Under conducive environmental conditions, fresh stems should flourish and produce new buds that flower.
1. Excess Nitrogen
When growing sweet peas, it’s a good idea to fertilize once or twice during the growing season with a slow-release granular product that has an N-P-K ratio that is lighter in nitrogen and higher in phosphorus and potassium.
This supports nutrient delivery and flowering rather than generating mounds of lush foliage which can happen when there is an overabundance of nitrogen.
It’s best to conduct a soil test before applying fertilizer, as too much phosphorus and potassium can adversely affect the availability and absorption of other essential nutrients.
Here’s a low-nitrogen product to try:
Geoflora Bloom contains three percent nitrogen, five percent phosphorus, and five percent potassium, for an NPK ratio of 3-5-5.
It also contains beneficial secondary nutrients: calcium to support cell health and magnesium and sulfur for effective photosynthesis.
Geoflora Bloom
Geoflora bloom is available from Arbico Organics in four, eight, 25, and 50-pound packages.
Plants fertilized with too much nitrogen display weak, lanky stems, are slow to bud, and produce mostly leaves, with few flowers.
If your fertilizer is nitrogen-rich, or you apply a product more than once or twice a growing season, and notice lankiness and sparse blooms, you may be inadvertently triggering bud drop.
Because sweet peas are already fragile, weakening their structure renders them more vulnerable to wind, our next topic.
2. High Winds
While there are compact dwarf varieties with more bushy growth habits, climbing L. odoratus vines may reach lengths of six to 10 feet.
Their delicate stems may withstand wind and possibly grow stronger because of it, a process called thigmomorphogenesis.
In reaction to external forces that cause mechanical stress, like wind, vining plants can develop thicker stems and cling tighter to structural supports.
However, buds and flowers can easily be detached when windblown.
At planting time, select a location that is not in the path of the seasonal prevailing winds in your locale.
If this is not an option, consider using sheltering materials in the growing space, such as slats in an open chain link fence or a lattice sheet.
Alternatively, consider cultivating in a wheeled pot with a climbing trellis that you can move into sunny, sheltered places throughout the day.
An attractive product you may like is the Allister Wood Planter Box with Trellis, available via Wayfair.
Allistir Wood Planter Box with Trellis
The overall dimensions are 50 inches high by 25 inches wide by 11 inches deep, including the climbing trellis. It weighs 11.68 pounds.
This item is made of durable, weather-resistant solid fir to last long and well outdoors. The reinforced planter box has two drainage holes and four optional rolling casters, two with brakes.
If high winds are predicted, and your growing space is susceptible, temporarily cover bushy potted specimens or trellised vines with netting until the danger passes.
3. Moisture Stress
Other possible reasons for buds or blooms to fall off unexpectedly are too much or too little water.
During the growing season, L. odoratus requires an inch of water per week, either from rain or the garden hose.
Excess rainfall, poor drainage, or watering when the ground is saturated can flood the roots, causing poor nutrient uptake and rotting.
This can also result in leaf yellowing, stem softening, wilting, and flower and leaf anomalies.
