Evaluating Buds for Cold Damage

In the first week of April, we experienced very cold temperatures across the province. Temperatures dropped down to -8 to -16, depending on the region. Due to the warm temperatures experienced in March, many buds were at silver tip to green tip. At these stages of bud development, temperatures were cold enough to cause damage. To evaluate bud survival, there are a couple options; either you can force cut branches to bloom inside or cut open the buds.

To achieve a good estimation of bud survival, collect enough branches to bring in 100 buds. Collect these buds from five representative trees from different areas of the orchard and from different heights in the canopy. Label the branches with tags or flagging tape by variety and location of where you collected the branches.

You can force buds to bloom by cutting off branches, taking them inside and placing them in a bucket of water (Figure 1). Like cut flowers, cut an inch off the end of the branch right before placing them in the water to increase the survival and longevity of these branches inside. Branches will take approximately five days to go from green tip to tight cluster and another five days to reach full bloom.

Figure 1: Branches collected form an orchard and placed in a bucket of water inside a heated building to force buds to bloom.

Figure 1: Branches collected form an orchard and placed in a bucket of water inside a heated building to force buds to bloom.

The second option is that you can cut open the buds when they reach tight cluster. You can wait for them to reach this stage in the orchard or cut branches from trees, take them inside and force them to progress to this stage. Cut open the buds with a sharp blade by making sequential horizontal cuts, starting from the tip of the bud progressing down to the base of the bud (Figure 2). After each cut examine the pistols for brown and black tissue which is an indication of a dead bud (Figure 3). After being cut for five to ten minutes, bud tissue, healthy or damaged, will start to brown from being exposed to the air. If buds are farther along in development than tight cluster, it may be easier to examine the pistol by making a longitudinal cut (Figure 4).

Figure 2. Apple buds cut open horizontally, revealing a healthy bud.

Figure 2. Apple buds cut open horizontally, revealing a healthy bud.

Figure 3. Buds cut open horizontally. The centre bottom bud has a brown spot indicating damage.

Figure 3. Buds cut open horizontally. The centre bottom bud has a brown spot indicating damage.

Figure 4. A bud cut open longitudinally revealing a healthy pistol.

Figure 4. A bud cut open longitudinally revealing a healthy pistol.

For a full crop of apples, only 10% of buds that are distributed evenly in the canopy are needed for a full crop of apples.

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For more information:
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