Buddleja is probably one of the best-known flowering shrubs in the world. Loved not just for their long sprays of purple or pink flowers, but also for their ability to attract insects from miles around. Hence the common name of the “Butterfly Bush”.
Fortunately Buddleja davidii is also incredibly simple to grow from seed, meaning that with a single one-off investment in a packet of seeds you can literally fill your garden with these beautiful plants in a year or two.
Indeed, this is exactly what I have done over the last few years. In this article I’ll outline exactly how to grow Buddleja davidii from seed, based on my experience of doing just that right here in the UK. Of course, the same methods should apply equally well in other temperate climates, such as for the many visitors we receive from North America.
Let’s get started…
Choose a Suitable Seed Tray or Plant Pot
Possibly the most challenging thing about growing Buddleja davidii from seed is just how tiny the seeds themselves are. Seriously – if you’ve never seen Buddleja davidii seeds then they’re like dust. You need to be able to deal with seeds that are so tiny they’re barely visible to the human eye.
Possibly the best solution is to start Buddleja davidii in decent-sized seed trays. Their width and length means that any Buddleja davidii seeds you accidentally drop should still make their way onto the compost where they can germinate. Attempting to plant Buddleja davidii in normal plant pots can be far more challenging, though is by no means impossible.
Fill With Rich Multipurpose Compost
For best results fill your seed tray(s) with fertile substrate, such as a peat-free multipurpose compost. This needn’t be too deep – just an inch or two of compost should be more than enough to get your Buddleja davidii seeds started. You can then separate out the seedlings as they grow large enough to handle.
Very Finely Scatter Buddleja davidii Seed Over the Surface
This is the challenging part of growing Buddleja davidii. Due to the tiny dimensions of Buddleja davidii seeds I suggest you get fully prepared before opening up the seed packet. Crucially, you want to avoid any air movement that could scatter the seeds far and wide.
For best results consider doing the actual planting indoors on a table. As a second option use your greenhouse. If your only real option is to plant your Buddleja davidii outside in the open air then definitely wait for a wonderfully still day where there is little or no breeze.
Gently tear open the seed packet and tip the seeds into the palm of your hand. Your job is then to attempt to distribute the seeds as evenly as possible over the surface of the compost. My preferred method is the tip by hand ever so slightly, then moving slowly over the surface of the compost gently tap my wrist with the other hand. This will gently tip the seeds off your hand onto the compost.
Buddleja davidii seeds aren’t just small; they also seem to germinate best when exposed to some sunlight. Consequently there is no need to cover the seeds at all if you don’t want to. If you do opt to add a surface layer of compost then barely cover them with the finest compost possible. Think of lightly dusting a cake with icing sugar.
Buddleja davidii seeds can be planted almost any time in spring or summer. Obviously the earlier in the season you get them started, the bigger the resulting plants will be before the cold weather sets in. March and April are an ideal time to start Buddleja davidii seeds.
Water the Pot Well & Cover to Retain Moisture
Buddleja davidii seeds need moisture to germinate. So soak the tray in lukewarm water to allow the compost to absorb plenty of water. I would recommend against watering from above with a watering can, less you disturb the tiny seeds at this stage.
Placing a cover over the tray makes sense for two reasons. Firstly, it helps the compost to retain moisture. Compost that dries out won’t end well for baby Buddleja davidii seedlings.
Secondly, and just as importantly, it helps to keep the seeds in place. You don’t want a spring breeze or an open window to scatter your seeds to the heavens after all.
Place in a Warm, Sunny Location
To help your Buddleja davidii seeds germinate as quickly as possible, place the tray somewhere warm and sunny such as a windowsill or (once the weather has warmed up in spring) an unheated greenhouse.
Be aware that Buddleja davidii seedlings are as tiny as the seeds themselves. You may need to look very carefully at the seed tray each day in order to spot those first few sprouts of greenery.
Understandably such tiny seedlings can take time to get going so you may need to be patient for the first few weeks. Once they reach a size where they can be safely handled your Buddleja davidii seedlings can be repotted into individual containers ready to grow on for your garden.
How Long Does Buddleia Take to Grow from Seed?
In my experience Buddleia seed tends to germinate quite quickly. I would expect fresh, healthy seeds to begin germinating within a few weeks of planting. However it will be some time before you’re enjoying a large butterfly bush.
Unless you’re very lucky and start your Buddleja davidii incredibly early in the season it is likely that your Buddleia will flower for the first time in its second year. In some cases it may take even longer.
To give a more specific answer, I planted some Buddleja davidii seeds last year. The plants reached about 6-12” in height in their first season. Yes, I know this is quite a large window of growth, but some seeds germinated before others, and some were attacked by pests part way through the growing season.
All my plants were kept in an unheated greenhouse throughout the winter months, to protect them from the worst of the British weather. Under these conditions, by mid-February my Buddleja davidii seedlings were starting to show signs of new growth, with fresh green leaves bursting out all along their wiry stems.
