Consider maintenance when choosing plants this spring
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EmailHeavy-feeding plants such as petunia require more maintenance from home gardeners than other species to ensure season-long color.
Appropriate nutrient management is essential for producing high-quality plants throughout each growth phase. Understanding how fertility requirements change over time allows growers to tailor their practices for optimal plant health and performance. Fertility needs vary not only by the specific stage of production but also by plant species.
During commercial production, seedlings may only need 25 to 50 parts per million (ppm) of nitrogen fertilizer during Stage 2 (opening of cotyledons) and Stage 3 (opening of first true leaves). While the plant is grown for sale, it falls into a light, medium or heavy fertility category (Table 1). For example, begonias need relatively low fertility compared to chrysanthemums. Once the plant is finished and sold to customers, its garden performance depends on pH and fertility levels provided.
Table 1. Greenhouse crops categorized by fertility requirements.
|
Fertility Category |
Greenhouse Crop Examples |
|---|---|
|
Light (100 to 150 ppm nitrogen) |
African violet, Aster, Begonia, Cosmos, Basil, Hydrangea |
|
Medium (150 to 200 ppm nitrogen) |
Campanula, Dianthus, Petunia, Geranium, Ipomoea, Gerbera |
|
Heavy (200 to 300 ppm nitrogen) |
Chrysanthemum, Poinsettia |
During the 2024 Michigan Garden Plant Tour, Mast Young Plants ran a fertility trial to show customers what different species will look like with either no fertility at all, one application of slow release fertilizer, or constant liquid feed at 150 ppm nitrogen. In the 2024 trial garden brochure, the photos shows the difference between different cultivars and the ranges of fertility and their garden performance.
Growers won’t be surprised that the plants that looked large and beautiful were those receiving constant liquid fertilizer at 150 ppm. For example, the petunia ‘Bees Knees Yellow,’ which has been chosen as a top performer at different garden trials, performed poorly when given no fertility (just clear water) after transplant compared to the plant receiving the 150 ppm of liquid fertilizer (Photo 1).
We would expect that any petunia, garden mum or heavy-feeding plant would look similar under the conditions. These plants require a little extra maintenance from the gardener to look their best. However, some plants looked a lot better than others with very little to no fertility provided. Begonia Adora ‘Velvet Red’, Coleus Main Street ‘Ruby Red’ and Coleus Talavera ‘Sienna’ all performed relatively well considering the low or no fertility throughout the season (Photo 2).
As consumers are shopping this spring, consider your watering and fertility habits if you expect season-long large, gorgeous plants. If you want to grow the gorgeous, full petunias seen at the garden center, you will need to continue the fertility regimen and even cut them back a couple of times throughout the summer. Many garden centers’ social media accounts will remind you (around the Fourth of July) to tidy up the plant habit heading into the second half of the growing season.
If you’re a someone (like me) that does not regularly fertilize plants, consider lower maintenance plants such as begonia and coleus. Michigan State University Extension also recommends referring to the top performing cultivars from 2024 as you are out shopping. Happy planting!
