The longevity and fruit production of a grapevine depend heavily on its initial establishment. Correct planting depth ensures the vine can access necessary water and nutrients while protecting sensitive biological structures. Getting the depth wrong can lead to serious issues, including disease, weak growth, or the death of the young plant.
Determining the Optimal Planting Depth
The proper planting depth is determined primarily by the type of vine material: whether it is own-rooted or a grafted vine. For own-rooted vines, the goal is to set the plant at the same depth it was growing in the nursery, or slightly deeper, ensuring the root crown is just at or below the final soil line. This approach prevents the uppermost roots from drying out, which can happen if the vine is planted too shallowly.
The planting depth for grafted grapevines requires careful consideration. A grafted vine consists of a scion (the fruiting variety) joined to a rootstock (a hardy root system) at the graft union, which appears as a noticeable bulge. This union must be positioned well above the finished soil level to prevent a condition called scion rooting.
Scion rooting occurs when the scion material, which is not phylloxera-resistant, grows roots into the soil from above the union, defeating the purpose of the resistant rootstock. To avoid this, the graft union must be kept 2 to 6 inches above the final soil line. Planting slightly deeper than the nursery mark and then pulling the vine up gently can help correctly position the roots and set the union at the proper height.
Preparing the Planting Site
Grapevines require deep, well-drained soil, as poor drainage is one of the most common causes of vine failure. Waterlogged conditions starve the roots of oxygen, leading to poor growth, disease, and eventual death.
The soil should be prepared to a depth of at least 24 inches to accommodate the extensive root system grapes develop. If the soil has a compacted layer, or “hardpan,” deep ripping or subsoiling is beneficial to allow for deep root penetration. A thorough soil test should be conducted one or two years prior to planting to assess and amend soil pH and nutrient levels, with a target pH range of 5.5 to 6.5 being suitable for most varieties.
To prepare the individual planting site, a hole should be dug that is two to three times wider than the root system. While the hole needs to be wide, it does not need to be excessively deep, as the goal is to spread the roots laterally rather than just vertically. After digging, the soil at the bottom of the hole should be loosened to prevent the formation of a slick, impermeable layer that can impede root growth.
Specific Handling for Different Vine Types
Bare-root vines are dormant and shipped without soil, requiring rehydration before planting. The roots must be soaked in water for a few hours up to overnight, as dehydration is a primary cause of loss in the first year.
Before placing the bare-root vine in the hole, the roots should be inspected and trimmed. Any broken, tangled, or excessively long roots should be pruned back to a length of 8 to 10 inches to encourage fresh, outward growth. The vine is then placed in the hole, and the roots are spread out like spokes over a small cone of soil at the bottom to prevent them from curling upward.
Containerized, or potted, vines require attention to the root ball. If the roots have begun circling, the plant may become root-bound and struggle to establish itself. Gently loosening the root ball or scoring the sides allows the roots to grow outward into the native soil.
After positioning the vine, backfill the hole with the excavated soil, tamping gently to eliminate air pockets around the roots. Initial watering is necessary to settle the soil and ensure good root-to-soil contact.