Hibiscus 'Resi' FULL BLAST™

We can responsibly say that today hibiscus belongs among common plants in Czech and Slovak gardens, be it woody shrubs of rose-of-Sharon (h. syriacus) or perennial hybrids of swamp hibiscus (h. moscheutos). Though, there is another hardy woody species called hibiscus paramutabilis which is quite rare in cultivation. A fine specimen is growing in the botanical garden in Linz, Austria. It has been used several times for hybridizing with h. syriacus in order to achieve larger flowers in attractive colours.

Resi is a Dutch variety of hybrid hibiscus (h. syriacus x h. paramutabilis) bred by Piere Theunissen and introduced by the nursery Piet Vergeldt Boomkwekerijen in 2008. In the US it is sold under the brand name FULL BLAST™. European Patent No. 33825 was granted in 2013 (expired in 2021). It bears large, up to 8-10 cm wide, pale lilac-pink to mauve flowers with a striking magenta eye. It blooms from mid-July until September if the plant is strong and old enough to set so many flower buds. The number and size of flowers are directly proportional to the age and strength of the plant.

Deciduous leaves are 8-11 cm long, distinctly divided into 3 lobes like fig leaves, medium green and matte. Same as most summer-blooming trees, they emerge quite late in spring, so don't worry about your plant if you don't see any new growth in April. Later in the season, yellowing of leaves is something that happens if newly transplanted plants are overwatered. Hibiscus loves water but must establish well first. Resi grows fast into an upright shrub of a broadly funnel-shaped habit and is often trained into standard trees because a tree packed with flowers all summer long will add interest to your garden. Or, as it can grow 30-50 % taller than h. syriacus at a faster rate, why not using it in an impressive flowering hedge?

Pruning is an issue that always gets me started here. Hard pruning leads to larger flowers, that's true, but also to production of long, immature, flexible twigs. The only time I recommend it is when you need to rejuvenate old plants – prune it hard in early spring by 50-75 % and let it grow for another 10 years or so.

Rose-of-Sharon is quite adaptable of soil type. It can take drought but does not look good if dry for too long. It loves moisture fully established plants thrive on occasional flooding in summer, but you cannot transplant it into standing water. Old plants dislike peat. Selective fertilizers enhancing flowering are convenient but not crucial. Place it in full sun only. Fully hardy to min. -29 °C (USDA zone 5) and not suitable for pots.

Last update 31-01-2024