These very same Buddleja davidii plants were finally positioned out in my borders in April, where they successfully flowered throughout July and August, attracting a mind-blowing number of butterflies from the surrounding area. At some points we literally ran out of fingers and toes to count all the butterflies on, especially on still, warm sunny days.
So while your Buddleja davidii seedlings may look rather underwhelming in their early days of life, your Buddleia bushes will soon take on a life of their own. By their third or fourth year your problem is more likely to be keeping your Buddleia under control with vigorous pruning.
Your Buddleia plants will continue to grow throughout their lives, unless pruned back in the right season. Left unchecked, Buddleia bushes can grow to considerable proportions so most gardeners opt to keep their mature Buddleia shrubs in check by pruning either in spring or fall.
Is Buddleia Easy to Grow?
Buddleia is incredibly easy to grow, either from seed or from cuttings taken from existing plants. This is perhaps why Buddleia can often be found growing as a “weed” on disused land. Here in the UK, for example, it is perfectly normal to see large Buddleia bushes growing alongside rail tracks all over the country. Even in the metropolis that in London it is possible to spot Buddleia growing on wasteland, supporting the local butterfly population.
While growing Buddleia from seed requires a degree of patience it is well within the capabilities of almost anyone, no matter how little experience they may have.
No special equipment is needed, and no fancy growing techniques are necessary.
Once planted out into your garden your Buddleia will pretty much take care of itself for years to come. The only thing you might want to do is prune it, typically in the early Spring, to prevent it getting too large for your garden.
Can You Grow Buddleia in Pots?
Buddleia can be grown easily in pots. Indeed, we have a number of Buddleia plants growing very successfully in containers on our patio area. Buddleia plants are so hardy that very little is required in the way of special care.
If you want to grow Buddleia in pots then simply transplant your seedlings into decent-sized containers filled with compost. Firm them in and water thoroughly so they can become established. That is literally it.
Does Butterfly Bush Like Sun or Shade?
Butterfly Bush should be grown in a sunny position, though they will still cope in partial shade. A south-facing aspect is ideal, though they will also tolerate east or west-facing borders so long as they receive direct sunlight for at least part of the day. Butterfly Bush doesn’t tend to do as well in full shade so is best avoided.
There are two reasons why Butterfly Bush should be planted in full sunshine if you can manage it. Firstly, of course, the plants themselves are able to grow and flourish, putting on more growth and a more impressive floral display.
Just as importantly, however, the butterflies that will feed from your Buddleia also love bright sunshine themselves. A flowering Buddleia in direct sunlight will attract the maximum number of butterflies possible, while those growing in partial shade may not have quite the same allure for your local lepidoptera.
Benefits of Growing Buddleja davidii
Before we sign off today I do want to take a moment for those currently on the fence. Why should you bother trying to grow Buddleja davidii from seed anyway? What place does the Butterfly Bush have in your garden?
Low Effort Gardening
Once you’ve planted your Buddleja davidii in the garden you need do almost nothing else, save perhaps for the occasional prune. Buddleja davidii is a perennial bush that will keep on coming back year after year, all while surviving almost any weather than our cold, damp winters throw at it. Each spring those lifeless stems will once more spring back into life and you can rest assured that soon enough your Buddleia will be covered in flowers.
Range of Colors Available
Traditional Buddleia has purple flowers. These are attractive enough in their own right, but these days there is a far broader range of flower colors available. Buddleja davidii may also come in pink and white, for example. Indeed, growing Buddleja davidii from seed is a great way to end up with a host of different boom colors. This adds yet more interest to your summer borders.
Fantastic for Wildlife
Buddleia’s “common name” of Butterfly Bush hints at its main attraction – it draws in butterflies from far and wide. On a good year, where the weather has been ideal for caterpillar growth, a Buddleia can be literally covered in butterflies.
However don’t let this common name let you think that Buddleia *only* attracts butterflies to your garden. It is just as appealing to bees, hoverflies and many nectar-drinking moths too. If you love wildlife then planting a few Buddleias can be a great way to draw a host of invertebrates into your garden. Indeed, we have one planted right outside a window of ours, and in sunny weather it can be better than watching TV.
While Buddleja davidii seeds may be tiny, once established the plants grow surprisingly quickly. By their second year you’ll be proud owner of quite an impressive bush. If you’re impatient you can even jumpstart that process by purchasing established Buddleia plants from a garden center, or taking cuttings from a friend’s bush.
Whatever you do, you’ll find that Buddleja davidii quickly fills out, and within two or three years it will take on a life of its own. If you’re starting a garden from scratch – such as in a newbuild house with nothing but a patch of grass out the back then Buddleja davidii is a great way to very quickly add interest.
Good for Privacy
The fact that Buddleja davidii grows quickly, and can also reach quite impressive dimensions, means that it can be ideal for providing privacy or shade if required. If you want to cover up something unsightly such as a rubbish bin or an ugly wall, or you want to reduce what your prying neighbours can see, then planting a few Buddleja davidii close together can be well worth the effort.