Blog search results for Tag: seedlings

Agrifood

Broad beans are an undemanding and valuable crop for all gardens. Probably originating in the Eastern Mediterranean and grown domestically since about 6,000BC, this plant was brought to Great Britain by the Romans.

Header image: a rich harvest of succulent broad beans for the table

Capable of tolerating most soil types and temperatures they provide successional fresh pickings from June to September. Early crops are grown from over-wintered sowings of cv Aquadulce. They are traditionally sown on All Souls Day on 2 November but milder autumns now cause too rapid germination and extension growth. Sowing is best now delayed until well into December. Juicy young broad bean seedlings offer pigeons a tasty winter snack, consequently protection with cloches or netting is vital insurance.

From late February onwards dwarf cultivars such as The Sutton or the more vigorous longer podded Meteor Vroma are used. Early cropping is promoted by growing the first batches of seedlings under protection in a glasshouse. Germinate the seed in propagating compost and grow the resultant seedlings until they have formed three to four prominent leaflets. Plant out into fertile, well-cultivated soil and protect with string or netting frameworks supported with bamboo canes to discourage bird damage.

SCIblog 8 March 2021 - Geoff Dixon - image of Young broad bean plants supported by string and bamboo canes

Young broad bean plants supported by string and bamboo canes

More supporting layers will be required as the plants grow and mature. Later sowings are made directly into the vegetable garden. As the plants begin flowering remove the apical buds and about two to three leaves. This deters invasions by the black bean aphid (Aphis fabae). Winged aphids detect the lighter green of upper foliage of broad beans and navigate towards them!

Allow the pods ample time for swelling and the development of bean seeds of up to 2cm diameter before picking. Beware, however, of over-mature beans since these are flavourless and lack succulence. Broad beans have multiple benefits in the garden and for our diets. They are legumes and hence the roots enter mutually beneficial relationships with nitrogen fixing bacteria. These bacteria are naturally present in most soils. They capture atmospheric nitrogen, converting it into nitrates which the plant utilises for growth. In return, the bacteria gain sources of carbohydrates from photosynthesis.

SCIblog 8 March 2021 - Geoff Dixon - image of Broad bean root carrying nodules formed around colonies of nitrogen fixing bacteria

Broad bean root carrying nodules formed around colonies of nitrogen fixing bacteria

Broad beans are pollinated by bees and other beneficial insects. They are good sources of pollen and nectar, encouraging biodiversity in the garden. Nutritionally, beans are high in protein, fibre, folate, Vitamin B and minerals such as manganese, phosphorus, magnesium and iron, therefore cultivating healthy living. Finally, they form extensive roots, improving soil structure, drainage and reserves of organic nitrogen. Truly gardeners’ friends!

Professor Geoff Dixon, author of Garden practices and their science (ISBN 978-1-138-20906-0) published by Routledge 2019.

Sustainability & Environment

Some plants such as lettuce require cool conditions for germination (<10 oC), a condition known as thermo-dormancy. This reflects the evolution of the wild parent species in cooler environments and growth cycles limited by higher summer temperatures. Transforming live but dormant seed into new healthy self-sufficient plants requires care and planning. The conditions in which seed is stored before use greatly affect the vigour and quality of plants post-germination. Seed which is stored too long or in unsuitable environments deteriorates resulting in unthrifty seedlings.

Aged seed

Aged seed

Seed is either sown directly into soil or into compost designed especially as an aid for germination. These composts contain carefully balanced nutrient formulae which provide larger proportions of potassium and phosphorus compounds which promote rooting and shoot growth. The amounts of nitrogen needed at and immediately post-germination are limited. Excess nitrogen immediately post-germination will cause over-rapid growth which is susceptible to pest and pathogen damage.

Minor nutrients will also be included in composts which ensures the establishment of efficient metabolic activities free from deficiency disorders. Composts require pH values at ~ 7.0 for the majority of seedlings unless they are of calicifuge (unsuited for calcareous soils) species where lime requirement is limited and the compost pH will be formulated at 6.0. Additionally, the pC will be carefully tuned ensuring correctly balanced ionic content avoiding root burning disorders. Finally, the compost should be water retentive but offering a rooting environment with at least 50 percent of the pore spaces filled with air. Active root respiration is essential while at the same time water is needed as the carrier for nutrient ions.  

Seedlings encountering beneficial environments delivering suitable temperatures will germinate into healthy and productive plants.

 Healthy seedlings

Healthy seedlings

Some plants such as lettuce require cool conditions for germination (<10 oC), a condition known as thermo-dormancy. This reflects the evolution of the wild parent species in cooler environments and growth cycles limited by higher summer temperatures.

Careful husbandry under protection such as in greenhouses provides plants which can be successfully transplanted into the garden. The soil receiving these should be carefully cultivated, providing an open crumb structure which permits swift and easy rooting into the new environment. It is essential that in the establishment phase plants are free from water stress. Measures which avoid predation from birds such as pigeons may also be required. 

Pigeon feeding

Pigeon feeding      

Netting or the placing of cotton threads above plants helps as a protection measure. Weeds must be removed otherwise competition will reduce crop growth and encourage pests and diseases, particularly slug browsing. Finally, the gardener will be rewarded for his/her work with a fruitful and enjoyable crop!