Autumn is a good time to check your citrus trees for magnesium deficiency. Citrus have a high magnesium requirement and magnesium is essential for the formation of chlorophyll (green colour) in leaves. Without enough magnesium plants will not be able to make sugars and starches, and growth will be poor.
Magnesium deficiency often shows up in citrus in autumn because magnesium is also required for developing fruit and many citrus species produce fruit over the cooler months.
Because magnesium is very mobile in plants, a shortage of this essential element results in magnesium being drawn from the older leaves to new growth. Deficiency shows as pale leaves, beginning with inter-vein yellowing of the outer edges of the oldest leaves, so that a green V remains with the point of the V at the leaf tip, and widest part of the V closest to the stem. In extreme cases, entire leaves may yellow.
Magnesium deficiency can occur in several ways. If soil is too dry roots can’t absorb magnesium, so regular watering of citrus is necessary. It is more common where soil is quite acidic and this can be remedied by watering in some dolomite, which will supply magnesium, plus calcium to raise the pH. If soil pH is in a suitable range for citrus, magnesium deficiency can also occur where heavy rain has leached it from soil, or where excess potassium has been added to soil – this includes use of wood ash, or overuse of seaweed fertilisers, which can cause a build up of potassium.
In these situations, a quick remedy to save this year’s crop is to dissolve some Epsom salts in a small amount of warm water, then dilute it in a full watering can of cold water, and water it into the soil under the outer part of the foliage canopy. You will need about 250 g of Epsom salts for a very young tree, and up to 2 kg for a fully-grown tree.
Magnesium is also important for sweetness of fruit. If your citrus fruits are not as sweet as you would like, it could be due to magnesium deficiency. However, a general yellowing or paleness of all leaves (chlorosis), while only the veins remain green, could be the result of iron deficiency. Iron deficiency begins in the youngest leaves. This can occur where soil is too alkaline for the tree to absorb iron. If the alkalinity occurred through an accidental overdose of lime or dolomite, the pH can be lowered by adding elemental sulphur to the soil around the tree. If soils are generally alkaline, including some well-rotted cow or horse manure that has NOT had lime added (under mulch, but not dug in) as part of your fertiliser will help reduce the pH by replacing some of the calcium ions in soil with hydrogen ions as it decomposes. To prevent crop losses, it is worthwhile checking soil pH around citrus trees each spring, and correcting it, if necessary.
See also: Feeding citrus
Autumn is a good time in most Australian gardening zones for maintenance work in the garden. My kitchen herb garden needed a serious renovation after three of our chooks escaped from their run during summer and made a total mess of everything. As summer was extremely hot and dry this year, I decided not to replant until after the weather cooled and we had some decent rain. Replacement plants were kept in the shade house until weather conditions were less stressful. In the meantime, I added some compost, worm castings, poultry based fertiliser, and seaweed tea to the soil; dug out weeds and errant roots of the mint family that had strayed far beyond their allocated area; and checked the soil pH. As it was barely on the acid side of neutral, I did not need to add any dolomite.
Although we grow some culinary herbs commercially, it is a nuisance to have to wander down to the herb beds when I want a few sprigs of something for a recipe. Consequently, my husband set up the framework for a kitchen herb garden close to the house. The finished garden measures 7 metres by 4 1/4 metres.
As the ground slopes slightly, the outer border of the garden was made from bricks retrieved from a demolished wall, and second-hand pavers provide pathways for easy access to all the herbs. The bird bath in the centre provides water for birds, bees and wasps that provide pest control and pollination. The garden has a permanent border of French lavender that serves several purposes. Lavender essential oils deter garden pests and, during the cooler months, the flowers are sold to a local florist. The hedge also protects the more delicate herbs from hot winds. There is a break in the hedge on the low side of the garden to allow cold air to drain away. A solid hedge traps cold air and allows frost to form. The herb garden also provides a suitable setting for my sundial.
I like to renovate my herb garden every three or four years as the perennial herbs such as rosemary, sage, thymes and mints don’t make as much strong, tender growth as the plants age. We find we get better production from younger plants that we grow from cuttings of the old stock. When I replant annual and perennial herbs, I always change their position in the garden as these plants also require a proper crop rotation to prevent soil diseases, and my herb garden is never completely full of herbs as I leave spaces for the rotation of annual and biennial herbs each season.
