The reason your sweet peas are not blooming is often because of lack of sun, high temperatures or too much fertilizer. Sweet peas are native to the Mediterranean and flower best in full sun, medium to low nutrient soil with regular watering. Heat waves can also temporarily prevent blooming.
Keep reading to learn why your sweet peas are not flowering and what are the best practices to promote flowering…
1. Lack of Sun (Sweet Peas Prefer 6 Hours of Sun to Flower)
Sweet peas are native to the Italian island of Sicily in the Mediterranean where they enjoy lots of sun and warm temperatures.
If your sweet peas are in the shade or in a location with less the 6 hours of sun light then there is likely to be a lot of leggy foliage growth but fewer flowers.
The amount of flowers a sweet pea displays is correlated with the amount of hours of sun with around 6 hours of sun considered optimal for flowering.
If your sweet peas are in a shaded location it then I recommend moving the pot or container to a sunnier location to help promote flowering or sow seeds in an area of the garden that naturally has more hours of sunlight.
2. Intense Heat Temporarily Prevents Sweet Peas Flowering
Sweet peas are native to the Mediterranean, so they are somewhat accustomed to high temperatures.
However most of the cultivars have been developed in Scotland (by horticulturist Henry Eckford) and therefore the modern varieties of the plant tend to be more adaptable to cooler climates so they can flower successfully outside of the Mediterranean climate.
If you live in a particularly warm climate or there is a heat wave in the Summer then the excess heat can occasionally cause the sweet pea to display fewer flowers as it struggles with the effects of heat and potentially drought.
There is not a specific temperature at which sweet peas stop developing flowers but it is rather a significant contrast in temperatures from mild to suddenly much hotter that tends to cause sweet peas to temporarily cease flowering.
Generally speaking it comes down to patience and ensuring the plant sufficiently watered and the sweet peas should begin to flower again once the heat wave passes or they become more accustomed to the higher temperatures.
In regions with very high temperatures sweet peas tend to flower best when they have morning sun and shade in the afternoon.
Around 5-6 hours of Morning sun is enough to promote flowers so shade in the midday and afternoon is useful in hot climates as it protects the sweet pea from intense sun and the hotter part of the day to find the balance of sun and avoidance of heat stress for optimal flowering.
3. Drought can Prevent Sweet Peas from Flowering
Along with intense heat, drought can be a factor for sweet peas not displaying flowers.
Because sweet peas originate in the Mediterranean they prefer well draining soil so the compost around the roots can dry out somewhat between bouts of watering.
However if they are planted in a small pots (less then 10 inches across) and located in full sun, the intense sunlight can very quickly heat up the pot which cause significant evaporation from the soil and causes the sweet peas drought stress which impacts on flowering.
Water sweet peas as frequently as required to keep the soil moist but not boggy. In difficult climates and with different weather patterns you have to adjust the frequency of your watering to suit the conditions.
If there have been many overcast days with occasional rain then watering once a week with a generous soak is usually appropriate.
However in the heat of Summer you may have to water 3 times a week to prevent drought stress and ensure the sweet peas have all the resources they require for flowering.
Sweet peas can be quite resilient in the heat and often recover from wilting or drought and display flowers when watered appropriately.
4. Pot or Container Size can Impact Flowering
The size of the pot or container that you plant (or sow the seeds) of your sweet pea in can have an impact of flowering:
- If the pot is too small then it can heat up in the sun and the soil can dry put completely on hot days.
- With smaller pots and containers there is less capacity for soil and less room for the roots to establish and access the nutrients and moisture required from flowering.
- Pots and containers should also have drainage holes in the base to allow excess water to escape so that the soil does not become boggy which stresses the sweet peas, prevents flowering and promotes the conditions for fungal diseases.
Plant sweet peas in a good size pot (about 10-12 inches across) to ensure that the seeds and developing plant have enough access to the soil and nutrients they require.
The hotter and dryer the climate the bigger the pot should be in order to ensure the compost does not dry out in arid conditions.
With the right sized pot or container and the right conditions the sweet peas should thrive and display abundant flowers.
5. Too Much Fertilizer Promotes Foliage Growth but Fewer Flowers
Applying fertilizer to the soil of sweet peas too frequently or in too high concentration can promote foliage growth at the expense of flowers and even harm the plants roots.
Sweet peas are native to the Sicily in the Mediterranean region of Europe and have adapted to growing in soils that are sandy and reasonably low in nutrients.
If sweet peas are growing in rich soil that has been amended with manure (which is high in nitrogen) or the soil has added fertilizer then sweet peas tend to display far fewer flowers but may have lush green foliage.
To ensure your sweet peas flower, it is better to recreate the conditions of the sweet peas native environment by adding horticultural sand or grit to the potting mix.
Adding sand or grit helps to:
- Improve drainage as sweet peas do not like boggy soil.
- Replicates the sandy, lower nutrient conditions in which sweet peas thrive and flower to their best.
Add around 10-20% of sand or grit by volume of the pot to the potting mix of your sweet peas (with the rest as multipurpose compost) to give the sweet peas the right soil conditions for flowering (Similar to the soil mix for other plants native to the Mediterranean such as lavenders).
Also it is worth avoid sowing sweet peas in bags of compost that are enriched with nutrients such as miracle-gro as this is contrary to the low to medium nutrient conditions that they prefer for flowering.
- Sweet peas do not flower in shady areas, excessive heat or in soil with too much Nitrogen or additional fertilizer.
- Sweet peas flower best when in full sun and in medium to low nutrient soils. Excessive heat can temporarily prevent flowering.
- Drought stress can also impact flowering if the are in a small pot without regular watering, however they prefer well draining soil to stay healthy and flower.
- Sweet peas are adapted to the soil conditions of Sicily and prefer medium to low nutrient soils to display flowers.