Planting density
For many years, the optimal planting density for avocados was debated, as this factor was considered crucial for achieving high profitability. In Chile, Mexico, and California, a square planting pattern was used for many years, maintaining all the trees until they reached maturity, at which point overcrowding began and productive potential started to decline. Once insufficient light and alternate bearing became unsustainable, diagonal row thinning began, giving the orchard a "second wind" that returned it to a more youthful state, producing high yields again for two to three seasons. However, it would inevitably fall back into the effects of insufficient light and alternate bearing.
The first high-density plantings were implemented in California with the Reed variety, achieving early maturity, large fruit size, and high yield potential. This planting method was replicated in Chile, but with the Hass variety, which exhibits a very different vigor and growth habit. Initially, very good results were achieved, but the orchards quickly declined due to overcrowding. The incorporation of Uniconazole was used to try to manage high-density planting in Hass, achieving excellent results at densities close to 1,000 plants/ha. This encouraged consultants and farmers to push further, seeking a faster production cycle to recoup their investment sooner. Not only was the project's production cycle accelerated, but the uniformity of orchards was also improved using seedling rootstocks, which had always shown high heterogeneity. By planting more than 1,000 plants/ha, the bad genetics, which always affected avocados with Mexican rootstock, began to be eliminated as the more vigorous and healthy specimens covered the space of the weaker plants, managing to completely cover the productive surface.
Many growers adopted high-density planting thinking that pruning would control vigor, but they couldn't overcome the lack of sunlight. The only factor that truly controls an orchard's vigor is crop load, which limits the size of the trees. If, due to poor management, the orchard falls into biennial bearing, the vigor explodes and quickly becomes stunted, losing all the advantages of high-density planting. Pruning is a management practice used in all fruit trees to illuminate the foliage and renew fruiting wood, maintaining the tree's youthfulness, but it should never be used to restrict its growth.
Finally, high-density planting led to experiments that exceeded all expectations, even deforming the Hass variety and accelerating the aging of the crop, without achieving the expected yields over time. Generally, trees were planted in a square pattern without leaving a wide alley to ensure sunlight on both sides, and subsequent thinning of diagonal or linear rows was never done in time for fear of reducing production. Currently, the most productive orchards are not high-density, but rather medium and even low-density orchards that have overcome overcrowding with Multi-Axis Rotation, internal foliage removal to achieve a fully open and ventilated structure forming a first, second, and third productive level, bearing fruit both inside and outside the tree. External fruit set, which is subject to weather conditions, can abort under certain circumstances, but internal fruit set always ensures production, achieving later flower opening with favorable weather and less stress. An open tree with a completely clean and well-lit structure can hold much more fruit than a high-density tree with excessive use of Uniconazole, where its height is ultimately limited and the extremely short internode foliage ends up preventing light from entering.
With the consolidation of clonal rootstocks, due to their greater vigor, rapid growth, and high cost, there has been a return to the past, favoring medium or short planting distances and seeking open, uncluttered canopies to accommodate as much fruit as possible, protected from wind, heat waves, and spring cold. Having an efficient, light-filled first, second, and third tier facilitates easy flower induction, resulting in high yields over time with good-sized fruit.
In conclusion, the high-density experiment yielded good results, but by returning to the past with medium and low densities with good lighting plus the change in genetics, the result today is categorically superior.
Gonzalo Vargas
