The season of plums! Learn and cash in on it

Plum trees are the most tolerant of all stone fruits. [Courtesy]

Plum is a seasonal stone fruit in the same family as peach, cherry and apricot. Plums are mostly available from December to February.

Cyrus Mwangi, a farmer from Kiambu says the fruit is mainly cultivated in central highlands which offer best-growing conditions. He offers insights on growing plums.

Ecological requirements

Plums are grown on a wide range of soils. However, deep, well-drained, medium-textured soil with a pH of between 5.5 to 6.5 is generally best.

Plum trees are the most tolerant of all stone fruits regarding heavy soils and waterlogging, and they tolerate drought better than peach trees do. It is important to choose suitable varieties adapted to a specific location.

Varieties

Plum cultivars include Shiro, Harry pickstone, Reubennel, Santa rosa, Burbank, Satsuma (Red Cardinal or Blood plum), Methyl, Cherry plum and Kelsey.

Propagation

Plums do not produce true from seed. Therefore to maintain ‘true to type’ cultivars, they must be propagated asexually by using grafting. Grafting can only be carried out if suitable rootstock material is available.

Myrobalan seedlings have been used as the principal rootstock for plums. They are resistant to drought and root and crown rot, but susceptible to root-knot nematodes and bacterial canker.

Shayo Elias (left) selling plum to a customer in Kakamega town, December 2016. [Benjamin Sakwa, Standard]

Planting

In most cases, a planting distance of five metres by six metres is recommended. A spacing of four metres by five metres is sufficient if trees are regularly pruned, which is done to maintain a balance between vegetative growth and fruiting.

When transplanting grafted seedlings, ensure that the graft union is about one inch from the ground. Ensure that the seedlings are set at the centre of the hole and the roots spread inside.

Varieties like Methly, Beauty and Santa Rosa are self-fertile, adequate cross-pollination is needed for other cultivars to ensure sufficient fruit setting for commercial purposes.

In case cross-pollinating varieties are needed, these should be distributed at a rate of about every third tree in every third row. Water young plants regularly for proper establishment. Mulching should be done to avoid moisture loss and to suppress weeds around the tree root zone.

Pests and diseases

Pests include plum curculio - a type of weevil that infests the tree, destroying fruit and causing it to fall prematurely, Aphids, Plum Moths, Plum Sawflies, mites. “There are traps to help mitigate some of these pests.

Spraying may not be advisable as the farmer might end up killing pollination insects,” says Mwangi. The most common plum tree diseases include black knot, plum pocket, brown rot, plum pox virus, perennial canker, and bacterial leaf spot.

Control of black knot requires both prevention and sanitation. Prune out all infected branches and destroy them by burning, burying, or throwing them away.

“Remove at least three or four inches of healthy tissue to ensure elimination of the fungus. Heavily infected trees should be removed completely,” says Mwangi.

Monica Achieng' sorting black plum at a street stall in Kisumu. May 20l9. [Denish Ochieng, Standard]

Harvesting

Depending on variety, plums are ready to be picked from 80 to 120 days after flowering. Fruits may be picked before they are completely ripe since they can finish ripening off the tree. Fruit maturity first begins at the top of trees and later at the bottom, which usually necessitates more than one picking which can go for seven to ten days. “Plums are highly perishable and must be picked and handled with care,” says Mwangi.

Market

Market for plums is available both at domestic and export level. Mwangi says farmers who meet criteria for export should go for it as it may be more fulfilling.