Growing seed for harvest 2: Beans, corn and tomatoes

Organic NZ Magazine: September/October 2005
Section: Farming and Horticulture
Author: Annie Wilson and Colin Walker

In the second of our series, Colin Walker of the Koanga Institute talks to Annie Wilson about saving heritage seed.

Now is the time to be organising the planting of the main summer crops. Here we will discuss saving the seed of three of those crops: beans, corn and tomatoes.



The first variety is Phaesolus coccineus or runner bean, a perennial which will last many years in the ground if regularly fertilised with well rotted compost. The classic that we all know is Scarlet Runner, a New Zealand staple, but the Koanga collection has others including White Butterfly, Black Seeded Runner and Sutton’s Giant. These beans are distinct with their large flowers and huge seeds.

Runner beans will cross pollinate in New Zealand with other coccineus types. Therefore if you want to save them for seed you can only grow one type in one garden area. Distances for cross pollination vary, but one kilometre between crops is generally considered safe.

You can, however, grow coccineus in the same area as Phaesolus vulgaris – bush or climbing beans, without them cross pollinating. Beans that climb are not necessarily what we call runner beans. It is important to distinguish between runner beans which will cross pollinate and climbing or bush beans which are self fertile and so will not cross pollinate.

Planting should begin in October in the north and whenever the soil is sufficiently warm elsewhere (15 degrees Celsius). Heritage climbing varieties come in a myriad of colours and flavours and include Bob’s and Yugoslavia (both shellout beans), Borlotti Stoppa, Dalmatian, King George, Purple Pod and Selugia, Emu, Blue Lake Runner, Gila Indian, Bosnia, Short Swiss, American, Westlandia, Africa, English Climber and Market Wonder.

The home garden is the perfect place to save beans for seed because picking the crop continuously for eating encourages more beans to grow, so you produce a larger seed bank.

Never take the first set for seed, and preferably wait until mid-season to start selecting. Twenty plants are needed for saving seed long-term (ten years and beyond) but for the short term (4–10 years) six plants will be sufficient. Choose beans that are large and strong, with the characteristics you prefer, avoiding any plants that may have disease.

Leave the bean on the vine and allow it to dry out completely before harvesting. A very rainy growing season could bring on mould within the seed pod, so check regularly, and bring in the pods to dry inside if there is a threat. Store in a labelled envelope in a cool dry place.

Broad beans are a separate variety – Vicia faba – and will cross pollinate, so grow only one variety at a time. Koanga have several varieties including Giant Windsor originally from Southland, and Sutton’s Dwarf whose compact growth makes it an excellent choice in windy areas. Red Seeded from the Nelson area keep their colour even when cooked, and Scottish, which came to New Zealand around 1863, have been growing in Southland successfully ever since. Broad beans are preferably planted in August in the North, but in the two southern zones they should have been planted in the Autumn.



Corn or Zea mays is more of a challenge for the home gardener since large quantities are needed to maintain genetic strength. It is an annual, pollinated by wind, so growing it in an area where maize is grown for stock feed should be avoided. On a small farm you need to grow a minimum of 500 plants for adequate cross pollination, so that 50–100 of the best corn cobs can be kept. They should be planted on a 30cm grid for best results.

Let the cob fully dry on the plant until the kernels are starting to indent or dry. This should be 3–4 weeks beyond the eating stage. In a very wet climate the stalk can be bent over, so that the sheath protects the seed within. This is done in South America in wet seasons. Once you have harvested, continue to dry the cobs indoors for another month.

When shucking the corn, the smaller seeds up to 2cm from both ends of the cob should be discarded as these do not produce good plants. Heritage varieties available include: Golden Bantam, Early Gem, Kaanga Ma, and Red Yellow Maize. There are also varieties from the Americas including Blue Hopi, a flour corn, Black Navaho, Rainbow Inca, Miniature Black Popping and Hokianga Corn, a flintcorn.



The tomato, Lycopersicon lycopersicon, is an annual plant, although a perennial in its native South America. It is self fertile and won’t cross. Some old varieties have shown a tendency to, but we have largely bred them not to. They are very flexible and fruit can be harvested for seed any time they mature, except for fruit from the first truss produced, since seed from this is genetically unstable. Choose for size and flavour, from disease-free plants, and allow the fruit to ripen on the vine.

The best way to process tomato seed is to follow the path taken in nature whereby the fruit gets wet and starts to ferment. Scoop out the seeds and pulp of the tomatoes you have selected and put in a jar with an equal amount of warm water. Screw on the lid (in order to contain the smell) and leave for 3–6 days depending on the temperature.

The mix should be fermenting strongly with white growth visible. Pour the mixture into a sieve and rinse well, leaving seed only. Dry on a plate or screen on a windowsill for 1–4 days. Seed can then be stored in a cool dry place for up to a year. Airtight containers should be avoided unless you are certain seed is really dry. A desiccant should be added otherwise.

The varieties of open pollinated tomato available are too numerous to mention here, but suffice to say they are superior in every way to the modern F1 hybrids that are bred for shelf life and uniformity of size and production. Choose a tomato that thrives in your particular area, for your particular needs. Cherry tomatoes for kids for example, beefsteak varieties for sandwiches, roma types for sauces and relishes, and all the rest for those salad days!

Curcubits (zucchini, pumpkin, cucumber etc.) should also be planted in the next while, and we will discuss saving their seed in the next issue.