Is this the perfect permaculture plant? Well, it ticks a lot of boxes – nitrogen fixer, tough evergreen shrub, makes a good hedge or windbreak, is a useful dense habitat, edible fruit, has perfumed white flowers, is a bee plant… what more could you want? The same claims can be made for its deciduous relative the Goumi, but the Silverberry has a huge advantage in Australia – it is easier to get hold of.
Silverberry is in the genus Elaeagnus making it a relative of the Goumi, the Russian Olive and the Autumn Olive, (neither of which are actually olives). The genus includes both deciduous and evergreen species which are known for their ability to fix nitrogen through bacteria in nodules on their root systems and for their edible fruit. As the botanical name suggests silverberry is a hybrid, a cross between Elaeagnus pungens, a ferocious, thorny climbing shrub and the silvery and much-better-behaved Elaeagnus macrophylla. The result of this naturally occurring cross is an old fashioned, super hardy and tolerant garden shrub with evergreen foliage, silver on the underside, tiny discreet but heavily perfumed white flowers in autumn and silver ripening to red fruit the size of a grape in spring.
The fruit is acidic but compelling in a similar way to the addictive sour fruit of its relative the Sea Buckthorn (Hippophae rhamnoides), but does need to be fully ripe to be enjoyable. It sweetens when cooked so slightly under-ripe fruit make a good jelly. There is a relatively large seed which has a pleasant flavour once the fibrous coating has been removed (just spit it out after eating the fruit and seed!) The seed flavour is described as tasting like a peanut, but we actually think it tastes like an almond. Yield is varied between plants and conditions with some sources suggesting greater fruit production from plants under some degree of stress. The presence of other cultivars such as the variegated forms “Limelight” or “Gilt Edge” has been shown to increase fruit set.
Silverberry fruit contains good quantities of vitamins A, C, E, antioxidants and fatty acids. These fatty acids are also found in its relative the Sea Buckthorn and have been investigated for their use in cancer prevention. The seeds are a good source of fats and proteins.
Silverberry will tolerate most soils, dry conditions, shade, wind, frost and salt spray – a truly indestructible plant for difficult conditions. It is hardy to -20 C but does not like waterlogged soil. Left to its own devices it will eventually grow up to 5m x 5m with new growth forming long stems over a metre long which will climb into the lower branches of nearby trees if allowed. All of these qualities make it an excellent fruiting hedge plant or member of a mixed hedgerow.
All members of the Elaeagnus genus form nodules on their roots in association with nitrogen-fixing bacteria, allowing them to generate some of their own nitrogen requirements from nitrogen in the air and also to release nitrogen into the surrounding soil for use by plants nearby. They do this when they are pruned and also the leaves dropped contain significant quantities of nitrogen when they break down in the mulch layer. Martin Crawford from the Agroforestry Research Trust in the UK suggests they release nitrogen in amounts as high as 23g/m2/yr and that the presence of one Elaeagnus will supply the nitrogen needs of 3 apples / pears of similar size (or 2 plums or nut trees which require more nitrogen).
Elaeagnus are known as actinorhyzal nitrogen fixers due to the type of bacteria they form associations with and they are particularly useful because they will still produce some nitrogen even when the plant is shaded. Legumes such as peas, beans and Tree Lucerne (Tagasaste) only fix nitrogen when they are grown in full sun.
All Elaeagnus are pollinated by bees and are an excellent source of nectar. As such, it is a useful late-flowering plant for the autumn bee garden.
Propagation is by cuttings, as it will not come true from seed. Try semi-hard cuttings 7 to 10 cm with a heel, in summer.
Other useful forms of Elaeagnus include a ground cover form of Autumn Olive (Elaeagnus umbellata var. rotundifolia), which has stunning silvery foliage and small round leaves. It should also flower and fruit although we have yet to see this on our plants. It does need a clip to keep it to a “taller” ground cover of about 60cm but makes a nice splash of silver in the garden and releases nitrogen whenever it is clipped. Elaeagnus macrophylla is a very silver taller plant with perfumed flowers although again we have yet to see fruit. It may be used to form a hedge to excellent effect as seen at the rear of the vegetable garden at Cloudehill in Olinda.
So what to do with this wonderful permaculture plant in design? Several scattered shrubs throughout an orchard would work to increase fruit yield and add nitrogen to the soil. A surrounding hedge would be even better. It makes a good windbreak with edible fruit or it has also been used to “fill in” the bottom of a tall farm windbreak which had lost its lower limbs. In smaller gardens it can form a hedge at the back of a border as shown in the photo,Single shrubs are useful in the back row or between other fruiting plants as it will tolerate the shade and not compete for nutrients. The ground cover form is excellent as an under planting for fruit trees.
Why is this not the perfect permaculture plant? Because it doesn’t actually have a good common name (Ebbing’s Silverberry is a mouthful) and no-one ever asks for an “Elly Agnes”!! Time for some re-branding perhaps?