When to prune...

When is the best time to prune dappled willows and purple sand cherry bushes. How much can I take off? The shrubs are approx 2 feet tall but they are growing straggly and uneven. Thanks.

IF there is growth that is going to be rocked about by strong winds in winter then remove some of the crossing branches as crossed branches being moved around and rubbing against other branches allows disease to enter the wounds made by the chaffing. Dead looking tips on branches can also be removed end of summer time, add mulches or whatever you need to give the plants help over winter IF you live in a cold area. You didn't say what zone your in so I'm guessing here.

Early spring when the weather begins to warm up a little, add a feed and fork it into soil, and then do a proper prune so your removing all unwanted branches AND allowing air to circulate through the branches as that stops any mould, when you prune, make sure you do the cut's about half inch above a bud as you don't want to damage buds at this time.
Clear away any grass / weeds growing close to the trunk and give a mulch to keep weeds ect away as these take nutrients and moisture away from the tree's your trying to build up the energy for.
Test that the roots are getting enough water by sticking your finger into soil AFTER you water, if the soil is still dry dig a hole in the soil close to roots, cut the bottom off a clear plastic container and remove the cap, then insert this (narrow end down) into the soil and back fill, when you water, fill the containers up with water and this helps water to get down to the roots where it is most needed, this also allows liquid feeds to be given when needed.
Hope this helps a little and you get the results you want.
Best Regards. WeeNel,

Thank you. Im in zone 7. Do you know how to get my shrubs to grow into trees? Empty on the bottom and leaves on top?

Joel do you mean growing into a tree like those plants you see trained into Lolly-pop shapes or do you mean like a proper tree.
To achieve the first type of Lolly-pop shape you have to do a few years of training and pruning, for the second type, as in a proper tree, almost impossible as a tree is a tree and naturally grows with a tall trunk but depending of what type of shrub you have, some shrubs over many years cant grow into tree's with maturity however they don't have the tall bare bottomed shrubs so get back to the thread with what type of shrub you have, then you can be told right away if what your planning for the shrub you have.

best Regards,
WeeNel.

You can begin training them as trees, but it takes time. At first it does not matter if you want a topiary patio tree or a more open and spreading landscape tree.

The lower branches are supplying nutrients and sun protection to the trunk.
If you cut them off too soon or all at once the plant will suffer.
I would do this: Each year cut off one or two of the lowest branches. Cut them off clean to the trunk. Do not remove more than those one or two in any one year..

Also, watch the branches that are growing up from the top. Is there one that is especially well centered and vertical? Keep that one. Prune the branches that are near it just a little. Take maybe a few inches to a half a foot off these branches, but do not remove them entirely. Here is why:
The growing tip of a plant produces hormones that tell the plant to send more energy toward that growing tip.
By keeping the one, best placed branch intact it will get more nutrients than the ones you trimmed.
Keep the ones you trimmed for a while because you do not want to cut them all off. The plant may sunburn, and the leaves on these side branches will still produce more food for the main branch.

After a few years of this sort of pruning you will start to see a more tree-like shape. A main trunk is showing up because you have been removing the lower branches @ 1-2 per year. It is well nourished because you have been leaving as much as possible of the leaves to produce more food for the plant.

If you are in an area with hot summers I would paint the trunk white to reflect a lot of the heat from the sun so that each branch you remove does not open up the plant to sunburn. In a few years, when the top starts spreading it will shade the trunk.

If you want the more formal topiary sort of patio tree (a lollipop) you can begin training that shape as soon as some branches and the main trunk get to the height an location you want.
If you want the more open and typical landscape tree, then just keep on they way you started. Once the branches are high enough to walk under you can start to leave them on, do not remove them unless they start to sag down and into your way.

The Dappled Willow is a fast growing plant that can be shaped as a shrub or small tree. Give it deep soaking and some fertilizer (don't over do it!) and it can be quite forgiving of pruning mistakes. Grows lots of branches to choose from. Prune in winter. Info from here:
http://www.monrovia.com/plant-catalog/plants/2082/dappled-willow.php

I cannot find such concise info about the sand cherry. If you prune it after flowering then you are sure to get more flowers next year, but dormant plants are often pruned in the winter, too.