If you’re anything like me, you probably love bougainvillea for its ability to flower nearly all year round (in the right climate), but you have probably seen bougainvillea that are a mass of flowers, and you’re wondering how to make yours bloom more, and for longer…
I am lucky enough in my job to speak to commercial growers of bougainvillea, and I picked their brains, asking for tips, tricks, secrets, and techniques to make them flower for longer. They told me…
To increase the amount bougainvillea blooms and to stimulate flowering, locate bougainvillea in full sun but ensure it is exposed to fewer than 12 hours of daylight as they are short-day plants. Watering potted bougainvillea once a week creates the optimal balance of moisture and drought stress to encourage more flowers.
We need to understand that bougainvillea are native to Brazil, and fewer hours of sunlight stimulate flowering as shorter days signal to the bougainvillea that it is the optimal time to display its flowers to coincide with the right environmental conditions at that time of year.
Shorter days are one of the most influential factors for increasing bougainvillea blooms. Keep reading to learn the 7 ways to increase the number of flowers and for flowers that are displayed for longer…
1. Bougainvillea Blooms More with Shorter Day Lengths
Bougainvillea is a little different! Whilst they require daylight, they will bloom more if they have shorter day lengths.
This peculiar feature is a result of adaptations in tropical environments where, in the dry season, the days are shorter than the nights, which signals to the bougainvillea that it is the right time of year to flower.
It is, therefore, for us to get our bougainvillea to flower, we need to replicate these conditions. Bougainvillea prefers at least 12 hours of uninterrupted darkness to flower. I
In this study by the University of Florida, they discovered that the optimal amount of daylight is between 8 and 11 hours, with the bougainvillea in darkness for the remaining hours of the day. If the period of darkness was interrupted with natural light, the bougainvillea did not flower.
Finding the best spot for your bougainvillea can, therefore, be a little challenging for those who live in northerly latitudes like me.
For example, the UK can have as many as 15 hours of daylight a day, as I am in New York, where peak sunlight hours can reach as many as 16.
We need to ensure there is no artificial light at night that interrupts the preferred 12 hours of darkness.
If you’re particularly keen (like me), this could be helped by using a cloche, horticultural fleece, or even an umbrella to shade your bougainvillea to replicate its natural conditions for flowering.
It is important to note that bougainvillea still requires lots of direct sunlight to flower, but the hours of sunlight should be restricted to slightly fewer than 12.
Encouragingly, bougainvillea is capable of flowering all year round if your climate has a mild winter, e.g., for those of you in a Mediterranean climate, but regardless of location, they will flower more with 12 or more hours of darkness.
Fun Fact: Bougainvillea flowers are actually small and delicate. The large colorful petals are not actually flowers but bracts which is a specialized leaf that has the function of attracting pollinators.
2. Water Less Often for More Flowers
Bougainvillea loves the heat and dry conditions – they are native to Brazil, after all!
Therefore, they mustn’t be watered too often as your other potted plants.
Bougainvillea is drought tolerant and should be treated a little differently from your hydrangea and rose displays but a little more like your lavender and Mediterranean herb collection.
I was told that the best watering cycle is to water your potted bougainvillea once a week with a thorough watering but refrain from watering if the soil feels moist to a finger depth. The soil should just feel as though it is drying out before watering again.
I always feel the soil with my finger to ensure it is dry before I water.
Watering less will solicit some drought stress and will stimulate the bougainvillea to display more flowers. This is the bougainvillea’s fascinating survival response, as blooms are the plant’s way of reproduction.
I personally water my potted bougainvillea once a week – and I am rewarded with this display of blooms.
Mature bougainvillea vines planted in garden boarders often do not require watering unless they are small plants that do not have an established root system yet or are in exceptional drought.
(It is important to note that you should water bougainvillea in different amounts at different times of the year. Read my article on how to water potted bougainvillea).
3. Direct Sunlight Promotes Bougainvillea Blooms
Direct sunlight is a must for bougainvillea. As you can imagine, they get this in abundance in their native Brazil – so it is really important that we recreate these conditions as best we can in your garden, wherever you are.
To do this, plant your bougainvillea in a sunny spot where they can absorb at least 6 hours of direct sunlight. This will ensure your bougainvillea has enough sunlight to stimulate a good display of flowers.
A good idea is to plant your bougainvillea in pots like mine; this enables you to move them to full-sun areas during the changing seasons.
Furthermore, you can then move these pots indoors during the winter if you live in a non-Mediterranean environment like me. This will help protect the plant from the cold and potential frosts.
(Bougainvillea often lose their leaves in Winter if they are outside of their optimal climate, however, the leaves can regrow in Spring with the right care, read my article on bougainvillea losing their leaves for how to save your bougainvillea).
