Citrus setting fruit

citrusflwrs1 I love warm, still spring days when the air is heavy with the sweet fragrance of citrus and Jasmine flowers, and the lethargic buzzing of bees that seem intoxicated by the perfume.
Citrus trees produce many more flowers than the tree could support if they developed to full maturity as fruit, and a reader has asked if she should remove some of the flowers.

This is not necessary, as most species of citrus will shed the excess flowers at the end of the flowering period when the developing fruit is no larger than a pea. A further shedding of tiny fruit often occurs when they are about 2 cm across. However, there are other causes of fruit drop beyond what the tree intends. Water stress and sap sucking by Bronze-orange or Spined-citrus bugs are common causes. A deficiency of copper (which is only needed in tiny amounts) will cause citrus trees to drop small fruit, and flowering stage is a good time to give your trees a drink of seaweed extract tea, especially if your soil is low in organic matter.

citrusfrtst1 Make a note of when your citrus trees flower because 3 months after flowering the final amount of fruit the tree will produce that season is established. At this time you can remove excess fruit, particularly on young trees.
On some species of citrus, flowers are well spaced as in the photo above. On other varieties flowers form in clusters and, even if only a third of the flowers in this photo developed into fruit, the weight of the fruit will cause new wood to bend downwards, resulting in a poorly shaped tree in years to come. The weight of excess fruit can also split young trees. It is worthwhile being patient with young citrus trees, and foregoing fruit until they have established a sturdy framework.
On older trees, simply pinch out any young fruit that will form a compacted cluster when mature to avoid putting too much weight on new wood at the end of branches.

Changing soil pH

If the pH of garden beds needs adjusting, organic gardeners have a distinct advantage over “chemical” gardeners, because mature compost has a pH of about 6.5 where all the major nutrients are freely available to plants, essential trace elements are available, and aluminium is locked out. Adding mature compost to topsoil when preparing beds will help to lower pH of alkaline soils, and raise the pH of more acid soils, as well as buffering plant roots from an unsuitable pH in surrounding soil. Where the amount of mature compost is limited, green manures and well-rotted manures will break down to add nutrients, microorganisms and humus to topsoil. Worm castings and other solid organic fertilisers provide nutrients in easily absorbed form. Garden beds should be prepared a month before planting to allow soil chemistry to achieve a balance.

To raise soil pH
In all acid soils, pH can be raised by the combined use of organic matter and the addition of calcium ions in the form of dolomite or lime.
Agricultural lime – (Calcium carbonate) is finely ground limestone (chalk). Mined limestone, i.e. not chemically treated, is a safe choice to raise pH in garden beds. Although it takes several weeks to have an effect, it is longer acting than other sources of lime, and can be watered in around plants. Agricultural lime can be worked into the top 15 cm of soil when preparing garden beds. It takes less lime to raise the pH of sandy soils than it does to change clay soils. To avoid an excess amount of calcium in soil, apply as recommended in the test kit, and test soil a month later.
I must say here that I have not found the application rate recommended by Manutec for “organic soils” to be accurate, if soils contain compost. It may have been calculated for soils where only manures are added.
Dolomite – (Calcium magnesium carbonate) is limestone with a higher proportion of magnesium than agricultural lime, and is applied in the same way. It is a good way to raise soil pH on sandy soils with fairly low organic matter content because both calcium and magnesium leach easily from these soils. In soils with high magnesium content, such as in South East Queensland, agricultural lime is the preferred way to raise soil pH.
Quick lime – (Calcium oxide) is made by heating limestone in a furnace to remove carbon dioxide. It is very caustic and unsuitable for garden use.
Hydrated or slaked lime – (Calcium hydroxide) is also known as brickies or builders’ lime because it is used to harden mortar. Hydrated lime is made by soaking quick lime in water to form hydroxides. It is more soluble and faster acting than agricultural lime, but its effects do not last as long. This lime can burn roots and should not be used on beds that contain plants. It should also be applied a month before organic matter and fertilisers or nitrogen can be lost through conversion to ammonia. Gloves and a mask should be worn when applying hydrated lime because it is very drying to skin and throat. Apply hydrated lime to the soil surface, and water it in.

To lower soil pH
Adding organic matter as compost, green manures, and animal manures, without including lime or dolomite, can be enough to adjust the pH of slightly alkaline soils because organic matter produces hydrogen ions as it decomposes.
Manure from cows, horses and sheep that have grazed on herbicide-free pasture can be used more liberally on alkaline soils. It has been calculated that 2–3 kilos of manure per square metre of bed area will reduce soil pH from 8.0 to 7.0. Manures release hydrogen ions as they break down, replacing calcium ions on the charged sites.
Elemental sulphur, sometimes sold as flowers of sulphur, will assist organic matter in reducing soil pH in more alkaline soils. Elemental sulphur is available from produce stores, and some nurseries. For soils with a sandy structure, apply at 35 g per square metre, or 100g per square metre for clay soils. Test soil after one month, to see if further applications are necessary.
Please note – Lime sulphur is a fungicide, not a soil conditioner.
Acidic fertiliser can assist when alkaline topsoil contains some organic matter and herbicide-free manures are not available. Multicrop’s Ecofish liquid fertiliser is registered by NASAA as an input for organic cultivation. The concentrate is very acidic and diluting it in water should modify the acidity, somewhat. It can be watered into the soil or used as a foliar feed for plants in alkaline soils.