Botanical notes

Plants are grouped into Families according to the structure of their flowers, fruit and other distinguishing factors, for example leaf arrangements, even chemicals they produce. So why are plant families important to the vegetable grower? Well, if you’re following a rotation system it is necessary to know what family your vegetables belong to. It is also useful, for the same reasons, to know which family your weeds belong to as well.

The reason for using a rotation system is to avoid pests and diseases specific to certain crops that would build up in the soil if you grew the crop in the same position every year. Some families are beneficial to the soil, such as the legumes (pea and bean family) which have a mutually beneficial relationship (symbiotic) with a species of bacteria, Rhizobium that fixes atmospheric nitrogen in nodules it forms on the host’s roots (hence the common advice when removing legumes to leave the roots behind in the soil). This nitrogen is then available for the host plant (the bacteria gets a place to live!) and if you leave the roots in the ground the following crop also benefits. Most of the common vegetable plants we grow are just in a few families:

• Solanaceae –potato, tomato, sweet pepper, chilli and aubergine (and many more)
• Brassicaceae (Cruciferae) –cabbage, broccoli, Brussel sprouts, kale, mustard and radish
• Cucurbitae-squash, pumpkin, marrow, courgette and cucumber
• Liliaceae- onion, garlic, leek, chives,shallots ...and lilies!
• Leguminosae- peas, beans and many green manures such as clover
• Apiaceae or Umbelliferae- carrot, parsnip, parsley, dill, celery, fennel, angelica..lots of other herbs and spices.

Of course these families are also represented on our plots as weeds. These may harbour pests and diseases from one season to the next providing a host while the vegetable plant is absent so it is useful to know what families your weeds belong to as well.

Jude Ongeri