Rose bonsai is a commonly asked-about species. It can be challenging, as rose is an herbaceous, cane-dominated growth perennial rather than a woody perennial. This means that we must have an in-depth understanding of pruning rose plants to be able to use them as bonsai.
One variety that lends itself well to bonsai is the Eijitsu rose multiflora. It is an exquisite dwarf variety of rose that originated in Japan.
This species has:
- A thick and radically-formed woody trunk
- Strong, fine, tight internodes
- Small branches
- Small flowers that create beautiful, tiny orange to reddish-colored rose hips
Overall, rose is underexplored and not fully understood as a bonsai subject—but putting in the work of cultivation and pruning can yield wonderful results.
Caring for Rose Bonsai
Like many broadleaf species, roses love water. So you should never let the soil fully dry out before watering again. Instead, rewater when the rose bonsai’s soil is on the dry side of damp—but still contains some moisture.
Multiflora roses thrive in warm or hot environments. They enjoy humidity as well, but that comes with its own issues. Although high humidity can prevent problems with insects such as spider mites, it can also facilitate disease more easily.
Roses like temperatures up to 90℉ and can even tolerate temps of over 100℉ if they are protected by a 30% shade cloth.
If you live in a colder environment and are cultivating roses in a shallow container, be careful not to let them free. Rose bonsai are more susceptible to cold when they are in an above-ground container.
Roses love full sun, as this is what allows them to proliferate. They photosynthesize through their stems and their leaf map.
Full sun is what empowers the canes to:
- Have tight inner nodes
- Have smaller leaves
- Become very strong; and
- Build up latent potential buds that can be turned into branching and ramification
Roses do well in full sun up to 90℉. If temps rise any higher, they will need a little shade to get a breather from the scorching afternoon sun.
Rose bonsai should be fertilized once a month with solid organic fertilizer. You can also use liquid fertilizer every week during the growing season.
If the leaves turn pale, an extra iron fertilizer can be used.
Rose bonsai should be pruned twice a year.
First, pruning should occur before the beginning of growth in the spring. You want to prune back to two nodes on the branching and prune off older, woody pieces that are starting to lose strength. This allows strong green branching to occur.
Over time, the biggest pruning consideration with rose bonsai is to reinvigorate water-conductive green branches while getting rid of older, more lignified growth that doesn’t conduct water well anymore.
A rose bonsai’s second pruning should be done right after the rose hips start to dry up and fall off—after flowering. This usually occurs mid-summer. This final prune both holds the shape of the tree and invigorates it with another spurt of growth. This allows the rose to go into the vascular formation phase of fall with higher water conductivity.
Rose bonsai should be repotted as the buds start to swell in the spring. Use up to ¼ inch of solid akadama soil as your interior size. Once you have an established root system, be careful not to bare the root when repotting.
Rose bonsai may be propagated from summer cuttings. Look for shoots that are about one year old and have hardened well. You may also be able to propagate by air layering.
The pest you must look out for with rose bonsai is the spider mite, especially if you live in an area with low relative humidity. Spider mites love to feed on rose bonsai stems and leaf rows.
A spider mite infestation often directly correlates to an overly aggressive fertilizer schedule and too much nitrogen. Rose bonsai should be fed with a moderate, or even light, application of fertilizer so as not to invite spider mites onto the plant.
A common disease for rose bonsai is powdery mildew. This occurs when the leaf mass is kept too wet and has poor air circulation, or if there is high relative humidity and a dense canopy.
Avoid watering the foliage of the tree to keep it from getting powdery mildew.
Young rose bonsai branches are easy to wire—but watch out for sharp thorns! Older branches are usually brittle and stiff, so be extra careful when wiring and positioning them.