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Growing Roses Indoors

05 July, 2018

            Growing Roses Indoors

"Loveliest of lovely things are they on earth that soonest pass away. The rose that lives its little hour is prized beyond the sculptured flower."

—William C. Bryant

Perhaps there no other flower has captured the attention of gardeners throughout the ages as much as the rose. Long the subject of art and literature, much has been said and written about it. The beauty of these flowers however, is matched by its difficulty in growing, especially in the hot sweltering tropics. This is hardly surprising as the genus Rosa originates from sub-tropical to temperate climates in East Asia to India, Europe and North America.

Having killed more than my fair share of roses, I've always thought that these were rather fussy plants, susceptible to pests and diseases that warrant frequent applications of not only TLC but also pesticides and fungicides. Indeed, many of the tropical growers have a weekly regimen of spraying to keep diseases and infestations at bay due to two reasons:  the first being that there is no winter which kills off many of the insect pests and second being that roses are often stressed by the heat. As we've had much wildlife coming to visit the garden—birds, butterflies and bees—I wanted to avoid harming these creatures as much as possible and prophylactic application was not something I wanted to do.

The other pressing reason for growing them indoors was the looming fact that there was no more available space for growing in the garden simply because there are too many plants.

As there was already some success with growing lavender hybrids in a kratky hydroponic system, on a spur of the moment I thought that roses might work as well. Researching this proved to be a little difficult, because almost nobody grows roses hydroponically. Google did provide some nuggets of inspiration, the first being that roses could be rooted in water and the second being the discovery of a nursery in Australia producing cut roses by growing the plants hydroponically in a coconut husk medium. Armed with that, the first rose I tried this on was an orange and yellow marbled mini rose from the garden center despite killing this particular variety twice.

1. Choosing plants

The first step is making sure the plants are fresh. As plants in the stores are usually in bud or bloom try to get one with buds that are not fully open yet because the flowers will be cut off later and we should try to conserve as much energy for the plant as possible so that rooting is faster. Avoid plants that have displayed any signs of wilting or yellowing leaves as these plants are stressed and difficult to revive.

2. Rooting the cuttings

Once the roses are back from the store, cut off all the flowers and flowers buds back to the highest vegetative stem node to conserve energy for rooting. Cut off all the stems as close to the base as possible but avoid including any woody material. Remove all leaves leaving only the highest two and place into a container with water reaching up only till 1 cm from the bottom of the stalks. Too much water will cause the stems to blacken and rot away.

The cuttings should be placed in a bright area but away from direct sun to avoid heat stress. The best would be to place them under grow lights, best at 250-350 µmol/m2/s2. The roots should form in about a week or two, sometimes the cuttings form may form many root nubs before lengthening them. The cuttings can be transferred to the growing container with nutrient solution once a few roots have formed and have lengthened to about 1 cm or more, like the plant on the right.

Note: If the cutting only grows nubs like the one on the left, do not transplant into nutrient solution yet. From experience, some of the cuttings do not grow roots despite the presence of the nubs, and tend to abort after growing a few new leaves. Such cuttings are best discarded.

For hydroponic culture its crucial for plants to grow new water roots rather than transplanting existing soil grown plants. Rose roots are brittle and difficult to adapt to hydroponic culture if they have been growing in soil.

3. Transferring to the nutrient solution

We now recommend using our HYDRO POWER C solution as we've had  successful trial results, at a dilution rate of 5 ml of fertilizer to 1000 ml of water. 

Plants are placed into a mesh pot with leca for stability and the entire pot is then placed into a glass jar or any container that fits. The mesh pot must fit into the larger container exactly, so that mosquitoes cannot enter and lay eggs.

As the newly rooted cuttings have fairly short roots, the solution level in the container needs to be checked and replenished (either nutrients or water is fine) every day for the first couple of weeks up till A in the photo.  Once the roots have grown longer into the solution, it does not need to be replenished so often and can be done every few days or even a week up to the maximum at B. This would be a Kratky hydroponic setup and I've used a sock to prevent light from getting into the solution which would result in a lot of algae.

4. Plant care

The plants can be grown under the same light conditions at the rooting phase at 12-14 hours of light per day. With indoor growing under LEDs, the temperature is kept at 26°C-32°C and at about 50-70% relative humidity.  With mini roses, new flower bud formation can be expected in about a month after transferring into a nutrient solution. Remember to top up with nutrient solution every couple of days and change the solution every two weeks or so. Pests can be controlled with white oils sprays so systemic pesticides are not necessary or recommended. As the leaves are kept dry, risk of fungal disease is low and fungicide is also not needed.

This plant shown below is about 5 months old, and getting so heavy that I have to hold it up or it would topple over. As you can see, it's not that difficult to keep these plants blooming!

If you think this is too much trouble to go through, you can purchase a plant from the store (only available in Singapore) and save yourself the extra work. We're also available for workshops and consultation for projects, please get in touch with us for more info.