Curtis Swift, Ph.D.
All of us have heard the suggestion to remove flower stalks from lavender the first year of planting. This is supposed to result in a more vigorous plant and better winter survival the first winter and a greater yield during the following years. This makes sense as flowers and seed production take energy from the plant which would otherwise be going into root development. Where is the research data to confirm that assumption?This is one of the lavender research projects I am conducting in western Colorado. To make this research project meaningful this project includes ten cultivars of lavender each planted seven times at random throughout the field for a total of seventy plots. Each plot consists of ten plants. The reason for the randomized planting is to ensure differences in sun/shade, water, nutrients, and soil nutrients levels/texture are taken out of the equation. In research lingo these are considered independent variables. What I want to test for is the variable of flowers removed and flowers left to develop and its affect on winter survival and yield.Growers will often plant different cultivars in a single row or block and consider this their method to determine which cultivar(s) do best at their site. What happens if the area where they planted one of these cultivars had a slightly different soil consistency than where the other cultivars were planted? Or, what if one cultivar receives a slightly different amount of water than the other cultivars? Any of these differences could skew the results. By planting the cultivars randomly throughout the field the effect of these variables would be reduced. The more replications you include in your research trial the better. You don’t want to make a decision on faulty data. When you average the results of yield, winter survival, etc. for all of the randomly placed plots for each cultivar, you will have a much better status for what does best at your site.
Here is an example of a randomized design with five cultivars (1 – 5) replicated six times.
Here is an example of a randomized design with five cultivars (1 – 5) replicated six times.
| Replication 1 | Replication 2 | Replication 3 | Replication 4 | Replication 5 |
| 1 | 2 | 3 | 4 | 5 |
| 5 | 3 | 4 | 2 | 1 |
| 4 | 1 | 5 | 2 | 3 |
| 5 | 4 | 1 | 3 | 2 |
| 3 | 2 | 1 | 5 | 4 |
| 1 | 4 | 2 | 3 | 5 |
Sometimes you will have the same variety next to each as shown with cultivar #1 in the third rep and cultivars 2 and 5 in rep 4. This is fine. Just make sure the cultivars are mixed up as much as possible. A scientist will typically use a table of random numbers or a statistical program to set up their trial.
In the Palisade Colorado trial, half of each plot of ten plants had the flower stalks removed last year and the other five were allowed to develop flowers. We are in the process of harvesting the flowers keeping the yield separate for each group of plants. When we finish we will have the weight in buds for each plot. The resulting one hundred and forty sets of data will be statistically analyzed to determine if removing the flowers resulted in an increase in yield for each of the ten varieties.In this trial we also collected data on winter survival and the percentage of damage each plant suffered. Some cultivars lost more plants during the winter than other cultivars. This will be taken into consideration when evaluating the flower removal portion of this project. The information on winter kill will be reported in an upcoming report.If the results in bud weight show there was no significant difference in yield between plants that had their flower stalks removed and those that were allowed to develop flowers, then the assumption “removing the flowers is critical to yield” will be busted. Since it takes time to remove the flowers and growers lose the first year of yield when removing flowers, this information has an economic impact on the grower. Collecting data again in 2013 will help confirm the research data. Stay tuned for the results of this research trial.
In the Palisade Colorado trial, half of each plot of ten plants had the flower stalks removed last year and the other five were allowed to develop flowers. We are in the process of harvesting the flowers keeping the yield separate for each group of plants. When we finish we will have the weight in buds for each plot. The resulting one hundred and forty sets of data will be statistically analyzed to determine if removing the flowers resulted in an increase in yield for each of the ten varieties.In this trial we also collected data on winter survival and the percentage of damage each plant suffered. Some cultivars lost more plants during the winter than other cultivars. This will be taken into consideration when evaluating the flower removal portion of this project. The information on winter kill will be reported in an upcoming report.If the results in bud weight show there was no significant difference in yield between plants that had their flower stalks removed and those that were allowed to develop flowers, then the assumption “removing the flowers is critical to yield” will be busted. Since it takes time to remove the flowers and growers lose the first year of yield when removing flowers, this information has an economic impact on the grower. Collecting data again in 2013 will help confirm the research data. Stay tuned for the results of this research trial.