Roots 'n' Shoots: September 2013

Saturday, 21 September 2013

Winter Leafy Vegetables: How to Grow - Vegetable of the Month

Winter Leafy Vegetables stats/requirements at a glance

Ease of Raising:
1/5 – Daily Check-ups
Water:
3-4/5 – Every 2nd day to daily
Sun:
3/5 - Full sun, dappled shade
Training:
2/5 – Minimal; dead, diseased & damaged
Fertilise/Feeding:
4/5 – Fortnightly
Time to Harvest:
1-2/5 – Immediate (purchase) to Soon (from seed)
Frost Hardiness:
3/4 – Moderately tender (can’t cope with severe frost)


Uses
Culinary
Most Problematic Nemesis:
Dry, hot conditions & Aphids
Container Plant:
Yes

Lettuce & Spinach Botanical Print

Plaque 1: Botanical Lettuces Horticulture; Jardin potager et jardin fruitier 1870, Vintage Printable
Plaque 2:  Spinach, Flora von Deutschland ├ľsterreich und der Schweiz 1885, Kurt Stuber Online Library
Plaque 3: Botanical Lettuces Horticulture; Jardin potager et jardin fruitier 1870 Vintage Printable

Quick intro

Given the success I had with the winter leafy vegetables (spinach, pak choi and lettuce); I decided it needed a posting. Leafy vegetables are hard to grow during the hot and dry South African summer, since they bolt (go to seed before producing crop) – the exception being chard. This at least puts some use to the bare vegetable plots in winter J. I am going to discuss the cut-and-come again varieties and not the head forming varieties.

Winter Leafy Vegetables


History

The ancient Egyptians knew about lettuce (4500BC) and cultivated it for its leaves and seed oil. Later it was cultivated by the Romans and Greeks. Lettuce was introduced to Britain by the Greeks. In Europe many new lettuce cultivars were developed during the 1800s.

Pak Choi’s origin lies within China and has been cultivated there since the fifth century AD. It isn’t as widely cultivated in the Western countries as it is in Southern China and South-East Asia.

Spinach is quite the ancient traveller. Originating in Iran (ancient Persia) it was brought to China (600AD) via India, it spread to Spain in the 1100s, then to Japan and Korea in the 1400s-1700s and finally made its way to Europe in the 1800s.

Science Stuff

Lettuce, Lactuca sativa, belongs to the Asteraceae family, which includes daisies. Lettuce is classified into two categories; cabbage and cos. Cabbage lettuces have rounded heads with soft/crispy leaves, whereas Cos lettuces have elongated, upright heads. Sometimes a third category is suggested for loose lettuces (leaf lettuces) that don’t readily form heads and are the cut-and-come-again/perpetual varieties.

Slammer green oak
Lactuca sativa

Pak Choi, Brassica rapa (Chinensis group: Brassica chinensis), is a member of the Brassicaceae (Cabbage & Crucifer family) and more related to the turnips than cabbages. Now the Asian greens have similar common names and this can be very confusing. Some of the other names for Pak Choi include; Bok Choi, Chinese chard, Chinese mustard, celery mustard, spoon mustard and Choy Sum. The main classifying feature of the Chinensis group is the fact that is does not make a head.

Spinach, Spinacea oleraceae, is classified within the Amaranthaceae family (formerly the Chenopodiaceae; Beet & Goosefoot family). 

Growing Winter Leafy Veg

All the leafy vegetables listed here require the same conditions to grow. I had them in the full sun (maybe I should put the pak choi in the partial shade next winter…). Anyways, you can also try growing them in full shade in summer, but I have given up on growing them in summer as they are weak, stringy things that bolt.

Sow the seeds once the heat of summer has passed, preferably temperatures below 20oC (68oF). You can stagger your crop by planting at three week intervals, but I don’t think the SA winter is long enough for that – we only sowed once. Five of the Pak Choi (it is verrryy prolific!) and 8 of each of the others should be more than sufficient for the average family (of three-four people). The leafies can be sown directly into the garden or as start-up punnets and transplanted once the first ‘true leaves’ appear.

Loose Leaf Lettuce
Lactuca sativa

Keep them well watered, else you’ll have bitter leaves – or worse, bolting leafies! I fed them every two weeks with Starke Ayres Nutrifeed as a half-strength liquid feed.

