Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Commercial determinate tomatoes may require pruning of “suckers”, those shoots that develop at lower nodes. Removal of one or more of these shoots up to the first fork, just below the first flower cluster, can improve fruit size, quality, and marketable yield on some varieties. Varieties that are very vigorous and tall with a lot of foliage such as BHN589 are the best candidates for pruning. Pruning will increase fruit size, increase early set, and reduce disease pressure by improving air movement and spray coverage. However, fruit numbers will be reduced. Pruning is best carried out prior to first stringing when shoots are small (2 to 4 inches long). They can be removed by bending the shoot backward where it easily snaps off. Later pruning with larger shoots may require the use of hand pruners to avoid excessive tearing. A second trip through the field after stringing may be required to remove late developing suckers. Always prune when foliage is dry to avoid spreading diseases. The amount of pruning required will vary by variety. Some varieties require little or no pruning or removal of ground suckers only (those coming from the cotyledon node); vigorous varieties may require the removal of ground suckers plus two additional suckers. Check with your seed-persons for pruning recommendations for the varieties you are using. Over-pruning can result in reduced yields and increased sunburn, blossom end rot, fruit cracking, and catfacing.