How to identify trellis systems on overwinter perennials? - Plant Care Guide

When overwintering perennials that use trellis systems, the "identification" isn't about the plant itself, but rather about assessing the type and condition of the trellis and how it impacts the perennial's winter survival and preparation for the next growing season. You need to identify if the trellis is permanent or removable, its material, and if it poses any risks to the dormant plant or requires specific winter maintenance. This ensures both the perennial and the support system are ready for colder months.

How Do Trellis Systems Affect Overwintering Perennials?

Trellis systems play a significant role in how perennials overwinter, sometimes offering crucial support, but also potentially posing risks if not properly managed. Their impact depends on the type of perennial, the trellis material, and the winter climate. Essentially, the trellis changes the plant's exposure and vulnerability during its dormant period.

Here's how trellis systems affect overwintering perennials:

1. Physical Support During Dormancy:

   • Prevents Splaying: For climbing or vining perennials that remain attached to the trellis (like some clematis or hardy jasmine), the trellis prevents the bare stems from splaying out or collapsing under the weight of snow or ice. This helps maintain the plant's structure and prevents breakage.
   • Keeps Off Ground: It keeps dormant stems elevated, preventing prolonged contact with cold, wet ground, which can reduce the risk of fungal diseases and rot.

2. Protection from Winter Elements:

   • Windbreak: A solid or dense trellis (like a wooden lattice against a wall) can offer some wind protection to the perennial's dormant crown and stems, reducing desiccation (drying out) from cold, dry winter winds.
   • Snow Accumulation: The trellis might cause snow to accumulate around the plant's base, which can act as a beneficial insulating layer, protecting roots and crowns from extreme cold.
   • Exposure: Conversely, an open metal trellis in a very exposed location might offer little protection and could even contribute to wind damage if stems are rigidly tied and cannot sway.

3. Risk of Cold Damage/Desiccation:

   • Air Circulation: While typically a benefit in summer, excessive air circulation around exposed stems on a trellis in winter can sometimes increase desiccation, especially if the plant is not fully hardy for the zone.
   • Cold Conduction: Metal trellises can conduct cold, potentially chilling stems more than if they were unassisted. However, this is usually a minor factor compared to other environmental conditions.

4. Damage from Freezing and Thawing:

   • Ice Buildup: In areas prone to freezing rain, ice can build up on the trellis and the perennial's stems, adding significant weight that could cause snapping or breaking, especially for more brittle-stemmed perennials.
   • Frost Heave (Indirect): While the trellis doesn't directly cause frost heave, ensuring its stability and proper anchoring can indirectly help by preventing disturbance to the soil around the plant's base.

5. Pruning and Maintenance Considerations:

   • Access: The trellis dictates how easily you can prune the perennial in late fall or early spring. Some perennials (like specific clematis types) are cut back almost to the ground, requiring removal from the trellis, while others are just lightly pruned.
   • Tying and Untying: Depending on the perennial and how it grows, you might need to tie its dormant stems more securely to the trellis or even carefully untie and lay them on the ground for extra protection (e.g., for borderline hardy roses or some hydrangeas).

6. Pest and Disease Habitat:

   • Hiding Spots: Trellises can inadvertently provide sheltered spots for pests or disease spores to overwinter, particularly in cracks or crevices of wooden trellises. Cleaning the trellis in fall is important.

In essence, a trellis system fundamentally alters a perennial's interaction with winter. Proper selection of trellis material, thoughtful placement, and appropriate fall maintenance are key to ensuring the trellis supports rather than hinders a perennial's successful overwintering.

What Type of Trellis Systems are Best for Overwintering Perennials?

The best trellis systems for overwintering perennials are those that are durable, stable, and designed to either provide necessary support without causing winter damage or allow for easy plant removal/protection. The ideal choice often depends on the type of perennial and your winter climate.

Here are the types of trellis systems best suited for overwintering perennials:

1. Sturdy, Permanent Metal Trellises (e.g., Steel, Wrought Iron, Heavy-Gauge Wire Mesh):

   • Description: These are built to last, often anchored deeply into the ground or securely attached to a wall.
   • Why they're best for overwintering:
     • Durability: Can withstand heavy snow and ice loads without collapsing or breaking.
     • Rigid Support: Provides strong, unwavering support for dormant woody stems, preventing splaying or snapping.
     • Minimal Maintenance: Requires little to no winter preparation itself, other than a general cleaning.
     • Pest Resistance: Less likely to harbor pests or diseases than porous materials like wood.
   • Ideal for: Hardy climbing roses, clematis (especially Type 2 & 3), hardy passion vines, wisteria (though these need exceptionally strong support).
   • Consideration: Metal can conduct cold, but for truly hardy perennials, this is generally not a significant issue. For less hardy plants, wrapping with burlap may be needed. You can find robust metal garden trellises.

