The importance of humus

Soil without humus is lifeless – it’s dead soil. Humus, the indigestible part of decomposed organic matter, literally converts soil into a living thing because it provides a habitat for beneficial fungi that feed nutrients to many plant families, and microorganisms that keep soil-borne plant diseases under control. It also keeps soil more moisture retentive, yet better drained; improves soil structure; holds nutrients in a form that is easily absorbed by plants; insulates plant roots by keeping topsoil cooler in summer and warmer in winter, and acts as a buffer against extremes in soil pH through a complex exchange of electrically-charged particles in soil. Regular replacement of humus in soil is absolutely essential to healthy plant growth. Humus can be added to soil as compost, green manures, well-rotted, herbifierous animal manures, poultry manures, organic mulches, decaying roots and plants.
The vegetable garden will require the lion’s share of organic matter, but it is very important to fruit trees, and many foreign plants, too. Many Australian natives prefer humus supplied through leaf litter, or leaf mould. Plants from arid soil areas have evolved to require only small amounts of humus.

Applying compost

The best way to add humus to your garden soil is mature compost, which is a mixture of worm castings, beneficial microorganisms, and humus. Compost is not only a fertiliser; it stimulates soil organism activity by providing them with food. Compost made from a variety of sources contains all the nutrient elements required by plants but, for those of us that don’t have an unlimited supply of compost, green manures are an excellent substitute.
In vegetable gardens, a 3–5 cm layer of compost can be applied to beds and mixed into the top 15 cm of soil. If mature compost is in short supply, adding compost to the planting hole or furrow when planting out seedlings or sowing seed will get your plants off to a flying start. Compost can be applied this way to flowering annual and spring bulb beds, too.
Under fruit trees, and around roses and herbaceous perennials, compost should be applied to a damp soil surface under the outer part of the tree or plant foliage canopy – i.e. not close to the trunk. Don’t scratch it into the surface. Many trees and shrubs have feeder roots close to the soil surface and these are easily damaged. If you have plenty of compost, it can replace the tree’s fertiliser, except for an annual application of seaweed tea. If you don’t have a lot of compost, it can form part of the fertiliser application. Every bit of compost that you can spare is very valuable.
The compost should then be covered with 5 – 8 cm of organic mulch to keep the compost damp – also keeping the mulch well clear of the trunk. When compost dries out it loses a lot of its benefits. The mulch will break down to contribute to good garden loam, but its most primary function is to keep the soil surface and compost damp.
If you apply compost annually under your fruit trees and shrubs, you will find that “so-so soil” will steadily convert to dark, sweet-smelling loam full of earthworms – just the type of soil these plants love. Your trees and shrubs will also be more resistant to pests and diseases.

Taking cuttings

Full Moon phase is a good time to take cuttings, and cuttings can be taken from deciduous plants from hardwood stems, while pruning. Always trim to a horizontal cut at the bottom of the stem to be used for cuttings, and make a slanted cut at the top, otherwise it is easy to plant deciduous cuttings upside down. The chosen section should contain 5 or more nodes (joints in the stem) to allow for trimming.
Fill pots with a sandy potting mix, and trim the base of the cuttings (with a horizontal cut) to just below a node. Position the cuttings around the inside edge of each pot spaced far enough apart to allow roots to spread. Try to have two nodes below the level of the potting mix. Water gently to settle the mix around the cuttings. Keep potting mix just damp, and keep cuttings in a warm, well-lit area out of direct sunlight and wind until the cuttings show signs of growth. Carefully move them into separate pots and feed with weak fertiliser tea, until ready for planting out.

Winter pruning

A Full Moon phase during winter is a good time to prune most deciduous plants. From 19th of this month is a good time to prune dormant trees and vines that tend to bleed (weep sap) if pruned in late winter. These include grapes, kiwi fruit, mulberry, birch, conifers, frangipani, maple and poplar. Pecans, which bleed readily and require minimal pruning, are best pruned during Last Quarter phase (from June 26th) when sap flow is lowest. Almonds should also be pruned early in winter because they flower earlier than other Prunus species. Other deciduous fruit trees can be pruned in winter with the exception of apricots and cherries. These trees are prone to bacterial canker if pruned when sap flow is low and cuts are slow to heal. Young apricot and cherry trees can be pruned in spring during First Quarter phase, and mature trees pruned after harvest during a Full Moon phase. Deciduous fruit trees grown for spring flowers rather than fruit are pruned during a First Quarter phase, after flowering.
It is a good idea to keep a container of methylated spirits with you when pruning and regularly wipe the blades of your pruning tools to avoid the risk of spreading and bacteria or fungal spores from one plant to another.

