American Holly (Ilex opaca)

image from: https://www.arborday.org/trees/treeguide/TreeDetail.cfm?ItemID=1071

Introduction:

The American Holly or Ilex opaca is considered a symbol of Christmas cheer. The American Holly is an evergreen so it has lasting beauty year round. It is also considered an ornamental tree which means that it adds visual interest and beauty to the landscape. It is best known for its use in Christmas wreaths. The year round tree provides cover and food for birds and has more than 1000 cultivars developed today. There are roughly 20 American holly species, 120 Asian species, and 200 English varieties. The American Holly has been around since the days of Pilgrims. it had been used by Native Americans to create various wood products and the berries were often used as buttons or for barter. It is believed that George Washington loved the American Holly and planted many around the White House.The popularity  has continued as it was adopted as the Delaware state tree.

image from: http://www.fcps.edu/islandcreekes/ecology/american_holly.htm

The Ilex opaca is grows best in hardiness zones 5-9. This shrub grows best in full sunlight or partial shade. More than 4 hours of direct sunlight are best. Acidic, well drained, loamy soils provide the best habitat for growth. The American Holly prefers normal moisture, but can withstand flood and drought conditions.  They are relatively easy to grow and can thrive in temperatures as low as 15 below zero. American hollies can adapt to less than ideal conditions.

A mature plant is 40-50 feet tall and 18-40 feet wide, but they grow slowly, at a rate of 12-24 inches per year. The leaves have a leathery texture and are 2-4 inches in length. They stay green all year long and have sharp tips. While they often grow in a pyramidal shape, they can be trimmed to create an attractive hedge. The greenish or cream flowers produce a pleasant aroma and give way to orange-red, berry-like fruit that is somewhat toxic to humans, but loved by a variety of songbirds. Hollies are either male or female. Female hollies produce large amounts of berries, but require a male holly in the vicinity to pollinate it.

Propagation Methods:

There are three ways to propagate hollies.

The first is by grafting. The best way to graft a holly is to use the T-budding method. This grafts the desired buds onto a developed rootstock. Grafting is often used in holly production because many varieties have been developed by producers and do not grow true to seed, so the only way to keep these varieties in production. The downside to grafting is the possibility of failure of the graft union and that it takes time and understanding to be completed.

The second is by cuttings. The cuttings must come from the canes of new growth. The cuttings should be taken when the plant is dormant. However, as with most hardwood cuttings, rooting hormone is necessary. Hardwood cuttings are harder and fail more often than other cutting types. This why they are often used less.

The last is by seeds. Seeds are an easy and cheap way to propagate hollies, but limit the varieties produced and can be time consuming.

Steps to Seed Propagation:

1. Obtaining the Seed: The seeds should be taken from healthy trees. The best time to collect seeds is in the late fall. The berries typically grow from September to November. It is important to remove the berries before they begin to dry and shrivel, but not before the seeds have a chance to fully develop. To collect the seed the skin should be removed. This can be accomplished by smashing the berry. The seed should then be washed to remove the pulpy insides of the berry. The guts of the berry often have chemicals that prohibit germination. To test viability the seeds can be placed in water. The viable seeds will be heavier and sink in water. Typically in nature, the berry would simply fall to the ground and sit over winter and the cold combined with rain would activate enzymes to eat those chemicals that prohibit germination. Rinsing the seed in cold water mimics this process and prepares the seed for germination.
2. Storage of the Seed: Once the seed is removed from the berry, it needs to be cleaned and stored properly. This means that the seed should be free of berry particles and placed in a contained at 4 degrees C. The container needs to be moist and should contain peat moss.  Storage with proper temperature and adequate moisture levels will extend the seed viability for possibly years. If the seed is not going to be stored, it can be planted right away.
3. Stratification of the Seed: Stratification is the necessary process to help seeds overcome their dormancy. Stratification helps simulate natural winter conditions. A box with drainage holes can be filled with about 1 to 2 inches of sand and the seeds placed on top. The box should then be burried just below the soil level in a shaded area. Another option is to fill a weather resistant flat with soiless potting medium and place the seeds on top. The seeds should then be covered with a layer about an inch thick of soiless medium in a level manner. The flats can simply be sat outside over winter and you should see some germination by spring. If not the seeds can be left out for a second winter. Seed propagation can take time. There is also no guarantee that the seeds will be the same variety as the parent plant.
4. Planting the Holly Seed: Seed germination is a very slow process. The American Holly can take up to a year fully germinate. Seeds should be planted in the springtime after an overwintering has occurred. The seeds should be covered with no more than a half inch of soil when planted. The seedling will do best in shady conditions for the first 2 years. It is important that the seedlings are kept free of weeds and grass growth during this time. Once the American Holly has reached 2 years of age, it can be transplanted. Transplanting should occur in the late fall as the tree is going dormant or early spring right before the new growth begins to grow.

