Pruning Lilacs on the Old Homestead - What I Learned...

Before Pruning

It is late winter in the Treasure Valley, and you live in a rural area in an older home. The poplars have aged out and there are several stumps in the yard. The silver maples bordering the pasture are taking over. The cottonwoods are huge and messy. You play pick up sticks after every storm. The sumac is long and leggy and the one and the only lilac has been ignored for a long time. It attacks you when you mow and is curling under the eaves. There is a plan to paint the house this summer, so a plan is required to minimize the lilac’s size, so I began my research!

The best time to prune a lilac is in the spring a month after it blooms. This gives the plant plenty of time to develop buds for the following year. If flowering is your main priority, this is a good time to prune.

Lilacs can also tolerate a “hard prune” also known as rejuvenation pruning when dormant, which is cutting all the old stems to within 6-12 inches from the ground. In the spring new stems will grow. The advantage to this is that it really does not require much skill. The disadvantage is that it could take up to 3 years to bloom again.  This is best for lilacs that are overgrown and no longer flowering.

Selective heading cuts are best for managing the size of the lilac. Heading cuts are made by pruning the terminal part of 30% of younger stems back to a bud. This will help maintain its natural shape.

An alternative to the “hard prune” is to thin the oldest lilac stems by 30% also known as renewal pruning, using the “Three-year Plan”, when dormant to open up the shrub and contain it in its allotted space. This will also increase light penetration and air circulation.

 This is what I chose. I planned to prune 30%, but not to top it using the following steps:

After Pruning

1.Remove dead and diseased limbs. Remove the debris. It already looks better.
2. Remove crossing branches.
3. Working from bottom, thin 30% of stems to open up the tree.

I laid a tarp on the ground for clippings and tried to evaluate how much I had removed. It has been suggested to me to take a picture before and after pruning to help determine when I had reached my 30% goal, remembering that 30% is an ‘eyeball’ estimate. Less is more as they say. There is always next year.

Leafed out and Bloomed!

How does the lilac look? Better, but not perfect. Leafing out will help it a lot. I checked it yesterday (03/26/26) and it is starting to leaf out, and I can see buds on the branches. If there is not hard freeze, it will bloom this season. Some sources advise fertilizing and mulching after pruning, but there was a substantial mulch of cottonwood leaves around it, and I can fertilize once water is available.

Conclusion: Reading about pruning and doing it are two different things. It didn’t turn out to be as daunting as I had feared. 

Xeriscape not ZEROscape

Drought tolerant landscape doesn’t have to mean gravel, and spiky gray plants. Xeriscape (xeri=Greek for dry and scape=view) emphasizes the use of drought tolerant plant species combined with creative landscaping practices to conserve water.

The following terms: water-wise, drought tolerant, water thrifty, and water smart all refer to plants requiring less water in a managed landscape. We all want to use less water in our landscapes and don’t want to be that house with the ugly brown yard.

Whether you have established landscape or total do-over, take a look at the following Eight Principles of Xeriscape:

1. Plant and Design comprehensively from the beginning.

• Lower your water bill.
• Create a more interesting landscape. Plan your annual flower and vegetable gardens and create a planting guide.
• Invite more pollinators into your landscape.
• Don’t just plant and hope for the best
• Create a landscape plan. Identify all the plants in your landscape, their water, sun, and soil needs, and the seasonal maintenance for those plants.
• Record the micro climates in your landscape. Record the plants you add and take out of your landscape and why. Record monthly and annual tasks to remind you when to perform them.
• Develop a fertilization and mulch plan.

Legacy buffalo grass lawn in Boise, ID

2. Create practical turf area. Consider size, shape, and appropriate grasses. Turf uses the highest percentage of water. When planning, consider regionally appropriate turf. Sheep’s fescue (Festuca ovina), and Buffalograss (Bouteloua dactyloides) are two examples of grasses that require less water and grow well in the Treasure Valley. Raise mowing height to 2-4 inches on your mower. The taller grass shades the ground so slows evaporation and promotes deeper root growth. Research shows mulching the clippings instead of removing them, can replace one application of fertilizer per year.

You might consider replacing some of the grass with a  more planting beds for flowers or vegetables. Don’t forget to check your HOA rules when considering the removal of turf.

3. Choose plants for your growing zone.
Once established, regionally appropriate native and low water use plants require little water beyond the normal rainfall (about 12 inches per year of precipitation in the Treasure Valley with 5 of those inches between April-October. Consider soil type, exposure to sun, and choose the right plant for those conditions. 

4. Consider improving the soil with organic matter.  Healthy soil retains water and absorbs excess nutrients, Have your soil tested for nutrient content, PH, soil composition and organic matter. The report will give you suggestions for adding anything that is lacking.

5. Strongly consider using organic mulches such as wood chips.  Adding mulch controls weed growth and slows evaporation, so conserves water. 

6.Irrigate efficiently. Create zones to provide the right amount of water at the right time by grouping plants according to their water needs. Your tree, shrubs, flower and raised beds have different water requirements than your lawn. Consider drip irrigation or soaker hoses for flower beds, shrub and trees. More targeted watering cuts down on weeds and uses less water.
Avoid sprinklers that produce a fine mist or spray high into the air in order to reduce water loss from evaporation and wind.  To check your sprinkler output, use tuna cans or similar straight-sided cans placed at various places around your lawn.  Run lawn sprinklers for 5 minutes and measure the output.  Now calculate the time needed to get  1 inch of water per week on your turf.
Water requirements change often so don’t just set automatic systems and forget them. Review the water requirements often taking into account rainfall, temperature and wind. Adjust the time you water accordingly.

7. Water Harvesting. Direct your roof water into rain barrels or onto your landscape. This recharges Idaho's aquifers as well as irrigating our arid environment. Here's how to build a rain barrel.

8. Maintain your established landscape.  Learn how to prune and fertilize each plant in your landscape and record the requirements in your maintenance schedule.

.Consider visiting xeric demonstration gardens in the Treasure Valley area. Hopefully they will inspire you to improve water conservation in your own home landscape.

The Idaho Botanical Garden has several gardens within its footprint, including The Water Wise Garden and The Fire Wise Garden.

 
These following two links will give you an extensive overview of xeric gardening.

Idaho Landscapes & Gardens | UI Extension (uidaho.edu)

Here's one extensive detailed resource for Intermountain Areas.