Pruning roses
In most areas, bush roses can be pruned during a Full Moon phase in winter, after they become dormant. If you have removed dead wood, suckers and crossed branches during the growing season, little winter pruning will be required. Where frosts are common, or rose canker (dieback) has been a problem, it is better to prune bush roses as late as possible – at the first sign of new growth when sap flow is higher. Then prune, with slanting cuts, during First Quarter phase to encourage strong growth. This will help reduce dieback because the fungus that causes rose canker lives on rose thorns. Roses are more susceptible to infection by this fungus when sap flow is slow and pruning cuts heal slowly. Careful pruning is the only way to avoid dieback, as there is no treatment for the fungus.
Climbing roses that are floribunda or hybrid tea sports can be pruned at the same time as bush roses, but climbers that only flower in spring are pruned before a Full Moon, after flowering.

Other ways to grow potatoes

Repeatedly, I come across advice to grow potatoes in a stack of car tyres. Old car tyres, when exposed to sun and rain, can leach heavy metals into soil. One of the heavy metals in car tyres is cadmium, which is known to cause cancer in humans and animals. Potatoes are very efficient at absorbing cadmium from soil, and it is not advisable to grow food crops, especially potatoes, in car tyres, or to use car tyres as compost containers.
However, if you are short of space, there are other containers suitable for growing potatoes.
Potatoes can be grown in double hessian bags, drums with plenty of drainage holes, stacked foam vegetable boxes, or wire hoops called potato cages. The newer, woven plastic feed bags may not be as efficient as the good old hessian bags, as they tend to break down quickly when exposed to sunlight. Most of these methods require one container per plant, but they allow for plenty of hilling-up and a hilled container plant will produce a larger crop than an un-hilled potato plant grown in a garden bed.
Always use a good quality potting mix for container plants, as the cheaper mixes tend to become water-repellent quite quickly, and garden soil tends to become compacted in containers. If soil is compacted, it is difficult for tubers to form. Potato plants are reasonably heavy feeders, so add a decent amount of complete organic fertiliser to the potting mix in the base of the container. Also, remember that potato plants take about 20 weeks to mature and growing mix in containers stays warmer than garden soil. Position the container where the mix won’t overheat in the warmer months.
Cultivation and hilling-up are as indicated in the “Growing potatoes” post here on Aussie Organic Gardening.
To grow potatoes in bags
Place one hessian bag inside another, and roll the sides of the bags down so that the seed potato has 15 cm of mix below and above it after sowing. As the plant grows, gradually unroll the sides as you add more potting mix.
To grow potatoes in small to medium drums
Seedlings will not receive as much light as those grown by other methods, as the seed potato is sown 20 cm from the base of the drum to allow plenty of room for hilling. Place drums in a well lit area. Ensure that the drum has plenty of drainage holes near the base. If the drum is deep, put several centimetres of gravel in the base of the drum before adding the potting mix.
To grow potatoes in foam boxes
This method requires two deep foam vegetable boxes of the same size for each plant. Make sure at least one box has plenty of drainage holes in the base. Place a sheet of wet newspaper in the base of a box with plenty of drainage holes, and cover the paper with 2 or 3 cm of gravel. Place 15 cm of potting mix in the box, sow the seed potato, and cover with another 15 cm of potting mix. Place a 60 cm stake in each corner of the box – these will hold the second box in position. Cut the bottom out of the second box. Hill the plant by placing the second box over the first, and adding more potting mix as the plant grows.
To grow potatoes in a wire cage
This method requires a 3-metre length of stiff wire mesh, about 1 metre wide. This will provide a hoop a little less than 1 metre in diameter. Wire used for concreting has holes large enough for harvesting chats through the mesh. Construct the hoop and mark the diameter on the ground. Sow 4 seed potatoes in the ground, evenly spaced within the circle, keeping them well inside the perimeter. As the plants grow, they have straw packed around them, or straw and compost, if it is available. Make sure the potatoes are well covered, or they will become green.

