Lavender Intercropping and Soil Management

Results of Soil Mixes

We measured the growth, bud yield, and overall plant health of the 2 inch lavender starts that were transplanted into 5 gallon pots containing three different mixtures. The results of these mixtures are listed below.

Soil #1 - 25% compost, 20% sand, 5% pumice, and 50% screened composted mulch (1in. or smaller).

Total Buds (32 plants) = 4 oz.
Average Height of Growth = 10 in.
Average Health = Best - many branches spread 90-100% of pot width

Soil #2 - 35% compost, 40% red cinder, 10% pumice, and 15% pecan shell hulls

Total Buds (32 plants) = 3 oz.
Average Height of Growth = 8 in.
Average Health = Good - many branches spread 60-75% of pot width.

Soil #3 - 75% compost, 25% native sandy loam

Total Buds (32 plants) = 1 oz.
Average Height of Growth = 5 in.
Average Health = Poor - very little spread of 20-30% of pot width.

In addition to these customized soil mixes we tested a commercial potting mix containing an approximated 30% compost, 30% perlite and pumice, 30% peat moss, and 10% screened composted mulch. It was only tested over one season but the growth was comparable to Soil #1 with the added benefit of requiring less water due to the water retention created by the peat moss. It was also significantly lighter than the customized soil mixes but at a much higher cost per cubic yard.

One of the additional benefits of these customized soil mixes is #1 and #2 had really good drainage and we did not encounter any problems with root rot like we have experienced before with various commercial potting mixes.

Results of Cover Crop Trials

The Buffalo grass has outperformed the other cover crops we attempted. The trial rows were supplied with supplemental water from micro sprinklers while the grass was initially getting established, but have since been growing without any additional water. The grass provides an ideal solution to foot traffic and year-round soil retention.

The Purple Poppy Mallow was determined not to be a good companion plant because it grew out on a vine without good ground coverage. The vines could climb over the lavender plants, shading them. The Purple Poppy Mallow did prove to grow well in the climate with it’s large taproot allowing it to survive each winter. It did well with surviving foot traffic. It did not provide a good ground coverage during the winter since it died back to the root.

The Prairie Zinnias continued to prove difficult to germinate. It does not appear to be an ideal solution for planting in the alleyway because of rarity of seed and difficulties to germinate. Prairie Zinnias do provide better ground coverage year-round than the Purple Poppy Mallow but would not be as durable to foot traffic as the Buffalo grass.