Plum trees generally bloom in late winter to early spring and depending on the climate, species, and the cultivar, their fruits ripen in May through September. Japanese plums are hardy in hardiness zones 4-10 of the USDA while European plums do well in zones 3-9, but it depends on the cultivar.
Majority of the plum trees are self-unfruitful, and they need cross-pollination to set fruit, and when planting, you need to plant at least two compatible varieties. The trees generally bear fruits about four to six years after planting. Plum trees also require pruning, winter chill, and the correct climate to produce an excellent yield.
How plums pollinate
For proper pollination of plum trees, you need to plant varieties that bloom at the same time. European and Japanese varieties bloom at different times and can therefore not act as pollinators for each other. The trees you choose need to be cross-compatible, and the pollinators should have enough pollen to set fruit successfully.
If bloom periods do not overlap, a self-fertile tree can be used to pollinate any other plum. Self-fertile species are generally used as universal pollinators, for example, ‘Santa Rosa.‘ This tree is self-fruitful, and it thrives in USDA hardiness zones 4-9.
What is chill for plums?
Winter chill is an extended time of cold temperatures, vital for nut and fruit trees. The amount of winter chill depends on the tree variety, and some need more than others. Most Japanese plums require 500-900 hours of temperatures below or at 450F, while the European plums usually need 700-1000 chill hours.
European varieties cannot grow in areas with too mild winters since they have moderate-high winter needs.
Do plum trees bloom every year?
Plum trees do not bloom each year since most of them require 3-6 years to mature after planting. But dwarf varieties may begin to bear fruits one year sooner than standard plum trees varieties. Some problems such as over-pruning the branches, over-fertilizing the trees, and frost injury of flowers may delay a plum tree’s bloom by at least one year.
A tree grown from a seed harvested from a plum tree may end up not bearing fruits. To get fruits from such trees, it is advisable to select a tree established from a nursery. If you see biennial bearing in your plum plants, it means they will flower and bear fruits each year. This blooming occurs after a year of heavy fruit yield.
Plum trees use a lot of nutrients to yield significantly and nearly exhaust their resources. They will then take up to one year to regain their strength and prepare to bloom the following year.
You can use fruit thinning to prevent biennial bearing on your plum trees. To do this, you need to trim the fruit in the early stages to allow each branch to have a plum every 4 to 6 inches.
Factors that affect plum tree blooming
You can get quality products from your plum trees if you take good care of them. The following factors will determine whether you will get a high or low yield from your trees;
If your plum trees are young, do not allow the soil to get too dry. However, you should not apply too much water, resulting in the rotting of roots or fungal diseases that will affect the trees. For older plum trees, you need to water deeply but infrequently to stimulate the root system’s growth. The roots grow broader and deeper stead of staying near the soil surface or remaining shallow, helping the plum trees survive during neglect or drought periods.
Many plum tree varieties can thrive in zones up to 5 and as far south as 7, 8, or 9 depending on the species. But, the trees may not survive further south since they need about 500-1000 hours of chilling hours in the winter. A plum tree that doesn’t get adequate chilling hours cannot break dormancy in the spring, which leads to a total lack of fruits and flowers.
Late spring frost can also be hazardous to your harvest. If your plum tree gets a cold snap after breaking dormancy in the spring, it can lead to the death of all flowers. If the plum tree produces flowers too early during a gentle winter, the flowers can die and destroy any chance of harvest that year.
Heavy annual pruning is recommendable for plum trees as it helps to prevent biennial bearing or broken branches. Pruning should be carried out during summer or winter, but the needs may vary as per the variety.
Before planting a stone or plum tree, it is advisable to add some compost to the soil. Fertilizing your soil provides organic matter and nutrients for trees when growing. You can use compost made from your regular kitchen and yard waste.
You can also supplement your compost with commercial fertilizers to give extra nutrients to the soil. You may conduct a soil test to establish if your ground needs more nutrients. Ensure that you do not over-fertilize your ground as doing this can kill or harm your plum trees. Avoid too much nitrogen fertilizer, which can prevent your trees from blooming.
Why your plum tree is not blooming
Plum trees need full sun to bloom and set fruit. If your plum trees do not get adequate sunlight, it may lead to a delay in flowering or lack of it altogether. It would help if you placed your trees to get a minimum of six hours of sunlight every day. Make sure that your trees are not placed where buildings and other plants shade.
Bacterial canker also prevents your plum trees from blooming. You will notice bacteria canker symptoms in the spring, including limb dieback, leaf spot, and rough cankers, that can cause flowers and young shoots to die and dry up. When the spring temperature drops and the moisture levels go up, the bacterium may be common. Splashing rain may also spread the disease and affect plum trees between 2 and 8 years old.
Fungi may cause brown rot and black knot that also prevent your plum s from blooming. Brown rot, also known as Monilinia fructicola, is responsible for blossom and twig blight, and many flowers that come out will change to brown and eventually die. The black knot, also known as Dibotryon morbosum, is active in the spring affecting new growth and disrupts average growth. It also overwinters in the twigs and branches.
Severe pruning of plum trees may also prevent them from producing fruits. Plum trees need little pruning once the framework is established. It is not advisable to prune hard and frequently, as this may affect the growth and the production of flowers. Removing large branches may harm the trees and cause wounds that will not heal properly, leading to easy access to disease.
Heavy pruning will also get rid of the one-year-old shoots that are vital for flowering.
Plum trees bloom in late winter to early spring, but it depends on the species, cultivar, and climate. You need to take good care of your trees and ensure that they get the essential nutrients and conditions to produce their fruits on time and in the correct amount.