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A cross between a gage and a plum, Opal has taken on the full sweet flavour of the gage side of its parents but with a slightly larger fruit. Plums are produced early in the year, late July in some areas, and continues for nearly ten days. The skin, marked with purple and red looks just ready for eating when ripe.

Far better disease resistance compared to most other varieties combined with vigorous growth makes this a plum tree that is suited to many areas of the UK.


PARENTAGE OF OPAL PLUM TREES


Opal is a cross between Early Favourite and Oullins Gage. It was bred in Sweden and released in 1925.

APPEARANCE, TASTE AND CHARACTERISTICS OF OPAL PLUMS


Opal is a very rustic and attractive looking plum when ripe, with a yellow background overlaid with reds and purples. The flesh is a light gold colour with a small stone which comes away easily. The flavour is delicious, more like a gage than a plum, sweet and juicy. Individual plums are an average size. Picked straight from the tree its probably the best tasting of all the plums.

Another added bonus is that the crops mature on the tree over a two week period, longer than normal. The crops are large and you need to keep a watch that it doesn't over-crop (see pruning below). It produces fruit early in the year, a week or so earlier than Victoria. Because this is an early variety it does best when grown in full sun to give the fruit enough sunshine to develop fully.

Opal plums

Opal plums
(picture courtesy National Archives)

Opal plums are grown to be eaten straight from the tree but they also perform well when cooked for jams or some pies. It does have a lot of juice so if you are looking to cook a classic plum pie we suggest that the drier Belle de Louvain is better. Opal does however make excellent plum crumble, our quick, cheap and tasty recipe can be found here.

Overall tree size is of course primarily dependant on the rootstock but also on the growing conditions. On average the following tree sizes by rootstock are for a fully grown tree after 7 years:

  • St Julien A - unpruned height 4m / 13ft, pruned height 3.5m / 11ft
     
  • VVA-1 - unpruned height 3.5m / 11ft, pruned height 2.5m / 8ft
     
  • Pixy - unpruned 3m / 10ft. pruned height 2.5m / 8ft

Our advice, regarding rootstocks, for growing an Opal plum tree in almost all conditions would be the St Julien A rootstock. You'll get a decent sized, relatively vigorous tree which won't swamp the average garden. If your garden is on the small size and your soil is well-drained and nutrient rich it may be worth thinking about a Pixy rootstock. However, even in a smallish garden we would suggest that an appropriately pruned Opal plum tree on Julien A rootstock would be your best bet.

Your tree should produce a small crop three years after it has been planted and will reach its full-cropping capability five years after planting.

One very common characteristic of this variety is that it over-crops. This can have two undesirable effects the first of which is that a large number of the fruits do not develop to full ripeness. The second effect is that the sheer weight of the fruit can cause branches to break. Both of these can be avoided by correct pruning - see below.

PRUNING OPAL PLUM TREES


All the normal rules for pruning plum trees can be ground on our page dedicated to this subject which can be found here. If you have an old or neglected Opal plum tree then more information about pruning these trees can be found here.

Specifically for Opal plum trees we would suggest the following pruning regime which will be better suited to their known weaknesses:

  • Pay special attention to thinning the fruits in mid June 2017. This will reduce the weight of the fruit produced and help to stop branches breaking under the weight of excessive fruit. It will also help the remaining fruit to ripen fully.
     
  • Prune in the first three years of your tree's life exactly as described on our plum pruning page which can be found here. This will establish a good basic shape.
     
  • Only prune lightly in subsequent years but prune each year.
     
  • If branches break cut them back to solid wood as soon as possible whatever time of year the breakage occurs. It's true that plum trees should best be pruned in June time but a breakage is an unavoidable type of self-pruning which will almost always result in damage which will let in infection. Far better to immediately prune back to solid wood and allow the tree to heal over the cut as quick as possible.

PESTS, DISEASES OF OPAL PLUM TREES


Opal is admirably resistant to diseases which affect plum trees in general but if your tree has problems then consult our pest and disease page.

