Preparing Gardens for a Challenging El Niño Winter: Seven Vulnerable Plants to Watch

Forecasters have issued clear warnings for gardeners across significant portions of the United States, pointing toward a formidable El Niño pattern that promises a challenging winter season. With the National Oceanic and Atmospheric Administration (NOAA) placing the probability of a very strong El Niño above 90 percent, meteorological models indicate a wetter-than-normal winter for much of the southern and central United States, California, sections of the Great Plains, and the Atlantic coast. Meanwhile, temperature patterns are expected to vary regionally, bringing warmer-than-normal conditions to the northern United States while leaving the Southeast potentially vulnerable to unexpected cooler spells.

While seasonal gardening discourse traditionally focuses on protecting vegetation from the punishing extremes of summer heat and drought, a cold and wet winter introduces an entirely distinct set of physiological stresses. When winter precipitation falls repeatedly and leaves garden soil saturated for weeks on end, plant roots are systematically deprived of vital oxygen. Compounding this issue is the activation of water molds, including soil-borne pathogens such as Phytophthora and Pythium, which thrive in waterlogged environments and frequently trigger devastating root rot. Furthermore, the relentless cycle of winter freezes and thaws introduces the physical threat of frost heaving, a process that can literally push shallow-rooted plants completely out of the soil.

Horticultural experts note that certain species struggle disproportionately when winter soils remain persistently cold and soggy. Mitigating these risks primarily involves meticulous attention to drainage, the strategic deployment of appropriate mulching materials, and precise timing for seasonal interventions. Most of these protective measures can be implemented well before the worst of the winter weather arrives, offering vulnerable flora a fighting chance against the incoming climate pressures.

Among the plants facing the greatest risk during a wet El Niño winter is lavender. This Mediterranean native handles low temperatures remarkably well when conditions are dry, but it struggles significantly when faced with a combination of cold and wet environments. Because lavender evolved on rocky, dry hillsides where rainwater drains away rapidly, soggy winter soil represents one of the leading causes of plant mortality. Gardeners are advised to avoid mulching lavender with moisture-retention materials like wood chips or straw, which hold dampness dangerously close to the plant’s crown. Instead, horticulturalists recommend a thin layer of gravel or mixed pebbles to promote rapid moisture dispersal. Additionally, halting irrigation once seasonal rains begin and refraining from late-season pruning helps ensure the plant does not expend energy pushing out tender new growth right before a hard freeze. For container-grown lavender, shifting pots beneath an eave or porch roof can prevent them from becoming continually waterlogged by heavy downpours.

Hens and chicks, scientifically classified as Sempervivum species, along with their hardy sedum counterparts, face similar environmental hazards. While these resilient succulents possess high cold tolerance and can survive harsh winters far to the north, stagnant moisture in the soil quickly spells trouble. The dense rosettes are prone to rotting from the base upward when water accumulates around them for extended periods. Applying a protective layer of gravel or coarse grit helps elevate the foliage above the damp soil surface. For potted succulents, removing collection saucers and elevating containers using specialized pot feet ensures that excess moisture drains freely rather than pooling beneath the base of the container.

Agaves represent another group of plants that can successfully withstand sub-freezing temperatures provided their root systems remain dry, a characteristic that allows many species to thrive in desert regions prone to cold nights. The combination of freezing temperatures and persistent moisture, however, often proves fatal. A winter marked by frequent rain can cause water to collect dangerously in the center of the plant’s rosette as well as in the surrounding soil. Consequently, agaves perform best when cultivated on slopes, landscape berms, or elevated raised beds that facilitate rapid drainage. When severe freezes are forecasted, covering the plants with heavy-duty frost blankets offers necessary protection, though these coverings should be removed promptly once freezing temperatures subside.

Fall-planted garlic spends many months overwintering in the soil, making it highly susceptible to environmental extremes. Beds that remain waterlogged for weeks can cause cloves to rot before they ever break the surface in spring. Furthermore, cool and wet soil conditions provide an ideal environment for white rot, caused by the fungal pathogen Sclerotium cepivorum, if the disease is already present in the local soil profile. To mitigate these risks, growers typically plant garlic in raised beds or mound individual rows several inches above surrounding pathways to encourage drainage. Applying an organic mulch, such as pine straw, after the soil has thoroughly cooled helps insulate the bed, smoothing out dramatic temperature swings that could otherwise heave the developing cloves out of the ground.

Tulip bulbs face severe threats from prolonged winter wetness, which encourages both bulb rot and the spread of tulip fire, a fungal disease driven by cool, moist weather conditions. Gardeners must select the absolute best-draining locations available for tulip cultivation, planting the bulbs at a depth of six to eight inches and withholding additional water when natural precipitation provides adequate moisture. Heavy, poorly drained garden beds are generally unsuitable for traditional bulb planting, making raised beds or containers a safer alternative for tulips and other fall-planted specimens like hyacinths that require similar soil conditions.

Coral bells, or Heuchera species, possess shallow root systems and low-sitting crowns, making them exceptionally vulnerable to frost heaving during winters characterized by alternating freeze and thaw cycles. Each freeze-thaw event pushes the crown upward, exposing delicate roots to cold winter air and drying winds. Applying a few inches of mulch after the first hard frost—while keeping the material carefully pulled back from the plant’s immediate crown—helps stabilize soil temperatures. Gardeners must also inspect these plants periodically after a thaw, gently pressing any heaved specimens back into the earth. Furthermore, heavy, wet clay soils can easily induce crown rot in coral bells, highlighting the importance of incorporating organic compost to improve soil structure before planting.

Strawberry plants face a dual threat during cold and wet winters. Waterlogged ground creates prime conditions for destructive root diseases such as red stele, caused by the pathogen Phytophthora fragariae. Simultaneously, freeze-thaw cycles threaten to heave strawberry crowns upward, leaving their root systems exposed to desiccation. While raised beds help alleviate chronic soil saturation, applying a loose layer of straw or pine straw over the plants after they have experienced several light frosts provides essential insulation. This protective layer is typically pulled back in the spring once active plant growth resumes.

Although winter weather forecasts can occasionally prove unpredictable and even a strong El Niño will impact different regions in distinct ways, basic preventative measures remain accessible and cost-effective. Implementing proper drainage strategies, utilizing appropriate mulches, and positioning vulnerable plants with care provide gardeners with reliable defenses against the unpredictable challenges of the coming season.