The garden looks quite bare at the moment (but it is easier to see the layout). I have very recently planted chives, rosemary, lemon thyme, marjoram, oregano, spearmint, eau-de-cologne mint, sweet basil, parsley, rose geranium, French tarragon and several more common thyme plants. The lemon grass clumps and the horseradish roots survived the chook attack, as did the soapwort. (Soapwort is not a culinary herb, but I didn’t know where else to put it). Coriander and dill will be sown later this month as they both do better here during the cooler months. After planting, the garden was mulched with finely chopped organic sugar cane residue as this will break down more quickly than other mulches, and add more organic matter to keep soil healthy.
This has nothing to do with gardening, but I thought I would share it with you as it was fun to make, and something to keep the children entertained when it is too hot or wet for them to play outside.
The cubby can be made from material scraps, or old curtains or bedspreads. I made this one for our granddaughters from discounted sale fabrics, only because I didn’t have any pieces large enough for the roof and walls. The roof and walls were made from cotton drill, and appliqué bits were made from scraps from my material bag. I purchased extra fabric so that I could wash the fabric before cutting out the pieces, as cheaper fabrics are not usually pre-shrunk before sale. A large window on the side opposite the door, and another on a short side allows good light and air circulation. Windows and doors can be any size that suits individual preferences. The windows are covered with scraps of mosquito netting or tulle to keep out flies and help the walls keep their shape. The curtains were made from a piece of café curtain fabric. The letterbox has a usable slot, and the door is a simple tent-style flap.
This type of cubby house is suitable for tables that have corner legs, rather than a pedestal support, and can be made to fit any size table. Measure the length and width of the top of the table the cubby is to fit. Add one cm to each measurement for an easy fit, plus 3 cm for seam allowances. The wall height is the distance from the table top to the floor plus seam and hem allowances. The girls love their cubby house, and it could be made in the style of a fortress or castle with tall, narrow windows. The design is limited only by one’s imagination. This type of cubby house is easy to erect and fold away. I also made a drawstring bag from scrap material for the folded cubby, for easy storage.
I sometimes hear garden experts say that organic fertilisers are not as high in nutrients as chemical fertilisers, so you have to use more of them. This is simply not true.
The American Association for the Advancement of Science (AAAS) reported in February, 2009 that hundreds of studies have shown that “incrementally higher levels of fertilizer negatively impact the density of certain nutrients in harvested foodstuffs.” They also reported that the complex way in which nitrogen is absorbed in organic cultivation results in more efficient assimilation of the nutrient, allowing organically grown plants more energy to produce antioxidants, and the formation of less nitrates. Nitrates in food can form carcinogenic nitrosamines in the digestive tract. AAAS Conclusions
Excess use of nitrogen fertilisers (including uncomposted manures and manure teas) promotes bursts of soft, sappy growth that is much loved by chewing and sap-sucking garden pests. Overuse of a particular nutrient can block the absorption of other nutrients. Nitrogen and phosphorus compete for absorption. Overuse of chemical nitrogen fertilisers can also result in deficiency of the less mobile phosphorus.
Organic fertilisers don’t need to be as high in nutrients. Organic fertilisers made from a variety of recycled organic matter will contain a full range of major nutrients and trace elements. Organic fertilisers in the form of compost, castings from worm farms, animal manures, leaf mould, and broken down green manure crops and organic mulch add humus to soil, but chemical fertilisers do not.
Humus, the most stable form of organic matter, consists of electrically charged particles called ions. Nutrient elements also carry a weak electrical charge. Humus has a large surface area and many charged sites to hold nutrient elements through electrostatic force where they are easily accessible to plants, and regulate their absorption so that nutrients are not absorbed by plants in toxic quantities. Humus also provides a habitat for a group of beneficial fungi that assist nutrition in a wide range of perennial plant families. Some chemical fertilisers, such as superphosphate, suppress the activity of these fungi and other beneficial soil organisms.
Although clay particles in soil also carry an electrical charge and are capable of holding some nutrients, without humus in soil, phosphorus can become locked up with iron, manganese or aluminium, and unavailable to plants, and nitrogen and sulphur can leach from soil.