Images from: http://www.hgtv.com/design/outdoor-design/landscaping-and-hardscaping/propagating-holly

Conclusion:

American Holly trees are best known for their role in Christmas decor for the holiday season. The tree growth is meant to be harvested around this time, so this is when the bright berries are present and the leaves remain green. There are many ways to propagate the beautiful berry bushes, but by far the most common is by seeds. However, seeds have many limitations when it comes to producing desirable varieties. Other methods such as cuttings offer a better guess at what type of traits will show up in the seedlings. Either way the American Holly has played an important role in the past and continues to be a beautiful accent to winter landscapes either as large hedges or in wreathes and swags for holiday decor.

Resources:

Directions for Holly Propagation Using Grafting. (n.d.). Retrieved November 19, 2015, from http://homeguides.sfgate.com/directions-holly-propagation-using-grafting-87675.html

Hartmann, H. (2011). Techniques of Propagation by Cuttings. In Hartmann & Kester’s Plant Propagation: Principles and Practices (8th ed.). Upper Saddle River, NJ: Prentice Hall/Pearson.

Home Home. (n.d.). Retrieved November 19, 2015, from https://www.arborday.org/trees/treeguide/TreeDetail.cfm?ItemID=1071

Propagating Holly – How To Grow Holly From Cuttings. (2009, May 1). Retrieved November 19, 2015, from http://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-cuttings.htm

Propagating Holly. (n.d.). Retrieved November 19, 2015, from http://www.hgtv.com/design/outdoor-design/landscaping-and-hardscaping/propagating-holly

Pear Tree Propagation:

Image from:  http://www.pearrecipes.co.uk/how-to-grow-a-pear-tree-from-a-pip/

General Information:

The Pyrus or Pear Tree dates back to prehistoric times and there are currently more than 3,000 varieties. There are only three types of pears grown in the United States including European, Oriental Hybrids, and Asian pears. European pears are known for their taste and soft texture, but are susceptible to fire blight. Oriental hybrids offer a large range of tastes and textures and can be good for canning. Asian pears are the most resistant to fire blight and generally have a hard texture similar to an apple. The most common pear cultivar is the European Bartlett, but it is not usually planted in the U.S because of the susceptibility to fire blight. Those that are more common for planting in the United States are Magness Pear, Blake’s Pride,  Shenandoah, Potomac, Orient, Kieffer, Shinko, and the Korean Giant.

Pyrus trees grow at least 30 feet high and 20 feet wide. Those grafted onto dwarf rootstocks are limited to 15 feet high and 10 feet wide. Most trees will be oval in shape. Pear tree fruit has a distinct shape, but most Asian varieties tend to look more like apples. The fruit has a gritty feel to it  because of the stone cells in the flesh. Most Pyrus trees grow in the hardiness zones 4-9 and they need full sunlight. Partial sunlight will result in a poor harvest.

Image from: http://www.pearrecipes.co.uk/how-to-grow-a-pear-tree-from-a-pip/

Propagation Techniques:

Sexual Propagation (Seeds):

Seedlings are not identical to their parents, so every seed is unique. This type of propagation is inexpensive, quick, easy to perform, and produces a large number of plants. The rooting systems produced by seeds tend to be symmetrical and downward which is a benefit to growers. Seeds are generally removed from the fruit of the desired rootstock and planted after stratification. The problem with seeds in the genetic variability and that some varieties do not produce seed or only produce small quantities of viable seed.

Cuttings

Hard wood and soft wood cuttings success rates vary between 30-90%. The lack of

dependability is one reason why cuttings are not utilized as often. Hard wood cuttings are generally collected from current year’s shoots during the fall and immersed in auxin. Softwood cuttings are generally collected during early summer and immersed in auxin at high levels. These cuttings will be placed in a greenhouse and misted occasionally to harden them off for fall. Both types of cuttings require humid storage environments for roots to form. Early harvesting typically requires shoots to grow in the nursery for one year before becoming large enough to transplant.

