Growing Tomatoes in a Greenhouse in June

June is ideal for cultivating tomatoes in the greenhouse. Read about irrigation of the plant and learn how to avoid common plant diseases. You will also get an introduction on how to prune and finally, which companion plants to consider for your tomato plants.

June is a great month for greenhouse gardening, especially for those who are growing tomatoes. Whether you are a novice or an experienced gardener, taking the right steps this month can ensure a bumper harvest in the weeks to come, and I’ll guide you through everything you need to know about watering, feeding, nipping out, truss pruning, companion planting, and using grafted tomatoes to get the most from your greenhouse tomatoes.

Watering

Proper watering is crucial in June as temperatures rise and tomato plants reach their peak growth. Consistency is key, as it can stop common problems like blossom end rot, which is caused by a calcium deficiency resulting from irregular watering.  Water your tomatoes early in the morning or late in the afternoon to minimise evaporation and reduce the risk of fungal diseases. Aim to keep the soil consistently moist but not waterlogged, this usually means watering every day or every other day, depending on your greenhouse conditions. Use a drip irrigation system, if possible, as it ensures even moisture distribution and prevents wetting the foliage, which can lead to diseases such as blight.

Truss Pruning for Larger Fruit

To maximise the size of your tomatoes, consider truss pruning. This involves removing some of the fruit on a truss (the cluster where tomatoes grow) to allow the remaining fruit to grow larger, this is especially important on larger, beef steak tomatoes where the weight of developing fruit can damage the plants. Typically, you should aim to keep about four to six tomatoes per truss. Remove the smallest or misshapen fruits, allowing the plant to concentrate its energy on developing fewer, but larger, fruits. Regularly check your plants and prune as needed throughout June.

Companion Planting

Companion planting can significantly enhance the health and yield of your tomato plants. Basil is a classic companion for tomatoes, not only improving the flavour of the fruit but also repelling pests such as aphids and whiteflies. Marigolds are another excellent choice, as their strong scent deters other harmful insects. Planting nasturtiums can attract aphids away from your tomatoes, acting as a sacrificial plant, while herbs like chives and parsley also make good companions, adding diversity to your greenhouse and promoting a healthier ecosystem by attracting predatory insects in to help with pest control.

Grafted Tomatoes

Grafted tomatoes are increasingly popular among gardeners for their vigour, disease resistance, and higher yields. These plants are created by grafting a fruit-producing variety onto a robust, supercharged rootstock. The result is a plant that combines the best traits of both, often outperforming traditional tomatoes by up to 75%. If you are new to grafted tomatoes, why not give them a try, they require the same care as regular tomatoes but often produce more fruit and are more resilient to common tomato diseases and can cope with cooler temperatures.

1. Ventilation: As temperatures rise, ensure your greenhouse is well-ventilated to prevent overheating. Use shading materials or whitewash on the glass to reduce direct sunlight and keep temperatures down.

2. Pest Control: Keep an eye out for common greenhouse pests like whiteflies, spider mites, and aphids. Regularly inspect the undersides of leaves and use organic pest control methods or introduce beneficial insects like ladybirds.

3. Support Systems: Ensure your tomato plants are well-supported. Use canes, trellises, or string to keep the plants upright and prevent them from collapsing under the weight of the fruit.

4. Pollination: In a greenhouse, natural pollinators might not be as prevalent. Gently shake the plants or use a small brush to transfer pollen between flowers to improve fruit set.

5. Monitoring and Adjusting: Regularly check your plants for signs of stress or nutrient deficiencies. Yellowing leaves can indicate a nitrogen deficiency, while blossom end rot is often a sign of calcium deficiency. Adjust your watering and feeding regime accordingly.