Growing potatoes

Gardeners in warm climates have more flexibility in when to sow potatoes. A winter crop, planted early, can mature in time to provide seed potatoes for a crop sown in a different bed, in summer. In cooler areas, where frosts can occur, early sowing can expose the plants to tuber rot, as they will be unlikely to poke their heads above soil before frosts are over. Late winter is a good time to plant potatoes in frost areas. In frost-free areas, potatoes can be sown in June or July.
Seed potatoes are sown in furrows that are 15 cm deep and 75 cm apart. Place seed potatoes 30 cm apart along the furrow, ensuring that some eyes face upwards. Rake soil over the potatoes to fill the furrow, and water gently to settle the soil. Firming soil around the potatoes can damage sprouts. The full moon phase is best for sowing potatoes and other suitable root crops.
Where winters are dry, it will help to apply mulch over the bed after sowing, as potatoes need soil that is consistently damp. Erratic watering is another cause of hollow heart in potatoes.
When plants are about 30 cm tall, start hilling them up about 10 cm at a time until the plants reach flowering stage. This will increase the number of tubers produced by each plant, as extra tubers will form from the buried stem. Potato plants should not need extra fertiliser if beds were prepared properly (see Potato beds post) but, if weather has been usually wet, an application of seaweed extract tea can be applied as plants start to be hilled.
Replace mulch after hilling to prevent any tubers produced close to the surface becoming green, and inedible. Remove flowers as they open, or the plants will divert energy into producing seed at the expense of the tubers.
When leaves start to yellow, you can harvest chats, as required, by digging carefully in the soil beside the plants. Mature potatoes for storage are best harvested during Full Moon phase, when the plants die off, and the skin cannot be removed by rubbing with a thumb. Use a gardening fork rather than a spade for digging up potatoes, and store in a dry, dark place.

Cottonycushion scale

These sap-sucking pests are can be found on the twigs and branches of a range of plants, including fruit trees. The pests themselves may not attract much attention unless the plant is heavily infested because they are reddish-brown in colour with black hairs, and only 5 mm in length. The part we notice as a pest is actually the scale’s egg sac – a grooved, white, wax structure, larger than the insect itself. The egg sac will contain up to hundreds of red eggs. (See photos below).

Before treating these pests – check that you haven’t confused them with the larvae of the mealy bug ladybird, which are also white and fluffy. Ladybirds and their larvae consume an enormous amount of scale insects and aphids, but many of the larvae are killed when they are confused with pests. Many pest predators are killed where copper sprays are routinely used, and scale infestations commonly follow spraying for other pests.
When the cottonycushion scale prepares to lay her eggs, she fixes herself to the twig. Give the white structure a poke, if it doesn’t move, it’s scale – ladybird larvae will scuttle off. When temperatures are below 24° C, and pest predators are absent, cottonycushion scale can be suffocated by spraying with white oil at 10 ml per litre of water. This will not kill the eggs, and the spray will have to be repeated in two weeks, to catch the newly hatched scale.
In warmer weather, suffocate spray with enough fine potter’s clay dissolved in water to make it cloudy. Pest infestation is a sign that plants need an improved fertiliser and/or watering program, or that you need to adjust your soil pH.

Planting trees, shrubs and vines

dripline Winter is the best time to plant deciduous trees, shrubs and vines, including roses and fruit trees. Evergreen plants do well if planted in spring in cool and temperate climates, or in early autumn where summers are very hot. Moon planters will plant these during Full Moon phase for best results.
Always make planting holes wider than deep. Feeder roots are situated under the outer foliage canopy where rain drips from the plant. A wide planting hole allows the easy spread of roots as the plant grows. Wide holes are extremely important where soil is heavy. Mulch should also be applied to the outer canopy area, not near the trunk. Mulch against the trunk can cause collar rot.
Having dug the planting hole, fill it with water and leave it for an hour or two. This practice serves two purposes. It allows you to check that the area is well drained, as few plants grow well in waterlogged soil. It also prevents water applied after planting being drawn away from the plant into surrounding drier soil. If some water remains in the bottom of the hole, plant the tree or shrub in a mound to improve drainage. If a lot of water remains in the hole, avoid planting in that spot until drainage is improved.
Don’t plant any deeper than the tree or shrub was in the pot. Bare-rooted plants will have a change of colour on the trunk that indicates the original planting depth. This will ensure that any graft is positioned above ground level. To avoid planting deeper, lay a garden stake across the top of the hole and position the plant so that the original depth is aligned with the bottom of the stake. If necessary, make a mound of soil in the bottom of the hole to that the original planting depth can be repeated. Spread the roots of bare-rooted plants over the mound before filling.
Fill in the hole, occasionally jiggling the trunk of bare-rooted plants to avoid air pockets around the roots, and mix some compost or worm castings through only the top 10 cm of soil. Organic matter in the bottom of the hole will cause the plant to sink as the organic matter breaks down. If you do not have compost to spare, place some well-rotted horse or cow manure on the soil surface, under the outer canopy, and cover it with 5–7 cm of organic mulch. The addition of organic matter when planting perennials is very important, as many foreign plant families (exotics), in particular, rely on a beneficial soil fungi called mycorrhiza to supply their roots with nutrients and water, and mycorrhiza live in organic matter. Without organic matter in soil, plants can struggle to absorb what they need for healthy growth, and will be more prone to pests and disease. Australian natives will benefit from the application of some leaf mould around them.
Gently firm soil around the plant, but do not trample the soil as roots can be damaged. Water gently, to settle soil, before applying mulch. Do not apply any extra fertiliser at planting time, but an application of seaweed extract tea can help reduce transplant shock.

