Native Cresses and Cabbages.

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Native Cresses and Cabbages

The spectrum of attributes and uses amongst the 3500 annuals or herbaceous perennials making up the Cabbage and Cress family (Brassicaceae) are impressive. Of the well known members, the vegetable varieties of Brassica oleracea ssp. (Cauliflower, Broccoli, Cabbage, Kohlrabi and Kale), the salad leafy greens from the Water Cresses, the staple root crops from the Radish and Turnip tribes and the spicy Black and Yellow Mustards (Brassica nigra & Sinapis alba) have well deserved reputations.

For the native plants enthusiastic there are the 150 Australian Brassicaceae of which 20 are indigenous Tasmanian species. Typical are the numerous edible species such as the peppery Slender Bitter Cress, Cardamine tenuifolia and moisture loving Perennial Marsh-Cress Rorippa dictyosperma.

Unfortunately, within the family there are many persistent agricultural and environmental weeds of which none are more persistent than Charlock and White Weed (Sinapis arvensis & Cardaria draba). The weeds, like many of the others have originated from medieval herb gardens.

As an offset to this weed problem, today's floral display gardens have benefited from the hundreds of years of fastidious plant selection to form many well-loved flower favourites. These include the cheery winter flowering Wallflowers Cheiranthus sp., bold colourful Stocks Matthiola incana and the sweetly scented Alyssum varieties (Lobularia maritima).

Other members originally cultivated in monastic gardens have given rise to an array of useful plants. These include medicinal herbs such as the decongestants (Wintercress, Barbarea sp.) and condiments (horseradish). However, one shouldn't forget the natural insecticides or biofumigants (Mustard green crops) and the vegetable oil/margarine sources derived from Rape seed, now commercialised under the marketing name of Canola.

Interestingly, a pronounced characteristic of these family members is their distinctive 4-petalled, cross-like flowers. This feature was used to derive the original family name of Cruciferae, Latin for Cross former.
Bush Tucker favourites

Water cresses, both native and introduced, have been part of our diets for millenniums. Tim Low in his book "Bush Tucker" pointed out that "this little herb with the big name of Rorippa nasturtium-aquaticum, is the only well known vegetable that has not been transformed by centenaries of horticulture". The supermarket version is exactly the same as the wild plants found in drains and rivulets. It actually contains more Vitamin C by weight than oranges!

Following the Colonial Botanist Joseph Hooker's conclusion that the greens from Native Cresses such as (Rorippa dictyosperma, Cardamine gunnii & C. tenuifolia), afforded excellent pot-herbage, the native varieties soon became popular as a means of reducing scurvy amongst bushmen and sailors.

Native Cresses were similarly collected by both the aborigines and early colonists, for use as spicy bush greens and/or peppery herbs. Aborigines steamed them on hot rocks within earthen pit-ovens, allowing their peppery flavours to infuse through their kangaroos and other game meats. These spicy infusions were commonly extracted from herbs such as the rare Rubble Pepper Cresses, Lepidium hyssopifolium (distinguished from other Lepidium sp. by the thick hairs on its flower stalks), the Tasmanian Pepper Cress L. pseudotasmanica and the endangered, endemic Thread Cress Stenopetalum linearis. Surprisingly, the only location where they still flourish is under the drip lines of large gums, she-oaks, wattles and even exotic pine trees, where competition is minimal.

Many leafy greens, including the endangered Native Winter Cress Barbarea australis were collected by aborigines along river flats and banks. Their zesty, tender young green shoots and their ground dried seeds and pods acted as a spicy condiment for game meats.
Degradation threatens their existence

Disappointingly, many of Tasmanian's Brassicaceae remain under threat of extinction. For example, the limited river side habitats for Barbarea are being subjected to altered flow regimes due to the effects of willows, in-stream dams and tree plantations. These degrading impacts reduce or often eliminate the natural flood cycles that are required for the Winter Cress's seed germination.

Over the history of pastoral activities, the preferential grazing for these tasty inter-tussock Native Cress species, by sheep, cattle and rabbits has all but eliminated them from native-grass pastures. Sadly, the tiny much branched annual herb Southern Shepherd's Purse Ballantina antipoda, which occurs in moss mats on basaltic or granitic seepage areas, is rarely seen today, due to this rabbit and wallaby grazing, whilst the annual herb Hutchinson tasmanica, (last collected by Gunn in 1848), is now assumed to be extinct for the same reason.
Brassica weeds are valued as medicine and food

Most Brassica weeds introduced from England and America have long histories of cultivation for a variety of food and medicinal uses. These include the agricultural weeds Wild Radish Rapanus sp., Field Cress Lepidium campestre and the yellow-flowering Indian Hedge Mustard Sisymbrium orientale along with the garden weed, Shepherd's Purse (Capsella bursa-pastoris).

