The Thornless Boysenberry (Rubus Ursinus X Ideaus ‘Thornless’) Care Guide

The Thornless Boysenberry, otherwise known as the Rubus Ursinus X Ideaus ‘Thornless’ or Red Ruellia, Elegant Ruellia, is a rather well known annual plant by gardening enthusiasts around the world.

Best known for its low maintenance and fast growth, this annual will likely liven up your house (or garden) with its green colored leaves. But, only if you learn how to take proper care of it for it to thrive.

Fortunately, taking care of your Thornless Boysenberry is not too difficult – as long as you follow our guidelines in this Thornless Boysenberry Care Guide. Now let’s get started.

The fundamental caring guidelines for every Thornless Boysenberry can be summed up into the following:

  • Water: The Thornless Boysenberry wants regular watering to enhance fruit production but as a landscape plant, too much water will be a problem.
  • Light: Keep your Rubus Ursinus X Ideaus ‘Thornless’ in an environment where it can receive full sun on a daily basis. 
  • Soil: Make sure to keep the Thornless Boysenberry in soil with well-draining properties, so ideally, one that is made of clay, loam, chalk, and sand.

That’s it – sunlight, water and soil! The basic 3 fundamentals for all plant care, and with the Thornless Boysenberry this is no exception. With these three elements, your leafy friend will live healthy and happy.

Thornless Boysenberry up close

Scientific / Botanical Aspects

In botanical terms, the Thornless Boysenberry belongs to the Acanthaceae family, the genus Ruellia and the species Elegans, hence its scientific (or botanical) name Rubus Ursinus X Ideaus ‘Thornless’ (ROO-bus ur-SEE-nus eye-DAY-us).

As with other Ruellia’s, the Thornless Boysenberry is a deciduous plant, which means it will shed its leaves annually once autumn comes.

Growing Region

The Thornless Boysenberry is a plant native to the Eastern Brazil.

You might be wondering why your Thornless Boysenberry’s native region is important. Well, if you know where your plant originally came from, you’ll know which environment conditions it prefers, and with it, knowledge on how to replicate it at home.

With this in mind, the Rubus Ursinus X Ideaus ‘Thornless’ will be most used to regions where the plant hardiness level falls between 8b, 8a, 9b, 9a, 10b, 10a, 11b, 11a and the ideal climate zone is between 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24.

Growth and Size


In terms of size and growth, the Thornless Boysenberry is a relatively fast grower, which makes things tricky for any plant enthusiast.


But, what size of Thornless Boysenberry are we talking about? What can you expect in terms of height, spread and spacing? Let’s dig in…

The Rubus Ursinus X Ideaus ‘Thornless’ can grow up to 2′ – 3′ (60cm – 90cm) in 2′ – 3′ (60cm – 90cm) and 2′ – 3′ (60cm – 90cm) in 2′ – 3′ (60cm – 90cm). 

These dimensions make the Thornless Boysenberry a relatively medium annual compared to others, so it’s best to keep this fact in mind since it will affect where you want to keep yours at home.

This is why experts recommend keeping an area of approximately 36″ (90cm) free so the Thornless Boysenberry can spread to its best extent.


In terms of watering, the Thornless Boysenberry is a fairly complicated plant to take care of.

This is mostly because it has a not so straightforward watering schedule and somewhat regular watering needs.

Specifically, most experts agree that the Rubus Ursinus X Ideaus ‘Thornless’ wants regular watering to enhance fruit production but as a landscape plant, too much water will be a problem.

Which is why it is considered a plant with relatively low needs in terms of water. 

Thornless Boysenberry care


As a rule of thumb, you should remember to keep your Thornless Boysenberry in soil with well-draining characteristics, as these will guarantee the right conditions for your plant to grow and thrive. 

When you consider this, this is why you should aim to choose soil that has good drainage properties to keep the right moisture levels at all times. 

But, if you want a ‘one-size-fits-all’ solution to watering your Thornless Boysenberry then you should consider the famous ‘finger’ test. To perform this test, you just need to put your finger in your plant’s soil and determine if it’s moist or not. If it is, then don’t water; if it isn’t, then please do. In any case, this test will allow you to know if your Thornless Boysenberry needs or does not need water, every time.

Soil Mix

As mentioned earlier, the Thornless Boysenberry prefers to have soil with good drainage properties at all times, reason why you need to make the soil mix out of clay, loam, chalk, and sand.

This is why most experts agree that the Thornless Boysenberry requires soil with high organic matter, and loam (silt), which will give you the right conditions it needs.

In addition to this, expert gardeners recommend having preferably alkaline, acid or neutral soil.

Light and Exposure

In terms of light & exposure, the Thornless Boysenberry requires full sun in order for it to thrive under the right conditions. 

Most experts agree that this annual will do well as long as you keep it in partial to full sun, and it will be able to grow properly.

Specifically, we recommend that you place your Rubus Ursinus X Ideaus ‘Thornless’ in little to partial shade (only 2-6 hours of direct sunlight a day), to full and direct sun (more 6 hours of direct sunlight per day).


Being a deciduous plant, the Thornless Boysenberry will shed its leaves annually once autumn comes.

But, you can expect it to have its ‘prime-time’ during the spring (late), the summer (early, mid, late), and during the fall.


You can expect your Thornless Boysenberry to flower around the spring, summer and the fall months from April to June (spring), from July to September (summer), and from October to December (fall).

The Thornless Boysenberry produces some beautiful white, or red/burgundy flowers around this time of year.


The leaves from the Thornless Boysenberry have a beautiful green color during most of the year.

Thornless Boysenberry plants

Attracts, Tolerance and Resistance

The Thornless Boysenberry is well known for being able to attract hummingbirds and butterflies, so keep that in mind when choosing your plant, as you’ll likely end up finding one or another in your garden.

Additionally, it has a special tolerance for animals like deer, so don’t worry if any of these come along, your Rubus Ursinus X Ideaus ‘Thornless’ will be fine.


Does your Thornless Boysenberry have any garden recommendations? Does it serve any gardening purposes? Here’s how you can get the most out of your new plant.

Most Rubus Ursinus X Ideaus ‘Thornless’ owners agree that this annual will look great in most cottage and rustic gardens of all types. 

Other owners consider that they complement well most gardens of mediterranean garden styles. 

In particular, the Thornless Boysenberry’s best location within your garden is in beds and borders, and in patio and containers, others use it for landscaping in a mass planting, border, kitchen garden, or a woodland garden.

Companion Plants

Thornless Boysenberry’s do well with some other plants beside it. One good companion plant is the Salvia, which will pair up nicely with your leafy friend.

Others consider that a nice Rosmarinus will work well too, so choose whichever you find works best for you!


Even though we covered a lot of care information for your Thornless Boysenberry, remember the basics: sunlight, soil and water, as these should be enough to grow a healthy plant at home.

Martin Duran

Hey y'all! My name is Martin Duran and I am from Cali, Colombia. Since 2018 I have been learning about plants and how to take care of them. Here's is my journey... “The clearest way into the Universe is through a forest wilderness.” ― John Muir

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