(5 Reasons) Why Your Sweet Peas are not Blooming

Have you ever wondered why sweet peas are not flowering? Several of my readers emailed me this very question with one writing…

“I have been growing my sweet peas in full sun all year and yet still no blooms…what am I doing wrong?!”

Fortunately, I have lots of experience growing sweet peas myself, as I work in a garden center and I’ve grown them from seed for sale, so I know how to identify the problem and get those sweet peas flowering!

Let’s cut to the chase…

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 and with regular watering. Heat waves can also temporarily prevent blooming.

I find that it’s the sweet peas’ preference for low-nutrient soil that is most commonly the problem, as it was with the reader I referenced at the top of the article.

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)

When growing plants, I find it’s always helpful if we understand where they grow in their natural habitat so that we can recreate these conditions in our gardens. Sweet peas are native to the Italian island of Sicily in the Mediterranean where they enjoy lots of sun and warm temperatures.

Do your sweet peas have lots of leggy foliage with few flowers? If your sweet peas are in the shade or in a location with less than 6 hours of sunlight, then there is likely to be a problem.

In fact, I have seen for myself that the number of flowers a sweet pea displays is correlated with the number of hours of sun, with around 6 hours of sun considered optimal for flowering (however, this can have a point of diminishing returns as we’ll discuss in the next section).

If your sweet peas are in a shaded location then I recommend moving the pot or container to a sunnier location to help promote flowering or sowing of seeds in an area of the garden that naturally has more hours of sunlight.

Our Sweet peas flower at their earliest in June or July, and the latest I’ve sown seeds and still had a good display of flowers is April for sweet peas, so realistically, you may have to wait until the following year to grow your sweet peas for flowering.

2. Intense Heat Temporarily Prevents Sweet Peas Flowering

As we discussed, sweet peas are native to the Mediterranean and are somewhat accustomed to high temperatures. A few years ago, I was baffled as to why my sweet peas weren’t flowering to the extent I expected.

What was wrong? The soil was well drained, the foliage looked healthy enough, and they were planted in full sun. I live in a climate that is typically significantly cooler than a Mediterranean climate, and this year, there was a heat wave with temperatures similar to those experienced in Mediterranean countries.

So I did some research and discovered something quite interesting about the cultivation of sweet peas, which held the answer!

Most of the cultivars were 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. Have you ever been to Scotland? I can assure you it’s much cooler than the Sciliy!

If you live in a particularly warm climate or experience a summer heat wave, as I did, 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 rather, there is a significant contrast in temperatures from mild to suddenly much hotter (this is my experience), which tends to cause sweet peas to temporarily cease flowering.

With my sweet peas, the flower buds just stopped developing, whereas some just refused to flower at all.

Generally speaking, it comes down to patience and ensuring the plant is sufficiently watered. The sweet peas should begin to flower again once the heat wave passes or they become more accustomed to the higher temperatures. In my case, they restarted flowering after a few weeks.

Do you live in a really hot climate? In regions with very high temperatures, sweet peas tend to flower best when they have morning sun and shade in the afternoon. I personally employed this tactic when I lived in arid southern California, and it was a great success!

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

So I have experienced firsthand that, 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 pot (less than 10 inches across) and located in full sun, the intense sunlight can very quickly heat up the pot, causing significant evaporation from the soil and causing the sweet peas drought stress, which impacts flowering.

I find this is particularly a problem if your sweet peas are in clay or terracotta pots, as these materials are breathable, which means the soil can dry out much quicker when it’s in full sun.

In these circumstances, experience has taught me to 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 (for example, if it’s overcast, then blazing sun the next in an unpredictable pattern).

If there have been many overcast days with occasional rain, then I’ve found that 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 as I did 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. When watered appropriately, they display flowers.

Success Tip: Do you live in a hot climate and have been struggling to get your sweet peas to flower? I plant my sweet peas in either a plastic or glazed ceramic pot, as these are impermeable, so they retain moisture much better. This has prevented the soil from drying out too quickly in the sun and alleviated the drought stress that was preventing my sweet peas from flowering!

4. Pot or Container Size can Impact Flowering

Have you considered whether the size of your pot is the reason your sweet peas are not flowering? The size of the pot or container that you plant (or sow the seeds) of your sweet pea in can have an impact on flowering because…

• If the pot is too small, then it can heat up in the sun, and the soil can dry out 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 for 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.

I learned this the hard way, so now I always plant my sweet peas in a good-sized pot (about 10-12 inches across) to ensure that the seeds and developing plants have enough access to the soil and nutrients they require.

Do you live in a hot climate? Here is the secret to success…The hotter and dryer the climate the bigger the pot should be to ensure the compost does not dry out in arid conditions.

If you can, I would transplant your sweet peas to a bigger pot if you suspect this is the problem. However, to be honest, you may have to wait until the following year and sow your seeds into a much bigger pot to address the problem.

My sweet peas always flower better in a more capacious pot!

5. Too Much Fertilizer Promotes Foliage Growth, but Fewer Flowers

Consider whether you have been heavy-handed with the fertilizer… It is a classic mistake a lot of gardeners make, but applying fertilizer to the soil of sweet peas too frequently or in too high a concentration can promote foliage growth at the expense of flowers and even harm the plant’s roots.

So one of my readers wrote in to ask me why their sweet peas weren’t flowering despite their best efforts…

“Planted a pkg of Sweet Peas in a whiskey barrel, with Miracle Grow fresh dirt, mid-June, they are 3 ft tall now, with no blooms. High temps 2 weeks ago, kept them watered throughout. Zone 8b. 6-8 hrs of sun daily. Why no blooms yet? Thanks!” – Deb

You can read the rest of the comment and my reply below the article but it made me think of something I should add to this article, which is that miracle gro often has added nitrogen in it to help plants grow. This is the opposite of what we want to make our sweet peas flower…

We need to think about the fact sweet peas are native to Sicily in the Mediterranean region of Europe and have adapted to growing in soils that are sandy and reasonably low in nutrients.

Have your sweet peas grown lots of lush foliage with few flowers? 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.

So what can we do to solve this? To ensure your sweet peas flower, it is better to recreate the conditions of the sweet pea’s 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.

I have done some testing on the optimal amount of sand in the soil mix for growing sweet peas. I’ve found that adding around 10-20% of sand or grit by volume of the pot (with the rest as multipurpose compost) gives the sweet peas the right soil conditions for flowering (Similar to the soil mix for other plants native to the Mediterranean such as lavenders).

However, I feel I should put some caveats on this. I don’t know what climate you live in, and climate can make a difference when growing sweet peas. Broadly speaking, I would say…do you live in a rainy climate? Then 20% sand is probably a better soil composition for your sweet peas as this can help mitigate the risk of overwatering and damp soil, both of which (as we discussed can reduce flowering).

Do you live in a dryer climate that perhaps more closely resembles a Mediterranean climate?

Then 10% sand in the soil mix is probably better as the soil should still drain well enough for your sweet peas, yet there is still enough compost to hold some moisture so that the potting mix doesn’t dry too quickly to the point your sweet peas are too stressed to flower due to drought and dry soil.

Like I said it is worth avoiding 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.

Do you have any more questions about sweet peas? Or perhaps you have a different experience you’d like to share? Please leave a comment at the end of the article. I offer free, tailored troubleshooting! I’d love to hear from you!

Key Takeaways:

• 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 they 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 medium- to low-nutrient soils are preferred for flower display.