They are generally are trouble-free as few pests are active during this time of year. I did notice however, with some warming temperature, that the aphids get to them. If these are a real problem, just zap them with my anti-aphid organic home remedy.

Other Winter Leafy Vegetable Tips

Mulching will help with water retention.

Thin out too densely planted leafies to prevent fungal disease.

Even though I had sown these in winter, the pak choi still went to seed when the day temperature goes above 15oC (59oF).

Pak Choi Bolting
Brassica rapa 
Chinensis Group
Pak Choi Bolting
Brassica rapa 
Chinensis Group






















Leafies can be grown in all the weird tiny spots of the garden or as a catch/fill-in crop between slow-growing vegetables (where they also mark out where the slower-growing vegetable has been planted).

Harvesting and Storing

The general rule is that you can harvest up to half of the plant at a given time. Harvesting regularly also stimulates the plants to produce more. Leafies are best harvested in the morning when they haven’t wilted yet and leaves cut with a knife or scissors.

You can’t really store the leafies on their own. All leafies can be left in a cup of water for 5-7 days. I also noticed that leaving them in the water for a day after harvesting takes away any bitterness. The Spinach and Pak Choi can be frozen, but then to go sloppy – so instead freeze them away as part of a ‘meal’. Such as, soups or stews, then it won’t matter too much if they are sloppy J.

Dash Spinach
Spinacia oleracea

Propagation

All leafies will go to seed when the weather warms up and the days become longer. If you can spare the space, let them set their seeds for easy collection.

Lettuces are self-fertile & self-pollinating meaning they do not need a pollinating partner. Seeds are harvested when dry and store in labelled glass jars. Seeds are viable for a whopping 6 years! The seeds are dormant after collection and can be used for next season’s plantings. Seeds need to be at 10-15oC (50-59oF) to germinate, higher temperatures (25oC+; 77oF) induces dormancy.

Pak Choi flowers are pollinated by insects (the bees appreciate the late-winter flowers when others are scarce). They need to be exposed to cold period in order to flower. Pak Choi may cross with other Brassica rapa spp., such as mustards and turnips – so hand pollinate and cover individual flowers for seed. Seeds mature from the bottom of the inflorescence upwards and the bottoms ones may burst before the top ones are ripe. Pick ripe pods (brown) and leave in a warm, dry place to cure. Pods burst open once ripe and seeds are separated from dried pods with a sieve. Seeds are held in 50oC (122oF) water for 20 minutes prior to sowing.

Pak Choi Flowers
Brassica rapa 
Chinensis Group
Pak Choi Seed Pods
Brassica rapa
Chinensis Group




















Spinach plants bare either male or female flowers. Males are borne on long and spindly stalk, whereas females are tight forming clumps at the base of the leaves. Females are wind pollinated. Seeds reach maturity once the plant leaves begin to yellow. Once plants are dry, strip the long stalks of seeds by pulling it through your hands from the base. Prior to sowing, hold spinach seeds at 50oC (122oF) water for 25 minutes to control seed borne disease.


Spinach Male & Female Flowers
Spinacia oleraceae
Afbeeldingen der artseny-gewassen met derzelver
Nederduitsche en Latynsche beschryvingen 1800
Kurt Stuber online library


My Winter Leafy Vegetables

I have a mixed seed pack of Starke Ayres loose-leaf lettuces:
‘Dorado’: Red loose leaf cos lettuce
‘Wahoo’: Green tango/curly loose leaf lettuce
‘Slammer’: Green oak loose leaf lettuce

Types of loose leaf lettuce

The other two are also Starke Ayres seeds:
Spinach: Baby Dash
Pak Choi


Pak Choi
Brassica rapa
Dash Baby Spinach
Spinacia oleracea














Do you grow specific vegetables in the winter? Or are you able to grow cool-season vegies year-round?

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Please share with fellow gardening enthusiasts via the various sharing buttons at the end of posts/pages! Else you can vote for posts through the Google reactions bar at the end of articles. To stay up to date I have provided several reader and social networking platforms with which to subscribe: TwitterPinterestRSS Feed Reader or Email/Follow directly using the Blog Followers widget on the left hand side toolbar. Thank you for reading and please feel free to ask if questions arise - I appreciate comments and ideas too! ­čść
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Saturday, 7 September 2013

Pesticide Resistance: Mechanisms & Prevention

I thought I would just share how pesticide resistance occurs in insect populations J. My studies are in the agricultural sector and I am familiar with this topic, so here goes…

Pests are considered resistant to a certain chemical compound (natural or synthetic compounds) when it is no longer killed or adversely affected by the chemical. Most pesticides target biological systems in order to control pest populations – “control” meaning; to reduce pest populations to levels that do not cause great plant or economical loss.

