50 years: sweet pea.
The credit runs: We are indebted for much of the preceding information to Leonard Yager, Extension Horticulturalist, Montana State College, Bozeman, Montana.
The sweet pea is a specialist's flower. It is a member of the legume family in which belong the garden peas, beans, alfalfa, and clovers. Except for the bean, these plants are more or less cool season in their needs.
The sweet pea specialist emphasizes the importance of good soil preparation for successful culture of this flower. Good drainage is essential. Dig the soil deeply, and add a generous amount of well-rotted manure or compost into the soil at digging time. Use commercial fertilizers with compost or manure. Apply these in drills on either side of the seed row at the time of sowing the seed, and at the same depth as the seeds.
Sow seed in early spring as soon as the ground can be prepared. Fall sowing also is satisfactory. Also you can start seed a month to 6 weeks before setting out plants by sowing in 3 to 4" (7.5 to 10 cm) pots. Set potgrown seedlings out after danger of hard frosts fire past. Avoid growing pot-grown seedlings in high temperatures as they may grow too weak and spindly.
Some sweet pea seeds are difficult to germinate. Cut off the seed coat opposite the growing point with a sharp knife. This will aid germination. Some growers place their seeds 1/2" (12.5 mm) deep in moist sand and transplant them in a week's time to flower pots and set out the small plants.
If the seeds are sown directly outdoors, sow seed in drills about 1/2" (12.5 mm) deep. Some growers advocate deeper sowing but no advantage is seen in this. Sow thinly, and later thin so the plants are about 6" (150 mm) apart. Wider spacing is recommended for the grower who is interested in securing exhibition blooms.
Sweet peas are a climbing plant and need some sort of support. Place the supports at the time the seed is sown or plants set. A wire netting support seems to be most popular. Others build a lath frame with tacks or nails set at 6" (15 cm) intervals along top and bottom. Weave stout string up and down over these nails for support for the vines. A third method is to use branchy twigs and place them near the plants. Or, as is practiced in England, sow seed in circular fashion and place the twigs in tepee fashion to support the plants.
Mulching with straw, or strawy manure, is highly recommended for keeping the soil cool around the base of sweet pea vines. Straw also helps conserve moisture and keep down weeds.
Water sweet peas thoroughly at 5 to 7-day intervals. Cultivate ground after irrigation or rains if it is not mulched.
Pick blooms often so seed does not form. Cut some of the blooms with a little foliage attached to aid in inducing more branching of the plants.
Pests of Sweet Peas
Aphids, or Plant Lice, are tiny, usually greenish, soft-bodies sucking insects, found on the undersides of the leaves of sweet pea plants. They are readily controlled with thorough dusting or spraying with an all-purpose garden insecticide.
Red Spider Mite is a tiny mite not readily seen with the naked eye. It attacks the vines during hot, dry weather. It causes light green and yellowish mottling on the foliage. Spraying leaves with water helps keep down this pest. Dusting or spraying with an insecticide containing Malathion will give an effective kill.
Mildew is a whitish powder appearing on the foliage. This can be controlled at the same time you are dusting or spraying for insects by using an all-purpose insecticide and fungicide.
This article is from 50 years ago and today's recommendations for control of these pests have changed somewhat. Serious infestations of both aphids and spider mites usually can be avoided by frequent misting or spraying with water. Insecticidal sprays, including soaps, are effective because they contain surfactants, which help the insecticide to spread over the body of the insect and penetrate its body covering. Applications may have to be repeated, particularly for spider mites, because the eggs are not affected by the insecticides. Insecticidal dusts are not effective against either of these pests, because they do not stick to the pests. Powdery mildew can be controlled by spraying an appropriate fungicide. All-purpose insecticides will not affect powdery mildew. Be sure to consult your garden centre or other expert before purchasing any pesticide.