On receipt of your plant you can place it outside provided the risk of frosts have passed. Put the plant into a larger pot, we recommend moving up in size by 2-3 inches using a free draining potting compost. For the larger pot size you can use two plants to ensure good foliage coverage and larger flower quantity, don’t forget to use a plant support system if you want the plant to grow upwards.
For continuous flowering during the autumn and early winter make sure you grow the plant up a support system which can be transferred indoors to protect against frost, when the time comes.
You can use slow release fertiliser such as Osmocote to give long lasting feed requirements through the summer.
Pinching the plant to get the correct shape is recommended, but please be aware if you pinch hard and every shoot you will not have flowers for 2-3 months, as flower buds will appear from leaf buds.
The shoots will grow 5-10 cm a week in the peak of summer, regular training will be required or pinching. If pinching is chosen to ensure the plant remains a manageable size please pinch the plant back to the first pair of true leaves, after the growing tip of the shoot, this ensures again that leaf buds are left for flowers to develope from.
Please be aware that the sap of Mandevilla is classed as a mild irritant. The sap is of milky appearance and can be clearly seen when pinching the plants, best to wear gloves just in case.
Light & Temperature
Day length will affect the flowering period for Mandevilla, generally day length of around 11-13 hours is needed to initiate flower buds. It can take two months for the first buds to appear and a further few weeks for them to fully open, this will vary from variety to variety.
With the flowering status you will see on the same stem, one fully open flower, also one large coloured bud, a tight bud and one very small bud
Flowers can be seen in the UK up to Christmas if the plant is given the correct conditions, please bring it in doors before the first frosts and place in a well lit area free from frosts. An ideal temperature of min 10°C (50F), a heated greenhouse or conservatory which can be cold or heated is an ideal environment to ensure further flowering, other options are to keep in a light porch, patio doors and windows, basically in as much natural light as possible and way from the frosts and keep dry.
By Christmas most of the flowers will finish or the buds will abort due to the poor growing conditions and the plant will remain evergreen and you will inevitable get leaf drop, this is a natural process for the plant to reduce the amount of foliage it will carry through the winter months.
Watering & Feeding
The plants are very sensitive to over watering, always allow the plants to dry between watering, make sure you water thoroughly, remember to water slowly so that all the soil gets wet.
You can use slow release fertiliser such as Osmocote to give long lasting feed requirements through the summer otherwise use a standard liquid fertiliser such as Tomrite, Phostrogen, Baby Bio and feed at least weekly, make sure you feed when watering or after watering as feeding into very dry soil can cause problems with levels of fertilisers.