Growing Conditions for Gladioli
are not fussy about and will succeed in almost any position, but to obtain the best results plant them in an open, sunny position where there is a fair depth of good top-soil that contains plenty of humus. Purely organic fertili-zers such as bone meal are better than artificial fertilizers. Gladioli like a reasonable amount of moisture at their roots during the whole of the growing period, but good drainage is essential so that the soil does not become sour and waterlogged.
PREPARATION OF THE SITE
Prepare the site in much the same way as for a vegetable crop. In the autumn, or as long before planting as possible, dig one spit deep and turn in a good dressing of decayed animal manure or rotted, and bone meal, leaving the surface rough after digging, particularly if the soil is heavy. In the winter, if the soil is deficient in lime, throw on a dressing of lime and work it into the top few inches, or, if the land is heavy, give it a dressing of old soot. Do not use both soot and lime in the same year.
Gladioli can be planted from March until the end of May, the exact time depending mainly on the locality, and particularly on the weather and state of the soil.
If theare to be grown for exhibition or cutting, plant them in rows. Draw drills with a hoe or trowel 18 in. apart and 4 in. deep in heavy soil or 5 in. deep in light soil. Set the corms in the drills, allowing 6 in. between the corms.
Plant the gladioli in rings or clumps of 5 to 7 corms if they are to be grown mainly for garden decoration. They can also be massed in beds and borders, in conjunction with a dwarf carpeting plant.
Keep the site free ofby hoeing.
DEVELOPMENT AND PROPAGATION
After the corm has been planted growth starts almost immediately, not only from a bud or buds at the top of the corm but also from the circular root-scar at the base. Just before the flowering stem appears a new corm starts to form at the base of the stem, immediately above the old corm, while a fresh root system develops between the base of the new corm and the top of the old one. Soon afterwards tiny cormlets on short stems begin to form and cluster round the base of the new corm. A few weeks after flowering the leaves start to go brown and die. The new corm will then be fully developed and the old corm shrivelled.
The development from bulblets after planting is similar, except that the new corms produced are larger than the original bulblets planted. They rarely produce a flower spike the first season, but many will flower in the second year. Propagation from seed follows much the same pattern. Small corms are produced during the first season, but flowers are not borne for at least 2 years.
Gladioli grown from corms and bulb-lets come true to the type and colour of the variety which produced them, but those produced from seeds are never true to colour and sometimes not even true to type.
The time of flowering varies widely according to the variety, but most catalogues indicate whether gladioli are ‘early’, ‘mid-season’ or ‘late’ flowering, so that a long flowering period can be planned if the varieties are carefully chosen.
If sprouted corms are planted at the normal time they will bloom appreciably earlier than unsprouted corms of the same varieties. To sprout gladioli, carefully peel off the brown outer skin of the corms in February or early March, and stand them close together in trays on the bench of a warm greenhouse. Keep the corms quite dry and soon the buds will start to swell and shoots push upward.
In exposed positions the large-flowered type will sometimes be blown over unless it is staked. If the gladioli are to be exhibited provide a stake or cane for each spike. If separate stakes are used for individual plants, make sure that the ties are loose round the stems to allow for growth and to enable the ties to slide up the stakes as the spikes develop. When the plants are in rows it is usually sufficient to provide stakes at intervals along each row, and to connect the stakes with stout string passed along each side of the plants. Staking is unnecessary for most of the other types of gladioli, particularly the primulinus hybrids.
WATERING AND FEEDING
Undue dryness of the soil at any time during the growing period can cause a check and thus jeopardize results. If the soil is really dry, start watering in late May. Give the plants a good soaking so that the water penetrates beyond the roots, and then, no matter what dry weather may follow, the plants need only be watered every 10 to 14 days.
Feeding is not necessary for gladioli grown for garden decoration or cutting if the soil has been liberally prepared. If they are to be exhibited, start giving the plants a mild feeding just before the flower spikes appear. A feed of old-fashioned liquid manure and soot water diluted to the colour of lager beer is recommended. If other feeding agents are used, make sure that they are organic rather than artificial, and that they are well watered in if used in powder form. Give the plants mild doses not more frequently than once a fortnight.
CUTTING THE FLOWERS
The best time to cut a spike is when the bottom floret is about half open, as the spike will then open fully in water and possible damage to the petals by wind and rain will be avoided. The flowers must be cut carefully, because when they are ready for cutting the new corms are only half developed, and drastic damage to the leaves will jeopardize future growth. Insert the blade of a sharp penknife through the flower stem, 4 to 6 in. above the ground, then, holding the bottom of the stem firmly with one hand, give the flower spike a gentle downward twist with the other. The spike will snap and can be gently drawn from its sheath of leaves without injuring them.
LIFTING AND STORING
In exceptionally mild winters gladioli corms will survive in the soil, but the risk is considerable. It is wise to lift the plants in the autumn when growth has stopped and the foliage starts to turn brown. Lift the plants carefully with a fork, removing the surplus soil and cutting off the growth about half an inch above the new corms. Leave them in a dry, airy place, like a potting-shed or greenhouse, and when they are perfectly dry store them in a place which is frost-proof as well as dry and airy. During the winter or early spring clean the plants by breaking off the old wilted corms at the base and removing the bulblets. Make certain at each stage that both corms and bulblets are kept in their separate varieties and correctly named.
It has been proved conclusively that the old method of lifting and keeping the stems and foliage intact until they are dried off and cleaned encourages the spread of disease. Damp storage will also cause disease to spread rapidly.
DISEASES AND PESTS
The chances of disease are slight as long as the advice given on lifting and storing is followed. If the foliage of one or two plants yellows prematurely during the growing period, lift these plants and burn them at once to prevent the trouble from spreading.
Few pests attack gladioli, but if there is a risk of wireworms or leather-jackets, which will mutilate the corms, dress the gladiolus site with a good soil fumigant a few weeks before planting.
These tiny black insects have, during the last few years, become unusually troublesome. The symptom of a thrips attack is the silvering of the foliage and petals, which is often mistaken for disease. If the attack is severe the flower buds may shrivel and fail to open. Check the thrips by spraying or dusting the plants every 3 weeks with malathion. Thrips have a habit of wintering on the corms, just underneath the brown outer skin, so after lifting and drying, sprinkle the corms with Gamma B.H.C. before finally storing them.