Here you can see half of the old boxwood hedge has been pruned. photo credit: A. Glas

This particular hedge is informal in style. Due its informal style, regular yearly pruning to maintain its shape is not necessary. However, over time informal hedges can begin to look tired and leggy. When this happens a significant renovation to restore its youthful charm becomes essential.

Luckily Buxus along with Cephalotaxus, Cryptomeria, Cunninghamia, Ilex, Sequoia, Taxus, and Torreya respond well to hard pruning and will regrow from older wood. As a result, large pruning cuts made on old wood are perfectly acceptable.

Frequent renovation will also eliminate such dramatic transformations as seen in these images. photo credit: A. Glas

Renovation pruning should be performed every 5 years or less to prevent large woody trunks. Frequent renovation will also eliminate such dramatic transformations as seen in these images.

Before making your first pruning cut, decide what the ideal final height of the hedge will be after a few years. photo credit: A. Glas

Before making your first pruning cut, decide what the ideal final height of the hedge will be after a few years. Boxwood are typically slow growing so once you have established a desired height, perform your pruning cuts 6 inches below that desired final height. This allows for several years of maintenance-free growth.

Boxwood will regrow from bare old wood but it will take longer to bounce back. Ideally pruning cuts should be made in a location where there is active growth. While performing the renovation, it is an ideal time to remove any dead, damaged, or diseased branches.

This over grown hedge has now been “tamed”. photo credit: A. Glas

When a dramatic renovation is needed, it is best to stagger large cuts over several years. Remove one third to one half of the large branches yearly over a two or three year period. This allows the plant to build up reserves and recover throughout the renovation process.

Mulching and fertilization is recommended after pruning; by doing so you will help the hedge regain its youthful glow in a timely manner. Happy pruning!

The post What’s Old Will be New Again appeared first on Scott Arboretum & Gardens.

The low profile of Allium christophii combines well with roses in the Dean Bond Rose Garden. photo credit: R. Robert

Many unwelcomed pests are attracted by odors emitted from plants. Members of the allium family, Amaryllidaceae, emit a sulfur/onion odor that masks the smell of other plants, but is undetectable to humans, so alliums serve as a good repellent to aphids, a common pest of roses.

Allium angulosum ‘Summer Beauty’ blooms during the heat of the summer, July to August. photo credit: R. Robert

The benefits of our “stinky friends” also extend below the soil. They keep subterranean pests such as grubs and nematodes at bay. Grubs grow into Japanese beetles which burrow into rose buds to eat the developing flowers. Another reason roses and alliums should be garden best friends.

Allium ‘Gladiator’ attracts all types of pollinators and beneficial insects. photo credit: R. Robert

In addition to the natural repellent mechanism, alliums are beautiful in the landscape. The long-blooming flowers range from large to enormous purple ball-like blooms making a striking presence in the landscape. The flower heads also dry nicely creating multiple-season interest.

Along with beauty, Allium offers the full package. It attracts beneficial insects such as hoverflies, bees, and parasitic mini wasps. For example, parasitic mini wasps feed on the pollen of Allium and other small flowers. The larvae of the wasps feed inside beetle grubs and aphids, killing many unwanted pests.

The purple of Allium ‘Gladiator’ compliments the many colors blooming in the Dean Bond Rose Garden. photo credit: R. Robert

The ornamental onion is available in a variety of sizes and bloom times. This beauty and function has made it a staple in our efforts to create a sustainable rose garden. Add it to your garden mix and you will not be disappointed.

The post Gardening Best Friends: Allium and Roses appeared first on Scott Arboretum & Gardens.

What is it

To explain this in more technical terms, biochar is produced by thermal decomposition of organic material under a limited supply of oxygen (O₂), and at relatively low temperature (<700°C). This process often mirrors the production of charcoal, which is perhaps the most ancient industrial technology developed by mankind. However, it distinguishes itself from charcoal and similar materials by the fact that biochar is produced with the intention of being applied to soil to improve soil health, to filter and retain nutrients from percolating soil water, and to provide carbon storage.

Where did the process come from? Five hundred years after native Amazonian people enriched their local soil with compost, mulch, and smoldering plant matter, the dark nutrient-rich soil remains. Amazonian dark earths (often called terra preta) hold plant nutrients, including nitrogen, phosphorous, calcium and magnesium much more efficiently than unimproved soil. Even after 500 years of tropical temperatures and rainfall that averages 80 inches a year, the dark earths remain fertile.

At Cornell University in Ithaca, N.Y., microbiologists have discovered bacteria in terra preta soils similar to strains active in hot compost piles. Overall populations of fungi and bacteria are high in terra preta soils, too, but the presence of abundant carbon makes the microorganisms live and reproduce at a slowed pace.

The result of the addition of biochar is a reduction in the turnover rate of organic matter in the soil, so composts and other soil-enriching forms of organic matter last longer. In field trials with corn, rice and many other crops, biochar has increased productivity by making nutrients already present in the soil more available to plants.

