Wandoo: on flowering, honey yield and fruit production

By Liz Manning, in conversation with beekeeper David Leyland and researcher Ryan Hooper

2010 is shaping to be a fantastic year for eucalypt flowering and fruit crops. The prolific flowering of marri (Corymbia calophylla) and powderbark (Eucalyptus accedens) trees around York and the Helena Catchment is being copied by wandoo (E. wandoo). Many trees are laden down in bud, ready to burst into flower. What happened!?

Recently I visited Pat and Bruce McGregor’s farm near York to photograph this massive budding event, something they have not previously witnessed in such quantities. As we drive around the farm, the wandoo trees portray a picture of health – vigorous green canopies full of bud and fruit in different stages of maturity, clearly visible by the glossy green-brown colour amongst the leaves. Bruce says many larger limbs have broken due to the weight of their load. It is difficult to believe that 8 years ago these same trees were a suffering serious crown decline, and looked extremely sick. Bruce and I have both seen wandoo take the opportunity and flower at various times throughout the year, including December, April, May, July, August and September.

Bruce McGregor shows off the heavy bud crop carried on his wandoo trees (photo by Liz Manning).

Bruce’s powderbark trees reveal an impressive crop of fruit as well as new buds amidst remnants of flowers (photos by Liz Manning).

To find out more about wandoo’s flowering and production cycles I talked with David Leyland, a beekeeper of 27 years who works bees in wandoo around York and Moora. Ryan Hooper has also keenly observed wandoo’s reproductive capacity and phenology. Ryan and Dave shared their observations and knowledge in answer to my questions.

Question: What is the time span from bud to flowering to seed development?
DL: It takes around 2 years from the first sign of bud to flowering. Once trees flower, within 12 months seed could be mature. Wandoo trees can carry up to three years of fruit and can continually put bud on if the seasons are right; rain and warmth can induce the tree to put on another crop. This is especially true in the York area. However, thunderstorms can have the opposite effect). For example, in 2008 when a humongous downpour knocked all the flowers off, the trees stopped flowering and I had to take the bees off. Over the last 10 years wandoo honey yields around Bruce McGregor’s farm near York have been very low. Other eucalypts such as Salmon gum take advantage of good climatic conditions by flowering at different times of the year, and carrying three years of fruit.

RH: Interesting. I agree except that in terms of seasonality it appears that North to South distinction (northern trees flower and perhaps produce buds spring-early summer; southern early summer to late summer) is moderated through years with favourable conditions. Although data has not specifically collected on optimal conditions, other studies on Eucs suggest that optimal conditions are related to moisture x temperature. Obviously moisture is not solely governed by rainfall as different species have different niche constraints and hence, water-use strategies. For Wandoo, an opportunistic growth strategy implies different conditions between years result in variations in times for bud production-maturity (and hence seed production) and different cycles of loss and gain of leaves and reproductive structures. Interested readers can click this link to find an excerpt of a study that I have carried out.

Question: 2010 has seen a mass flowering from a number of eucalypt species (marri and powderbark). Wandoo is also carrying an enormous crop of bud. What does this mean for flowering, nectar and honey production? Does this change with different locations, soils, and climatic conditions?
DL: Temperature and climatic conditions certainly have a strong influence what happens. Normally with marri when it flowers it yields nectar and honey, with every 3rd year being a bumper year. However, the recent hot windy conditions over December – February shortened the marri flowering to only four to five weeks. At Chidlow the marri flowering was only average, while along the York Rd up to Bruce’s farm, the flowering was very good, but this could be much less next year.

Jarrah will sometimes flower but not produce nectar, or it can flower and then abort its fruit, or abort the buds before they flower. About 60% of jarrah’s buds can be aborted before it flowers. Powderbark can yield well but it is very unreliable. However, over the last 10 years it is becoming more reliable. This year the powderbark has given its best flowering for a number of years.

The wandoo trees are looking really healthy and carrying a huge crop of flowers which should mean a good honey yield, but this depends on temperature and rainfall. We will need good winter rains. Wandoo does not seem to abort as much as jarrah, however thunderstorms can knock the flowers off and reduce crop, as happened in the spring of 2008, at Bruce’s farm. In Walebing (20kms south of Moora) the wandoo flower crop looks good but is not as impressive as York. The wandoo around Moora have consistently produced about every 2nd year; sometimes 2, 3, & 4 years in a row.

RH: Don’t know much about nectar production, but I know a range of soil types occurs under Wandoo and therefore, it would be expected canopy density, bud production etc., to vary according to these what we as scientists call “micro-niche factors”

Question: Has the decline of wandoo affected its flowering and honey?
DL: Yes, over the last 10 years the trees haven’t flowered as well or yielded much nectar, particularly around York. The last time I worked wandoo on Bruce’s farm was 2008. At Walebing there have been no obvious signs of wandoo decline as has happened in York, but I have observed decline occurring in the last 2 years and can see it moving up the Great Northern Highway.

RH: Yes, but only with severe decline. Also, recovering trees once beyond a threshold of foliage re-growth (2-4 years growth) are producing buds and flowering as normal.

Question: Despite declining rainfall, wandoo’s health is improving. What have you noticed about the flowering over the past 10 years?
DL: A lot depends on when the rain falls. If rain falls in October then marri will flower well. Wandoo can flower at different times throughout the year. If the weather is warm enough in June and July, the wandoo will flower and only seems to stop when the weather gets too cold and wet. Once weather conditions change, the trees will start flowering again. At times wandoo can flower but not yield nectar. This has apparently happened in areas north of the Great Eastern Highway, around Clackline and Toodyay.

You can see the affect of the drought on Jarrah, but it doesn’t seem to have affected the wandoo and powderbark in their health or their honey production. We seem to have been through a lean period, but this now appears to be changing. Over the last 10 years flowing and honey yield seem to be improving.

RH: I am very interested in Dave’s observations and they appear to differ to mine with respect to a focus on rainfall per se and ambient cycles for flowering but nevertheless life would be boring without different perspectives. I found rainfall to be mediated at the micro-niche scale (that is soil type, stand structure etc.,) which in turn varies according to spatial and temporal traits for resource use. Therefore flowering varies seasonally (within natural windows set by temperature x moisture) and inter-annually. All my observations for a short 8month stint with DEC are in the excerpt that you can find at the website of the ‘Wandoo Recovery Group’. Links between flowering and climate, soils, health etc., go beyond nectar production, in my view, but perhaps are beyond the scope of this particular blog.