How to Thin Plum Trees in 5 Simple Steps
Plum trees are excellent producers and beautiful additions to the garden. Like other fruit trees, they benefit from thinning. Join gardening expert Melissa Strauss to walk through the steps for big, juicy plums and a strong, healthy tree.
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When it comes to trees that are both functional and beautiful, plums sit comfortably near the top of the list. Their attractive form, gorgeous spring floral display, and gem-like fruits make an excellent addition to the landscape.
Sweet and juicy, plums provide a hearty helping of fiber along with other vitamins and minerals that contribute to a healthy diet. They’re full of phytonutrients, and particularly high in anthocyanins, which give them their blue and purple tones. These are great inflammation reducers. Basically, they are one of nature’s perfect foods, and you can grow them right in your garden.
When it comes to getting the biggest, sweetest plums, there are a few factors at play. Your plums need fertilizer, plenty of water, and the space and energy to put on weight and mass. Thinning is an integral step in making this happen.
Bubblegum ‘Toka’ Plum Tree
How to Thin Plum Trees in X Simple Steps
- Unique and Delicious Flavor
- Cold Hardy and Resilient Tree
- Consistent and Heavy Fruit Production
- Perfect Pollinator Partner
Why Thin Your Plums?
The primary reason for thinning any fruit tree is to increase the quality of the fruits. It also has some great benefits for the tree in general. In the wild, the thinning process takes place naturally through wildlife and other environmental factors. In cultivation, we can be precise and deliberate about it, making it an even more effective practice.
Reduce Limb Breakage
Thinning fruit is important for maintaining the integrity of young trees, especially their branches. Initially, your plums will be tiny and won’t weigh much. However, as they gain weight, they can be taxing to branches, especially thinner, weaker ones.
Weighed-down branches can affect the shape of the tree. All that fruit can also cause thinner branches to snap clean off! Reducing the number of plums per branch, according to the branch size, will help reduce the occurrence of breakage.
Increase Fruit Size and Improve Quality
The most obvious reason for thinning your fruit is to increase the size and quality of the plums themselves. A tree has just so much energy to apply to producing fruit, leaves, and growth in general. Leaving an overabundance of plums will make the tree exhaust that energy and leave you with sub-par plums, and possibly, a tired and weak tree.
When you remove some of the plums, you allow the tree to spend more energy on those left to create larger, more robust fruits. It also leaves some nutrients and energy to support the tree itself, for better production in years to come.
Prevent Overbearing
Finally, thinning your plums helps to prevent overbearing. Overbearing is an overloading of fruit in one year, which deprives it of nutrients and weakens it for the following year. Proper pruning and thinning are the best ways to prevent this.
When a fruit tree suffers from overloading, the fruit is subpar, and it is unlikely to produce much the following year. All that fruit deprives the tree of the energy it needs for its roots and foliage.
If you allow your tree to overbear, you risk a lousy harvest the following year, as it will need to replenish its stores and channel energy back into root and branch growth. As a result, it won’t bloom as prolifically, and fewer flowers mean fewer plums.
So let’s get down to the business of thinning that plum tree.
Step 1: Don’t Wait Too Long
Plum trees flower in early spring, and within a month after blooming, the fruit should be clearly developing. You want to be able to determine which are the most robust plums, because those are the ones to leave in place.
Around this time, your tree may naturally drop some fruit, which is great because it leaves you less decision-making. When the plums are about 1/2 to 1 inch in diameter, you are ready to set to work.
Step 2: Leave One Fruit Per Spur
Plum trees produce on small, stubby branches called spurs. Each spur is just a few inches long, and they form along the main branches as they mature. Most of the time, these form on branches once they reach two to three years old. Each one will produce a cluster of flowers, and then fruits will develop in their place.
Make sure when you prune your plum tree that you don’t remove these spurs, or you’ll find yourself with no fruit at all. I made this mistake with my first apple tree and was sad to miss out on fruit for several years! As the tree produces more spurs, you can thin out the older ones. When the spurs grow too close together, you’ll end up with an overabundance of fruit.
When you set about your task, your aim should be to remove all but one plum from each spur. If you need to thin further, you can do so afterward. But, for the first pass, focus on those spurs and leave them with one plum each.
Step 3: Choose the Healthiest Plums
Obviously, when you remove the excess fruits, you’ll want to select the healthiest plums to leave on the tree. Inspect each cluster and identify the ‘king fruit.’ This will be in the center of the cluster, and will often be the largest at this point. While it’s likely the largest, it’s not usually the nicest, and is often misshapen. That one should be the first to go.
Once you’ve removed the ‘king fruit’, inspect the rest of the cluster for any other misshapen plums, and any with other blemishes or defects. Essentially, you want to remove all but the biggest, healthiest plum on the spur.
Step 4: Space Fruits Properly
After your first pass, you should take stock of the entire tree and how many plums there are on each branch. More important than the actual number of fruits is the amount of space between them. The size of the branch also matters, as thinner branches won’t support as much weight.
The ideal space between plums should be between three and six inches. On thinner branches, leave six inches of space between fruits, even if that means leaving a spur empty. This will keep those thinner branches from bending and snapping.
You can typically leave one fruit per spur without intervention on the larger, stronger branches. However, as I mentioned, older branches may have many spurs, and they may be closer together than three inches in some cases. In this event, keep your plums about three or four inches apart, once again selecting the healthiest and discarding the weaker fruits.
Step 5: Remove Gently
When it comes to removal methods, you have some options. If you want to be exact about your snipping, use a small pair of harvesting snips or sharp scissors. This isn’t usually the preferred method, though, as getting those snips between fruits without nicking them can be challenging.
The most common method is to pluck the excess plums off by hand. They are small, so use your thumb and forefinger only. Grasp them gently between two fingers and twist lightly as you pull upward. They should come loose easily without knocking off the rest of the cluster.
The result of thinning your plum tree will be the largest, best-tasting fruit it can produce. It will also preserve energy for the tree, allowing it to continue growing and developing, and applying energy to the roots. You’ll have a stronger tree and better fruit without the risk of missing out on fruit next year.
