the remaining roots or crown. The plant will look settled, but it’s crucial to provide adequate moisture to help it establish.

Visual Progression of Hosta Division and Replanting

The process of dividing a hosta in the fall can be visualized through a series of distinct stages, each representing a critical step in ensuring the plant’s future health and vigor.

1. Initial Excavation: The process begins with a healthy, mature hosta clump. Using a spade or garden fork, carefully loosen the soil around the perimeter of the clump, working outwards to avoid damaging the roots. Gently lift the entire clump from the ground, revealing the extensive root ball.
2. Root Ball Separation: Once the clump is out of the ground, gently shake off excess soil to expose the root system and crown. For smaller divisions, the clump might be pulled apart by hand, separating sections where roots and shoots naturally divide. For larger, more established clumps, a sharp spade, a soil knife, or even two garden forks inserted back-to-back into the crown can be used to divide the plant into smaller, manageable sections.

   Each section must contain both healthy roots and at least one viable shoot or eye.

3. Trimming and Inspection: After division, inspect each section for any damaged or diseased roots and trim them away with clean pruning shears. Remove any decaying foliage or spent flower stalks. This step is crucial for preventing the spread of disease and encouraging new root growth.
4. Replanting the Divisions: Prepare new planting holes in their desired locations, ensuring adequate spacing and suitable soil conditions. Place each divided section into a prepared hole, ensuring the crown is positioned at soil level or slightly above. Gently backfill the hole with soil, firming it around the roots to eliminate air pockets.
5. Watering and Mulching: Immediately after replanting, water each division thoroughly to settle the soil and hydrate the roots. A layer of mulch can then be applied around the base of the plant, which helps retain moisture, regulate soil temperature, and protect the newly planted divisions during the transition period.

Advanced Techniques and Considerations

While the basic steps for dividing hostas in fall are straightforward, certain situations and hosta varieties benefit from advanced approaches. Mature, large specimens and specific cultivars may require modifications to the standard division process to ensure optimal success and plant health. Understanding these nuances can elevate your hosta propagation efforts.

Dividing Very Large or Mature Hosta Specimens

Mature hostas can develop massive root systems and dense foliage, making them challenging to divide. The key is to manage the size and access the crown effectively.

For exceptionally large hostas, it is often beneficial to first reduce the top growth by cutting the foliage back significantly, typically to about 6 inches from the ground. This reduces the plant’s water demand and makes it easier to handle. Once the foliage is reduced, carefully excavate around the entire perimeter of the clump, digging a wide trench to expose as much of the root ball as possible.

Loosen the soil from the roots. If the clump is too large and dense to break apart by hand or with a shovel, a sharp spade or even a pruning saw can be employed to cut through the root mass and crown. Aim for divisions that have at least one growth eye and a substantial portion of healthy roots. It is sometimes easier to tackle very large hostas by digging them out entirely and then working on them on a tarp or flat surface where better leverage and visibility are possible.

Suitability of Specific Hosta Varieties for Fall Division

Most hosta varieties are well-suited for fall division, but some may exhibit slightly different responses or require minor adjustments. Generally, the more vigorous and fast-growing the hosta, the easier it will be to divide.

Smaller, slower-growing varieties, or those with particularly fibrous root systems, might benefit from slightly earlier fall division to allow for more establishment time before winter. However, even these can be successfully divided in fall if proper care is taken. Varieties known for their dense growth habit, such as many of the large-leaved ‘King’ or ‘Empress’ types, may require more effort in breaking apart the clump, as described in the section on mature specimens.

Conversely, hostas with a more open, rhizomatous growth pattern might divide more readily. There is no definitive list of hostas unsuitable for fall division; rather, it’s about adapting the technique to the plant’s growth habit and vigor.

Impact of Soil Type on Fall Hosta Division Success, How to divide hostas in fall

The composition of your soil plays a significant role in how well hostas establish after division, especially when dividing in the fall. Soil that retains moisture but drains well is ideal.

Heavy clay soils can become waterlogged, particularly during autumn rains, which can lead to root rot in newly divided hostas. If you have clay soil, amending it with generous amounts of organic matter, such as compost or well-rotted manure, before replanting is crucial. This improves drainage and aeration. Sandy soils, on the other hand, drain very quickly and may not retain enough moisture for the divisions to establish.

In sandy conditions, incorporating organic matter also helps improve water retention. Loam, a balanced mix of sand, silt, and clay, is generally considered ideal for hostas, providing good drainage and adequate moisture retention. Regardless of your soil type, ensuring good soil structure around the divided plants will promote better root development.

Benefits of Dividing Hostas to Improve Air Circulation

Over time, hosta clumps can become so dense that they impede air circulation within the plant. This can create a microclimate that is conducive to fungal diseases and can also reduce the vigor of the plant.

Dividing hostas effectively addresses this issue by creating smaller, more manageable divisions. As the plant grows, these divisions will not form such a dense, impenetrable mass. Improved air circulation means that moisture dries more quickly from the leaves and crowns, making it harder for fungal spores to germinate and infect the plant. This is particularly beneficial for hostas grown in humid climates or shaded conditions where air movement is naturally limited.

Furthermore, by separating the plant into smaller units, each division has more resources available to it, leading to stronger growth and more robust foliage in subsequent seasons.

Conclusive Thoughts

So there you have it, the not-so-secret art of dividing hostas in fall. It’s a process that’s both practical and rewarding, turning one plant into many, and giving your garden a fuller, more vibrant look. By following these steps, you’re not just propagating plants; you’re investing in the future beauty of your garden, ensuring those lush hosta clumps continue to impress for seasons to come.

Go forth and divide, my fellow plant enthusiasts, and may your gardens be ever green and ever growing.

Essential Questionnaire

When is the absolute latest I can divide hostas in fall?

You can divide hostas up until about six weeks before your ground freezes solid. This gives the newly divided plants enough time to establish some roots before winter truly sets in.

Can I divide hostas if they still have flowers or seed pods?

While it’s best to wait until after flowering and seed pod development, you can still divide them if necessary. Just be aware that the plant might expend more energy on flowering than root establishment.

What if my hostas are in a very sunny spot? Can I still divide them in fall?

Yes, but you might want to consider temporarily shading them after replanting, especially if you’re in a region with lingering warm spells. This helps prevent stress on the divided sections.

How do I know if a hosta clump is too small to divide?

Generally, if a clump is too small to easily get a spade or knife into to create divisions with at least a few eyes (buds) and a decent root system, it’s probably best to let it grow larger.

Is it okay to divide hostas that look diseased or have pest damage?

It’s usually not recommended. Dividing stressed or unhealthy plants can spread problems to new divisions and make it harder for them to recover. Address the underlying issue first.