Alstroemerias can be planted throughout the year as a means of staggering the onset of the first flowering flush. However, the most popular planting times are September - November for an early spring flush and April - June for winter production.
Alstroemerias require an open well-drained soil. The crop is deep rooting and cultivation to a depth of 40 - 50 cm is necessary. Adequate organic matter should be incorporated and the site sterilized. Alstroemerias like a slightly acid soil, pH 6.5 being ideal. Mixing in coarse peat as a soil conditioner is very beneficial.
Soil analysis should be used as a guide to determine the amount of base dressing to apply. In general low nitrogen, moderate phosphate and high potash is required. If high salt levels occur in the soil these have first to be reduced by leaching with clear water.
Plant in beds 100 - 112 cm wide with paths at least 50 cm wide. Plant two rows per bed at 40 - 45 cm between rows. Spacing in the row should be 35 - 45 cm depending on variety. Planting depth should be such that the top of the pot is at soil level.
To encourage rapid root growth a minimum temperature of at least 14 °C should be given for the first few weeks after planting. During the autumn and winter a minimum temperature of 10 ° - 12 °C should be maintained if flower production is to be encouraged during this period. When light levels are poor the minimum temperature can be reduced to 7 ° - 8 °C.
Ventilation temperature should be 16 ° - 18 °C. As the spring crop develops and light levels improve the minimum temperature can be allowed to rise. It is important to give sufficient ventilation to control humidity and maintain a buoyant atmosphere. Rapid fluctuations in humidity can cause plant stress and severe leaf tip scorch on some varieties. During the late spring and summer period the crop should be kept cool. Ideally the soil temperature should not rise above 20 °C. Shading at this stage is beneficial.
Watering and Feeding
Water plants in well after planting. During full growth soil should be kept reasonably moist. In the winter period watering can be reduced significantly. Liquid feed should be commenced when the crop is growing actively using a balanced nitrogen and potash feed.
Soil analysis should be used as a guide to determine the feeding programme particularly when the crop is more than one year old and a nutrient imbalance may need correcting.
It is important that the crop is properly supported. Strong end supports are required with intermediate cross supports spaced approximately every 3 metres.
At least three nets should be used with more for taller varieties. Bottom nets can be 12.5 cm long mesh with upper nets at least 20 cm x 20 cm to make harvesting easier. The nets should be spaced 30 - 35 cm apart. The top layer of netting will need to be at a height of about 150 cm for the taller varieties. The bottom net should be sufficiently low to avoid excessive tucking in of new shoots.
During the growing season it is desirable to pull out non-flowering stems, but always leaving enough growth to sustain the plant. Carried out on a routine basis thinning will improve the strength and quality of the flowers and keep the plant open with good access for light and air movement.
The frequency and amount of thinning will vary with variety and the age of the crop. A newly planted crop should be thinned once the plants are established and then periodically as the flush develops. Older crops will need more thinning out to maintain good quality flowering stems.
Another method of checking the thin growth is by pinching out the top of the stem. This is less labor intensive and discourages excessive regrowth of non-flowering stems. It is probably best to use this method in combination with thinning out.
Alstroemerias are day length sensitive and a flush can be advanced in short day conditions by lighting.
The details of an optimum lighting programme have still to be determined but satisfactory results can be achieved by giving a 13 hour day, with lighting at 40 - 60 lux, from mid September to mid November for an autumn flush and end December to late March for a spring flush.
Stems should be harvested when the first bud is either partially or fully open depending on customer requirement. Stems can be cut or pulled provided no piece of rhizome is pulled with the stem thus damaging the plant. If stems are cut the old flower stumps should be removed at the end of the crop. After harvesting the flowers should be placed in water as soon as possible especially during warm sunny weather. Flowers can be stored for a few days if necessary in a cold store at 2 ° - 3 °C. A flower conditioner can be used to improve lasting quality.
Grading standards will depend on market requirement. Generally a top grade requires a minimum of 5 °C heads with lower grades proportionally less.
These can build up on flower buds and young shoots.
A build up in summer can cause severe damage.
These attack the young developing shoots.
This can be prevented by maintaining a buoyant atmosphere with correct heating and ventilation.
These are caused by soil inhabiting fungi. Affected plants collapse with dry and withered foliage. They should be removed with some surrounding soil to prevent spread. Suspect soil should be sterilised before replanting.
No part of this guide may be reproduced in any form without prior permission.
The recommendations contained in this guide are fairly general and should be used as such. Specific advice available on request. No liability is accepted by the authors of this guide for any misinterpretation of the recommendations contained therein.