POLLINATION PARTNERS FOR OPAL PLUM TREES


Opal plum trees are in pollination group 3 and is self-fertile and will produce a good crop without any other plum trees nearby. It will successfully pollinate the foloowing other plum tree varieties:
  • Avalon - pollination group 2, partially self-fertile
     
  • Belle de Louvain - pollination group 3, self-fertile
     
  • Blue Tit - pollination group 4, self-fertile
     
  • Cambridge Gage - pollination group 3, partially self-fertile
     
  • Coe's Golden Drop - pollination group 2, self-sterile, needs another pollination partner
     
  • Czar - pollination group 3, self-fertile
     
  • Denniston's Superb - pollination group 2, self-fertile
     
  • Excalibur -┬ápollination group 2, partially self-sterile
     
  • Farleigh Damson - pollination group 3, self-fertile
     
  • Haganta - pollination group 3, partially self-fertile
     
  • Herman - pollination group 2, self-fertile
     
  • Jefferson - pollination group 2, self-sterile
     
  • King Damson - pollination group 2, self-fertile
     
  • Langley Bullace - pollination group 3, self-fertile
     
  • Merryweather - pollination group 3, self-fertile
     
  • Reine Claude de Bavay - pollination group 3, self-fertile
     
  • Rivers Early Prolific - pollination group 2, partially self-fertile
     
  • Sanctus Hubertus - pollination group 2, self-sterile, needs another pollination partner
     
  • Shropshire Prune - pollination group 3, self-fertile
     
  • Victoria - pollination group 3, self- fertile
     
  • Warwickshire Drooper - pollination group 2, self-fertile
     
  • Yellow Pershore - pollination group 2, self-fertile

BUYING AN OPAL PLUM TREE


Opal is available in larger garden centres and those which specialise in fruit trees. It is not normally available in supermarkets and diy centres. It is widely available online and we would recommend Blackmoor who, from our own personal experience, have good prices, prompt delivery and offer a personal service if you have any queries. Click here for the page where they sell this variety.

SUMMARY CHARACTERISTICS OF OPAL PLUM TREE



UUSE
: Primarily eating but can also be used as a cooker

SKIN COLOUR / TEXTURE: Background yellow with red and purple markings

FLESH COLOUR: Golden yellow

TASTE AND TEXTURE:: When fully ripe it's sweet

FRUIT SIZE:: Slightly smaller than average

TREE SIZE: Average

REGULARITY OF CROPPING: Excellent

POLLINATION:: Self-fertile

POLLINATION GROUP: 3

FULL NAME: Prunus domestica 'Opal'

AWARDS: RHS Award of Garden Merit

SPECIAL FEATURES: Good taste as an eater, good disease resistance.

OPAL FRUIT PRODUCTION TIME


The average flowering time (optimum time for pollination) and date when fruits are ripe in the UK for the Opal plum tree are set out below. If you have set your home town we can give you a more accurate estimate, if you have not set your home town (do it now by clicking here) the dates below will be the average for the UK.

Your town has not been set, the average main flowering time for your Opal plum tree in the UK is the third week of April. Fruit will be ready for picking in the first week of August. Click here if you want to set the dates to your home town.

Flowering and fruit production dates vary according to the weather in any particular growing season so the above dates may well change slightly from one year to the next. The flowering date above is when the plum tree produces the maximum number of blossoms, it will also produce blossom, although less, a week or two either side of the date given.

COMMENTS / QUESTIONS LEFT BY OUR READERS

Date: 14 February 2019 From: Elly
QUESTION: I bought an Opal plumb tree today and it has thorns. Is this usual for an Opal plum tree?

QUESTION: Opal plum trees do not have thorns. I would definitely question the seller (who is it out of interest?) about this and unless you receive a very good answer ask for a refund.

Wild plum trees sometimes have thorns on them but they are definitely not Opal plum trees.


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