PLEASE NOTE; The following is an excerpt from JM Fortiers’ Market Gardeners Masterclass. It does not include appendices, tables or the complete technical sheet from the Masterclass, it is meant as a guide only.
INTENSIVE SPACING
- English: 1 row per bed spaced every 50cm on the row.
- Lebanese: 1 row per bed spaced every 33cm on the row.
These are parthenocarpic varieties meaning they don’t need to be pollinated planted on 75cm beds with 45cm pathways and trellised in a modified umbrella style. Final density for English cukes is 1.8 plants/m2. For Lebanese cukes,final density is 3 plants/m2.
FERTILISATION
- Bimonthly application of compost (2-1-1), alfalfa meal (2-0-2), feather meal (11-0-0)Sul-Po-Mag (0-0-22) and potassium sulfate (0-0-50).
- Perform an EC (electrical conductivity) test every 2 weeks to monitor the progression of the fertilisation. The EC will determine if we need to fertilise or not.
- We fertilise once on one side of the row, then on the other side 2 weeks later. The EC test is to be conducted before fertilisation on the side that is meant to be fertilised that week.
PRUNING, SUCKERING TRELLISING
Pruning cucumber plants needs to be done at least once a week, but preferably twice a week. Otherwise, the plant tends to set more fruits than it can support, which ultimately leads to new fruits being aborted.
For both English and Lebanese cukes, in the first 2 weeks, or before the plant reaches 60cm high, all the fruits should be pruned off the plant. By limiting the number of fruits on the plants while it’s establishing its roots, you will have higher total yields. After the first two weeks, follow these simple pruning guidelines:
English cukes: Prune to leave 1 fruit every 2 nodes and remove all tendrils + suckers.
Lebanese cukes: Leave all fruits, but remove all tendrils + suckers.
Lebanese cucumbers are more vigorous than English, hence the reason why their fruits are not removed.
In both cases, wind the plant around the twine clockwise. We prefer winding the plant around the string, instead of using clips to the trellis. It is faster and eliminates having to carry around material requiring manipulation.
Pruning and winding should be done twice a week. When the head of the plant reaches the wire, attach it with a clip and train it to grow along the wire to its right. Until the main head reaches the next plant, let all the suckers grow, these will form new heads that will be shooting down. Once the main leader reaches the next plant, clip it to the wire for support, and let it grow downwards. By that time, you should have about 3 suckers that have developed into new heads. These are growing downwards (from the top wire heading towards the ground) and are treated just like the main head, pruning off fruits, tendrils and suckers every week. When the main leader reaches down to 5 fruits (10-12 nodes), prune off its head, which will stop this stem from producing any new fruits. Production continues on the
other leaders until they also reach 5 fruits, at which point, you can top them too. This goes on as long as the plants keep producing, but ultimately after 10 to 12 weeks, production declines considerably. It is therefore time to replace the plants with a new succession. To make sure we don’t have a gap in our production, we plan for this new succession to start producing 10 weeks after the plants it replaces.
PRUNING LEAVES
Similar to removing suckers, pruning leaves allow the plant?s energy to go toward fruit production, instead of excess vegetative growth. Removing the lower leaves also increases airflow, which can reduce the incidence of disease.
You can begin pruning the bottom leaves when the head of the plant reaches the top of the trellising wire. At that point, the plant should have +/-18, 20 leaves and you can remove 1-2 leaves every second week. The leaves most appropriate to remove are those on the lower parts of the plant that may be shaded or crowded. Additionally, if
you see any leaves that appear diseased, remove these and dispose of them. As with pruning suckers, it is best done early in the morning and only when the foliage is dry, in order to avoid any potential spread of disease.
PLANT PROTECTION
Pest control is a major part of successful greenhouse cucumber growing. How to deal with the problem will depend on many different variables, but prevention and observation should be your primary tools. The aim is to favour a plant positive approach to pest management, avoiding using pesticide use when possible and working with predatory insect introduction instead. It’s the way to go, but it requires preparation and advance planning.
In our climate, certain insects are sure to become problematic if not handled preventively with the help of certain infrastructure: Cucumber beetles and the damage they do by spreading bacterial wilt can be mostly avoided by installing insect screens in the openings of the roll ups. Highly recommended.
Spider mite populations are greatly reduced by keeping humidity levels in the greenhouse above 60%. We achieve this by adding fogging misters to the cucumber greenhouse. These are set on a simple watering clock that will have them turn on every hour (or half-hour on very hot days) for a few seconds. Diseases are also very context-dependent. The first lines of defense is to use cultivars that are disease resistant. Using varieties that are resistant to both downy and powdery mildew is a must. In our experience, fungal problems (Alternaria and Cercospora leaf spot) are more effectively treated by spraying biological-based fungicides, rather than other certifiable sulfate solutions. A bio-fungicide like Serenade (which works with Bacillus subtilis) contains living bacteria or fungi that help reduce pathogenic microbes by competition or antagonism. Such biological products don’t harm beneficial insects and other non-target organisms. We often mix with copper for more effectiveness. Pythium and the damage that it does to the transplants is often a result of soil that was not warm enough when the plants went into the ground. A product like Rootshield, a biological fungicide, can also be very effective in preventing pythium outbreak, especially with the first planting of the season.
Removing sick plants and cleaning your hands when handling them is also vital in protecting against bacterial or viral infections. Diseased plants should not be put in the compost, but in the garbage. Another important practice is eliminating habitats suitable for insect survival. You do this by completely removing plant residues once the production is done. Planting a new succession directly after the other is not a good idea, hence the importance of
having more than one greenhouse for continual production.
For anything specific, a good resource guide is your best bet. Vegetable MD online from Cornell University is one example of where to look.
POLLINATION
Most greenhouse cucumber varieties have been hybridized not to need pollination. The cultivars we use are parthenocarpic, and will develop fruits without the help of pollinators, this is why we can use screens to protect against cucumber beetles and other insects in the greenhouse.
WHEN IT GETS HOT
Cucumber plants will shut down and abort their fruits if temperatures stay above 30C for too long during the day. To help the plants cope on very hot days, these measures help:
- Ventilate 24h/7 and as much as possible.
- Roll-up sides and all openings should be open to their maximum
- Install shade cloth over the greenhouse
HARVEST
When production starts, cucumbers are harvested 3 times a week and in peak production, everyday. All the fruits that are about the size will be harvested and graded at the end of the harvest. To speed up the harvest we use tree planting bags. All damaged or split fruit is put aside during harvest. We harvest with tree planting bags and clippers using both of our hands, clipping the fruits as close as possible to the main stem of the plants, then cutting the stem closer if necessary. English cukes should be 30cm long and of uniform fullness throughout, and Lebanese cukes should be 13cm long. If all is going well, you should be harvesting 2-3 fruits per plant/per week. Before storing the fruits, don’t forget to mark the date of the harvest in order to practice effective rotation of stock.
DPI NSW Greenhouse Cucumber Growing Guide
