“I had a wonderful show of flowers on my fruit trees this year so why haven’t I had much fruit to follow?” This must be one of the most common questions I am asked when carrying out evening talks and question times and without getting too technical it can be a very awkward one to answer. The problem is that a number of reasons can relate to plants not fruiting even after carrying a good display of flowers. Indeed, when you look into the complex system of pollination you begin to wonder how plants manage to fruit at all.
Weather conditions can play an important part in the potential fruiting of plants and with many trees, including apples and pears, frost is the biggest problem particularly at flowering time. We need to understand that pollen, once it lands on the stigma of a flower (that’s the female bit), must germinate and grow down a pollen tube, which tunnels through the flower to a tiny chamber containing the ovules. Only when these ovules are
do they become seeds. The fruit itself develops around these seeds as protection and will often attract animals, like us, to eat them and therefore spread the seeds near and far.
Back to pollination and if the weather conditions are not conducive to the pollen germination, for example frosty weather, then fertilisation will not take place and there will be no, or very little fruit to follow. When you cut open an apple you will notice that there are a number of seeds or pips within the core and each of these needs to be fertilised by an individual pollen grain before fruit is produced. If you have ever had an odd shaped strawberry or raspberry then the problem is usually caused through the same reason, poor or incomplete fertilisation of the ovules.
Other aspects can also affect pollination, as anyone who has grown tomatoes can verify and dry air conditions within a glasshouse will very often prevent pollen from doing its job. Tomatoes will not set fruit in a dry atmosphere and the spraying of plants with water during hot dry conditions and regular damping down of paths with water is recommended in order to keep the atmosphere humid which in turn helps pollination.
Even when fruit has set other obstacles can prevent or cause abnormalities in development as the reproductive mechanism goes through a rapid phase of changes. Most fleshy fruits, again like tomatoes and apples, have a high demand for water, usually at a time, (early summer) when it can be in short supply. Calcium is particularly important at this time and as a constant supply is required for cell development and a shortage of water means a shortage of calcium resulting in the collapse of cells. In apples calcium deficiency shows as bitter pit which is brown spots within the white flesh, while in tomatoes the same deficiency shows up as black flesh around the flower area, known as blossom end rot.
All the time a fruit is developing the right nutrients must be available to the plant in order that various stages can be reached. Potash is often mentioned for application around fruit as this element encourages ripening but too much of a good thing can also cause problems. It is therefore important that the right amount of nutrients is used for the feeding of fruiting plants and fortunately as long as you stick to well-known fertiliser it is difficult, but not impossible, to overfeed.
Here it is perhaps worth mentioning that some plants will produce a fruit without the need for pollination, cucumbers being a prime example, in fact, pollination of a cucumber is a disaster as it sends the fruit bitter and therefore inedible. To solve this problem of pollination we now have all female varieties of cucumber but it’s not fool proof. A cool spell of weather in summer will often promote male flower production, even on all female varieties, so do beware.
As we go through the summer other factors as well as the weather will have a go at making sure that our fruit never gets to the harvesting stage. June drop in apples is a time when the tree decides if it can manage with the fruit it is carrying, if not it will shed a few or many as the case may be. Pests and diseases will also be having a good go at wrecking the harvest plan. They don’t even have to ruin the fruit, just making it inedible will prevent a harvest, but if the seeds survive the plant will be happy, even if we are not.
Gardening is always a bit of a challenge because just as we are trying to produce fruits on some plants so we are trying to prevent them on others. Once a plant flowers and fruits, or to be more precise produces viable seed then its main task is over and it can either die as is the case with annuals, or shut down and stop growing as with most perennials. This is why with these ornamentals we are always removing old flowers so as to keep the floral display going for as long as possible. It must be remembered that no plant is performing for us humans, it’s a case of survival of the species and that’s it. End of story
John. E. Stirland.