Those who attended the Summer Seed Exchange at Tropical Edibles Nursery last month went home with seeds, cuttings, huli, bulbs and a few keiki plants to install. Careful installation of the next generation can affect the health as well as the survival of your new plants.
If you have enough seeds, you may want to test them for viability before you actually plant them in a seeding medium or in your garden. Small seeds can easily be tested by placing them between two wet paper towels for a week or two. Keep the paper towels moist by spraying them whenever they lose moisture. Larger seeds are best tested in soil but you can put several in a single pot and wait to see how many germinate. If none of the seeds germinate within the two-week period, do not lose heart. Searching online for information about the plant and finding out how long it usually takes for its seeds to germinate can be quite helpful. An excellent book, “Seed to Seed” by Suzanne Ashworth, offers advice on collecting and germinating many vegetable seeds.
Some seeds germinate more rapidly if they are scarified or soaked ahead of planting. Bean seeds are helped by soaking for about 24 hours. Parsley seeds should be soaked similarly to encourage a short germination period. Seeds with particularly hard shells may need scarification in addition to or instead of soaking. Nasturtiums can be encouraged by a tiny clip in the shell with a nail file or by abrading the seedcoat with a file. More information on encouraging seed germination can be found at groworganic.com/organic-gardening/articles/tips-for-germinating-hard-to-start-seeds.
Seeds for root vegetables should be planted directly in your garden as transplanting can damage your crop. Though not usually an issue in Hawaii, soil temperature can be an important determinant in germination. Moist soil above 60 degrees and out of direct sunlight is the best environment for encouraging germination.
Any cuttings that were not planted immediately should be kept moist either in wet newspaper, moist soil or water. To get them started growing, most will do best in a damp medium of half vermiculite and half perlite. Once the medium is ready, remove most of the leaves from your cutting and dip the rooting end into a rooting hormone; then place at least 2 inches of the cutting into the medium. Keep the medium moist and in a cool location until you see new leaves appear and the plant is somewhat resistant to a gentle tug. Resistance means that roots have started to grow. Once your plant has put out a few new leaves you can strengthen it in a larger pot with a little fertilizer or put it directly into your garden.
Several folks went home with taro huli. These can be stored for a few weeks in damp newspaper but should be planted sooner rather than later. Planting them directly in the garden will give the corms the best opportunity to grow large.
Ginger and turmeric rhizomes were also available at the exchange. Young, moist awapuhi or culinary ginger starts should be planted within a week or two. Dry turmeric and ginger rhizomes can be stored for a month or more. They will keep better on a counter rather than in the refrigerator.
Several onion sets or bulbs were also available at the exchange. Dry bulbs can be stored for several weeks before they lose viability. These can be kept in the refrigerator. When you are ready to plant, bury the bulb and if you see a shoot, leave a bit of it above the soil line to photosynthesize and get the plant going.
Tropical gardening helpline
Richard asks: I am seeing more and more purple nutsedge in my lawn. Is there any organic way of getting rid of it?
Answer: Purple nutsedge, Cyperus rotundus, also known as nutgrass, is a true sedge with triangular blades. Purple nutsedge has brownish flowers, and its underground tubers occur in chains. It grows well here and is hard to eliminate.
The underground tubers and rhizomes connecting them are the primary source of purple nutsedge infestations. Though the plants produce some seeds they are not all viable and have a low germination rate. Limiting the production of tubers by removing the plants as well as their underground network is the best way to control an infestation organically. Removing all young plants when they appear offers the best possibility at reducing or preventing an infestation. Consistent shoot removal will eventually exhaust the energy in any remaining tubers and, over time will cause nutgrass decline.
If you can prevent nutgrass from getting established, you can avoid the problems an infestation can cause. Removing small plants as soon as you see them, hopefully before they develop tubers, and eliminating the wet conditions that favor nutgrass growth can be helpful.
In addition to continually removing small plants, you can reduce nut grass populations by drying out or shading areas where they grow. Black weed cloth can prevent the plant’s growth and can be put down in cleared areas.
As with most plants we consider weeds, they often have medicinal or cultural uses in other places or earlier times. If you want to cultivate purple nutsedge and eat it to prevent dental cavities, you would be following ancient wisdom. An article in The Washington Post reports on a study indicating that prehistoric humans in central Sudan ate purple nutsedge as a carbohydrate and it seemed to have protected their teeth from cavities.
If you still want to eradicate nutgrass you should know that only a few herbicides are effective at controlling sedges and none is organic. A list of those with good records against this weed can be found at ctahr.hawaii.edu/oc/freepubs/pdf/L-9.pdf.
Email plant questions to konamg@ctahr.hawaii.edu for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook.