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Q MISSING LIMES

What is wrong with my lime tree? It’s in a big pot and I have fed it citrus plant food and Epsom salts. Yet the tree is not healthy and there are no limes coming from the few flowers. KATE THOMSON, TAUP

AYellow leaves on citrus are often a sign of a lack of nutrients but in this case the stippled pattern indicates an infestation of tiny sap suckers called thrips. They shelter under leaves, piercing the cell walls to get at the sap. Thrips are so small that they are often not detected until the leaf shows signs of damage. Look for tiny black specks of excrement under the leaves and tiny, barely visible mites. Sometimes, there may be fine webbing around the leaf midrib and where leaves join the stems.

Mites usually appear in summer. Plants stressed by uneven watering or irregular feeding are more vulnerable to a buildup of mite populations.

Spray monthly with mineral oil over summer to keep mites under control. These sprays work on contact – smothering the mites – so you need to cover the stems and both sides of the leaves for the spray to be effective. Alternatives are Naturally Neem or vegetable oils. Don’t use oils not registered for use on food crops.

Limes are one of the least hardy citrus varieties so make sure the lime is in the warmest part of your garden and is well protected from frost. An alternative for cold areas is the much hardier ‘Limequat’ which is a hybrid between a West Indian lime and a kumquat. The small, oval, yellow fruit can be substituted for limes in any recipe.

Although most citrus grow happily in containers any potted plant needs more care than one in the ground. Make sure the container is large so it is less likely to dry out. The water supply needs to be regular – consider a dripper on a timer if necessary. Lack of water can cause fruit drop or lack of juice so water daily during dry weather. Mulch the surface of the mix in the pot to conserve water but make sure the mulch doesn’t touch the trunk to avoid collar rot.

Make sure the pot can drain freely as sitting in saturated mix also stresses plants in pots.

Regular feeding is better than giving the tree its annual dose in one go. Use slow release citrus fertiliser in spring and summer plus liquid feed each month when the tree is actively growing.

Old potting mix gets stale, compacted and can become hydrophobic so irrigation or rain can not soak in. Refresh the mix over winter when the tree is showing least signs of growth (or after harvest for winter-fruiting citrus). Add a wetting agent like Saturaid so water is evenly spread throughout the potting mix and there is less run off. Barbara Smith

Q DYING APPLE TREE

Our ‘Gala’ apple is dying back at an alarming rate. It’s 20 years old and has been sprayed regularly with copper and Mavrik Insecticide. Is there any hope for our backyard apple tree? KAREN MILES, WHITIANGA

AKate Marshall from Waimea Nurseries says the burrs on the trunk are typical of woolly apple aphid infection. As there are so many burrs showing on the trunk and branches the infection has been there for some years. It is too late for this tree. If you want to plant another apple in the same place choose a tree grafted on either M116 or M793 rootstock as they are resistant to woolly apple aphids.

Affecting both apples and pears, woolly apple aphids ( Eriosoma lanigerum) are a serious orchard pest. These sap-sucking pests can cause leaf distortion, fruit deformity, and loss or even death of whole branches or trees.

Adults overwinter on the roots and branch. Large numbers of juveniles (nymphs) migrate up and down the tree during the growing season forming white, waxy-coated colonies.

Populations on the roots cause galls preventing nutrient and water flow and stunting the tree. Aerial colonies cause burrs on branches and trunks.

If you spot the early stages of a woolly aphid invasion blast them away with a high-pressure squirt from the hose or spray with neem oil or insecticidal soap. However for long-term control it is recommended that gardeners grow varieties on woolly aphid resistant rootstocks. Barbara Smith

Q BANISH FENNEL

Our new property has sandy clay that needs a crowbar to dig. Fennel covers a steep bank. We’d like to grow veges and low lying native shrubs. How do we get rid of the fennel and establish a garden? MICHELE NETTLETON, MAUPUIA

AThe soil may be rock hard in summer but might be easier to work in autumn or spring after a bit of rain. Talk to your neighbours and see if there is a seasonal window of opportunity for planting. While you are at it, ask them how they managed their own tree planting. Local knowledge is always helpful.

Adding humus (compost, manure, bark, plant material, post peelings, straw, arborists’ tree shreds or any other organic material you can lay your hands on) improves all soils but it does take a while. Don’t even try to dig it into the soil, just lay thick layers of mulch and top up often.

If you are after quick results you could spray the fennel. But better in the long term would be to use the fennel as mulch. Slash and drop it on the ground (preferably when it is not in flower). Cover with old carpet or cardboard and other mulch. Let it break down a bit then plant into it.

Plant small grade plants. They are cheaper, easier to lug up the hill, easier to plant, need less water and establish faster than large ones.

For vegetable gardens try the lasagne method of building up growing beds with layers of manure and mulch on a base of cardboard. Plant into a top layer of compost or potting mix. Add new layers of mulch as the material breaks down. Barbara Smith