Nasturtiums are known for their vibrant, trumpet-shaped flowers and attractive, rounded leaves. These annuals are simple to cultivate, offering both ornamental beauty and edible parts, as their leaves and blossoms possess a pleasant peppery flavor. Successfully growing nasturtiums begins with proper planting technique. Understanding the correct depth and conditions for sowing ensures the seed establishes a robust root system and produces abundant growth.
Essential Planting Depth and Spacing
The correct depth for sowing nasturtium seeds is shallow, typically ranging from one-half to one inch deep. This range provides enough soil coverage to maintain consistent moisture around the large seed for germination. It is also shallow enough to allow the emerging seedling to push through the soil surface without expending too much energy.
Sowing the seeds too deeply can delay or prevent sprouting, as the embryo may exhaust its stored energy before reaching the light. After placing the seed, gently cover it with soil and firm the surface lightly. This ensures good contact between the seed and the surrounding soil particles, facilitating water uptake.
Spacing depends on the variety, as nasturtiums are divided into bush (dwarf) and trailing types. Bush varieties, which maintain a compact shape, require ten to twelve inches between each seed. Trailing or climbing varieties produce long vines and need twelve to eighteen inches of space to accommodate their expansive growth. Adequate space prevents overcrowding, promotes air circulation, and reduces the risk of fungal diseases.
Timing and Site Selection for Sowing
Nasturtium seeds are sensitive to cold temperatures and frost. Direct sowing should occur only after the danger of the last spring frost has passed and the soil has warmed up. An ideal soil temperature for germination falls between 55°F and 65°F.
Planting seeds directly into the garden is recommended because nasturtiums develop a delicate taproot that dislikes being disturbed. Transplanting seedlings started indoors often causes root shock, which can stunt the plant’s growth. Sowing directly where the plant will mature bypasses this setback and ensures a more vigorous start.
Selecting the right location is important for flower production. Nasturtiums flourish in full sun, meaning at least six hours of direct sunlight daily. While they can tolerate partial shade, reduced light exposure often results in more foliage and fewer flowers.
Soil Requirements and Preparation
Nasturtiums prefer lean, even poor, soil conditions. They do not require a rich growing medium and thrive in soil with a moderate to low fertility level. The soil must be well-draining to prevent seeds and roots from sitting in overly saturated conditions.
A common mistake is planting nasturtiums in soil heavily amended with compost or high-nitrogen fertilizers. Excessive nitrogen encourages the plant to produce an abundance of leaves at the expense of flower development. The plant’s energy is diverted toward vegetative growth, resulting in foliage but a lack of blooms.
To prepare the planting site, avoid adding fertilizer or nitrogen-rich amendments. Simply loosen the existing soil to a depth of six to eight inches to ensure good drainage and aeration. If the native soil is heavy clay, incorporating sand or grit can improve the structure without adding unwanted nutrients.
Initial Care and Germination
Immediately after planting, the seeds require consistent moisture for successful germination. Water the area gently but thoroughly to settle the soil without washing away the seeds. The soil surface should be kept evenly moist until seedlings emerge, which typically occurs within seven to fourteen days.
Once seedlings have developed their first true leaves, reduce the frequency of watering. Nasturtiums are drought-tolerant once established and prefer to dry out slightly between waterings. Overwatering after germination can lead to root rot.
If you have sown multiple seeds and they all germinate, you may need to thin the seedlings to the recommended spacing. Simply cut the weaker seedlings off at the soil line with small scissors, leaving the strongest plant to develop fully.