Walnut - Background Information
Walnuts are from the Persian Walnut Juglans regia. This species is sometimes incorrectly termed English Walnut but the species seems to have evolved in Persian or at least close to the Black Sea. The area north of Iran in Kyrgyzstan is especially rich in Juglans species.
Commercial walnut varieties are grown from specially selected variants ("cultivars") grafted onto a robust root stock (usually American Black Walnut or a walnut hybrid). While some isolated walnut trees grown from seed may produce satisfactory crops, these typically produce trees with poor (or no) nuts worth collecting. While like with other fruiting trees like apples, the very rare variant may produce a "Granny Smith", don't count on it. So don't waste your time trying to propagate from fresh walnuts from your local greengrocer. Very few will germinate and, if they do, the progeny are unlikely to produce usable nuts (and you will only find this gloomy prognosis confirmed several years later).
Results of Field Grafting (end 2007)
The bud grafts have been growing like topsy and are typically much bigger than the graft growth on pre-grafted trees from 2005. Nothing like having a good root system. The trees in the photo below are a mix of root stock ready to field grafted in early 2008 and ones with the previous field grafts.
Note that our walnut plantings look rather different from many others, especially those in the drier irrigation areas. While we keep grass and weeds down along the rows, we keep a good grass cover in between rows. We find that this keeps the ground moister in hot weather and is good for the health of the soil. (Put a spade down into the soil anywhere in the paddock and you will come up with at least one earthworm.)
Note also the close "hedgerow" planting that is now considered best practice even with these potentially big trees. (The idea is that this will keep tree size down and also encourage earlier nut cropping.)
Field Grafting of Walnuts
Pre-grafted Walnuts (2005)
Only about half the walnuts seeds planted out directly into the field in 2004 germinated. This we found out later was due to us planting them out prior to their having enough chilling from the cold nights. (The ones we planted out later had the best germination rate.) This contrasted with the seeds we planted out in seed germination mixture late in the winter of 2003 where we had >95% come up.
Consequently we decided to buy in some pre-grafted walnut trees to fill in the gaps in the rootstock trees and also to expand in the area under planting. The following links are to pages summarising our experiences with these pre-grafted trees.
Propagation from Seed (2003)
Propagation from seed is for the rootstock only. The commercial nut producing stocks are especially selected and propagated by grafting onto a hardy rootstock.
The rootstock is from what would typically be a timber-producing variety of walnut. In our limited experience, the rate at which the seeds from Black Walnut (Juglans niger) produce viable plants is surprisingly high. We have even found that some walnut seeds that did not germinate the year they were sown actually germinated a year later.
Transplanting a walnut seeding into a growth tube after only a few weeks growth, here exposing the roots and the split half of the walnut seed. These plants show amazing vigour.
Walnut plant 1 year old three weeks after the first buds have appeared after winter.