Harvesting native lilies

Bulbine bulbosa is a perennial lily native to grasslands in eastern and southern Australia. It has grass-like leaves growing from a compressed stem or bulb. In the wild, it produces leaves in autumn, followed in spring by one or more unbranched flowering stems. In cultivation, mature fruit produces from one to thirteen black, angular seeds. The fruit matures sequentially from the base of the stem. Usually, one to three fruits open on a stem in one day. It is common for shedding fruit, immature fruit, two or three open flowers and unopened buds to be present on the one stem at one time.

Harvesting seed efficiently from Bulbine bulbosa is difficult. Once each fruit opens, the seed is easily dislodged. A high recovery of mature seeds can be achieved by hand harvesting fruit every one to three days just before their opening and shedding their seed. But hand harvesting is tedious and time-consuming.

An alternative may be to harvest intact stems, allow them to dry, and recover the seed when it falls from the dried fruit. Although fewer seeds might be collected using the alternative method, the method might still be worthwhile because of the savings in time.

With the range of reproductive stages up a given stem, it was not obvious when to harvest each stem, nor to what extent the seed would continue to develop and mature once a stem was cut from the plant and allowed to dry. The experiment investigated the influence of the harvest method of Bulbine bulbosa on total seed yield and seed size. The conventional hand harvesting method, where stems remained on the plant and fruits were harvested as they reached harvest maturity, was compared to storing harvested stems in a controlled environment.

1. Fruit was harvested as each reached harvest maturity (hand harvest)
2. Stems were harvested when the first fruit was at harvest maturity (early harvest)
3. Stems were harvested when the third fruit reached harvest maturity (intermediate harvest)
4. Stems were harvested when the sixth fruit reached harvest maturity (late harvest).

The plants were placed on a nursery trolley in a completely randomised arrangement and hand-watered for the duration of the experiment.

For treatment 1, each fruit was hand-harvested as it reached harvest maturity. For stems in treatments 2, 3 and 4, the first, the first three and the first six fruit, respectively, were not counted as part of the harvest.

However, the seeds from these fruits were collected and counted as they represented seeds lost from the harvest for these treatments.

At harvest commencement, the following information was recorded for each stem:

1. Number of fruit aborted
2. Number of fruit (including those that will be discarded in treatments 2, 3 & 4)
3. Number of open flowers
4. Number of unopened buds

Statistician’s description of study design

John’s study used four independent groups corresponding to four harvesting methods. It was a completely randomised design: there was no blocking.

Variables measured at harvest commencement

• Number of fruit at harvest commencement
• Number of open flowers
• Number of unopened buds

Variables measured at harvest completion

• Number of fruit harvested
• Number of seeds from harvested fruit
• Number of fruit discarded
• Number of seeds discarded
• Harvest duration in days

Summary

John found that there was a viable alternative to the traditional method of hand harvesting seeds from Bulbine bulbosa. Overall, yields for alternative harvesting methods were lower than the traditional method and yields decreased as the alternative harvest time got later. However, the yield from early harvesting method was not substantially lower than the hand method; of the three methods investigated, it is the best alternative to hand harvesting.

This figure shows 95% confidence intervals for mean seed yield adjusted for number of fruit at harvest commencement.