Empty Greenhouse Space? How about Producing Trellised Cucumbers?

2016 Summer
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Are you looking at empty greenhouse or high tunnel space now that your bedding plants, hanging baskets, and containers have been sold and moved out?  Consider growing trellised, parthenocarpic cucumbers.  This crop can be successfully grown both in soil and in soilless media, so any structure will do.  Unlike tomatoes and peppers with long days to harvest from seeding, you can begin to harvest cucumbers 45-50 days from seeding, so even a mid-July seeding can provide a good return on investment.


When we first began growing cucumbers in tunnels, we were targeting only the early, high value market, prior to the glut of field-grown cukes.  Then we discovered the visual beauty and high-quality fruit that was possible growing cucumbers indoors and trellised.  By hanging and excluding pollinators during fruit set and maturity, the fruits are largely long and straight with very low cull rate.  By keeping cucumber beetles excluded from the crop, plants don’t experience bacterial wilt and the fruits are free of feeding scars.  This makes for beautiful fruit that have consistently brought higher prices than field grown.

Through sequential planting and replanting production is possible from April through November.  When faced with space limitations when growing spring annuals, planting cucumbers can be postponed until late June or July.  This planting will be producing fruit by mid-August and stay in production until mid-November with a bit of added late season heat.  These late season cucumbers generally market well compared with the late field-grown cukes.


While any cucumber can be grown indoors, the parthenocarpic varieties are ideally suited for these conditions.  Several years of trialing these varieties at the PSU SE Research Farm has given us the following list (all are parthenocarpic):

Coritno (Johnny’s Seeds): This variety has the dark green skin and bumpy appearance of a field-grown cucumber but sets high yields of straight fruit that taste great and market well.

Lisboa (Seedway Seeds): Very similar to coranto, but just a shade below in quality and yield.

Katrina (Seedway Seeds): This is one of the Beit Alpha types with very thin, smooth, light green skin.  The skin is nearly bitter free.  It performed strongly in PSU SE trials.

Picolino (Seedway Seeds): This is another of the Beit Alpha types with very thin, smooth, light green skin.  The skin is nearly bitter free.  Picolino was our top performer in the PSU SE farm trials.  It came in earliest and producing the longest.

Socrates (Seedway Seeds): Same as Katrina.


Excelsior (Seedway Seeds and others): This is a typical pickling variety that is extremely crisp so performs well in farmers markets.

Iznik and Unistar (Johnny’s Seeds): If you’ve got a market for mini-cukes, both of these varieties are excelenet performers.  Don’t skip a day of harvesting or these will no longer be ‘mini’.

Definition: parthenocarpic: fruit that does not require pollination of fertilization of the ovule to set fruit.  When seeds are present, they are sterile.  In cucumbers, parthenocarpic varieties should be protected from pollinators or fruit quality can suffer.  The most common symptom when parthenocarpic varieties are pollinated is misshapen or curved fruit.

Planting and soil

As noted in the opening paragraph, both soilless and soil-grown production work well.  Soilless media will add a bit to the investment, but through multiple uses over several years, this cost can be managed.

For soil grown, work in about half of the crops expected fertilizer needs using granular materials based on a recent soil test.  According to Knott’s Handbook for Vegetable Growers, cucumbers need #100-125N, #100 P, and #150-200 of K per acre.  Based on those started numbers and applying 50^ of expected nutrients needs at ‘plowdown’, a grower would need to apply #1.5 N, #1.5P and #2.25-3 K per 100’ of row preplant.  Translated into an actual granular fertilizer #15 of 10-10-10 plus, #3 Potassium Sulfate.

In work done at the Penn State Southeast Research Farm, we’ve found that a 6“ in row spacing and 45-5’ between row spacing has worked well (2 plants per 12” pot).  We allow one fruiting node to form off of the main stem before pruning and trellis straight up.  In NY growers have told me that they plant on 12” spacings but leave 2-3 fruiting nodes per break from the main stem before pruning, and MN growers report using a 4” in row spacing with a single fruiting node.  MN growers also tell me that they trellis theirs at angles with each plant going opposite the next for better ventilation and sunlight capture.

Everyone uses a combination of tomato twine tied to purlins or cables, vine clips and vine wrapping to keep the vines vertical.  The vines must be pruned and trained weekly with the occasional second pruning and training during high growth times.

If direct seeding, apply MetaboliK SB at 3.2oz + PhytoGro Xtra at 2oz. per 10 gallons transplant solution for a great germination.  Add #.8 of 10-45-10 to the mix if transplanting to aid with rapid establishment.

Katrina CucumbersFertilization

There are two paths to providing the necessary nutrients to achieve high yields of superior quality fruit: 1) Pulse feeding 2-3 times per week based on a pounds per acre per day model.  And 2) Constant feed on a six days on, 1 day off model using a ppm-based program (the day off is to run clear water in order to minimize the buildup of excess salts).  Both ‘programs’ are below.  Tissue testing at least twice during the season is highly recommended, so your nutrient can be adjusted based on actual plant needs.