2. Sturdy Wooden Trellises (Pressure-Treated or Naturally Rot-Resistant Wood):

   • Description: Trellises made from durable wood like cedar or pressure-treated lumber. Often larger and more decorative.
   • Why they're best for overwintering:
     • Strong Support: Provides good structural support for climbing plants.
     • Natural Look: Blends well with garden aesthetics.
     • Insulation: Wood is a poorer conductor of cold than metal, potentially offering slight insulation to attached stems.
   • Ideal for: Similar to metal trellises – climbing roses, clematis.
   • Consideration: Wood can rot over time, requiring periodic inspection and maintenance. Ensure good air circulation to prevent moisture buildup against the wood, which can foster fungal issues.

3. Cable or Wire Systems (Espalier, Arbors, Pergolas):

   • Description: Wires or cables stretched between posts or attached to walls, used to train plants in specific shapes (espalier) or provide overhead support for arbors and pergolas.
   • Why they're best for overwintering:
     • Extremely Strong: If properly installed with tension, wires are incredibly strong and virtually impervious to snow/ice loads.
     • Aesthetic Integration: Often blend seamlessly into the garden design.
   • Ideal for: Permanent woody vines like wisteria, hardy kiwi, climbing hydrangeas, or climbing roses that are allowed to develop strong, permanent woody structures.
   • Consideration: Requires specific installation and may not be suitable for plants needing a very dense climbing surface.

4. Removable or Collapse-and-Store Trellises (for Tender or Herbaceous Perennials):

   • Description: Lighter-weight structures that can be easily detached from their anchors, or are designed to be folded or dismantled.
   • Why they're best for overwintering:
     • Plant Protection: Allows you to untie and lay tender perennials on the ground for winter protection (e.g., burying under mulch) or move potted plants and their trellises indoors.
     • System Protection: Prevents damage to the trellis itself from heavy snow or high winds if stored away.
   • Ideal for: Mandevilla (if overwintered indoors), some annual vines that can be regrown annually, or light support for herbaceous perennials that are cut back in fall. You might look for collapsible trellises or easily detachable options.

Trellis Systems to Use with Caution or Avoid in Winter (Especially in Cold Climates):

• Flimsy Plastic Netting: Prone to breaking, stretching, or freezing onto plant stems, causing damage.
• Thin Bamboo Stakes: Not strong enough to withstand heavy snow or ice; easily snap.
• Unanchored Trellises: Will likely blow over or collapse, potentially damaging both plant and structure.

The best choice boils down to the perennial's hardiness, its growth habit, and the severity of your winter. Prioritizing strength, stability, and appropriate material will ensure your trellis system effectively supports your overwintering perennials.

How Do I Prepare Perennials on Trellis Systems for Winter?

Preparing perennials on trellis systems for winter involves specific steps to protect both the plants and the support structures from cold, ice, and wind damage. The approach varies slightly depending on the perennial type and the trellis's permanence. The goal is to ensure the plant's survival and a strong return in spring.

Here's how to prepare perennials on trellis systems for winter:

1. General Garden Cleanup (Around the Trellis):

   • Remove Debris: Clear away any fallen leaves, weeds, or general garden debris from around the base of the perennial and the trellis. This reduces hiding spots for pests and disease spores.
   • Inspect for Pests/Diseases: Do a final inspection for any active pests or signs of fungal disease. Treat any issues before winter sets in.

2. Watering in Late Fall:

   • Deep Watering: For hardy perennials, especially evergreens or plants with woody stems that stay on the trellis, give them a deep, thorough watering in late fall before the ground freezes solid. This hydrates the plant and its roots, providing crucial moisture to combat winter desiccation (drying out from cold winds).
   • Avoid Soggy Soil: Ensure the soil around the base of the plant is well-drained. Standing water around the crown or roots in winter is a leading cause of rot.

3. Pruning Strategy (Species-Specific):

   • Know Your Perennial's Pruning Needs: This is paramount.
     • Hard Cut Back (e.g., some Clematis, Honeysuckle): Some herbaceous perennials or certain clematis varieties (like Group 3) are meant to be cut back drastically in late fall or early spring. If this is the case, untangle them from the trellis and prune them back to the appropriate height (often a few inches from the ground or to 1-2 feet).
     • Light Trim / Maintain Structure (e.g., Climbing Roses, woody vines): For woody perennials that retain their structure over winter, perform only a light tidy-up. Remove any dead, diseased, or crossing branches. Do not do a hard prune in fall, as new growth stimulated by pruning won't have time to harden off before cold hits.
     • Wait to Prune: In very cold climates, some gardeners prefer to wait until early spring to prune any kind of perennial, allowing the dead foliage or stems to provide some winter protection.

4. Securing the Plant to the Trellis:

   • Gentle Tying: For perennials that remain on the trellis (e.g., climbing roses, permanent clematis, wisteria), inspect their ties. Ensure they are secure but not too tight (which can girdle stems). Use soft materials like garden twine, stretchy plant ties, or fabric strips that won't cut into stems as they expand.
   • Add More Ties: If anticipating heavy snow or ice, add additional ties to major stems for extra support.

5. Protecting the Trellis (if applicable):

   • Inspect Stability: Check the anchors, posts, and overall stability of the trellis. Tighten any loose bolts or re-secure posts if they've shifted.
   • Remove Light/Temporary Trellises: If your trellis system is lightweight, removable, or designed for annuals (e.g., thin plastic netting, bamboo teepees), consider removing it from the garden and storing it for winter. This protects the trellis from damage and makes spring garden cleanup easier.

