Lesson 4 - Flowers, fruits and seeds
The vegetables in this group include those with edible flowers or buds, such as broccoli, cauliflower or globe artichokes; the many fruit-bearing plants, particularly cucurbits (pumpkins, cucumbers, etc.) and those in the Solonaceae family (capsicums, tomatoes, chillies, eggplant); and the seed-bearing vegetables, including legumes (peas, beans) and sweet corn.
For the edible flowering vegetables let’s look in detail at one example, a plant that’s easy to grow and has multiple uses in the kitchen – Broccoli (Brassica oleracea var. italica). Widely grown widely across Australia but cultivated in the Mediterranean for many hundreds of years, modern forms of broccoli were bred and selected in Italy – hence the reference in the botanical name (var. italica). Grown for its dense, edible heads of small, multiple flower buds, there are three main types of broccoli: ‘heading broccoli’ producing large central heads of compact buds; ‘sprouting broccoli’ with many smaller side florets or heads; and broccolini, a hybrid between traditional forms of broccoli and Chinese broccoli. Within these types there are many different names cultivars, the most common being ‘Calabrese’ the compact head found in most supermarkets. Some of the sprouting broccoli cultivars are purple in colour, adding an interesting dimension to the garden when growing. Then there is the beautiful ‘Romanesco’, which grows into a stunning, almost conical head of lime-green florets arranged in a rising spiral pattern.
It is a vegetable best planted as seedlings during autumn and winter, although if growing in warmer climates make sure you choose a ‘heat tolerant cultivar, as some tend to bolt under these conditions. In southern areas of Australia, growing broccoli over the cooler months helps reduce problems with pests, including Cabbage White Butterfly. Like many other vegetables, broccoli seedlings should be planted in rich, well-drained soils with full sun. Individual plants have very large leaves, so generous spacing, ideally 25-60 cm, between individuals is recommended, depending on the cultivar. This also helps air circulation around the plants and increases the production of side shoots. Broccoli will take between 10 to 14 weeks to harvest from planting, although sprouting broccoli can be harvested a little earlier than this. If growing central head types, harvesting the main stem results in the multiple side shoots for many weeks, while this happens normally for sprouting types, although early harvesting promotes more shoots to develop. Always keep an eye on pests as they can be problematic as the crop matures, particularly Cabbage Aphids and Cabbage White Butterfly. These insects can sometimes be very difficult to see in the tight, compact heads of broccoli and are particularly problematic over warmer months.
Diggers tip
We recommend you use a fine, insect-proof net over your brassica plants to eliminate problems with Cabbage Aphids and Cabbage White Butterfly. Alternatively, use an organic spray like Neem oil which is extracted from the seeds of the Neem tree (Azadirachta indica). However, if you are gardening organically you will attract aphid predators like Ladybirds and Lacewings, Wasps and Praying Mantis.
There are many fruit-bearing vegetables that we could look at in detail in this lesson, particularly those found in two large and diverse plant families – Cucurbitaceae and Solonaceae. Cucurbitaceae, referred to as the squash or gourd family, includes vegetables such as pumpkins, cucumbers, zucchini and squash, as well as melons and watermelons. The Solonaceae family is often known as the nightshade family and includes many ornamental and productive plants, as well as some that have poisonous or toxic properties, such as Tobacco and Datura. There are many common vegetables in this family, including capsicums, chillies, eggplant and potatoes; in this lesson, we will look at one of the most popular crops – tomatoes
There are two main ‘types’ of tomatoes – determinate and indeterminate. Determinate tomatoes are bushy, more compact and grow to a maximum (‘determinate’) height, making them ideal for small spaces and containers. Many gardeners don’t bother with regular pruning of lateral shoots and while they benefit from some level of staking or support, they don’t need as much as indeterminate tomatoes. The fruit tends to ripen at the same time, making them excellent choices for preserving. Examples include ‘Roma’ 'Principe Borghese' and ‘Tiny Tim’. The more common type are indeterminate tomatoes which have a vine-like growth habit, often becoming quite vigorous once established. They require good support structures, as well as regular pruning and tying as the plants grow. Many gardeners use strong metal trellising or lattice to support plants, installing this in the bed before planting. Pinching the leading shoot to a maximum height and removing some side laterals as the plants develop makes them easier to manage, increases individual fruit size and improves air movement and light access. Indeterminate tomatoes tend to mature a little later than determinate types and are very productive but ripen over a long period, potentially for several months, even as the weather cools. Examples include ’Grosse Lisse, ‘Amish Paste’, ‘Black Cherry’ and ‘Green Zebra’
Aside from categorising tomatoes on their growth and form (determinate vs. indeterminate), we can also classify them based on their fruit shape (e.g. ‘beefsteak’, ‘plum’, ‘grape’, ‘cherry’), whether they are heirloom or hybrid cultivars. Heirloom tomatoes are those that have been grown by gardeners for many decades mainly for fruiting traits (colour, flavour, shape) and are ‘open pollinated’ meaning they come true to type when grown from seed. Hybrid tomatoes are those that have been developed by deliberately crossing different plants to produce a new cultivar with specific characteristics, such as disease resistance, larger fruit or reduced size. To grow new hybrid tomatoes each year you need to purchase new seeds, they will not grow ‘true-to-type’ from any collected seed.