Results are especially dramatic when biochar is added to good soil that contains ample minerals and plant nutrients. Research continues (The International Biochar Initiative), but it appears that biochar gives both organic matter and microorganisms in organically enriched soil enhanced staying power.

Biochar is the carbon-rich product that results when biomass such as wood, manure, or leaves are heated with little to no oxygen available – it is the solid material obtained from the carbonization of biomass. photo credit: R. Robert

Digging in nuggets of biochar — or adding them to compost as it is set aside to cure — can slow the leaching away of nutrients and help organically enriched soil retain nutrients for decades rather than for a couple of seasons.

How is it produced? Carbonization: The process of converting feedstock into biochar involves a combination of time, heat, and pressure; exposure factors that can vary between processors, equipment, and feedstocks. There are two main processes: pyrolysis or gasification. Energy products in the form of gas or oil are produced along with the biochar. These energy products may be recoverable for another use, or may simply be burned and released as heat.

Biochar can be made from a wide variety of biomass feedstocks. As a result, different biochar systems emerge on different scales. These systems may use production technologies that do or do not produce recoverable energy as well as biochar; they range from small household units to large bioenergy power plants.

What does it do?

• Reduced leaching of nitrogen into ground water
• Increased ion-exchange capacity resulting in improved soil fertility
• Moderation of soil acidity
• Increased water retention
• Increased number of beneficial soil microbes

• Reduced need for fertilizer results in reduced emissions from fertilizer production.
• Increased soil microbial life, results in more carbon storage in soil.
• Because biochar retains nitrogen, emissions of nitrous oxide (a potent greenhouse gas) may be reduced.
• Turning agricultural waste into biochar reduces methane (another potent greenhouse gas) generated by the natural decomposition of the waste.
• Carbon sequestration

Biochar improves water quality by helping retain nutrients and agrochemicals in soils for use by plants and crops, resulting in less pollution. As a soil enhancer, biochar makes soil more fertile, preserves cropland diversity, and reduces the need for as many chemical and fertilizer inputs.

Is biochar production sustainable? Of all the key factors that will support the fastest commercialization of the biochar industry, feedstock supply and sustainable-yield issues are the most important, from both a broad sustainability perspective and from financial and commercial points of view. This will require the sources of biomass selected for biochar production to be appropriate and be able to withstand a comprehensive life cycle analysis.

Biochar can and should be made from waste materials. These include crop residues (both field residues and processing residues such as nut shells, fruit pits, etc), as well as yard, food, forestry wastes, and animal manures.

Large amounts of agricultural, municipal and forestry biomass are currently burned or left to decompose and release CO₂ and methane back into the atmosphere. Making biochar from these materials will entail no competition for land with any other land use option.

Biochar is tilled into existing beds. photo credit: A. Glas

How do I use it?

The answer to this question comes down to your existing soil. Sandy soils benefit from the help to hold onto vital moisture and nutrients. Clay soils benefit from better texture to drain excess water while retaining the nutrients and providing space for developing roots. Rich loamy soils benefit from smaller amounts that help retain existing moisture and nutrients as well as providing spaces for beneficial microbes and mycorrhizal fungi. Before incorporating biochar, perform a soil test to determine your soil type.

The following are general recommendations for usage:

http://carboncultures.com/how-much-biochar-do-you-need

Applications:

• into turf grass via aeration holes
• in structural layers while constructing golf course greens
• broadcast and uniform mixing while applying new topsoil
• in growing media for potted nursery production
• to the surface of large planting beds, orchards, or in-ground nursery operations
• subsurface banding
• broadcasting applications on large turf areas or woodlands
• layer under newly constructed structures and paved areas for carbon   sequestration

This cover crop was mowed to a half-inch in mid-April and then tilled under. photo credit: A. Glas

What are we trying at the Scott Arboretum?

Over the past three years, the Dean Bond Rose Garden has gone through a renovation, beginning with soil testing and the addition of lime to adjust the pH to neutral.

A cover crop of crimson clover (Trifolium incarnatum), buckwheat (Fagopyrum exculentum), and hairy vetch (Vicia villosa) was planted. photo credit: A. Glas

The garden was then divided in half. Both sides received a cover crop of crimson clover (Trifolium incarnatum), buckwheat (Fagopyrum exculentum), and hairy vetch (Vicia villosa). This cover crop was mowed to a half-inch in mid-April and then tilled under. The “half” of the garden closest to Parrish Hall received a half-inch broadcast spread of BioChar before being tilled.

As the Dean Bond Rose Garden grows over the next several years, visitors and gardeners can make a direct comparison of the benefits of biochar.

You can try biochar in your own garden this year with the 2015 Potting Mix and BioChar Sale through Scott Arboretum (available at the Members Plant Exchange and Sale) or through Redbud Native Nursery. Mail orders are due by May 9, download here.

The post Bio Char: Exploring a New Soil Amendment appeared first on Scott Arboretum & Gardens.