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Garden Design for the Future

air date: January 22, 2015

Explore the future of landscape architecture with Texas A&M University Landscape Architecture students Ixchel Granada and Aaron Kotwal.  On tour, landscape architect Curt Arnette restored habitat as he sculpted land, directed water, and gave artistic notice for the family’s outdoors connection. Daphne answers: When and why do we add compost?  Plus, find out how to grow her Plant of the Week, native Mexican plum, a small tree that bursts with fragrant white flowers in February to support bees and other pollinators. It’s time to start winter pruning and cleanup! John Dromgoole demonstrates a few tips for cutting back perennial shrubs and clumping grasses.

Question of the Week

Why and when should we add compost?

Adding compost to beds is a great way to nourish the soil and keep it healthy.  Most people add compost to the soil, spading in 2 to 4 few inches as recommended, when they first build a new garden bed.

But you need to add it every year, or even seasonally, depending on the situation.

Once you’ve built the bed and established the plants, you can’t incorporate any new soil amendments and till them in, but you can spread them on the surface of the bed, the same way you might add mulch.

Compost adds a small amount of nutrients that are released slowly, but more importantly, it helps build good soil structure; and the structure of your soil is very important.

Too heavy, and the clay particles stay bound together, holding too much water.  But too porous, and the soil falls apart, holding no water at all. Adding compost to soil helps balance out both of those issues, creating a better balance of water-holding vs air-holding capacity to support plant growth.

Compost, being organic matter, breaks down over time, due to the activity of soil microbes. This is a good thing, since it releases a small amount of nutrients for your plants.  But it also means that the volume of the soil diminishes, slightly, as the organic matter breaks down into smaller aggregates.

In vegetable beds, add a small amount of compost when you replant new crops every season to replenish what’s been lost with hungry crops.

In perennial beds, add a thin layer of compost, instead of mulch, in the winter, when you prune back all the top growth. Then follow with new mulch in the spring.

Replenishing mulch is similar to adding compost, since bark and wood chips break down to smaller aggregates, basically, compost.

But there’s no need to overdo it. Like having too much clay or too much sand, too much organic matter in soil also isn’t good.  So strike a healthy balance.

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Plant of the Week

Mexican Plum

Mexican Plum

Prunus Mexicana

This plant is native to our area. It's a deciduous tree with beautiful, fragrant spring blooms in February and early March. These white flowers, similar to apple flowers, are highly attractive to bees. It is a Prunus species like other plums, and so it does have similar flowers and it will look similar and have a similar shape. This tree is very small, about 20-25' tall, so it makes a nice specimen tree in smaller yards. The branches are thin, and the canopy spreads very wide. It's very open so this tree makes a nice sculptural element in the winter. It also has very interesting bark as it ages. This bark peels and is very dark with stripes so it's a very interesting element as well. It uses low to medium water, which is also great, takes full sun and - it's rare for a tree - but it also takes light shade. Most any soil type is fine and this tree does have edible fruit from mid-summer through fall. The fruit is dark purple and has a very thick skin so many people like to make jams and jellies out of it instead of eating it fresh.

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