The Q&A Archives: Rosa Rugosa

Question: Neither of the two rosa rugosa have bloomed. They look healthy and have doubled in size but have not bloomed since I planted them two years ago.

Answer: Based on your description I am not certain why they would not have bloomed. Here are a few possible causes.

Roses -- including rugosas -- bloom best in full sun, meaning at least six hours of direct sun including the hour of noon. If they are in too much shade, they will bloom less or not at all.

These roses bloom on old wood that grew the year before. Sometimes, incorrect pruning can remove the flowering wood and so there are no blooms. A new bush would not need much if any pruning. After a few years, you might need to thin the bush by removing some of the oldest branches by cutting them out at the base. These bushes are pruned right after they bloom. If you have pruned them at other times of the year (for example in early spring as one would prune a hybrid tea) then you may have inadvertently prevented them from blooming.

Another possible reason could be overfertilizing. These roses do fine with an annual topdressing of compost along with a spring application of slow release or granular fertilizer such as 10-10-10 per the label directions. Using an organic mulch also helps feed the soil gradually over time as it breaks down. Over fertilizing with nitrogen can cause an excess of vegetative growth at the expense of flowers.

Finally, if your plants were very immature and small, it may take them a few years to become fully rooted and established and mature enough to bloom.

I hope this helps you troubleshoot.

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