“Are plumerias poisonous?” asked Charlyn Montane in an e-mail. Montane, who gardens in Fountain Valley, noted that “Hawaiians make beautiful leis (garlands and necklaces) from the flowers,” but was concerned about “the white milky sap that flows out” when she cuts a flower stem. This white sap, known as latex, can cause a rash on the skin of sensitive individuals, so it is advisable to wear gardener’s gloves when pruning a plumeria or removing its flowers. Incidentally, if you allow the sap to flow out after cutting a flower stem, you can place it in water in a vase where it will last 3-7 days. You can also float the flowers in a bowl where they will last for 2-4 days. In both cases, water should be changed daily.
Plants that produce latex sap, described as lactiferous, are more common in tropical or subtropical habitats than in temperate ones. The reason is that their bitter, toxic latex protects them from herbivores, which are more abundant in climates that are warmer throughout the year. Other well-known lactiferous species include poinsettia (Euphorbia pulcherrima), milkweed (Asclepias spp.), edible fig (Ficus carica), rubber plant (Ficus elastica), and lettuce (Lactuca sativa); “Lac” in the Lactuca genus name of lettuce references its milky sap. The dogbane (Apocynaceae) plant family to which plumeria belongs is replete with popular plants that are lactiferous, too, including vinca (Catharanthus roseus), star jasmine (Trachelospermum jasminoides), Natal plum (Carissa spp.) and oleander (Nerium oleander).
During a recent trip to Israel, I visited the Dead Sea where I saw mass plantings of desert rose (Adenium obesum), another dogbane family member. When first setting eyes on it, you might mistake its flowers for those of its cousin, the oleander, a species that grows wild throughout Israel, although desert rose is native to East Africa. However, although desert rose thrives in the Dead Sea climate, where daily temperatures average over 100 degrees during the summer, it cannot survive in cold weather and is therefore grown in containers in Southern California and brought indoors at summer’s end. A distinguishing feature of desert rose is its caudex, or swollen trunk base — from which its species name of obesum derives — utilized for storing water and nutrients in the inhospitable desert environment it calls home.
Charlyn Montane had another question, and it concerned the disposition of dahlia tubers after flowering ends. “My dahlia flowers have finished blooming,” she wrote, “and I have cut the stalks down to 6 inches high. Should I take the tubers out of the soil and store them in a dry paper bag with sawdust until February? Or should I leave them in the flower bed where I am now planting and watering sunflowers, etc?” If you intend to water the bed where they grew and you wish them to grow again, to be completely safe, their removal and storage with sawdust in a paper bag in a cool place — such as a garage — is a good idea. However, as long as the soil where they grew is well-drained, watering should not be a problem. My daffodil bulbs and gladiolus corms are located in spots where, after their flowers have faded and foliage has turned brown. Summer water is applied, but my soil is fast-draining, so these underground storage structures do not rot, and the same would be true of your dahlia tubers if planted in similar soil. Incidentally, in the manner of potato tubers, dahlias can be propagated by their tubers being cut into pieces where each piece has at least one eye from which new shoot growth can develop.
Montane also offered this advice concerning seed germination: “Instead of starting flower or vegetable seeds in little pots or plastic cells, I find it easier to do this: Take lightweight aluminum loaf pans and poke many holes in the bottom. Plant two rows of seeds down the length of the pans. When plants are 3 inches high, pluck them out with your fingers or a trowel and plant them in your prepared area in the ground. Some of the seedlings in the pans will need more time to grow than others before being transplanted.”
The fact that Montane’s seedlings reach proper size for transplanting at different times aligns with the concept of succession planting, where seeds or seedlings of a single crop are planted at intervals of a week or two. This practice ensures that the harvest of a certain vegetable or bloom time of a certain flower is extended over a longer period of time than when all seeds or seedlings have been planted at the same time. At ten-day intervals, plant lettuce, spinach, arugula, radishes, and fast-growing varieties of bush beans.
If you are thinking of saving seeds, know that wet and dry seeds have different initial procedures to facilitate this process. Wet seeds, such as those in tomatoes, cucumbers, and melons, should be spooned out and dropped in a jar with water to ferment for three or four days. Stir seeds daily, and the viable ones will eventually sink to the bottom. Remove these seeds and put them on a paper towel to dry. Dry seeds are easier since they can be left on the plant until the capsules or pods that contain them become hard and change to brown, and the seeds themselves turn dry, as is the case with beans and annual flowers, for example. Lettuce flower heads, when ready for harvest, will remind you of dandelion heads when they begin to turn to silver fluff, which is not a coincidence since the two plants share daisy family kinship. A seed is attached to each piece of lettuce fluff, so the ripening flower heads should be picked before they open completely and seeds disperse. Place seed pods, capsules, or flower heads in paper bags where they will soon open and seeds will drop.
Estela Bueno, who gardens in Torrance, e-mailed as follows: “I read your column regarding the Meyer lemon peels being eaten, with the pulp inside left intact. I had the same experience many years ago. I resolved it by cutting several branches of my rosemary bush and putting them in between branches of the lemon tree. That solved the problem.”
Do you have a gardening experience or horticultural advice to share with readers of this column? Or is there a special plant story you wish to tell? If so, email it to joshua@perfectplants.com. Your questions and comments, as well as gardening conundrums and successes, are always welcome.
California native of the week: Gumweed (Grindelia stricta venulosa) is native to coastal dunes and slopes where it thrives as a ground cover, growing 1 1/2 feet tall and spreading to a diameter of seven feet. It is covered with yellow daisy flowers from spring until fall. Flower buds are plastered with gummy white resin to protect them from predators. Great Valley gumplant (Grindelia camporum) is a shrub that grows six feet tall and three feet wide and is more suited to hotter, inland locations. Both species are highly attractive to native bees, butterflies, and beneficial insects.