Seedlings that are pot-bound or have tightly coiled roots are likely to develop root problems later. Most modern trays have individually moulded cells for each seedling. Trays designed for root training have cells with vertical grooves to direct the roots downwards, and have slots to air-prune the roots and reduce root coiling. Before taking delivery, remove a few seedlings from their trays or pots and check their root structure. A good size for seedlings is between 15 and 30 cm.
Large seedlings are harder to use with hand planting tubes, but are well suited to machine planting.
The stem of tree seedlings should be strong, and have a diameter greater than 2.5 mm at the base. Hardiness Before planting, ensure the seedlings have been 'hardened', that is, 'weaned off' shade and nutrients, at the nursery. Deep green, lush and soft foliage indicate unhardened seedlings that may suffer from transplant shock, dry conditions and frost. Reputable nurseries sell only 'hardened' seedlings. If possible, collect your seedlings from the nursery close to the date of planting out.