Green With Envy: Sabrina Hahn answers readers’ gardening questions on avocados, orchids and citrus gall wasp

Every Saturday inside The West Australian Sabrina Hahn sets out to help gardeners with their thorniest plant problems. This week, she’s looking at a mysterious (but delicious) variety of apple, a case of the dreaded citrus gall wasp, and an avocado tree that’s not behaving as expected. To submit your own question to the Green With Envy column, published inside Saturday’s The West Australian, write to Ask Sabrina, GPO Box D162, Perth, 6001 or email home@wanews.com.au. Please include your full name and suburb. Due to the volume of questions, not all of them will be answered. Apple of my eye Q Do you think this is an English Bramley apple? It is a beautiful cooking apple. Fluffs up when cooked. The tree is on our farm at Gibson and is over 60 years old. It keeps well too. It is rather neglected but is still producing fruit. I’ve just stewed a pot. Rather tart, so not ripe yet, but still delicious. Marilyn Hart, Esperance A This could be a Bramley. The fruit is a large flat, round shape, with bright green skin, and it’s tart when eaten raw, fluffy when cooked, and larger than a Granny Smith. The other identification key is the russet colour on the top of the fruit. The flower buds on Bramley apples are deep pink, opening to beautiful soft pink-tinted flowers. However, Bramleys are a triploid apple, meaning they need two other pollinators to set fruit. Gravenstein, Gala, Cox’s Orange Pippin, Golden Delicious, Fuji, and Jonathan are good pollinating partners. Tumble dryer Q We have been doing compost for years. We have three compost tumblers we turn every day. Can you tell us why our compost clumps into balls and comes out dry instead of looking like potting mix? We put vegetable scraps and lawn clippings in. Julie Warren, Bedfordale A Successful composting requires the right amount of moisture, oxygen, carbon and nitrogen. You need to add half a watering can of water to a half-full tumbler and ensure the carbon (dry material like hay and straw) and nitrogen (wet material like manure, green lawn clippings, weeds) are in the ratio of 4 parts dry to 1 part wet, and is turned every day to spread the moisture and bacteria evenly throughout the material. Adding seaweed solution and fresh comfrey leaves to the blend will also help the bacteria to grow. Pest’s sheer gall Q I thought the citrus gall wasp was spread by the gall wasp laying eggs on fresh green shoots. But the attached photo shows the gall developing from an old branch, not on fresh shoots. Does this mean the wasp eggs can remain in the branch though the galls had been cut out and destroyed and the only option to rid the tree of gall wasp is to pull it out and destroy it? T Wallace, Dianella A Gall wasp can drill into the hard stems of citrus, not just the new growth. They cannot fly very far but if your neighbours have an infested tree, the wasp will fly over the fence and lay eggs in your tree. Constant pruning of galls will help control them. The best time to remove galls is from February through to May to prevent the eggs hatching. Life after death Q I’ve bought and enjoyed many phalaenopsis orchids over the years but, until now, I’ve never seen one that has sprouted a new plant from the stem after the flowers have died and been removed. Is this unusual and how can I propagate it? Jonathan Kester, Jane Brook A Many orchids produce roots further up the stem where leaves have emerged and are called monopodial orchids. These plants grow vertically, with roots and new plantlets emerging from nodes on the stem or old flowers. It’s a clever way of reproducing clones of itself. Vanda, dendrobium and epidendrum orchids do the same. Simply cut the new shoot off and replant into orchid mix, but don’t plant it too deep.