Broad beans and peas

If you live in a frost area, make a note of when you sow peas, sweet peas or broad beans and when they start to flower. The foliage of these legumes is frost hardy, but the flowers are not. Yet, they do not crop well when temperatures are too warm. Peas can take from 7 to 10 weeks to produce flowers, and broad beans can take from 7 to 13 weeks to produce flowers, depending on local temperatures. Sowing too early or too late for local conditions can result in a disappointing crop. As a general rule where frosts occur, do not sow seed until 10 weeks before the usual last frosts in your area. If you have unusually late frosts, you can protect your plants with a temporary plastic canopy, if a frost is predicted.
It is too late to grow broad beans as a crop in warmer areas, but they can be sown in all areas as a green manure crop where you intend to sow tomatoes next spring. Broad beans inhibit the growth of fusarium wilt – a fungal soil disease that can affect a wide range of plants, including tomatoes. If grown as a green manure, the plants are slashed when knee high. Broad bean seed sold for green manures may be called fava, or faba, bean.
Peas, broad beans (and sweet peas) like a humus-rich soil with a pH of around 6.5. They will need an application of complete organic fertiliser (see post on Fixing nitrogen). Legumes also need the presence of molybdenum and cobalt in soil for good growth, and an application of seaweed extract tea to the bed before sowing, will ensure these trace elements are available.
Try to avoid periods of heavy rain when sowing legumes because they can rot before germinating in cold conditions. Having said that, we had a 98% germination rate for our peas that endured a week of heavy rain after sowing in a raised bed. The seed had been saved from last year’s crop and had not been treated with anything. I am at a loss to understand why major seed manufacturers feel the need to coat their legume seeds with toxic fungicides.


Recent storms have not only limited gardening time; they have played havoc with our power supply and phone lines. Consequently, computer work and posting on the internet has been difficult. However, I did find time after the Full Moon to get the asparagus bed ready for spring.

I always wait until our asparagus foliage has developed a yellowish-brown colour before cutting back the plants to several centimetres above ground level. Asparagus plants withdraw nutrients and carbohydrates from the foliage and store them in the roots during their period of dormancy; in the same way that bulbs store nutrients to provide spring growth. Cutting back asparagus (and spring bulbs) while foliage is green will weaken the plants.
After cutting back the plants, I remove any weeds and test the pH of the bed, as asparagus prefer a soil pH of 6.5 for good growth. The soil pH in our bed was 7.0 so it will not be necessary to add any dolomite to the bed this year. Then I give the bed a thorough watering and a good drink of seaweed extract tea (see post on Seaweed tea). This delicious vegetable and medicinal herb originated along coastal areas and riverbanks, and will appreciate the full range of trace elements that seaweed provides. They are also salt-resistant plants and are one of the vegetables that will do well where soils or water supplies are saline. However, they don’t particularly like heavy clay soils, and mixing some well-washed river sand through the topsoil before planting crowns will assist spear production.
Asparagus are fairly heavy feeders with a high nitrogen requirement. I fed mine with some organic poultry complete fertiliser, some semi-mature compost to provide food for the large family of earthworms in the bed, and some not too fresh horse manure. Manures are slightly acidic and will help bring the pH back a little. I then covered the bed with 5-7 cm of fluffed-up organic mulch. Apart from an occasional watering to keep the bed just damp, the asparagus will not require any attention until spears start to appear in spring.