Root preparation: Do I cut roots?
In the UK one should consider preparing the Brugmansia for overwintering around mid-autumn (October/November), depending on your latitude. If pot plants are in the ground they should be dug up, pot and all (if you have planted out using this method),or removed from the large summer pot and any roots dangling out of the pot should be cut off with sterilised secateurs.
The roots from Brugmansia dug up without a pot in autumn can be cut back using a sharp spade/ small saw until they fit into their overwintering pot (20ltr pot is fine), using fungicide on the cut roots to avoid disease. The root ball should be allowed to dry during the dormant period to reduce rotting and if the plant is wet from rain, leave the foliage intact, and place somewhere with good air flow to encourage water uptake and transpiration through the leaves. This will dry the plant out more. Water should only be given to overwintering Brugmansia when absolutely necessary. With most of the foliage dropped and the Brugmansia cut back, the root system becomes dormant. Over winter, roots will develop, and this sets the root system up well for the following spring and little intervention is needed for successful growth later the following year.
Autumn pruning has a threefold purpose:
· To reduce the size of the plant for storage
· To reduce pathogens penetrating green leafy parts of the plant
· To keep the shape of the plant for the following spring
Pruning Preparation: How much shall I cut back?
When cutting back Brugmansia you should assess where the ‘Y’ branching is occurring and cut back above this ‘Y’ point, above a node. ‘Y’ branching indicates a mature stage of flowering in the plant, and it will give the plant a head start the following spring, producing a good early flush of flowers. Cutting below the ‘Y’ will retrospectively push the plant back into a juvenile growth stage and it will not flower until a ‘Y’ branch forms later that summer.
‘Y’ branching can occur at different heights, in different cultivars, so it really depends on which Brugmansia you have and how much space you have to store it. I would suggest if you can keep the ‘Y’ and a node above on each branch this will be fine and cut everything above this point. Vegetative cuttings in this area above the ‘Y’ take very well in a glass of water and room temperature, should you want more plants the following spring.
New green shoots from branches and roots can be removed as you want to encourage lignification at these points.
Wounds resulting from cutting back should be treated with fungicide spray.
When dormancy is forced by cooler temperatures in the UK, Brugmansia do get stressed by this and are more prone to pathogens than other times of the year. Sterilising secateurs is good practice when pruning between different plants, using boiling water or alcohol gel on a tissue.
Overwintering quarters: Where should I put my Brugmansia?
Brugmansia can be kept growing in glasshouse over the winter, given sufficient heat (20⁰C), but this can be costly and result in diminished flowering the following spring. For the majority of Brugmansia, the best place for them is a basement/cellar, garage, shed, or greenhouse which is frost free and ventilated in some way. Temperatures from 5⁰C to 12⁰C are most favourable for most cultivars and species. B.versicolor and B.Insignis are the only species which suffer at the lower temperatures and prefer a toasty all round 15⁰C over winter. Some hybrids, which include these species, may also show a similar behaviour. Cooler sphaerocarpium varieties prefer 3-5⁰C as winter lows such as B.sanguinea or B.vulcanicola.
Cooler temperatures also have the added benefit of slowing the spread of pests such as aphid or white fly.
Heat can be applied via a horticultural heat fan (added ventilation too), oil filled radiator, or low wattage horticultural heat tube. Bubble wrap (large bubbles) is an excellent insulator and can assist to keep temperatures above freezing and save you money on heating. I wouldn’t recommend using paraffin heaters, due to the fumes emitted, but maybe in times of a power cut this may be essential. Keeping the plants in the house quarters (garage, cellar) could save money but do remember to ventilate well.
TIP: If the greenhouse is cold, under (1-2⁰C) lift the plant off the ground and insulate under the pot with a thick layer of bubble wrap/hessian and then fleece around the plant to ensure survival of your Brugmansia through the coldest parts of winter.
Checking my plants over winter
Brugmansia plants should be checked twice a week for fungal disease or pests, and any fallen foliage or plant material removed to prevent Botrytis fungal disease. The root ball should not be allowed to dry out completely and water should be added carefully BUT not allowed to get wet. Special attention to this detail is even more important in cold snaps, where it has the potential to seriously damage the roots and kill the plant.
The Arrival of Spring
When the danger of frost has passed the plant can be removed from its winter hibernation and allowed to slowly adjust to the light of the spring. Avoid direct sunlight and acclimatise slowly. As foliage appears slowly increase the water bit by bit until the plant shows good signs of vegetative growth. Top dress the pot with fresh soil and feed low Nitrogen feed to encourage more vegetative growth before the flowering season, from May onward, when feed should change to a high potash content.
Get cracking! Have a think about how you might overwinter your plant. Purchase the materials you need, so you are ready and prepared! Try the shopping list below as a start for your overwintering your Brugmansia:
Fan for ventilation