Test when the first flower bud is sighted and again as the first fruit is ready to harvest.  A good cucumber tissue sample consists of 2-25 leaves of the fifth leaf in from the growing tip with petiole collected from average plants.  Keep a special eye on Ca, Mg, and K levels as they are challenging to maintain and watch out of excessive levels of N.

Pulse Feeding: Cucumbers need approximately #.25-.3 N per acre per day.  There are 7,.260’ of cucumbers in a standard mulched acre.  Since cucumbers are generally planted on 12” centers, that gives us a per acre population of 7,260 plants.  As we are growing them indoors, lets convert this to 100’ of Row: #25N/72.6 (decimal equivalent of our planting size from an acre) = #.0035 N per 100’ per day.

Double these numbers if planting on 6” centers and triple them if planting on 4” centers.  We’ll work in 2 windows, ‘up until flowering’ and ‘after flowering’:

Pre flowering: We need #.0070N per 100’ per day.  Since we are splitting that between 28-16-7 and 10-20-20, each will provide #.0035N per day.  The math: .0035/.28 = .0125 lb. of 28-16-7 + .0035/.10 = .035lb of 10-20-20.  Grams are easier to work in at these low numbers, so .0125×454 (grams per pound) = 5.6g of 28-16-7 + 16g of 10-20-20 per day.  Multiply each by 3.5 days for a twice per week feeding and you get 11 grams of 28-16-7, plus 56 grams of 10-20-20 per twice per week feeding per 100’ of row.

Double these rates if working in soilless media and consider adding a pelleted, controlled release fertilizer at label rates to each pot that you reapply after 8-10 weeks.

Post Flowering: like tomatoes, peppers, watermelons, and muskmelons, cucumbers require plenty of K to develop properly and keep pushing development of new flowers.  Switch to 4-18-38 at the onset of flowering.

New formula: #.007 N per 100’ per day using 4-18-38, .007/.04 = #.175.  #.175 x 454 (grams per pound) = 80 grams per day.  80g x 3.5 = 280g of 4-18-38 per 100’ of row on a twice per week feeding program.

Constant Feeding: Here we are basing our nutrients on a ppm of N.  These needs change as the plants grow so we will build a schedule.  Zero week is right after transplanting or once the first true leaf has expanded for direct seeded plants.

Weeks from transplanting Desired ppm based on N Plant Food and amount per gallon of stock solution using a 1/100 proportional injector
0-2 weeks 75 50g 28-16-7 + 141g 10-20-20
3-4 weeks 150 100g 28-16-7 + 282g 10-20-20
5-6 weeks 200 950g 4-18-38 + 380g 10-20-20
7-8 weeks 200 4.2lb. 4-18-38 (2k)
90-10 weeks and beyond 200 4.2lb. 4-18-38 (2k)


SiMag 58 can be added directly into the fertigation stock tank along with the other fertilizers to maintain magnesium levels, assist with keeping potash levels up, and to provide silica to promote growth and also to aid in managing insects and diseases.  Add this to stock solutions at 1 tablespoon per gallon of stock solution or as indicated by tissue test results.  Once per week inject either CalStore or MetaCal at label rates separately from any P containing fertilizers to maintain Ca levels.

Pest Management

Major cucumbers pests include: cucumber beetles, spider mites, western flower thrips, aphids, powdery mildew and downy mildew.  Of these, vectoring of the bacteria that causes bacterial wilt by cucumber beetles is the most significant.  When growing outdoors we are forced to apply broad spectrum insecticides regularly to manage these pets.  Indoors we can apply screening to the inlets and rolled up sides to keep cucumber beetles out of the greenhouse.  Once you no longer have to apply broad spectrum insecticides, it is much simpler to run a biologically-based program.

Alternating Grandevo with Venerate and Met-52 provided us with a mite and insect-free environment.  Including the new ISP Silicon materials SiGuard and SiMag58 will greatly assist in preventing spider mites and thrips from reaching damaging populations.

Powdery Mildew (PM) and Downy Mildew (DM) are hazards in keeping a steady supply of cucumbers ripening.  A biological program consisting of Regalia – Actinovate – MetaboliK HV-1 applied 5 days apart will provide a good basis for disease prevention.  Being ready to add a PM or DM material to this program as seasonal conditions require can largely prevent these diseases.  In general, the insect/mite program/disease prevention program/foliar nutrient program are all compatible in tank mixes.  The first time you create a new blend, be sure to try it proportionally in a jar test, then apply it to a few plants, wait two days and see if any damage occurs.  Keep good notes on what works, and what doesn’t.


Harvest daily if possible.  Every other day harvesting will also work but expect some of the fruit will be oversize during ideal growing conditions.  Cut the fruit from the vines rather than pulling so as not to damage your carefully trained and trellised vines.  It’s also recommended to refrigerate if at all possible, for an extended storage life.

Be ready for loads of the highest quality cucumbers you’ve ever grown! They will be straight, blemish-free and absolutely delicious.

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