Tomatoes need sunny and warm conditions to grow well. The ideal temperature range for growing tomatoes is around 18 to 28°C during the day and nighttime temperatures above 13°C. Temperatures below 10°C can slow their growth and of course frost can even kill plants outright. It’s a good idea to plant once the risk of frost has passed, which will be October-November in most southern states. Hot weather, particularly temperatures above 32°C for extended periods, can lead to heat stress and sun scorch in tomatoes. Providing some shade can help alleviate these problems.
It's best to plant tomatoes as seedlings into well-prepared beds with a soil pH that is slightly acidic (pH 5.5-6.5). Determinate tomatoes tend to be spaced 40-60 cm apart, while indeterminate tomatoes need, sometimes 70-90 cm apart. Don’t be afraid to plant the seedlings deep, this can lead to 2-3 additional leading shoots and provided these are then trained and managed they will be very productive. Most plants will begin to produce fruit within 60 to 100 days from planting, with smaller, determine tomatoes being the earliest and larger fruiting cultivars taking much longer. Make sure you keep tying tomatoes as they grow and particularly as the fruit develops, the weight of the which can sometimes cause stems to snap. In southern climates tomatoes start to ripen from January and continue into April and even May.
Diggers tip
How do you remember which is a determinate and which is an indeterminate tomato?
Determinate tomatoes are determined to grow on their own! While indeterminate tomatoes need a little guidance on how to grow.
The final group of vegetables in this lesson are also fruits, but it’s not the fruit or fleshy part of the plant that we eat, rather the edible seeds such as corn, peas and beans. Peas and beans are legumes in the family Fabaceae and are among the earliest of domesticated plants with a cultivation history extending back thousands of years. High in protein, legumes include staples such as lentils and soybeans, as well as other common edible plants such as peanuts and chickpeas. In this lesson we will look at a very common legume – beans (Phaseolus vulgaris).
Like other vegetables, there are many different types of beans and categorising them is a way to better understand them. Some beans are categorised around the properties of the bean pod and how they are used, such as ‘stringless’ beans, wax beans and dry beans. However, in terms of cultivation there are two main groups of beans as vegetables – bush or dwarf beans and climbing or pole beans.
Bush beans are annuals that grow into a short, bushy plants not requiring any support to grow them successfully. They are grown over warmer months in temperate climates, reaching to between 30 and 60 cm in height at maturity. The seed should be sown directly into prepared beds, in fertile, well-drained soils with a neutral pH. Beans have nutritional needs that are a little less than many other vegetables. As a legume, beans can fix atmospheric nitrogen on their roots through a symbiotic relationship with bacteria (Rhizobium sp.), so go easy on the addition of nitrogenous fertilisers before planting and as they grow. There is something thrilling about bean seedlings germinating one to two weeks after sowing, their cotyledons appearing first, followed by large and distinctive true leaves. The plants should be spaced to 10-20 cm between plants after germination, depending on the cultivar. Most bush beans will take 50-60 days to harvest from sowing with regular picking of the young pods encouraging greater productivity.
Diggers tip
Many gardeners use successional sowings of bush beans every few weeks to extend the harvest over several months. Examples of Diggers cultivars include ‘Baby Sun’ and ‘Stringless Pioneer’
The other main type of bean is a climbing bean or pole bean. Climbing beans are twining climbers or vines that need a support structure to manage their growth and ease of harvest. The support structure should be around 2 metres high and well-fixed to the ground as climbing beans can be extremely productive when they start cropping. Examples include tripods, trellis systems and A-frame structures made from timber, bamboo, wire mesh or steel. The structures enable beans to grow vertically, maximizing light and air circulation, ensuring better yields. Some in this group as annual plants, meaning they need to be replaced each year, examples include ‘Blue Lake’ and ‘Purple King’. Others are perennials that can grow in the same location for 3-5 years, the best example being the beautiful Scarlet runner bean (Phaseolus coccineus).
Climbing beans should be in rows around 1 m apart with plants spaced to 15-20 cm and will start to produce a crop 60-90 days after sowing. As plants reach the top of the support structure, it’s a good idea to pinch out the tips to promote lower lateral stems. Climbing beans tend to be much more productive than bush beans, but like them, regular picking of the pods every few days stimulates the development of more pods.
Diggers tip
Some climbing beans are perennials that can grow in the same location for 3-5 years, the best example being the beautiful Scarlet runner bean (Phaseolus coccineus).