Galls or stem swellings on citrus trees need to be removed by pruning by the end of August, as very tiny black wasps emerge from the galls in September and October ready to lay a new batch of eggs in citrus stems. Because these wasps are poor fliers, they tend to reproduce on the same tree unless blown by wind to a new host.
Unlike many other wasps that assist pollination or are pest predators, the citrus gall wasp is a true pest. Eggs are laid in young stems of citrus trees, particularly lemon and grapefruit varieties, and the native finger lime. The larvae remain within the stem, stimulating the growth of cells, and causing a gall or swelling to form on the infested stem by early summer. Trees that are repeatedly attacked will become weaker and produce less fruit.
Originally, only coastal gardens of New South Wales and Queensland were affected, however, this wasp is spreading to other areas of Australia.
Do not add galls to the compost heap. Burn them, or dispose of them in a sealed plastic bag. It is very likely that the gall in the photo missed last year’s pruning because it is unusual for galls to reach that size in one season. As you can see, the tree in the photo is also affected by scale, and it is more common for citrus gall wasp to attack stressed trees. After pruning, water the tree thoroughly, and feed it with a complete organic fertiliser and as much compost as you can spare. A drink of seaweed extract tea will help it to resist further pest and disease attack.
Not only do organic ‘Midnight Purple’ potatoes add interest to a potato salad, purple potatoes are very good for you. Like richly-coloured berries, purple potatoes are full of anthocyanin pigment, an excellent anti-oxidant that we are told is important in maintaining good health. Purple potatoes also contain chlorogenic acid, which is beneficial to the health of our blood vessels and, of course, important fibre. There is a range of purple potatoes now available, with varying degrees of colouring. I particularly like the Midnight Purple ones as they are an intense purple all the way through.
If you would like to grow your own, Green Harvest have a good selection of purple potatoes, see: Green Harvest potatoes.
This ugly little creature is the larva of the leaf-eating ladybird. Stressed plants in prolonged hot, dry conditions attract these pests. The larvae become almost black as they reach pupa stage. Both adults and larvae of leaf-eating ladybirds are particularly fond of the Solanum family (tomato, potato, eggplant) and the melon or squash family where they do a lot of damage to leaves.
The adult leaf-eating ladybird has 26 or 28 spots in rows across its wing covers. They are slow moving and drop to the ground when disturbed. In summer, if you see the adults on leaves in your garden, be sure to look under the leaves for their eggs. Remove small leaves containing eggs and, on large leaves, use a knife to scrape the eggs into a container. As I dislike spraying my garden, I just squash the adults and larva with a gloved hand.
Unfortunately, the damage done by these ladybirds and their offspring have resulted in many gardeners spraying other species of ladybirds that are voracious pest predators. Both adults and larvae consume a considerable quantity of pests such as aphids, scale and mites, and one type of ladybird feeds on fungus. Peter Chew and his family have an excellent website, Brisbane Insects and Spiders, where gardeners can easily identify which creatures are beneficial to their gardens and which are pests, and includes a Ladybird Field Guide.
The photo below shows both larva and pupa stages of the 28-spotted ladybird.
A common problem affecting otherwise healthy tomato and capsicum plants during heat waves is blossom end rot, where partly formed fruit develops a dark, sunken patch furthest from the stem.
This is caused by calcium deficiency, and is not a disease. Like us, plants need a good supply of calcium to form a strong structure. Hot and very windy days increase transpiration (water loss) from plants in the same way we perspire to keep cool, and calcium can only be absorbed by plants as water-soluble, electrically-charged ions. This problem can also affect zucchini, pumpkin and melon plants.
During heat waves, daily watering rarely solves the problem. A deep watering a couple of times a week is more beneficial. If soil around plants is mulched to keep roots cooler and reduce water loss, an efficient way to water quickly is to place juice or soft drink bottles, neck down, beside plants. See: Watering in drought conditions
Other causes of blossom end rot are:
• Erratic watering
• Soil is too acidic (soil pH less than 6)
• Poor fertilising routine
• Overuse of fertilisers high in nitrogen or potassium, including some seaweed fertilisers
• Rarely, in very alkaline soil where calcium becomes insoluble.
