New Hampshire winters can be brutal and unpredictable. Mild, above-freezing temperatures can be followed by days or even weeks of temperatures below zero. An average winter In New Hampshire has about 10 to 15 winter storms, however, more than once we have seen winters with as little as three storms. With such microclimate fluctuations, how do plants survive New Hampshire winters?
To answer this accurately, we need to break it down into three areas of risk:
Low-Risk Plants
Deciduous shrubs very rarely suffer winter damage because they go completely dormant. They shed their leaves and go fully dormant. Damage is usually limited to a late frost that kills the flower buds, or a new growth that resulted from pruning too late in the season.
Medium-Risk Plants
Unlike deciduous plants, evergreens are always in a state of semi-dormancy. Needled evergreens in particular tend to adapt well. Needles will often turn a different color and stomata (breathing pores) on needled evergreens are relatively small and protected. Winter damage on needled evergreens is usually limited to new growth exposed to harsh winds.
High-Risk Plants
Broadleaf evergreens tend to get winter damage most often. When broadleaf evergreens like rhododendrons feel the warm sun in late winter, the leaves open up and the plant tries to draw moisture from the ground. However, the ground is frozen so moisture is drawn out of the leaves. This is called “desiccation” – the plant can only draw moisture from the leaves.
New plantings are also high risk in their first winter because the plants haven’t put out a root system yet. Special care needs to be given to new plants to ensure they make it through the winter.
How To Avoid Winter-Damaged Plants
- Choose plants in USDA Hardiness Zones 5 or 4
- Plant broadleaf evergreens in the spring
- Plant high-risk plants in a protected area and avoid southern exposures
- Water deeply in the fall
- Prune mid-late summer
- Mulch heavily
- Spray Wilt-Pruf (anti-dessicant) on the underside of leaves in December and February
Cold-Hardy Plants for New Hampshire Landscapes
Although there are hundreds of cold-hardy New Hampshire plants to choose from, here’s a list of 10 of the most common which are compatible with USDA Hardiness Zones 4 and 5. These shrubs are suitable for a variety of landscaping needs and offer a mix of aesthetic and functional benefits.
Deciduous Shrubs
- Ninebark (Physocarpus opulifolius)
- Redtwig Dogwood (Cornus sericea)
- Dwarf Korean Lilac (Syringa meyeri ‘Palibin’)
- Spirea (Spiraea japonica and hybrids)
- Mock Orange (Philadelphus coronarius)
- Hydrangea paniculata (e.g., ‘Limelight’, ‘Pinky Winky’)
- Elderberry (Sambucus canadensis or Sambucus nigra)
- Smokebush (Cotinus coggygria)
- Forsythia (Forsythia x intermedia)
- Winterberry (Ilex verticillata) – a deciduous holly.
Needled Evergreen Shrubs
- Dwarf Alberta Spruce (Picea glauca ‘Conica’)
- Bird’s Nest Spruce (Picea abies ‘Nidiformis’)
- Mugo Pine (Pinus mugo)
- Eastern Hemlock (Dwarf Varieties) (Tsuga canadensis cultivars)
- Juniper (Juniperus communis or Juniperus horizontalis)
- Dwarf Japanese Black Pine (Pinus thunbergii ‘Kotobuki’)
- Blue Star Juniper (Juniperus squamata ‘Blue Star’)
- Arborvitae (Dwarf Varieties) (Thuja occidentalis cultivars)
- Yew (Taxus cuspidata or Taxus x media)
- Golden Globe Arborvitae (Thuja occidentalis ‘Rheingold’)
Broadleaf Evergreen Shrubs
- Boxwood (Buxus sempervirens) – cold-hardy varieties like ‘Wintergreen’ or ‘Green Velvet.’
- Rhododendron (Rhododendron catawbiense or hybrids)
- Mountain Laurel (Kalmia latifolia)
- Pieris japonica (e.g., ‘Mountain Fire’ or ‘Cavatine’)
- Oregon Grape Holly (Mahonia aquifolium)
- Bearberry (Arctostaphylos uva-ursi)
- Leucothoe (Leucothoe fontanesiana cultivars)
- Euonymus (Euonymus fortunei) – varieties like ‘Emerald Gaiety.’
- Inkberry Holly (Ilex glabra) – cold-hardy cultivars like ‘Compacta.’
- Wintergreen (Gaultheria procumbens)
Landscape Design Services
If you are thinking about adding new plants to your yard, call our landscaping division and ask us about our landscape design services.
Plant Health Care
If you have existing plants and are concerned about their health, give our turf care division a call to schedule a free consultation.