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Fruit and nut harvesting net
This is a design for a sheet to catch fruit, nuts or other produce that falls from trees.
It is a recognized technique to place sheets on the ground around fruit or nut trees to easily collect the harvest. This is easy to implement when there is grass or bare ground beneath the trees. However, in forest gardening, a potential problem encountered is that produce that falls from the canopy layer trees may fall into lower layers (shrubs, perennials and groundcover plants). Not only is it very difficult to place sheets on the ground in this situation, but also it is even harder to see and retrieve all of the produce as it falls among other plants, reducing overall yield. With larger falling fruit, plants below may even sustain minor damage.
Posts are placed in the ground so that the canopy spread of the tree is encircled. A sheet of the same area as the posts is sourced. At the center of the sheet a hole is cut which matches the diameter of the trunk. A linear cut is made from this central hole to one edge of the sheet so that it can be fitted around the tree trunk. This cut is roughly stitched or taped back once the sheet is in situ. As harvest time for individual tree species approaches, the sheet is suspended from the posts. This is at a level above the shrub layer but below the canopy layer, probably around 1.5m to 2m from ground level.
The edges of the sheet are at a higher level than the center of the sheet, so that falling fruit or nuts are funnelled into the center of the sheet. At the lowest point of the sheet, there is another hole from which a tube directs the falling produce into a collection vessel which is emptied periodically. The tube is made from an offcut of the same material as the sheet and is stitched or taped into place. Duct tape would help maintain its shape slightly.
A forest garden might be designed as a repeating pattern of guilds built around individual trees. If this collection method is considered at the same time as designing the forest garden, then posts can be positioned so that they can support multiple sheets for different trees (see diagram). The sheets can be moved from tree to tree as different tree species come into harvest and others finish cropping. A small clearing is also left for the collection vessel to stand in place when it is needed. A path to easily access the collection vessel is also worked into the design. To suppress weed growth in the clearing and on the path, a mulch of woodchipping is applied annually, or resilient groundcover is sown, such as white clover (will tolerate some foot traffic).
- The posts must be strong enough to hold the sheet in place. The easiest way to do this is to bury them in the ground, by at least 2 feet unless they are to be set in concrete. Metal posts would last longer than wood, but have higher embodied energy and will be subject to rust unless galvanized or painted in rust protecting paint. Wooden posts can be hardened with fire as a basic form of delaying rotting, or the buried end of the posts could be wrapped in plastic sheet. Wooden posts can be also pressure treated, etc.
- 3 posts would be the minimum to create a triangular area, although 4 posts would offer a square shape which can cover a larger area.
- The sheet must be durable so that it can be re-used for years. The sheet might need to be in place for a month or more, so the sheet must not block too much light for lower plants. Clear plastic sheeting, such as is used in polytunnels (polythene) might work, but this will get blown by the wind easily. A fine net might be more suitable, but the holes must not be big enough that the produce is able to fall through them. A net would be blown around by the wind less. Perhaps these could be sourced from fishing nets, or the nets that gardeners use to stop birds getting at crops. The material would ideally be resistant to UV light degradation. The "seams" of the sheet must be weatherproof. The sheet would likely need to be secured to the trunk as well as the posts, without disrupting the overall funnel shape. This could be done with nails, although any wounds in the bark should be kept to a minimum as they will potentially act as a point of entry for pathogens.
- Some fruit may be easily bruised as it falls, so placing a bed of straw or hay at the base of the collection vessel, or similar measures might be needed.