Pesticides can affect the nervous systems of insects, killing them directly or affect reproduction, such as decreasing the amount of offspring each generation. Pesticides can also be general, affecting a wide variety of insects, or target-specific, affecting a specific insect (aphids) or an insect suborder (Sternorrhyncha: Aphids, scale bugs and whiteflies).

Pesticide resistance is due to a beneficial mutation. The mutation usually occurs in the biochemical site affected by the pesticide, which is then rendered unrecognisable by the pesticide. Resistance can also be due to an increase of detox systems in the insect cell or chemical pumps that pump the pesticide out of the insect cell. These resistance mechanisms are inherited by the offspring of resistant parents. The evolutionary process behind the survival of the beneficial mutation each successive generation is known as natural selection, the Darwinian mechanism of survival of the fittest.


Blue: Susceptible
Red: Resistant

Resistant mutations accumulate through natural replication errors within the DNA of the organisms. Resistant organisms (Parental generation) will survive and reproduce. Their offspring (F1: First generation) will survive subsequent pesticide treatments, and over several insect generations (can be as little as 1-2 years) a resistant population will develop.

Pesticide resistance can remain in insect populations after the product has been discontinued for as much as 2 years. After which the resistant mutation will decrease slowly. After a few years pesticide susceptible insects will dominate the population once more. Resistant insects have a reproductive deficit in an environment with no pesticides, they produce less offspring than susceptible insects and subsequently decrease in the population.

The prevention of pesticide resistance is to use pesticides correctly:

├╝    Use pesticides according to the manufacturer’s instructions (not more and not less). This goes for both the concentration at which the pesticide is made and the frequency of use. This prevents resistance and reduces the impact on the environment.

├╝    Changing the Class of pesticide (such as chlorinated hydrocarbons, cyclodienes, organophosphates, carbamates, pyrethroids, neonicotinoids) every season will prevent resistance to a single type of pesticide. Mixed, combination or multiple class pesticides will result in multiple-pesticide resistant insects.

├╝    Specific pesticides (such as those just for aphids) will reduce the chance of poisoning other beneficial insects or the induction of resistant in non-target insects.

├╝ Make up enough pesticide for your present application. If you are left with some remaining pesticide-solution, pour it into a plastic bag, tie off and throw into the dustbin - this prevents any pesticides going into the water supply. Wash out pesticide equipment with soap (dish-washing liquid is fine); this will help break down any residual pesticides in the water.




Preferable pest management systems include the use of pest predators, crop rotations and preventing pests from attacking stressed plants (good soil, regular water = healthy and resilient plants) in the first place - AKA Integrated Pest Management: IPM. Planting pest and disease resistant cultivars also go a long way in preventing pest populations form reaching epic proportions in the garden. If a plant does not grow well in your garden or is a weak specimen it is better to remove it than face a constant battle with it harbouring pests (one of the reasons I don’t really like sacrificial companion plants).

I don’t advocate against the use of pesticides, but I don’t judge those who do use them either. In rural communities, the use pesticides on crops is the only way for them to sustain themselves and feed their families. So instead of telling everybody not to use pesticides, I supply information on safe and effective use. I prefer natural remedies to pesticides. For some environmentally safe and home-based pest control recipes, check out Pest Control.


That basically sums it up J.

Related Posts

Insectary - attracting pest predators and beneficial insects to your garden
Pest Control - Organic control recipes

Biological Control:
Mantis
Wasps
Flies
Ladybeetles

Pest Profiles
Leafhoppers

______________________________________________________________________________

Please share with fellow gardening enthusiasts via the various sharing buttons at the end of posts/pages! Else you can vote for posts through the Google reactions bar at the end of articles. To stay up to date I have provided several reader and social networking platforms with which to subscribe: TwitterPinterestRSS Feed Reader or Email/Follow directly using the Blog Followers widget on the left hand side toolbar. Thank you for reading and please feel free to ask if questions arise - I appreciate comments and ideas too! ­čść
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