The old English herb 'Splitting Jenny' or 'Common Bitter Cress' (C. hirsuta) is better know to nurserymen today as the irrepressible 'Flickweed'. From its ripe pods seeds are ejected for metres. These germinate rapidly on any moist substrate creating a huge weed problem. The only positive feature is its tasty Water Cress- like foliage.

Although attractive and tasty in salads, the weedy Nasturtium (Tropaeolum majus) derives its name from Latin for 'nose-twisting' alluding to its pungent leaves. These were cooked as tasty green, whilst the seed pods were pickled as capers.

Another useful weed, introduced as ballast in early1800's, is the beach weed American Sea Rocket Cakile edentula. It provides spicy mustard-like young shoots which emus adore. More importantly, the seeds often sustain the rare Orange Bellied Parrot prior to migratory flights across Bass Strait.

Shepherd's Purse is another good example of the variety of uses given to many of these weeds. Its young crisp leaves were cooked in soups and stews, whilst by grinding their dried peppery pods and seeds, mustard and a tenderising salt were produced. The seeds were sprouted and eaten like Watercress presenting a rich in Vitamin C source. As a medicine, in the form of a strong decoction, it stopped internal bleeding and was regularly used during childbirth to contract the uterus. Many of the Cabbage family's weeds contain sufficient amounts of the active ingredient isothiocyanate ITC to gain herbalists recommendations as an anti-carcinogen. They also are noted for their ability to break up congestion in the lungs but too much can cause a Depression of the thyroid function.
The first Weed called Woad

When the Roman's invaded England they were greeted by a horde of barbaric warriors painted with a bright blue dye extracted from the Woad plant (Isatis tinctoria). This very resilient herb, which is covered with masses of golden flowers in spring and forms a deep foraging root system, was the source of a highly valued dye. By the 15th century, Woad was in such huge demand as a fabric dye; it attracted the princely sum of 10/- per cwt at London markets. This resulted in it being cropped far and wide across England. However, by the 16th century many alternative dyes were available and Woad became less valued. The lack of interest initiated its escape across the countryside, finally becoming a bugbear to farmers who desperately tried to eradicate it. The modern day term weeding is a corruption of the olde term 'woading'.
Brassica's active ingredients are ideal soil bio-fumigants

Most of the older folk can remember their Mum's repetitive plead "Eat up your Cabbage and Brussels sprouts or there will no dessert".

Little did our mums know that these vegetables were an acquired taste and definitely not for the sensitive palates of kids. This is due to the strong flavours associated with the sulphur containing compounds (Glucosinulates), which after chewing; release a strong flavoured derivative called Isothiocyanates or ITC. The attraction for this strong taste is akin to how a mature palate has developed a liking for red wine.

This ITC is very toxic to a range of plant pests and diseases. By growing mustard cover crops or including cabbages, broccoli, Brussels sprouts, native cresses etc, in agriculture crop rotations and vegetable gardens, the soil will be naturally bio-fumigated by the residual ITC. Substantial enhancement in plant health of the following-on agricultural crops or vegetables is clearly evident.
Bio-diesel and Insecticides from reused Canola Oil

The Cabbage family member Canola leads the forefront in alternative fuel technology. Recycled Canola oil has become valuable following its conversion to bio-diesel using a catalysed methanol. Today petroleum based diesels are being mixed with this bio-diesel resulting in significant reduction in air pollution. Ironically this process is leading refineries away from the mineral oils and back to original vegetable based diesel fuels.

An important by-product of bio-diesel production is a Natural Mustard Insecticide containing ITC.
Cabbage White Butterfly is friend or foe?

One important insect which devastates crops from the Cabbage family is the Cabbage White Butterfly. It is rapid flying white butterfly, which is not only an attractive garden member but also supplies a major food source for our native birds.

Although it is a problem for all Brassica growers, they are easily controlled by well timed applications of the parasitic Bacillus thurginensis marketed under the name of 'Dipel'. These little bugs parasitise their bottled-shaped, cream coloured caterpillars and swiftly interrupt their lifecycle.
Conclusion

It is hard to image the world without the contributions made by many of the well known Cabbage and Cress family members. However, care is needed to ensure that their gene pool remains as diverse as possible by including in revegetation projects, where possible some of its rare indigenous members.

Article contributed by Phil Watson