Grafted trees are generally more robust, hardier and reliable growers than seedling trees. They also produce an earlier crop of higher quality nuts. To produce home grown walnuts for eating growers simply must opt for grafted trees.
Below we outline the main benefits of grafted trees over seedlings.
Time to first bearing
Typically seedlings take between 10 and 12 years to first bear; some never
From grafted trees nuts are usually carried within 3-4 years, occasionally after only 2 years.
Grafted trees carry walnuts much earlier in their lives, clearly enhancing their economic potential.
When seedlings do bear nuts they are often small, stained, frequently fail to part from their husk and are generally of little commercial merit.
Grafted trees carry nuts of known character, shape, kernel fill, shell colour and thickness.
Leafing & flowering
Many seedling trees leaf too early in the season, a problem as frosts of -1.5°C in the spring will kill new growth and eliminate nutlets. Flowering patterns are highly variable and erratic, causing problems with pollination.
The leafing of grafted forms is generally mid-late season. Flowering patterns are understood.
Seedling walnuts develop into an array of different shapes and sizes
The vigour, habit and ultimate size of most named cultivars are known. This means that planting distances can be meaningfully used with grafted trees in the knowledge that the mature trees will be of a constant size.
Whilst many seedlings make useful timber trees, they are highly variable in
this regard. Vulnerability to frost means that they are more likely to develop
forked or 'sympodial' structures.
Many cultivars of J.regia are known to make substantial vigorous trees. Late leafing means that they suffer less from frost damage and loss of their dominant 'leader'. As a result many grafted cultivars have real potential for agro-forestry.
Resistance is variable. Some trees are very prone to bacterial blight, a common
Whilst not all grafted varieties are disease resistant, in general they are as robust as 'wild' seedling stock. Varieties such as Broadview are particularly noted for their good health and easy management.
As walnuts generally bear on terminal buds it is vital that the new wood ripens and overwinters successfully. Some seedlings are very delicate and can suffer from "Dieback" in severe winters.
Most of the varieties of grafted walnuts listed here originate from climatic zones which are far more inhospitable than our own. "Winter kill" is not a factor for them under the British climate.