2016 SUMMER TOMATO TRIAL
CAN YOU GROW TOMATOES WITHOUT TOO MUCH FUSS?
• Last summer, the Auckland Botanic Gardens set out to investigate how best to grow tomatoes outdoors without blight, bugs and blossom-end rot ruining your crop. The Botanic Gardens actively avoid using sprays so one of the aims of their trial was to find out how much (if any) chemical intervention is required to get a great crop in Auckland‘s humid climate. • For the trial, 152 plants of 13 varieties were sown (in mid-August), grown on, and planted out (at the end of October) in trial beds prepared with 1 cup of biofert/m². The plants were spaced 80cm apart in rows running north to south, in full sun, and exposed to the prevailing wind. The laterals were removed and the plants were tied to supporting trellis. • Some plants were sprayed weekly with liquid copper, while control plants were not. However, last summer wasn‘t bad for blight and only one ‘Money Maker‘ plant in the trial was affected, so it was impossible to tell if the copper sprays made any difference. • Is liquid fertiliser worth it? No. Despite fortnightly applications of seaweed-based liquid fertiliser during the growing season, there was no noticeable difference to either yield or flavour. “An unnecessary expense,“the trial team concluded.
SMALL, MEDIUM & LARGE
• Of the 13 varieties chosen, five were cherry tomatoes, five were medium-sized and three were large meaty types.
• There wasn’t much variation in the weight or size of the cherry varieties, regardless of how they were grown, but ‘Sweet 100' and ‘Sweet Gold' produced the greatest numbers of tomatoes.
• Of the medium-fruited cultivars, ‘Juliet' had a significantly higher number of fruit but because they weighed less on
average, the other cultivars produced similar yields. The individual fruit of ‘Chef's Choice Orange' and ‘Early Money' were larger and heavier.
• Big isn’t always best. Of the three largefruited cultivars, ‘Country Taste' was the most prolific. The plants of ‘Beef Maestro' weren‘t particularly vigorous and were first to die back (before the end of the trial), causing their grades to slip! Meanwhile, ‘Marriage Big Brandy' didn't always live up to its name, with some plants producing juicy big whoppers while others yielded cherry-sized tiddlers. • If you’re impatient, note that there was a one-month difference between the earliest and latest varieties to ripen. ‘Sweet Gold' and ‘Gold Nugget' were quick to colour up, while ‘Beef Maestro' and ‘Marriage Big Brandy' came in last. This isn't unusual, as cherry tomatoes always ripen first. In general, cherry varieties seem to do better than other tomatoes.
TROUBLESHOOTING TIPS
• Transplant seedlings on a lean. Instead of planting them with their stems upright, set them into the soil on a 45-degree angle, with half the stem below the soil surface. This encourages extra aerial roots off the stem, anchoring them more firmly in the soil and thus providing better support during the growing season.
• To beat blight and mildew, plant in an open, breezy spot. Remove lower leaves in midsummer, use soaker hoses and keep the roots cool with mulch. Healthy plants are more pest- and disease-resistant.
• Crop rotation is important. If you‘ve had problems before, find a new spot for your tomatoes each year, or grow them in planter bags or containers of fresh soil.
• Possums a pest? Use foliar fish fertiliser. They hate the smell. It also keeps whitefly away from tunnelhouse tomatoes.
• Blossom end rot (when a sunken patch of rot appears at the base) is symptomatic of a calcium deficiency, but inconsistent watering is the cause, as a lack of water stops calcium flowing through the plant to the ends of the fruit. Don‘t let the soil (particularly in pots) dry out; daily watering is better than a once-weekly downpour. Also, hose in granular fertiliser thoroughly. Blossom end rot is more prevalent early in the season and affects individual fruit rather than the whole plant. Pick them off.
• The tomato/potato psyllid looks like a tiny cicada. It sucks sap and transmits pathogens that weaken host plants, leading to yellow foliage, stunted growing tips and leaves that look cupped or curly. The flowers can drop and the fruit that follows is often small. Psyllid populations peak in late summer; they can knock out 7-8 generations in a single season. Hang sticky traps or try neem oil as insecticides will also take out pollinating bumblebees and natural predators such as hoverflies and steely blue ladybirds. Physical barriers work, such as a frame covered in fine insect mesh, though you will have to hand pollinate your plants once fully enclosed.
• Stinky green shield beetles suck beans and tomatoes dry. I‘ve learned to live with them, but if you‘ve found a cunning solution, we‘d love to hear it. Email your tips to mailbox@nzgardener.co.nz. ✤