A suitable soil pH plays an important role in efficient absorption of a full range of nutrients. Adding extra fertiliser when soil is too acid or alkaline for particular species of plants will not help their growth. Humus in soil assists in maintaining a suitable pH. See:Changing soil pH
Although we tend to worry about plants getting enough fertiliser, fertiliser plays a relatively small, but essential, part in plant growth. The major contributors to plant energy are water and carbon dioxide. In the presence of sunlight, the green parts of plants can convert these into carbohydrates, which form the cell structure of plants. You could say, in fact, that plants are solar powered.
Pieter has had a severe aphid infestation on his zucchini plants, and applying a dishsoap/water spray not only killed the aphids, it also killed the plants. He wants some tips on a better way to deal with aphids.
Aphids are fairly easy pests to get rid of without resorting to chemical pesticides. Aphids have a lot of natural predators, but the sprays will also kill these, resulting in more intense pest infestations in future.
Moderate infestations of aphids can be blasted off plants with a jet of water from a hose or a spray bottle set to ‘stream’. For plants with hairy leaves (such as zucchinis) apply water early in the day so that leaves can dry before night. If you blast them with water before serious damage occurs, predators will be able to control any escapees.
Severe infestations can be removed with a soap spray, but not with detergent or bathroom type soap, which has a caustic soda base. The soap used in soap sprays to kill pests has a potassium base, and is available from nurseries, or can be purchased by mail order from Green Harvest. ‘Natrasoap’ does not leave a residue on plants, nor will it burn leaves if used in temperatures below 30° C.
In order to prevent future infestations of aphids, avoid overdoing nitrogen fertilisers because aphids are pests that are attracted to a flush of soft, sappy growth that excess nitrogen, or erratic watering, produce. Controlling weeds in the growing area can also help prevent aphid attack. Many weeds are host plants for aphids, allowing a large colony of pests to establish before you notice them. As aphids can carry viruses for which there is no cure, prompt removal of these tiny pests is advised.
When sowing seed directly into garden beds, or when planting out seedlings, or planting shrubs and trees, always make sure that soil in the growing area is thoroughly dampened BEFORE sowing or planting. Then, after sowing or planting, you only need to add enough water to settle soil around the seeds or roots. Soil should be what is known as “dark-damp” before you add seeds or plants.
This practice is very important because, if soil in the growing area is relatively dry and you only apply water to the seed row or plants after you put them in the soil, some of the water you apply will be drawn away from the seeds or plants into the surrounding drier soil. The dispersion of water into drier soil is a common cause of germination failure, or seedlings, shrubs and trees drooping several days after planting.
When sowing seed, or planting out seedlings, thoroughly water the furrows or planting holes first. Check that you haven’t just wet the top centimetre of soil. For successful germination, soil must remain dark damp, and a very light application of fluffed-up organic mulch across the growing area or between rows can help prevent water loss through evaporation. Seeds sown in dark-damp soil don’t usually require soaking before sowing, with the exception of silver beet and beetroot as these have a thick, corky outer layer. If legume seeds are sown in dark-damp soil, they do not require soaking beforehand because over-wet legume seeds may rot before germination.
When planting shrubs, trees and vines where soil is not dark damp, fill the planting holes with water and plant only after the water has drained away. After planting, apply enough water to settle soil around the roots and apply a 5-7 cm of organic mulch to prevent water loss through evaporation.
Onion weed (Nothoscordum inodorum) seems to cause problems for quite a few gardeners who are unsure about organic ways to be rid of this pest. I did cover onion weed previuosly in a post on perennial weeds but, as it is a common problem, it might be worth covering it separately.
It is fairly easy to eradicate it from lawns, by keeping grass growing vigorously. Healthy lawn grass will out-compete onion weed in a fairly short time and no other treatment is necessary. In fact, onion weed in lawns is merely a sign that your lawn needs a bit more TLC.
Onion weed in garden areas is an entirely different problem. Because onion weed is a perennial weed, it stores nutrients and carbohydrates in its bulbs to generate growth in the following season, in the same way as spring bulbs such as daffodils. Trying to pull out or dig up these weeds in garden areas results in the parent bulbs releasing tiny bulbs (bulbils) from the base of the main bulb. These grow into mature plants, and all the digging has achieved is multiplication of the problem. To get rid of onion weed, you have to prevent the bulbs storing food for growth. Onion weed can also produce seed. Cutting off the foliage at ground level will prevent the plants making carbohydrates in their leaves, and also prevent seed forming.