Micro-propagation:

The replicate is a clone of the tree put into tissue culture which allows growers to keep the genes of their best trees when creating new orchards. This method is effective and quick,  but has high labor and equipment costs which is why its used by few for propagation of pears. Researchers are generally the only ones to use this, but it is thought that this method will become more common in the future. Seedling tops, young shoots or suckers are gathered from a mature pear tree. This plant material will then be sterilized and transferred to a nutrient rich medium with sugars and plant hormones. It is important that the plant material contains an auxiliary bud. Long day periods of light allows the bud to produce new shoots. After shoots begin to form, the culture is exposed to darkness followed by short-day periods of light to allow for proper growth. After a while, the plants will be ready to come out of tissue culture or to be sub-cultured.

Grafting:

Grafting is the most common method of Pyrus propagation. Grafting allows growers to quickly swap out different bud wood, but keep the full grown rootstocks, so that they do not have to wait 30 years for the trees to fully mature before receiving bountiful harvest.

The materials needed are the scion wood which is the wood that  contains the bud, the rootstock which houses the well developed roots, a fine-toothed saw, pruning shears, grafting knife, grafting wax, and string.

Step 1: Selecting the Scion- It is important to select bud wood that produces good fruit and is free of diseases or pathogens. It should meet the requirements that the individual growers is looking for regarding flowering, fruiting, and form.

Step 2: Gathering the Scion- The scion needs to be removed after the tree has gone dormant which is typically late fall or early winter. The cuttings should be small twigs of new growth, They should be no wider than a pencil and about 8-12 inches long. If they need to be stored, it must be done in an air tight plastic bag with high moisture and placed in a refrigerator. Scion wood is typically stored until spring when the grafting can occur outdoors.

Step 3: Selecting the root stock-  You are looking to select a hardy and disease resistant plant to be the rootstock. The seedling should be one to two feet tall and have ample roots.

Step 4: Remove scion from storage- After it is a safe time to begin working with plants outside typically after the concern of frost is behind us, the scion wood should be removed from storage.

Step 5: Selecting the graft type- Either a cleft or an inverted t graft can be done.

A cleft graft involves cutting both side of the scion wood towards the base to form a tapered wedge. The rootstock then receives a slice down the center of it. The cut should only be as deep as the exposed area on the scion wood. A screwdriver can be used to hold the cleft wider until the scion is securely pushed in. Care needs to be taken to prevent breaking either portion of the graft. String can be used to tie the graft union together tighter if the scion seems to fit looser than it should. It is important to ensure that the two pieces have permanent contact with no air spaces in between them. After the union has been made, grafting wax should be applied and cover the entire length and width of the graft to prevent desiccation and drying out. It may also be important to apply was to the exposed tips of the scion to protect them as well. Attaching a plank to the tree to support it will it heals and protect it from the wind and animals is essential.

Image from: http://etc.usf.edu/clipart/23600/23677/cleft_graft_23677.htm

An inverted t graft uses only buds from the scion wood and places the buds into the root stock. To remove the bud, a small knife is used to gently shave off the twig from the top down. It is important to not touch the green side of the bud to prevent contamination. The bud should be removed by holding the outside bud left from when the leaves were removed. An inverted or upside down t should be made into the rootstock. It works best when the cut is made between buds, not by removing the bud of the rootstock. Once the cut has been made, the scion bud should be gently worked into the t cut until it rests beneath the tree bark. The buds can be grafted anywhere on the scion as long as it is roughly 6 inches above the soil. Once the bud is in place, it should be wrapped with parafilm or electrical tape to hold it in place. It is important to wrap around the bud. The bud can only grow through one layer, so if it gets covered it must only be once.

Image from: generalhorticulture.tamu.edu

Step 6: Caring for the Grafted Tree- It is important to care for the grafted tree similarly to caring for a seedling. After 2-3 weeks, you can unwrap the graft union and check to see if it has taken . With the cleft graft the scion will begin to produce green buds. With the t-bud, the bud will be green if it has taken and brown if it had failed. The buds should be left unwrapped. A cut needs to be made 2 inches above the bud about 3/4 of the way around. This portion of the scion will be removed and the bud will be allowed to grow as the main trunk. Do not remove the old trunk until the bud is about 4 inches in length.

Conclusion:

While there are many methods to propagate a Pyrus tree, the most common is grafting. Pyrus trees can be grafted using multiple grafting and budding techniques. Grafting is the most common method because it is less expensive and allows the grower to quickly and effectively change the cultivar of pears growing in their orchard without starting from scratch with a seed or seedling.

Resources: