User 1010888, via Pixabay

I spent a good chunk of my summer break up a ladder and on the carport roof picking plums and lowering laden buckets down via a rope to my parents, waiting expectantly below. It’s become somewhat of a ritual and we make deliveries of bags and boxfuls around the neighbourhood afterwards, as there is far more fruit than we can handle. The trees are seedlings, resulting from stones hurled out the back door and into the undergrowth in summers past. We’ve ended up with an Omega-like wannabe that’s ripe in early January as opposed to March and a small, dense-fleshed yellow-flushed-with-red plum that we think might actually be a plumcot. They are prolific, versatile and thriving in the somewhat damp western climate.

February is indeed the month of ‘peak plum’ and I’ve just spent the last week bottling, jamming and dehydrating the last of the rooftop haul. Not a minute too soon either, as a case of Black Doris will be landing on my doorstep any day now. In the middle of all these plummy pursuits, I stopped to think about my absolute favourite plum varieties and realised they are all named after someone…so this month, in my ‘top picks’ section I’m going to give you a little back story on each of my selections.

Why should you make room for a plum tree or two in your backyard? They are the hardiest and most adaptable of all the stonefruit; prolific, low-maintenance and hardy–tolerant of a wide range of environmental conditions. The plum family tree is incredibly diverse, so somewhere in amongst its branches you will surely find your match – be it red, yellow, green or purple-fleshed, ditto for skin colour, large and juicy for eating underneath the tree, small and tart for flavoursome jams, firm-fleshed and especially suited to drying or baking and every possible characteristic in between. It's a good idea to do a bit of research once you have found a favourite and make sure it has a mate in the form of a polliniser variety – some plum varieties act as universal pollinisers for others, but some have specific requirements in this department.

Plums: a short family history

Plums belong to the genus Prunus, which sits within the Rosaceae or rose family – as I’ve mentioned previously, this group also gives us many of the most commonly cultivated fruits and nuts from almonds to raspberries via apples and pears. Native to China, the Middle East, North America and Europe, plums can be divided into two main groups: The Old World plums, which include the familiar cultivated fruits that you may have heard classified as European plums (Prunus domestica, I think of these as the classic elongated, egg-shaped fruit with a prominent longitudinal crease) and the closely intertwined gages, damsons and sloes (P. insititia and P. spinosa); Japanese plums (P. salicina) and the cherry plum or myrobalan varieties (P. cerasifolia). The New World plums are also known as ‘plum cherries’ and are a diverse group, native to and dispersed across North America, much less common here in the Southern Hemisphere. There are also outliers such as P. mume, the umeboshi plum treasured in Japanese culture. Likely one of the first domesticated fruits, it is thought plums travelled (along with many other food crops) with the Romans into northern Europe. As plum stones have been found amongst the remains of Iron Age hill forts in Southern England, evidence points to plums as fruit, at least in their dried form, being present in the British Isles even earlier.

Common names for plum fruit are as varied as the fruit themselves – when is a plum not a plum? When it’s a prune, gage, sloe, bullace, damson, mirabelle, cherry plum or umeboshi of course! The most common and familiar commercial plum varieties belong to the Japanese, and to a lesser extent, the European families, so I will concentrate on those here. The less-familiar types, such as damsons, have experienced something of a cult revival in recent years and as such, I feel they warrant an article of their own.

Suitable climates and growing conditions

Due to their good nature and adaptability, plums of both Japanese and European varieties can be grown right throughout New Zealand. European cultivars have slightly higher chilling requirements to set fruit (1000-1800 hours) than Japanese (500 to 1000 hours) so the former may be better suited to cooler southern regions as they also flower later, when the danger of late frosts has mainly passed.

Plums form small to medium trees at maturity if carefully managed, but can present issues if left to grow above five or six metres in height. European plums have an upright growth habit and are generally smaller in stature and less vigorous than their Japanese cousins, which can have a somewhat floppy but vigorous growth habit and often need careful management in the form of topping to keep them at a practical height.