Remember, it is important to consider the shorter day length for increased blooms, as well as the intensity of the sun.
4. Warm Temperatures Increase Flowering
Warmer temperatures mean increased bougainvillea blooms. This is particularly important for those of you who live in cooler climates.
Night temperatures should be, optimally, around 65°F (18°C). However, bougainvillea are relatively hardy and have good adaptable qualities and can manage cooler (but not cold!) night-time temperatures and still display lots of flowers.
I recommend placing your bougainvillea in a sheltered location so that cold winds do not stress the plant.
If the nights are too cold, the plant can become stressed. In colder climates, it is important to grow your bougainvillea in pots and bring them indoors in the Winter as they cannot tolerate severe frost.
I place my pot in a sunny window spot so that it gets the indoor warmth and the light of the sun for optimal blooms.
Whilst my bougainvillea flowers a lot less in winter and sometimes even loses its leaves, it always revives when I place it back outside in Spring!
5. Use Less Fertilizer for More Flowers
Using too much fertilizer will cause your bougainvillea to grow lush green foliage at the expense of flowers!
If your Bougainvillea are well established and planted out in borders, they should require little to no fertilizer. They are likely thriving in that position because they have well-drained soil – rather than fertile soil (see point 6 on drainage).
If your Bougainvillea is in pots, then I advise using some half-strength all-purpose fertilizer to ensure they have the correct nutrients for flowering and not too much nitrogen (the chemical responsible for that lush green foliage). Apply the fertilizer at the start of spring once any threat of cold weather has passed. Remember, Bougainvillea is not cold hardy!
Pro tip: I personally have seen great results by stopping using fertilizer when the day lengths begin to shorten as the ‘stress’ of less available nutrients also stimulates flowering.
This is in the same way that drought stress can also incentivize the bougainvillea to prioritize reproduction by flowering- rather than growth on its leaves, roots, and vines.
6. Well Draining Soil Increases Blooms
As we discussed, bougainvillea has adapted to growing in soil that has good drainage. They do not tolerate boggy, over-watered soil as the roots can rot. To increase blooms, make sure your bougainvillea has good drainage.
The specialist growers who grow bougainvillea told me that horticultural grit is the best soil amendment to improve drainage – this will help replicate the well-draining soil conditions the bougainvillea has in their native Brazil.
When creating a potting mix for bougainvillea I use the same formula as potting for Mediterranean herbs with one third horticultural grit and 2 thirds peat free compost to ensure the optimal balance of soil moisture for the bougainvillea to display flowers.
If you are planting in pots, make sure the pots have drainage holes in the base to allow excess water to escape efficiently after watering. Pots may be the location of choice for bougainvillea as you can control the drainage more than you can with your garden borders.
7. Pruning Bougainvillea for More Flowers
I think this is the most important tip.
Bougainvillea displays its flowers on new seasons growth rather than old wood; therefore, to increase your bougainvillea flower display, it is important to prune your bougainvillea in either late Winter or early Spring before Spring growth starts growing.
I discovered that if you don’t prune your bougainvillea, then it can grow leggy with fewer flowers, so some tactical pruning is always recommended.
Pruning should not be too heavy as this can divert too much energy to grow new shoots and vines, but rather, light pruning is best for stimulating flowering and can help you keep the bougainvillea in a desired shape on your trellis or support structure.
Watch this helpful YouTube video for how to prune your bougainvillea to increase the concentration of flowers:
(For all more tips and all the best practices of bougainvillea care, read my article on how to care for bougainvillea in pots).
If you have any questions or need bougainvillea advice, please leave a comment below, and I will help you out. If you found this article helpful, I’d appreciate a share on social media!
Key Takeaways:
- To increase the number of bougainvillea flowers, ensure bougainvillea has 12 hours of uninterrupted darkness each night. Bougainvillea are short-day plants requiring fewer daylight hours than darkness to stimulate flowering. Water bougainvillea less often in Summer to create drought stress, which promotes blooms.
- Bougainvillea originates in Brazil’s hot and dry conditions, where it flowers more in at least 6 hours of direct sunlight or more. Too much shade prevents bougainvillea from blooming. Bougainvillea requires direct sun to stimulate flowering yet also requires more hours of darkness than daylight.
- Apply a half-strength fertilizer to potted bougainvillea in the Spring to ensure the bougainvillea has the nutrients it requires to display flowers. Scale back the use of fertilizer as soon as flowers emerge as a slight nutrient deficit causes stress, which promotes flowering.
- To increase the number of bougainvillea flowers, prune the vine in early spring. Bougainvillea flowers on new growth so pruning in Spring helps to stimulate new growth on which the bougainvillea displays its flowers.