Understanding Grafted Ornamental Trees

Ornamental fruit trees aren't the only species cultivated for a weeping habit, but they're among the most popular for home landscapes. That magnificent weeping cherry has clearly outgrown its original planting space—a common issue to consider when purchasing any ornamental tree. Other frequent challenges with grafted trees include water sprouts, suckers, and disease susceptibility. The grafting process itself stresses one or two areas of the plant, potentially reducing overall vigor.

How Is Grafting Done?

A single graft merges a less hardy cultivar onto very hardy rootstock—for instance, a weeping crabapple grafted to standard crabapple rootstock, yielding a tree better equipped to withstand the elements. This works by aligning the cambium layers so they grow together.

A double graft uses the same technique—combining hardy rootstock with a hardy main trunk section called the interstem—but goes a step further by grafting the desired cultivar to the top of the trunk. This upper portion, the scion, is the only part producing the desired leaves, flowers, and fruit. The interstem and rootstock control the tree's mature size. Grafted trees can fail within the first few years, especially under severe weather stress. The key to buying a healthy tree: purchase from reputable nurseries offering at least a one-year guarantee. Ask the grower what type of graft was done, and understand the tree's mature size and care requirements.

Water Sprouts

Epicormic branches—known as water sprouts—are easily recognized on weeping varieties. They grow straight up and fast, sometimes reaching 3–4 feet in a single season. These branches won't flower or fruit but drain energy from the tree. Prune them close to the collar as soon as they appear.

Suckers

Suckers emerge from the rootstock and also sap the plant's energy. They're difficult to control, but the root cause is often improper planting depth. The graft union must remain above ground to prevent sucker growth. If the tree is already planted and suckers appear, clear soil from around the base and prune suckers as close to their source as possible, then replace the soil. This won't prevent future suckers, but frequent removal keeps them from affecting the tree's vigor.

Disease

Like any wound, the graft union is vulnerable to disease and insect invasion. Before purchasing, inspect the graft union carefully for cracks or irregular growth. Cherry and plum are especially prone to disease at wounds or weak crotches. Large globs of amber-colored material may ooze from the wound or beneath the bark, eventually turning black. Consult your nursery for management advice.

Location

As emphasized before, know the mature size of the tree you're buying. If a weeping cultivar is grafted to the interstem of a full-size tree, you won't be able to contain it as it matures. Know what you're buying.

Some Popular Varieties of Weeping Trees

Coniferous

• Needle juniper (Juniperus rigida)
• Tolleson's weeping juniper (Juniperus scopulorum 'Tolleson's Weeping')
• Weeping Eastern red cedar (Juniperus virginiana 'Pendula')
• Weeping Alaska cedar (Chamaecyparis nootkatensis 'Pendula')
• Weeping Serbian spruce (Picea omorika 'Pendula')
• Weeping white spruce (Picea glauca 'Pendula')

Deciduous

• 'Chaparral' weeping mulberry (Morus alba 'Chaparral')
• 'Louisa' weeping crabapple (Malus x 'Louisa')
• Golden weeping willow (Salix alba 'Tristis')
• Weeping Eastern white pine (Pinus strobus 'Pendula')
• Weeping European beech (Fagus sylvatica 'Pendula') and (Fagus sylvatica 'Purple Fountain')
• Weeping European larch (Larix decidua 'Pendula')
• Weeping Higan cherry (Prunus subhirtella 'Pendula')
• Weeping katsura (Cercidiphyllum japonicum 'Pendulum')
• Weeping Norway spruce (Picea abies 'Inversa')