A warm-colour spectacle in the summer garden: the Mexican sunflower sends up vigorous stems to 150 cm, crowned with red-orange flowers that draw pollinators from the whole neighbourhood.
About the variety. An extraordinarily robust annual, tolerant of drought and intense heat. The flowers attract bees and beneficial insects in great numbers. Tall stems may benefit from staking in windy spots.
Itinerário técnico
Como cultivar mexican sunflower?
Um guia de cultivo passo a passo, da sementeira à colheita.
pH ideal 6.0 to 7.5Temperatura ideal 18 to 28 °CCompasso 30 to 45 cm in the row, 40 cm between rows
Sementeira
Sow in trays on the surface, covering with only a very thin layer of soil, six weeks before the last frosts, or direct where it is to grow once the soil is above 12 °C, and plant or thin to forty five centimetres. Germination takes seven to ten days. Protect the sowing from birds and rodents with netting, because the seed is a tempting target and vanishes within hours. This variety reaches 150 centimetres or more in height, so choose a sheltered spot and put the stake in at planting time: fitting a support to a grown plant breaks roots and branches.
Solo
It adapts to almost any soil as long as it is deep and free draining, at a pH between 6.0 and 7.5. The root goes down a long way, which is why it stands drought well. It does not need rich soil, but the giant varieties appreciate compost in the planting hole.
Clima
It wants full sun and heat, between 18 °C and 28 °C. It resists drought and strong heat, which makes it an easy crop inland in Iberia. The main problem is wind: tall plants go over easily, so plant somewhere sheltered or stake the giant varieties. Inland in Portugal and Spain heat rather than cold is the limiting factor: in weeks above 35 °C the plant stalls and light shade over midday pays for itself. Where summers are short, always choose the shorter cycle varieties and start them early in a heated tray. In Italy it is an easy crop: in the centre and south plant from April onwards and the only real care is light shade through the July and August heat; in the Po valley and the north wait for the late frosts to pass and pick the sunniest spot you have. Sow only once nights stay above 10 °C: a sowing in cold soil rots or comes up thin, and nothing is gained by rushing. It flowers late, from August on, and keeps going until the first frosts: in short summer regions it only pays when started in trays.
Fertilização
Its needs are moderate. One to two kilos of mature compost per square metre worked in before sowing covers most of the cycle. If the leaves pale, one watering with a balanced liquid organic feed halfway through is enough. Never use fresh manure, which burns roots and encourages disease.
Rega
Water regularly for the first weeks, then less often but deeply so the root goes down. Step it up at flowering, the phase of greatest need. Once established it is remarkably drought resistant.
Controlo de Infestantes
Hand weed in the first weeks, while the plant is small and loses every contest for light and water. Once it is established, mulch with five to seven centimetres of straw, dried grass or leaves: it holds weeds back, keeps moisture in and stops rain splashing soil onto the lower leaves, which is how most diseases begin. Always hoe shallowly so you do not cut the roots running just under the surface.
Controlo de Pragas
Birds eat the seed at sowing: cover it well or protect with netting; the heads are small and need no bagging. Aphids and thrips attack the young leaves. Slugs eat the seedlings. Against them, sow a little thicker and thin later, or protect with an ash barrier until the plant has four leaves. Head caterpillars bore into the centre in hot years.
Doenças
Downy and powdery mildew affect the leaves in humid conditions. Sclerotinia rots the stem and head and is the most serious disease, favoured by wet soil and short rotations. Rust makes orange pustules. Water at the base and never over the foliage, and space the plants well so air moves through: nearly all these diseases start with wet leaves. Use a four year rotation and do not repeat sunflower in the same bed.
Colheita
Cut the flowers early in the morning with a long stem, as the head is opening: it lasts well in the vase and the plant answers cutting with more flower. It is not grown for seed and has no fleshy head like a sunflower: if you want seed, let a few flowers dry on the plant and collect the small achenes once the receptacle is dry and brittle. Deadhead regularly and it flowers until the first frosts. The reference colour is orange.
