Seed Germination - Nothing's coming up!

Planting a vegetable garden has a variety of challenges. But how disappointing when the seeds are planted and nothing comes up! Here are primary reasons for poor seed germination.

 1. Planting depth – small seeded vegetables like carrots and onions can easily be planted too deep. If planted too close to the surface, the seed can easily be washed away during heavy rains. Consult the seed packet for proper planting depths. 

2. Temperature – some seed need the soil temperature to warm up before they will adequately germinate, while other cool season vegetables like onions, germinate best in a cool soil. 

 3. Water -  too little and seeds will not germinate or will dry up after germination. With too much water, seeds and seedlings can die from lack of oxygen or be overcome by fungi. Even under normal moisture conditions, different species of fungi and bacteria can cause seeds to rot.  Seeds and seedlings should always be kept moist, but the soil should not remain soaking wet.  

 4. Soil pH - each vegetable seed as well as other plants will have its range in which it will germinate best. 

5. Herbicide residues -  may still be active in the soils causing poor germination.  A high fertilizer content in the soil could also hamper germination. 

6.  Insects will often feed on  seeds and young seedlings.

7. And finally, the seed itself! Poor seed germination can particularly be a problem in humid climates.  Relative humidity influences the moisture content of the seed. The higher the moisture content, the lower the germination rate will be, especially, after one year.

As a general rule, vegetable and flower seeds can be kept for one year without appreciable decrease in germination. Storage, however, may be extended to 10 or more years under proper conditions; seed moisture and temperature are the most important factors. The drier the seeds, the longer they will store.

In humid climates such as Hawaii, storing vegetable seeds in a dry, sealed glass container should keep most seeds viable for a year. For longer storage, place seeds in a moisture-proof container and store in the refrigerator.

Longevity of vegetable seeds will also vary depending on the species.  For example, collards, cucumber, endive, radish and water cress produce some of the hard seeds, rated as lasting 5 years. Next come beets, cabbage, cauliflower, eggplant, kale, mustard, squash, swiss chard, tomato, turnip, watermelon, rated at a 4 year longevity; asparagus, beans,  carrot,  celery,  chinese cabbage, New Zealand spinach, pea, and spinach, at 3 years; leek,  sweet corn, okra and pepper are rated at 2 years; and finally, the last group is rated at a mere 1 year longevity - lettuce, parsley, parsnip and onion.

Photo: Purdue University

Pineapples - Easily Propagated

Can the top of the pineapple fruit be cut off and planted in order to produce a new plant? The answer is YES! There are many variations on how to propagate pineapple. The drier the environment, the more precise the instructions need to be followed. In Hawaii, especially in high rainfall areas, propagating pineapple is relatively easy. 
  

The simplest method is to cut off the top of the pineapple, called the crown, as you normally would do when cutting the fruit. Let the top sit in a shaded, dry area for 2-7 days. Before planting, remove the dried fruity portion and some of the lower leaves exposing  ½ -1 inch of the stem. Letting the crown sit for several days will seal the wound and make it less susceptible to rot. When planting, keep in mind that the mature plant can grow to 3-4 feet in diameter and height. Mature plants also have a tendency to fall over, thus planting several together, they will give each other support.

Alternatively, the stem can be placed in a shallow glass of water. Be careful to place only the stem and not the leaves in the water.  After a short time, roots will form; it is then ready to be planted outside.  

Poor Germination?

I planted some seeds and only a few came up.  

  

Several elements are essential for seeds to germinate.  Water is, of course, number one.  But seeds must also have an adequate supply of light, oxygen and the proper temperature range. In a few cases seed need darkness to germinate. Seeds can be buried too deep, or too close to the surface where birds or wind may carry them away. This is often true of carrot seeds.  Furthermore, the possibility of disease, fungi and bacteria, in the ground can rot the newly planted seeds.  

Some seeds need special care. Certain ones have seed coats which are extremely thick. Particular care must be taken with these in order for the water to penetrate that coat. Soaking in warm water is one means. Seeds such as lupine, locust (Robinia) and others need to be scarified, which means they need to be mechanically scratched in order for the water to penetrate. This may be done with common instruments like sandpaper or a file. Soaking in hot water is another means of scarification. Still other seeds will not germinate, or break dormancy, unless they are exposed to a period of low temperatures and moist conditions. Certain seeds germinate only after a fire. Not all seeds are created equal.

Storing Seed

Store dry, clean seeds in an airtight container marked with their name and date saved.  Store around 40 degrees F with low humidity.  The refrigerator is a good place for this. Seeds of many plants remain viable for up to 5 years, if properly stored. Some plants like delphinium, onion and parsley, produce seeds that must germinate immediately after they ripen or they lose their viability.

