Watering
Water alstroemerias regularly during a prolonged dry spell, but they are relatively drought-tolerant. Water alstroemerias in pots and any in a greenhouse.
Fertilising
Add a slow-release fertiliser in the spring to encourage flowering. Use a high-potash fertiliser for any container-grown alstroemerias such as comfrey or tomato feed.
Staking
Alstroemerias can reach over 60cm (2ft) and their big lily-like flowers can make them top heavy, so unless they are in a very sheltered spot, the taller varieties will need staking so they don’t collapse in the wind or rain. Tap in a cane and tie in the stems, or if you have a big patch of alstroemerias, stretch jute netting over them.
Deadheading & harvesting
Keep harvesting the flowers or deadheading any faded flowers. The best way to pick or deadhead alstroemerias is to pull them like rhubarb, rather than cut the stems. Hold the lower part of the stem and give it a quick, stout yank – you’ll have a very long, sometimes twisty stem, but they can be trimmed easily if you want them for a vase.
Doing it this rough way (rather than cutting) provokes more flowering stems to form and gives you a more productive plant.
For more on the technique, scroll down to watch our video on harvesting alstroemerias below.
Dividing
After settling in for a couple of years, alstroemerias spread below ground, little by little. Propagate alstroemerias by division every couple of years to avoid congestion. The roots are fragile and need to be lifted and divided with care and replanted immediately. Do this during their dormant period in early autumn or alternatively in April.
Divide the clump and replant elsewhere in the garden in a planting hole that’s about 20cm (8in) deep – add a handful of grit to the planting hole to improve drainage.
Overwintering
Like dahlias, alstroemerias are tender tubers. They become hardy easily once established, and with our increasingly mild autumns and winters, all it takes is a good mulch over the colder months and they will emerge again the following season.
Mulch deeply for the first couple of winters to give them the best chance, and particularly if you live in a cooler part of the country.
It’s worth noting that hardiness used to be a problem with some species and earlier-bred hybrids; they would start to shoot in April and would then be cut down by frost, which would knock them right back. But modern, early-flowering varieties are made of sterner stuff. Some can be cut down by frost and just come straight up again.
