Dec. 16, 2018
PollinationThe chief pollinator of guavas is the honeybee (Apis mellifera). The amount of cross-pollination ranges from 25.7 to 41.3%.
ClimateThe guava thrives in both humid and dry climates. In India, it flourishes up to an altitude of 3,280 ft (1,000 m); in Jamaica, up to 3,906 ft (1,200 m); in Costa Rica, to 4,590 ft (1,400 m); in Ecuador, to 7,540 ft (2,300 m). It can survive only a few degrees of frost. Young trees have been damaged or killed in cold spells at Allahabad, India, in California and in Florida. Older trees, killed to the ground, have sent up new shoots which fruited 2 years later. The guava requires an annual rainfall between 40 and 80 in (1,000-2,000 mm); is said to bear more heavily in areas with a distinct winter season than in the deep Tropics.
SoilThe guava seems indiscriminate as to soil, doing equally well on heavy clay, marl, light sand, gravel bars near streams, or on limestone; and tolerating a pH range from 4.5 to 9.4. It is somewhat salt-resistant. Good drainage is recommended but guavas are seen growing spontaneously on land with a high water table-too wet for most other fruit trees.
PropagationGuava seeds remain viable for many months. They often germinate in 2 to 3 weeks but may take as long as 8 weeks. Pretreatment with sulfuric acid, or boiling for 5 minutes, or soaking for 2 weeks, will hasten germination. Seedlings are transplanted when 2 to 30 in (5-75 cm) high and set out in the field when 1 or 2 years old. Inasmuch as guava trees cannot be depended upon to come true from seed, vegetative propagation is widely practiced.
In Hawaii, India and elsewhere, the tree has been grown from root cuttings. Pieces of any roots except the smallest and the very large, cut into 5 to 10 in (12.5-20 cm) lengths, are placed flat in a prepared bed and covered with 2 to 4 in (5-10 cm) of soil which must be kept moist. Or one can merely cut through roots in the ground 2 to 3 ft (0.6-0.9 m) away from the tree trunk; the cut ends will sprout and can be dug up and transplanted.
By another method, air-layers of selected clones are allowed to grow 3 to 5 years and are then sawn off close to the ground. Then a ring of bark is removed from each new shoot; root-inducing chemical is applied. Ten days later, the shoots are banked with soil to a height 4 to 5 in (10-12.5 cm) above the ring. After 2 months, the shoots are separated and planted out.
Pruned branches may serve as propagating material. Cuttings of half-ripened wood, 1/4 to 1/2 in (6-12.5 mm) thick will root with bottom heat or rooting-hormone treatment. Using both, 87% success has been achieved. Treated softwood cuttings will also root well in intermittent mist. In Trinidad, softwood, treated cuttings have been rooted in 18 days in coconut fiber dust or sand in shaded bins sprayed 2 or 3 times daily to keep humidity above 90%. Over 100,000 plants were produced by this method over a 2-year period. Under tropical conditions (high heat and high humidity), mature wood 3/4 to 1 in (2-2.5 cm) thick and 1 1/2 to 2 ft (45-60 cm) long, stuck into 1-ft (30-cm) high black plastic bags filled with soil, readily roots without chemical treatment.
In India, air-layering and inarching have been practiced for many years. However, trees grown from cuttings or air-layers have no taproot and are apt to be blown down in the first 2 or 3 years. For this reason, budding and grafting are preferred.
Approach grafting yields 85 to 95% success. Trials have been made of the shield, patch and Forkert methods of budding. The latter always gives the best results (88 to 100%). Vigorous seedlings 1/2 to 1 in (1.25-2.5 cm) thick are used as rootstocks. The bark should slip easily to facilitate insertion of the bud, which is then tightly bound in place with a plastic strip and the rootstock is beheaded, leaving only 6 to 8 leaves above the bud. About a month later, an incision is made halfway through 2 or 3 in (5-7.5 cm) above the bud and the plant is bent over to force the bud to grow. When the bud has put up several inches of growth, the top of the rootstock is cut off immediately above the bud. Sprouting of the bud is expedited in the rainy season.
At the Horticultural Experiment and Training Center, Basti, India, a system of patch budding has been demonstrated as commercially feasible. A swollen but unsprouted, dormant bud is taken as a 3/4 x 3/8 in (2 x l cm) patch from a leaf axil of previous season's growth and taped onto a space of the same size cut 6 to 8 in (15-20 cm) above the ground on a 1-year-old, pencil-thick seedling during the period April-June. After the bud has "taken", 1/3 is cut from the top of the seedling; 2-3 weeks later, the rest of the top is cut off leaving only 3/4 to 1 1/4 in (2-3.2 cm) of stem above the bud. This method gives 80 to 90% success. If done in July, only 70%. In Hawaii, old seedling orchards have been topworked to superior selections by patch budding on stump shoots.
CultureGuava trees are frequently planted too close. Optimum distance between the trees should be at least 33 ft (10 m). Planting 16 1/2 ft (5 m) apart is possible if the trees are "hedged". The yield per tree will be less but the total yield per land area will be higher than at the wider spacing. Some recommend setting the trees 8 ft (2.4 m) apart in rows 24 ft (7.3 m) apart and removing every other tree as soon as there is overcrowding. Where mass production is not desired and space is limited, guava trees can be grown as cordons on a wire fence. Rows should always run north and south so that each tree receives the maximum sunlight. Exudates from the roots of guava trees tend to inhibit the growth of weeds over the root system.
Light pruning is always recommended to develop a strong framework, and suckers should also be eliminated around the base. Experimental heading-back has increased yield in some cultivars in Puerto Rico. In Palestine, the trees are cut back to 6 1/2 ft (2 m) every other spring to facilitate harvesting without ladders. Fruits are borne by new shoots from mature wood. If trees bear too heavily, the branches may break. Therefore, thinning is recommended and results in larger fruits.
Guava trees grow rapidly and fruit in 2 to 4 years from seed. They live 30 to 40 years but productivity declines after the 15th year. Orchards may be rejuvenated by drastic pruning.
The tree is drought-tolerant but in dry regions lack of irrigation during the period of fruit development will cause the fruits to be deficient in size. In areas receiving only 15 to 20 in (38-50 cm) rainfall annually, the guava will benefit from an additional 2,460 cm (2 acre feet) applied by means of 8 to 10 irrigations, one every 15-20 days in summer and one each month in winter.
Guava trees respond to a complete fertilizer mix applied once a month during the first year and every other month the second year (except from mid-November to mid-January) at the rate of 8 oz (227 g) per tree initially with a gradual increase to 24 oz (680 g) by the end of the second year. Nutritional sprays providing copper and zinc are recommended thrice annually for the first 2 years and once a year thereafter. In India, flavor and quality of guavas has been somewhat improved by spraying the foliage with an aqueous solution of potassium sulfate weekly for 7 weeks after fruit set.