If you have old seeds, or seeds of questionable viability, place some of them between a paper towel that is kept constantly moist and between 65 and 70 degrees F.  Check daily for germination.  If the rate is poor, consider buying new seeds.

What is a cocktail tree? Grafting Different Fruit on the Same Tree

Different varieties of the same species can be grafted together. This is often done to extend the harvest period. As an example, if the Kahaluu variety of avocado were grafted onto a Sharwil avocado, the fall/winter picking season for Kahaluu would be extended into the spring by the Sharwil (winter/spring).

In addition, two varieties can be grafted on one tree in order to save space, especially, if a second variety is needed as a pollinator. In general, plants with the same genus, but of a different species, can be grafted together. Among citrus species, lemon, orange, grapefruit can be put on one tree. One word of caution, lemons are a vigorous growing tree. When lemons are put together with a slower growing citrus, care must be taken to prune the lemon graft, or else it will quickly out grow the other species.

Many deciduous fruit trees can be grafted together.  Peaches, nectarines, plums and apricots can all be harvested from one tree.

Plants belonging to different genera are less successfully grafted, although there are some cases where this is possible. For example, quince, genus Cydonia, may be used as a dwarfing rootstock for pear, genus Pyrus. Plants of different families cannot be grafted successfully, such as orange on a peach.

For more detailed information on budding and grafting avocados, citrus or deciduous fruit trees, the University of California website has excellent information:  https://ucanr.org/freepubs/

Air Layering

Questions often arise concerning air layering of plants. This is a method of reproducing a plant in order to create another exactly like the original. It has been used successfully as an alternative means of propagating some plants difficult to root, i.e. plants where grafting or cuttings have not been successful or where seeds do not come true to type.  Another advantage to air layering is that these plants have the ability to bear fruit much sooner than a seedling. Some fruit trees may take 10 years to fruit from seed. Plants such as citrus, figs, lychee, longan, mountain apples, camellias, azaleas, croton and dieffenbachia are frequently propagated by air layering and bear fruit (where applicable) in less time than seedlings.

How to Proceed

After selecting the branch you want, come down about a foot from the tip.  Here you will remove a one inch wide ring of bark by making two parallel cuts (1 inch apart) around the circumference of the shoot. This will leave the branch with a “naked” or barkless band.  Don’t cut through the branch, just cut deep enough so the outside bark peels off.  This is known as girdling.

Then wrap the wound with moist, unmilled sphagnum moss. You may need to tie some twine around it to keep it in place. Cover the moss with plastic wrap to form an airtight pouch. Alternatively, you may want to place the moss first, then wrap both moss and plastic around the wound at the same time. Make sure the moss is moist – not wet. Some gardeners will place a final wrapping of aluminum foil to shade the area from the hot sun. Also, some add a little rooting hormone to the wound to speed up the rooting process - a light dusting will do. For many trees, this is not necessary. 

Tie the bundle at each end, secure enough to prevent moisture loss.  Later, when roots are visible, all around the bundle, cut the branch just below the developing roots, remove plastic and plant the newly rooted branch in a pot.  Keep it in the shade until the plant develops more roots. Rooting time will vary depending on the type of plant and the season.  Some plants will begin to show roots in 4-6 weeks, others may take up to 2 years.

In the process of air layering, the removal of the bark (girdling) prevents carbohydrates from flowing down past this point, but still allows water and mineral nutrients to flow upward to the leaves. This keeps the leaves of the shoot from drying out, but the presence of the carbohydrates and the water in the sphagnum moss, will cause dormant buds in the area to grow into roots.

For optimum rooting, make air layers in the spring on shoots produced during the previous season, or in mid-summer on mature shoots from the current season's growth. On woody plants, stems of pencil size or larger are best. 

East Hawaii Residents:  Master Gardeners' Annual Plant Sale is Saturday, April 25, at 8:00am-Noon at the Komohana Agricultural Center. Nick will be there to answer questions.

Propagating Plumaria Trees

Plumaria trees can be propagated from cuttings, normally 1-2 feet long. This method preserves the characteristics of the selected cultivar. Before placing the cutting in the ground, they need to “cure” in a dry place for at least two weeks. Then, it is important to plant them in a well-drained soil; they may also be planted in a pot. Although not required, treating the base of the cutting with a rooting compound (0.3% indolebutyric acid) will enhance rooting.  

Plumeria can also be propagated from seeds collected from the tree. It is interesting to note that seeds from trees with white flowers produce mostly white-flowered seedlings; dark red will produce red, and yellow will produce yellow. On the other hand, pinks and multicolored plants will produce a range of colors in their seedlings.

Plumeria blooms can easily be strung into a fragrant flower necklace known as a "lei" in Hawaii.