Although some plum varieties are self-fertile, it is best to plant at least two varieties as most require a degree of cross-pollination. European plums require European pollinisers and Japanese plums need other Japanese varieties nearby. For a good New-Zealand-specific plum polliniser chart, see https://www.waimeanurseries.co.nz/how-to-guide/grow-plums/

Plums propagated from seed vary widely in the type of fruit they produce and although some chance seedlings are brilliant, many tend towards mediocrity. Given this unpredictable nature and the time from sowing to fruit-producing maturity, your best bet is to purchase grafted plants of a known cultivar from a reputable nursery.

Site selection and planting

In general, plums will tolerate a similar temperature range to apples and pears and will handle regular frosts pretty well. Choose a sunny, warm site with some shelter for optimum growth and pollination conditions. Although tolerant of a wider range of soil conditions (including heavy/clay soils, wetter soils and compacted soils) than most other stonefruits, waterlogged situations are still best avoided to prevent root rots. Also bear in mind the choice of rootstock – plum rootstocks are hardy, with the tolerance of wetter soils, but a plum grafted onto a peach rootstock will have the peaches’ sensitivity to waterlogging and disease conferred to it.

Plant your plum trees in the dormant period, late autumn to winter. Allow a spacing of 3-6 metres between trees at planting. Consider a support framework for Japanese varieties in the establishment stage. Work some compost into the planting hole and keep the area under young trees free of grass and weeds.

Culture and care

Keep adequate water levels up to your plum trees, especially during the fruit development phase. Having said this, they do have a degree of drought tolerance, so those in drier districts need not despair. Certain varieties (Japanese cultivars and European prunes) actually do better in low-humidity environments. As the fruit begins to ripen, ease back the irrigation to prevent developing or exacerbating fungal disease and avoid watery-textured, bland fruit.

In terms of fertiliser applications, allow 250-500 g of a balanced general fertiliser per year of age for young trees, up to a maximum of 5 kg/tree at maturity. Apply this in spring, at the beginning of the growing season and always prior to rainfall or irrigation to help move nutrients into the soil for uptake by the plant’s roots. You can apply mulch under the trees to help conserve water and nutrients, but keep the trunk clear to avoid collar rots.

Pruning

As with all stonefruit, plan to prune your trees in summer after harvest to prevent the ingress of fungal diseases such as Silverleaf (Chondrostereum purpureum) which can devastate plum trees. Immediately seal all pruning cuts with a proprietary paint or paste. Plums are ideally suited to an open-centre vase shape framework, however, there are some differences between the Japanese and European cultivars that need to be taken into account.

Japanese plums

These are generally more vigorous in terms of growth habits so require more pruning, both in the quantity of material removed and frequency (ideally annually). Fruit is borne on spurs and one-year-old lateral growth. Initially, select four to five leaders and allow fruiting arms to develop off these. You may need to thin the fruit in years of heavy bearing – thin clusters and space these out where necessary, you can base the spacing roughly on the expected final fruit size. Thinning also helps even out biennial bearing (a heavy crop one year, light crop the next) to which plums are prone. Remove strong upright shoots and try not to allow the tree’s height to get away from you.

European plums

To establish, select four to five leaders as for Japanese plums; fruiting arms will again develop off these. Keep the centre of the tree clear to allow light penetration and airflow. Fruit is borne on short spurs which will develop fruiting buds during spring and summer on the new season’s growth and produce fruit the following season. Spurs can remain fruitful for up to five years, hence pruning to renew fruiting wood may only be necessary every second or third year.

Pests, diseases and what to do about them

As mentioned before, plums are pretty hardy, but there are a few specific pests and diseases to keep an eye out for.

In terms of insect pests, the pear or cherry slug, Caliroa cerasi, is probably number one. Tatty-looking leaves covered in shot-holes are a giveaway – look closer and you’ll probably see small slug-like globs clinging to both leaf surfaces. These are actually the larvae of a type of sawfly – misleading in name and nature, as they are not true slugs just as much as the adult insects are not true flies, instead belonging to the Hymenoptera, the order that also includes wasps, bees and ants. Confused yet?! C. cerasi is a common pest on many fruit crops within the Rosaceae, found also on cherries, apples, pears and quinces. I’ve seen them reach plague proportions and they are capable of eventually skeletonising leaves so you may need to take action with an insecticide application. Softer options for the home garden include neem oil, pyrethrum-based sprays or Yates Success Ultra, active ingredient spinetoram, which is derived from a soil bacterium. Follow the label directions – this will also deal with any leafroller caterpillars present on the foliage.

Apart from the fungal disease Silverleaf mentioned in the pruning section, the other disease you are likely to run into on a plum tree is bladder plum (Taphrina pruni - also known as pocket plum). It’s another fungal disease, likely to be encountered in spring when the conditions are cool and wet – the disease overwinters in leaf and flower buds with the spores spread by rain splash. If you notice strangely-enlarged, spongy plum fruit in the month or so following flowering, bladder plum is the likely culprit. In the first instance, you can apply a copper oxychloride spray as the buds begin to swell in spring and repeat it a fortnight later. If this window has passed, remove all the infected material and burn or dispose of it in municipal waste – then plan for a copper spray the following season as suggested above.

Varieties: My top picks

My all-time favourite plums are a mixture of European and Japanese varieties and are suited to a number of end uses. Alphabetically (to avoid any form of favouritism) they are:

Angelina Burdett (European)
Purple-black skin; greenish-yellow flesh.
Polliniser: Another European plum, e.g. Greengage.

A medium-sized prune plum which has excellent flavour when eaten fresh as well as wonderful cooking qualities. Some of the prune plums do not have great flavour when eaten fresh, as their meaty, dry, high-sugar flesh is far better suited to drying and baking atop cakes. My first ever bag of prune plums was a dismal, under-ripe failure. Angelina Burdett is juicy and aromatic and also makes excellent dried fruit – a freestone plum, so just halve, pop out the stones, turn the halves inside out with your thumbs and dehydrate for 16 hours on a medium/55°C heat setting. A dip in citrus juice will help preserve the colour. In central New Zealand, Angelina Burdett ripens around mid-late January.

This plum was raised in England around 1850 by Mr Dowling of Woolston, Southampton. Who was Angelina Burdett? A philanthropist nonetheless – more formally she was the 1st Baroness Burdett-Coutts, the daughter of a well-heeled banker. Despite inheriting astonishing wealth in 1837, which made her one of the most affluent women in England, she lived a life of generosity towards others, spending most of her money on scholarships, endowments and philanthropic causes – including a home for vulnerable young women, co-founded with Charles Dickens. It seems befitting that this superb plum bears the baroness’s name.

Black Doris (hybrid, likely a sport of the original Doris, which is P. cerasifolia x P. salicina).
Purple-black skin; red-black flesh.
Pollinisers: Elephant Heart, Santa Rosa, Duff’s Early Jewel.

You will be familiar with this lady as the quintessential Kiwi tinned plum – soft, syrupy-tart flesh with papery skin still adhering in places. She is ripe in mid-late February and I was hoping to be able to provide, as I have for Angelina above, some information on who Doris actually was. The original Doris plum was a product of the esteemed plant breeder Luther Burbank (more on him later) who appears to have just fancied the name. Any more than that is impossible to extract – as this amusing piece by Lynda Hallinan details: https://www.stuff.co.nz/life-style/food-wine/82969680/the-origins-of-the-black-doris-plum

Apart from bottling and producing a meaty, well-flavoured jam, I’ve recently discovered that Black Doris makes the most amazing dried plums – and again, being freestone, the job is not a difficult one. Follow the method as for Angelina Burdett above, but be particularly careful in ensuring the fruit is completely dry before storing. I lost half a jar due to mould last year and it was a sad day.

Burbank (Japanese)
Red skin flushed with yellow; yellow flesh.
Pollinisers: Self-fertile, but Santa Rosa, Duff’s Early Jewel and Omega may assist.

Luther Burbank, the revered American plant breeder and botanist was responsible for the development of over 800 new plant strains and varieties over the course of his 55-year career. Amongst his creations lie the Russet Burbank potato of fast-food French fry fame, the Shasta daisy, a spineless cactus for use as cattle feed, the universal Japanese polliniser plum ‘Santa Rosa’ and also amongst the 120 new plum cultivars he developed, one bearing his own name. My paternal grandmother had a Burbank plum tree which cropped extremely heavily one year and it took us a good day to harvest all the fruit. Fruit size is medium tending towards large, clingstone, juicy and sweet with aromatic flesh. In my mind, it is first and foremost a dessert fruit but makes pretty good jam too.

Coe’s Golden Drop (European)
Yellowish-green skin and flesh
Pollinisers: Greengage and reportedly President too.

This is the number one plum of my childhood. We had a large, perennially laden tree in the backyard growing up and its offspring in the form of seedlings and grafted trees are still with us. We didn’t have any pollinisers in our garden, but I assume a neighbour must have as the crops always seemed plentiful. Interestingly, some nursery-bought Coe’s Golden Drop trees we purchased in the late 1990s as mates produced large but completely tasteless fruit, so there must be some inferior sources of scionwood floating around out there.
Coe’s Golden Drop predates 1800 and was raised by Jervaise Coe, a market gardener from Bury St. Edmunds in Suffolk, England, reportedly from the stone of a Greengage fertilised by a White Magnum Bonum plum. Although apparently prone to biennial bearing (I don’t remember the off years from my youth…) which renders it unsuitable for commercial production, it is amongst the most highly-flavoured of all the plums, sweet, juicy and freestone to boot.

Luisa (Japanese)
Red and yellow skin; yellow flesh.
Pollinisers: Self-fertile

My final selection is the youngest of the bunch and currently enjoying rave reviews and a semi-cult following here in the Antipodes. Luisa is a large, elongated, mango-shaped plum with a beak at the blossom end (the shape is European plum-like) somewhat reminiscent of Burbank in colouring and flavour and ripe in February. The flesh is super juicy, sweet and well-flavoured if not subject to overwatering close to harvest. The fruit makes a jam that you can almost pass off as apricot – which leads me to have more than a sneaking suspicion this plum somehow hovers close to the apricot side of the family tree in a genetic sense.

In terms of history, I had originally heard this was a roadside find but recently read that it was discovered in a garden in Hillcrest, Hamilton around 1985. Luisa’s only downfall is in the dental sense – the tip of Luisa stones have a habit of coming adrift at some point in the growing season, separating off and ending up embedded in the beak end (and less commonly in the stem end) of the fruit – a nasty surprise to chomp into if you’re not expecting it. The fruit is pretty much freestone, so I suggest halving the plums so you can conduct a thorough inspection and removal operation prior to consumption.

What to do with your crop

My annual plum priorities extend to:

Some bottled fruit for winter consumption – usually Black Doris (whole) and Luisa (halves). The latter is quite curious in flavour and appearance when cooked, the juice takes on a pink tinge from the skins while the fruit stays orange-y. This year I’ve also bottled whole plumcots in syrup with the addition of about 40-50 ml of brandy in each jar (hic). Use the bottling method in last month’s apricot column and you won’t go far wrong.

Plum jam – usually again using Black Doris and Luisa. This is almost exclusively for use on pikelets, in jam tarts and for making these amazing Austrian jam buns - buchteln: http://thelittlelibrarycafe.com/blog/tag/Teaching

Dried fruit - using prune plums and ‘ordinary’ plums, the method described in Angelina Burdett section above. If you have a surfeit of overripe bananas and can’t face another smoothie or banana cake, retrieve some stewed plums from the freezer and thaw them. Blend 50:50 plums and soft squishy bananas with a splash of citrus juice or leftover syrup from bottled or canned fruit, spread on oiled, solid dehydrator trays and dry for 10 hours on the medium/55°C setting. The result is a very intensely flavoured fruit leather that makes a high-octane snack for people on the go.

If you stumble upon a source of prune plums, look out for a recipe for Pflaumenkuchen, alternatively known as Zwetschgenkuchen. It’s a traditional German cake, usually based on a yeast-raised dough, generously topped with prune plums (zwetschgen), melted butter and cinnamon sugar. If you halve and free-flow freeze some prune plums you can enjoy this brunch-worthy weekend treat year-round. Just saying!

Anna-Marie Barnes is an active member of the New Zealand Tree Crops Association who endeavours to grow and preserve as much of her own fresh produce as possible. When the weather’s no good for gardening, she can usually be found inside working on a batch of homemade cheese or soap.

The New Zealand Tree Crops Association is a voluntary organisation promoting interest in useful trees, such as those producing fruit, nuts, timber, fuel, wood, stock fodder, bee forage and other productive crops. Find out more about the NZTCA here: https://treecrops.org.nz/

 

Image credits

Fruit tree - Julia Filirovska via Pexels
Plum bowl - Mareefe via Pixabay
Prune plums - Pixel via Pixabay