diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 1c325d7734f..d023aa317c7 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -8,8 +8,12 @@ jobs:
 - job: Linux
   strategy:
     matrix:
-      py35-min:
-        conda_env: py35-min
+      py35-bare-minimum:
+        conda_env: py35-bare-minimum
+      py36-min-all-deps:
+        conda_env: py36-min-all-deps
+      py36-min-nep18:
+        conda_env: py36-min-nep18
       py36:
         conda_env: py36
       py37:
diff --git a/ci/requirements/py35-min.yml b/ci/requirements/py35-bare-minimum.yml
similarity index 100%
rename from ci/requirements/py35-min.yml
rename to ci/requirements/py35-bare-minimum.yml
diff --git a/ci/requirements/py36-min-all-deps.yml b/ci/requirements/py36-min-all-deps.yml
new file mode 100644
index 00000000000..1829f2a11e3
--- /dev/null
+++ b/ci/requirements/py36-min-all-deps.yml
@@ -0,0 +1,43 @@
+name: xarray-tests
+channels:
+  - conda-forge
+dependencies:
+  - python=3.6.7
+  - black
+  - boto3=1.9.235
+  - bottleneck=1.2.1
+  - cdms2=3.1.3
+  - cfgrib=0.9.7.2
+  - cftime=1.0.3.4
+  - coveralls
+  - dask=2.4.0
+  - distributed=2.4.0
+  - flake8
+  - h5netcdf=0.7.4
+  - h5py=2.10.0
+  - hdf5=1.10.5
+  - hypothesis
+  - iris=2.2.0
+  - lxml=4.4.1  # optional dep of pydap
+  - matplotlib=3.1.1
+  - mypy==0.720  # Must match .pre-commit-config.yaml
+  - nc-time-axis=1.2.0
+  - netcdf4=1.5.1.2
+  - numba=0.45.1
+  - numpy=1.17.2
+  - pandas=0.25.1
+  - pip
+  - pseudonetcdf=3.0.2
+  - pydap=3.2.2
+  - pynio=1.5.5
+  - pytest
+  - pytest-cov
+  - pytest-env
+  - rasterio=1.0.28
+  - scipy=1.3.1
+  - seaborn=0.9.0
+  # - sparse  # See py36-min-nep18.yml
+  - toolz=0.10.0
+  - zarr=2.3.2
+  - pip:
+    - numbagg==0.1
diff --git a/ci/requirements/py36-min-nep18.yml b/ci/requirements/py36-min-nep18.yml
new file mode 100644
index 00000000000..8680e412a99
--- /dev/null
+++ b/ci/requirements/py36-min-nep18.yml
@@ -0,0 +1,17 @@
+name: xarray-tests
+channels:
+  - conda-forge
+dependencies:
+  # Optional dependencies that require NEP18, such as sparse,
+  # require drastically newer packages than everything else
+  - python=3.6.7
+  - coveralls
+  - dask=2.4.0
+  - distributed=2.4.0
+  - numpy=1.17
+  - pandas=0.25
+  - pytest
+  - pytest-cov
+  - pytest-env
+  - scipy=1.3
+  - sparse=0.8.0
diff --git a/ci/requirements/py36.yml b/ci/requirements/py36.yml
index 7e852b5c260..187a9c79fbf 100644
--- a/ci/requirements/py36.yml
+++ b/ci/requirements/py36.yml
@@ -15,9 +15,10 @@ dependencies:
   - flake8
   - h5netcdf
   - h5py
+  - hdf5
   - hypothesis
   - iris>=1.10
-  - lxml
+  - lxml    # optional dep of pydap
   - matplotlib
   - mypy==0.720  # Must match .pre-commit-config.yaml
   - nc-time-axis
diff --git a/ci/requirements/py37-windows.yml b/ci/requirements/py37-windows.yml
index 31af80357ad..24297327393 100644
--- a/ci/requirements/py37-windows.yml
+++ b/ci/requirements/py37-windows.yml
@@ -15,9 +15,10 @@ dependencies:
   - flake8
   - h5netcdf
   - h5py
+  - hdf5
   - hypothesis
   - iris>=1.10
-  - lxml
+  - lxml    # optional dep of pydap
   - matplotlib
   - mypy==0.720  # Must match .pre-commit-config.yaml
   - nc-time-axis
diff --git a/ci/requirements/py37.yml b/ci/requirements/py37.yml
index 72b6c76ea37..5a328c64cf9 100644
--- a/ci/requirements/py37.yml
+++ b/ci/requirements/py37.yml
@@ -15,9 +15,10 @@ dependencies:
   - flake8
   - h5netcdf
   - h5py
+  - hdf5
   - hypothesis
   - iris>=1.10
-  - lxml
+  - lxml    # optional dep of pydap
   - matplotlib
   - mypy==0.720  # Must match .pre-commit-config.yaml
   - nc-time-axis
diff --git a/xarray/tests/test_plot.py b/xarray/tests/test_plot.py
index 5ce75ad2396..99a72d68ad8 100644
--- a/xarray/tests/test_plot.py
+++ b/xarray/tests/test_plot.py
@@ -1962,7 +1962,7 @@ def test_datetime_hue(self, hue_style):
         ds2.plot.scatter(x="A", y="B", hue="hue", hue_style=hue_style)
 
     def test_facetgrid_hue_style(self):
-        # Can't move this to pytest.mark.parametrize because py35-min
+        # Can't move this to pytest.mark.parametrize because py35-bare-minimum
         # doesn't have mpl.
         for hue_style, map_type in zip(
             ["discrete", "continuous"], [list, mpl.collections.PathCollection]