There is nothing like the taste of vine-ripened tomatoes, and this is how my neighbour, Cheryl, keeps her tomatoes cropping through winter on the Mid-North Coast of NSW. The tomato plants self-seeded in the rose garden in front of her north-facing verandah and, as they grew, she trailed the foliage across the verandah surface. The plants get plenty of sun during the day and the verandah roof keeps the plants warmer at night and protects them from frost. This clever idea has worked very well and Cheryl has so many tomatoes, she has been giving them away.
Tomatoes can also do well during the colder months in pots on a protected north-facing verandah, as the potting mix in black plastic pots stays warmer than soil in garden beds. Fruiting on tomatoes depends on warm air and tomatoes do not need bees for pollination. Don’t forget to water the plants regularly, and give them a light application of complete organic fertiliser as flowers start to form, to ensure a sweet-tasting crop.
Early winter is the time to eradicate this weed pest, although I’ve noticed young growth of this weed in May on the Mid North Coast of NSW. Bindii (Soliva pterosperma), or “Jo-Jo” as it is called in some places, or “onehunga” in New Zealand, is a delicate-looking lawn weed that produces carrot-top or ferny foliage.
In late winter and early spring, each branch produces a rosette of spiky seed heads that detach from the rosette into individual seeds with a sharp spine that attach themselves to the soles of shoes, and make walking barefoot or sitting on grass a painful experience. By the time the plants produce seed heads, the branches will also produce roots from stem joints and removal is difficult. For successful removal this diabolical weed has to be eliminated before the seed heads form. From now until the end of June is a great time for action, in any moon phase if seed heads haven’t formed.
If you don’t have a steam or flame weeder, young plants are easy to dig out in early winter if you only have a light infestation. For more wide-spread infestations, the good news is that several companies have produced certified-organic weed sprays. Certified-organic weed sprays
Spot-spraying with Yates ‘Nature’s Way Weed Spray’ or Organic Crop Protectant’s ‘Slasher’ will burn off the weeds, while Organix’s ‘Weed Blitz’ works by removing the outer coating of foliage and seeds, causing cells to collapse. A Google search will direct you to a local supplier.
Bindii is more common where lawns are undernourished. Vigorous lawns usually out-compete this weed. To avoid future problems, in late winter, water the lawn and fertilise with organic complete fertiliser and seaweed extract tea, and do not mow the lawn too short as this weakens lawn growth – raise the mower a notch or two. Dynamic Lifter granules are easy to apply to lawns.
With high temperatures predicted for many areas of mainland Australia this week, I would like to remind you that you can find tips on helping your garden to survive extremely hot temperatures here: Heat wave protection
Have you ever wondered why they were called eggplants? This variety is the reason. The small white fruit, which look like hens’ eggs hanging on a bush, has a delicious flavour but has been very difficult to find in recent years and I was delighted to finally find some seeds. Yates has ‘White Star’ and there is a variety called ‘Easter Egg’ available from an Australian grower on eBay.
Aubergines (Solanum melangena) are a member of the tomato family and require a similar position, soil preparation, and soil pH. However, they require warmer conditions for germination than tomatoes and are usually sown 1 cm deep in small pots in a warm, protected position. The small, white variety produces a compact bush and can be grown in beds or pots. Aubergines need staking because the stems are brittle, and they appreciate a light application of poultry-based, complete fertiliser as buds form. Regular harvesting increases production. Cut fruit from the plant with a 2 cm stem when the skin is firm and shiny.
A strong, healthy root system that allows your tomato plants to absorb enough water and nutrients is essential for producing a good crop and allowing your plants to produce their own pest-deterrents. Tomatoes in their natural state, grow along the ground and will form auxiliary roots along their stems, but our method of growing tomatoes tied to stakes prevents this.
However, you can give them a helping hand to produce extra roots before planting out by lying potted seedlings on their side when they are 10-15 cm tall. Leave them like this for a week or so, depending on the growth rate, and remember to stand them upright for watering. As you can see in the photo, the main stem with make a 90-degree turn, and root buds will form on the horizontal part of the stem. Plant them out with the growth tip vertical and the horizontal stem just below the soil surface. Or, you can remove the seed leaves and plant them up to just below the next set of leaves, then hill soil around them slightly as they grow.