6. Insulation/Protection for Borderline Hardy Plants:

   • Mulch the Base: Apply a 2-4 inch layer of insulating mulch (straw, pine needles, shredded leaves) around the base of the plant after the ground has frozen (to prevent rodent nesting). Keep mulch a few inches away from the crown and main stems to prevent moisture buildup and rot.
   • Burlap Wrap/Shelter: For less hardy perennials that are susceptible to windburn or extreme cold, consider wrapping the plant and its attached trellis in burlap or creating a temporary windbreak. Ensure good air circulation within the wrap. Some people use burlap wraps for plants for this.

7. Potted Perennials on Trellises:

   • Move Indoors: If you're growing a perennial (like a Mandevilla in a cold climate) in a pot with a trellis, bring the entire unit indoors to a cool, bright, or dormant-appropriate location before the first frost.
   • Insulate Pots: For hardy perennials left outdoors in pots, insulate the pot by wrapping it in burlap or bubble wrap, or placing it inside a larger, insulated container.

By carefully executing these steps, you prepare your perennials on trellis systems to endure the winter successfully, ensuring they emerge healthy and ready to climb and bloom again in the spring.

What Are Common Problems with Trellised Perennials in Winter?

Even with careful preparation, trellised perennials can face specific challenges and problems during winter. These issues often relate to environmental stresses interacting with the plant's structure and its attachment to the trellis.

Here are common problems with trellised perennials in winter:

1. Physical Damage from Ice and Snow Load:

   • Cause: Heavy snowfall or, more critically, freezing rain (ice storms) can accumulate on the perennial's dormant stems and the trellis structure.
   • Symptoms: Branches snapping, stems bending or kinking, or the entire trellis collapsing under extreme weight. This is particularly problematic for perennials that retain a significant woody structure over winter (e.g., climbing roses, wisteria).
   • Prevention: Use strong, durable trellises (metal or heavy-duty wood), ensure proper anchoring, and for very heavy snowfall, gently brush snow off branches if accessible and safe.

2. Desiccation (Winter Burn/Drought):

   • Cause: This primarily affects broadleaf evergreens or woody perennials in exposed locations. Cold, dry winter winds, especially combined with frozen ground, pull moisture out of the plant's stems and bark faster than the roots can absorb it.
   • Symptoms: Bark appearing shriveled, branches turning brittle, and browning or crisping of any remaining foliage (even if it's supposed to be evergreen).
   • Prevention: Deep watering in late fall, providing windbreaks (burlap screens), and applying mulch.

3. Frost Heave:

   • Cause: Repeated freezing and thawing cycles in the soil can cause the ground to expand and contract, pushing smaller or newly planted perennials (and their shallow roots) partially out of the soil.
   • Symptoms: The plant's root crown appearing lifted or exposed above the soil line.
   • Prevention: Apply mulch after the ground freezes to stabilize soil temperature. Gently push plants back down if heaving occurs.

4. Crown Rot / Root Rot:

   • Cause: Poor drainage combined with excessive winter moisture (from rain or melting snow) can lead to waterlogged conditions around the plant's crown and roots. This suffocates roots and creates an environment for fungal diseases.
   • Symptoms: Mushy, black, or foul-smelling tissue at the base of the plant or around roots. Above-ground symptoms (like wilting or lack of vigor in spring) might only appear when it's too late.
   • Prevention: Ensure excellent drainage at planting, avoid planting in low spots, and keep mulch away from the crown.

5. Pest or Disease Overwintering:

   • Cause: Some pests (e.g., scale insects, spider mites) or fungal spores can overwinter in cracks or crevices of the trellis, or on the plant's dormant stems.
   • Symptoms: Unexpected early infestations in spring, or visible signs of fungal growth on dormant parts.
   • Prevention: Thorough fall cleanup around the plant and trellis, dormant oil sprays (if appropriate for the plant and pest), and good air circulation.

6. Damage from Untimely Pruning:

   • Cause: Pruning herbaceous or woody perennials too hard or too late in fall can stimulate new, tender growth that is very susceptible to cold damage.
   • Symptoms: Blackening or dieback of new shoots, potentially leading to more extensive damage or even the death of the plant if the crown is compromised.
   • Prevention: Know your plant's specific pruning needs and timing. For most perennials, major pruning is best done in late winter or early spring.

7. Rodent Damage:

   • Cause: Voles, mice, or rabbits can sometimes chew on the bark of dormant perennial stems, especially when other food sources are scarce. Mulch piled too close to the stem can provide cover for rodents.
   • Symptoms: Girdling (bark chewed all the way around) or visible chew marks on lower stems.
   • Prevention: Keep mulch away from the stem base, use tree guards for susceptible plants, or implement other rodent control measures if issues arise.

By understanding these potential problems, gardeners can proactively implement appropriate winterization strategies to protect their trellised perennials, ensuring they return healthy and strong when spring arrives.