In an unused garden area, you can do this by slashing, or mowing, the foliage to ground level, then covering the area with black plastic for several months. Anchor the edges of the plastic with planks, bricks or whatever you have to prevent it blowing away. Deprived of moisture and the sunlight that enables it to store carbon dioxide as carbohydrates (photosynthesis), the bulbs will weaken and die. Avoid using clear or light plastic, as these will still allow the plants to photosynthesize and, in some conditions, they can actually improve weed growth.
In garden beds that are being used, onion weed is more difficult to eradicate because the bulbils can be released whenever you disturb the soil. Cut off the foliage at ground level with shears to prevent it making food for the bulbs. Then mulch the beds with 5–7 cm of mulch. You may have to cut back foliage several times as soon as it appears. If you do this consistently, bulb growth will become progressively weaker, and you will eliminate the problem without disturbing the soil and stimulating the growth of more bulbs.
When you have a chance to leave a particular bed lying fallow, you can give the bed the black plastic treatment. Onion weed is more commonly found in undernourished soils, or where soil pH is unsuitable for healthy plant growth. Where onion weed has been a problem, check your soil pH, and improve organic matter content in soil to prevent the problem recurring.
I’ve had to neglect my blog somewhat in recent months as I have been kept busy preparing and promoting the new edition of my book Easy Organic Gardening and Moon Planting, which was released last Monday. I wrote the book to encourage more Australian and New Zealand gardeners to have a go at organic gardening and discover how easy it is, and how it is better for our health and the environment. For details, click on the ‘About’ button at the top of this page.
WAHMania’s competition to promote the new edition has now closed, and we will be announcing the winner here on Thursday, 12th March.
With the weather cooling slightly, I am looking forward to being able to spend more time catching up with my own gardening, and helping readers with any gardening problems.
HOMEMADE WORM FARM My husband has been busy with his chain saw carpentry again. He rescued a shower base bathtub from the local tip to make a small worm farm that could be set up in a shady spot near the house. This makes it easier for me to collect worm castings for my seedlings and pot plants. Worm farms are a wonderful way to recycle food scraps and household waste into fabulous 100 % organic complete fertiliser with a neutral pH.
Old bathtubs are hard to come by in our area, as they are popular for recycling as water troughs for horses. However, this tub was missing the plug rim and unsuitable for use as a water trough, so it was a lucky find.
Using his trusty chain saw, Brian built a simple frame for the tub, using scrap hard wood pieces from around the farm. The cover consists of recycled hardwood planks, placed side by side, across the top of the farm. Only the two end planks are attached to the frame. The loose planks allow me to expose as much, or as little, of the worm farm surface as I want when adding food or collecting castings. A large square of fly screen was placed across the base of the tub before filling to prevent the worms and castings falling through the drainage hole. A bucket is positioned under the drainage hole of the tub to catch the liquid that drains from the worm farm.
A layer of edible bedding is needed across the bottom of the farm container for to keep the worms damp and protect them from temperature fluctuations. I added some of the digested matter from our main worm farm for bedding as this contained both worms and worm eggs to ensure that numbers in the new worm farm will build up more quickly. However, for new worm farmers, bedding can be shredded and soaked coconut husk fibre (Coco peat), or damp, aged cow or horse manure, and the starter worms are placed over the bedding where you want them to feed. I added some chopped scraps (in a 2-cm layer) to one half of the surface of the farm, so that the worms would be concentrated in that area. The surface of the farm was then covered with wet newspaper and the cover planks over the top of the farm. (A temporary plastic cover goes on when heavy rain is predicted.) Food is replaced as often as necessary. If your worm farm is new, don’t give them too much food at first or it will be a while before they eat all the food, and it will start to smell. But, if you don’t give your worms enough to eat, their growth and reproduction will be slow.
As worm numbers increase, they will be able to process larger quantities of waste. Once the worms have turned the food and bedding in their area into castings, I start putting food at the other end of the farm. This allows me to collect castings more easily from the other half and pour water through the processed bedding to collect some liquid for my plants. It is not recommended to pour water through undigested food in worm farms in case the food has been affected by fungal or bacterial disease. However, using common sense and following the organic principle of “feed the soil, not the plant”, avoids problems with liquid fertilisers.