Plant of the Month - Petersfield Physic Garden

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Plant of the Month

July
Black Walnut

The fruits of Walnut Tree (genus Juglans) which grows at the Southern end of the garden are now becoming conspicuous as they swell to produce the familiar nuts. The tree which was heavily pruned 18 months ago but has grown appreciably since then and is now fruiting well. It is not until late in the autumn however, that the nuts will ripen and be good to eat.

The deciduous tree, which was introduced to Europe from Canada in 1629, is large attaining heights of 30-40 metres. It produces its leaves late in the spring and its flowers follow, the male in the form of catkins and the female in terminal clusters. The roots secrete a herbicide into the soil to prevent competing vegetation from growing to which potatoes and tomatoes are particularly susceptible. The fruit a corrugated nut covered by a semifleshy dark husk falls in October. During the ripening process the shell becomes hard and encloses the seed kernel which is generally made up of two halves separated by a partition.

The black walnut is of a high flavour but due to its hard shell is not grown commercially for nut production. Walnuts are a nutrient dense food and are also a good source of polyunsaturated fatty acids which are beneficial to the heart.

The trunk of the tree is widely used as a timber for furniture making and was fashionable as a veneer. The husks of the black walnut are used to make ink for writing and drawing and has been used by great artists including Leonardo da Vinci and Rembrant. They may also be used to make a dye which in classical Rome was used to colour hair.

Ground walnut shells were also used in American aviation for cleansing aircraft parts as they were inexpensive and non-abrasive. However after a fatal helicopter crash where it was revealed that walnut grit had clogged an oil port the practice was discontinued.

Come back in October for the ripened fruit but you might be too late as the local squirrels are very quick off the mark!


 
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